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+The Project Gutenberg EBook of Handbook of Medical Entomology, by 
+William Albert Riley and Oskar Augustus Johanssen
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Handbook of Medical Entomology
+
+Author: William Albert Riley
+        Oskar Augustus Johanssen
+
+Release Date: November 11, 2010 [EBook #34279]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK HANDBOOK OF MEDICAL ENTOMOLOGY ***
+
+
+
+
+Produced by Bryan Ness, Iris Schimandle, Brownfox and the
+Online Distributed Proofreading Team at http://www.pgdp.net
+(This file was produced from images generously made
+available by The Internet Archive/American Libraries.)
+
+
+
+
+
+Transcriber's Note: ae character replaced with ae. Accents have been
+removed. The degree symbol has been replaced with ^o. The times symbol
+has been replaced with lowercase x. The symbol mu/micro has been
+replaced with lowercase u.
+
+
+
+
+[Illustration: Some early medical entomology. Athanasius Kircher's
+illustration of the Italian tarantula and the music prescribed as an
+antidote for the poison of its bite. (1643).]
+
+
+
+
+HANDBOOK OF MEDICAL
+
+ENTOMOLOGY
+
+WM. A. RILEY, PH.D.
+
+Professor of Insect Morphology and Parasitology, Cornell University
+
+and
+
+O. A. JOHANNSEN, PH.D.
+
+Professor of Biology, Cornell University
+
+[Illustration]
+
+ITHACA, NEW YORK
+
+THE COMSTOCK PUBLISHING COMPANY
+
+1915
+
+
+COPYRIGHT, 1915
+
+BY THE COMSTOCK PUBLISHING COMPANY,
+
+ITHACA, N. Y.
+
+
+Press of W. F. Humphrey
+Geneva, N. Y.
+
+
+
+
+PREFACE
+
+
+The Handbook of Medical Entomology is the outgrowth of a course of
+lectures along the lines of insect transmission and dissemination of
+diseases of man given by the senior author in the Department of
+Entomology of Cornell University during the past six years. More
+specifically it is an illustrated revision and elaboration of his "Notes
+on the Relation of Insects to Disease" published January, 1912.
+
+Its object is to afford a general survey of the field, and primarily to
+put the student of medicine and entomology in touch with the discoveries
+and theories which underlie some of the most important modern work in
+preventive medicine. At the same time the older phases of the
+subject--the consideration of poisonous and parasitic forms--have not
+been ignored.
+
+Considering the rapid shifts in viewpoint, and the development of the
+subject within recent years, the authors do not indulge in any hopes
+that the present text will exactly meet the needs of every one
+specializing in the field,--still less do they regard it as complete or
+final. The fact that the enormous literature of isolated articles is to
+be found principally in foreign periodicals and is therefore difficult
+of access to many American workers, has led the authors to hope that a
+summary of the important advances, in the form of a reference book may
+not prove unwelcome to physicians, sanitarians and working
+entomologists, and to teachers as a text supplementing lecture work in
+the subject.
+
+Lengthy as is the bibliography, it covers but a very small fraction of
+the important contributions to the subject. It will serve only to put
+those interested in touch with original sources and to open up the
+field. Of the more general works, special acknowledgment should be made
+to those of Banks, Brumpt, Castellani and Chalmers, Comstock, Hewitt,
+Howard, Manson, Mense, Neveau-Lemaire, Nuttall, and Stiles.
+
+To the many who have aided the authors in the years past, by suggestions
+and by sending specimens and other materials, sincerest thanks is
+tendered. This is especially due to their colleagues in the Department
+of Entomology of Cornell University, and to Professor Charles W. Howard,
+Dr. John Uri Lloyd, Mr. A. H. Ritchie, Dr. I. M. Unger, and Dr. Luzerne
+Coville.
+
+They wish to express indebtedness to the authors and publishers who have
+so willingly given permission to use certain illustrations. Especially
+is this acknowledgment due to Professor John Henry Comstock, Dr. L. O.
+Howard, Dr. Graham-Smith, and Professor G. H. T. Nuttall. Professor
+Comstock not only authorized the use of departmental negatives by the
+late Professor M. V. Slingerland (credited as M. V. S.), but generously
+put at their disposal the illustrations from the MANUAL FOR THE STUDY OF
+INSECTS and from the SPIDER BOOK. Figures 5 and 111 are from Peter's
+"Der Arzt und die Heilkunst in der deutschen Vergangenheit." It should
+be noted that on examining the original, it is found that Gottfried's
+figure relates to an event antedating the typical epidemic of dancing
+mania.
+
+                                                  WM. A. RILEY.
+                                                  O. A. JOHANNSEN.
+
+  CORNELL UNIVERSITY,
+  January, 1915.
+
+
+
+
+ADDITIONS AND CORRECTIONS
+
+vi line 11, for Heilkunft read Heilkunst.
+
+18 line 2, for tarsi read tarsus.
+
+32 line 21, and legend under fig. 23, for C. (Conorhinus) abdominalis
+      read Melanolestes abdominalis.
+
+47 legend under figure for 33c read 34.
+
+92 line 22 and 25, for sangiusugus read sanguisugus.
+
+116 legend under fig. 83, for Graham-Smith read Manson.
+
+136 line 10, from bottom, insert "ring" after "chitin".
+
+137 line 3, for meditatunda read meditabunda.
+
+145 line 7, from bottom, for Rs read R_5.
+
+158 line 20, for have read has.
+
+212 after the chapter heading insert "continued".
+
+219 line 10, from bottom, for Cornohinus read Conorhinus.
+
+266 line 1, fig. 158j refers to the female.
+
+272 line 5, insert "palpus" before "and leg".
+
+281 line 6, for discodial read discoidal.
+
+281 last line, insert "from" before "the".
+
+284 line 5, for "tubercle of" read "tubercle or".
+
+305 lines 19, 28, 44, page 306 lines 1, 9, 22, 27, 30, page 307 line 7,
+      page 309 lines 8, 11, for R_{4+5} read M_{1+2}.
+
+309 legend under fig. 168 add Bureau of Entomology.
+
+312 line 36, for "near apex" read "of M_{1+2}".
+
+313 running head, for Muscidae read Muscoidea.
+
+314 line 29, for "distal section" read "distally M_{1+2}".
+
+315 legend under fig. 172, for Pseudopyrellia read Orthellia, for
+      Lyperosia read Haematobia, for Umbana read urbana.
+
+323 and 325 legends under the figures, add "After Dr. J. H. Stokes".
+
+328 line 7 from bottom for Apiochaeta read Aphiochaeta.
+
+
+
+
+CONTENTS
+
+
+CHAPTER I
+
+INTRODUCTION                                                  1-5
+
+  Early suggestions regarding the transmission of disease by
+    insects.
+  The ways in which arthropods may affect the health of man.
+
+
+CHAPTER II
+
+ARTHROPODS WHICH ARE DIRECTLY POISONOUS                       6-56
+
+  The Araneida, or Spiders.
+    The tarantulas. Bird spiders. Spiders of the genus
+      Latrodectus. Other venomous spiders. Summary.
+  The Pedipalpida, or whip-scorpions.
+  The Scorpionida, or true scorpions.
+  The Solpugida, or solpugids.
+  The Acarina, or mites and ticks.
+  The Myriapoda, or centipedes and millipedes.
+  The Hexapoda, or true insects.
+    Piercing or biting insects poisonous to man.
+      Hemiptera, or true bugs.
+        The Notonectidae or back-swimmers. Belostomidae or giant
+          water-bugs. Reduviidae, or assassin bugs. Other
+          Hemiptera reported as poisonous to man.
+      Diptera; the midges, mosquitoes and flies.
+    Stinging insects.
+      Apis mellifica, the honey bee. Other stinging forms.
+    Nettling insects.
+      Lepidoptera, or butterflies and moths. Relief from
+        poisoning by nettling larvae.
+    Vescicating insects and those possessing other poisons
+      in their blood plasma. The blister beetles. Other
+      cryptotoxic insects.
+
+
+CHAPTER III
+
+PARASITIC ARTHROPODS AFFECTING MAN                            57-130
+
+  Acarina, or mites.
+    The Trombidiidae, or harvest mites.
+    The Ixodoidea, or ticks.
+      Argasidae. Ixodidae. Treatment of tick bites.
+    The mites.
+      Dermanyssidae. Tarsonemidae. Sarcoptidae, the itch mites.
+        Demodecidae, the follicle mites.
+  Hexapoda, or true insects.
+    Siphunculata, or sucking lice.
+    Hemiptera.
+    The bed-bug. Other bed-bugs.
+  Parasitic Diptera, or flies.
+    Psychodidae, or moth flies. Phlebotominae. Culicidae, or
+      mosquitoes. Simuliidae, or black-flies. Chironomidae, or
+      midges. Tabanidae, or horse-flies. Leptidae or
+      snipe-flies. Oestridae, or bot-flies. Muscidae, the
+      stable-fly and others.
+  Siphonaptera, or fleas.
+    The fleas affecting man, the dog, cat, and rat.
+    The true chiggers, or chigoes.
+
+CHAPTER IV
+
+ACCIDENTAL OR FACULTATIVE PARASITES                           131-143
+
+  Acarina, or mites.
+  Myriapoda, or centipedes and millipedes.
+  Lepidopterous larvae.
+  Coleoptera, or beetles.
+  Dipterous larvae causing myiasis.
+    Piophila casei, the cheese skipper. Chrysomyia macellaria,
+      the screw-worm fly. Calliphorinae, the bluebottles.
+      Muscinae, the house or typhoid fly, and others.
+      Anthomyiidae, the lesser house-fly and others.
+      Sarcophagidae, the flesh-flies.
+
+
+CHAPTER V
+
+ARTHROPODS AS SIMPLE CARRIERS OF DISEASE                      144-163
+
+  The house or typhoid fly as a carrier of disease.
+  Stomoxys calcitrans, the stable-fly.
+  Other arthropods which may serve as simple carriers of
+    pathogenic organisms.
+
+
+CHAPTER VI
+
+ARTHROPODS AS DIRECT INOCULATORS OF DISEASE GERMS             164-174
+
+  Some illustrations of direct inoculations of disease germs
+    by arthropods.
+  The role of fleas in the transmission of the plague.
+
+
+CHAPTER VII
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC ORGANISMS         175-185
+
+  Insects as intermediate hosts of tape-worms.
+  Arthropods as intermediate hosts of nematode worms.
+    Filariasis and mosquitoes.
+  Other nematode parasites of man and animals.
+
+
+CHAPTER VIII
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA          186-211
+
+  Mosquitoes and malaria.
+  Mosquitoes and yellow fever.
+
+
+CHAPTER IX
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA          212-229
+
+  Insects and trypanosomiases.
+    Fleas and lice as carriers of Trypanosoma lewisi.
+    Tsetse-flies and nagana.
+    Tsetse-flies and sleeping sickness in man.
+    South American trypanosomiasis.
+    Leishmanioses and insects.
+  Ticks and diseases of man and animals.
+    Cattle tick and Texas fever.
+    Ticks and Rocky Mountain Spotted fever of man.
+
+
+CHAPTER X
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA
+(CONTINUED)                                                   230-240
+
+  Arthropods and Spirochaetoses of man and animals.
+    African relapsing fever of man.
+    European relapsing fever.
+    North African relapsing fever of man.
+    Other types of relapsing fever of man.
+    Spirochaetosis of fowls.
+    Other spirochaete diseases of animals.
+  Typhus fever and lice.
+
+
+CHAPTER XI
+
+SOME POSSIBLE, BUT IMPERFECTLY KNOWN CASES OF
+ARTHROPOD TRANSMISSION OF DISEASE                             241-256
+
+  Infantile paralysis, or acute anterior poliomyelitis.
+  Pellagra. Leprosy. Verruga peruviana. Cancer.
+
+
+CHAPTER XII
+
+KEYS TO THE ARTHROPODS NOXIOUS TO MAN                         257-317
+
+  Crustacea.
+  Myriapoda, or centipedes and millipedes.
+  Arachnida (Orders of).
+    Acarina or ticks.
+  Hexapoda (Insecta).
+    Siphunculata and Hemiptera (lice and true bugs).
+    Diptera (mosquitoes, midges, and flies).
+    Siphonaptera (fleas).
+
+
+APPENDIX
+
+Hydrocyanic acid gas against household insects                318-320
+  Proportion of ingredients. A single room as an example.
+    Fumigating a large house. Precautions.
+
+Lesions produced by the bite of the black-fly                 321-326
+
+
+BIBLIOGRAPHY                                                  327-340
+
+
+INDEX                                                         341-348
+
+
+
+
+CHAPTER I.
+
+INTRODUCTION
+
+EARLY SUGGESTIONS REGARDING THE TRANSMISSION OF DISEASE BY INSECTS
+
+
+Until very recent years insects and their allies have been considered as
+of economic importance merely in so far as they are an annoyance or
+direct menace to man, or his flocks and herds, or are injurious to his
+crops. It is only within the past fifteen years that there has sprung
+into prominence the knowledge that in another and much more insiduous
+manner, they may be the enemy of mankind, that they may be among the
+most important of the disseminators of disease. In this brief period,
+such knowledge has completely revolutionized our methods of control of
+certain diseases, and has become an important weapon in the fight for
+the conservation of health.
+
+It is nowhere truer than in the case under consideration that however
+abrupt may be their coming into prominence, great movements and great
+discoveries do not arise suddenly. Centuries ago there was suggested the
+possibility that insects were concerned with the spread of disease, and
+from time to time there have appeared keen suggestions and logical
+hypotheses along this line, that lead us to marvel that the
+establishment of the truths should have been so long delayed.
+
+One of the earliest of these references is by the Italian physician,
+Mercurialis, who lived from 1530 to 1607, during a period when Europe
+was being ravaged by the dread "black death", or plague. Concerning its
+transmission he wrote: "There can be no doubt that flies feed on the
+internal secretions of the diseased and dying, then, flying away, they
+deposit their excretions on the food in neighboring dwellings, and
+persons who eat of it are thus infected."
+
+It would be difficult to formulate more clearly this aspect of the facts
+as we know them to-day, though it must always be borne in mind that we
+are prone to interpret such statements in the light of present-day
+knowledge. Mercurialis had no conception of the animate nature of
+contagion, and his statement was little more than a lucky guess.
+
+Much more worthy of consideration is the approval which was given to his
+view by the German Jesuit, Athanasius Kircher in 1658. One cannot read
+carefully his works without believing that long before Leeuwenhook's
+discovery, Kircher had seen the larger species of bacteria. Moreover, he
+attributed the production of disease to these organisms and formulated,
+vaguely, to be sure, a theory of the animate nature of contagion. It has
+taken two and a half centuries to accumulate the facts to prove his
+hypothesis.
+
+The theory of Mercurialis was not wholly lost sight of, for in the
+medical literature of the eighteenth century there are scattered
+references to flies as carriers of disease. Such a view seems even to
+have been more or less popularly accepted, in some cases. Gudger (1910),
+has pointed out that, as far back as 1769, Edward Bancroft, in "An Essay
+on the Natural History of Guiana in South America," wrote concerning the
+contagious skin-disease known as "Yaws": "It is usually believed that
+this disorder is communicated by the flies who have been feasting on a
+diseased object, to those persons who have sores, or scratches, which
+are uncovered; and from many observations, I think this is not
+improbable, as none ever receive this disorder whose skins are whole."
+
+Approaching more closely the present epoch, we find that in 1848, Dr.
+Josiah Nott, of Mobile, Alabama, published a remarkable article on the
+cause of yellow fever, in which he presented "reasons for supposing its
+specific cause to exist in some form of insect life." As a matter of
+fact, the bearing of Nott's work on present day ideas of the insect
+transmission of disease has been very curiously overrated. The common
+interpretation of his theory has been deduced from a few isolated
+sentences, but his argument appears quite differently when the entire
+article is studied. It must be remembered that he wrote at a period
+before the epoch-making discoveries of Pasteur and before the
+recognition of micro-organisms as factors in the cause of disease. His
+article is a masterly refutation of the theory of "malarial" origin of
+"all the fevers of hot climates," but he uses the term "insect" as
+applicable to the lower forms of life, and specific references to
+"mosquitoes," "aphids," "cotton-worms," and others, are merely in the
+way of similes.
+
+But, while Nott's ideas regarding the relation of insects to yellow
+fever were vague and indefinite, it was almost contemporaneously that
+the French physician, Louis Daniel Beauperthuy argued in the most
+explicit possible manner, that yellow fever and various others are
+transmitted by mosquitoes. In the light of the data which were available
+when he wrote, in 1853, it is not surprising that he erred by thinking
+that the source of the virus was decomposing matter which the mosquito
+took up and accidentally inoculated into man. Beauperthuy not only
+discussed the role of mosquitoes in the transmission of disease, but he
+taught, less clearly, that house-flies scatter pathogenic organisms. It
+seems that Boyce (1909) who quotes extensively from this pioneer work,
+does not go too far when he says "It is Dr. Beauperthuy whom we must
+regard as the father of the doctrine of insect-borne disease."
+
+In this connection, mention must be made of the scholarly article by the
+American physician, A. F. A. King who, in 1883, brought together an all
+but conclusive mass of argument in support of his belief that malaria
+was caused by mosquitoes. At about the same time, Finley, of Havana, was
+forcefully presenting his view that the mosquito played the chief role
+in the spread of yellow fever.
+
+To enter more fully into the general historical discussion is beyond the
+scope of this book. We shall have occasion to make more explicit
+references in considering various insect-borne diseases. Enough has been
+said here to emphasize that the recognition of insects as factors in the
+spread of disease was long presaged, and that there were not wanting
+keen thinkers who, with a background of present-day conceptions of the
+nature of disease, might have been in the front rank of investigators
+along these lines.
+
+
+THE WAYS IN WHICH ARTHROPODS MAY AFFECT THE HEALTH OF MAN
+
+When we consider the ways in which insects and their allies may affect
+the health of man, we find that we may treat them under three main
+groups:
+
+A. They may be directly poisonous. Such, for example, are the scorpions,
+certain spiders and mites, some of the predaceous bugs, and stinging
+insects. Even such forms as the mosquito deserve some consideration from
+this viewpoint.
+
+B. They may be parasitic, living more or less permanently on or in the
+body and deriving their sustenance from it.
+
+Of the parasitic arthropods we may distinguish, first, the _true
+parasites_, those which have adopted and become confirmed in the
+parasitic habit. Such are the itch mites, the lice, fleas, and the
+majority of the forms to be considered as parasitic.
+
+In addition to these, we may distinguish a group of _accidental_, or
+_facultative parasites_, species which are normally free-living, feeding
+on decaying substances, but which when accidentally introduced into the
+alimentary canal or other cavities of man, may exist there for a greater
+or less period. For example, certain fly larvae, or maggots, normally
+feeding in putrifying meat, have been known to occur as accidental or
+facultative parasites in the stomach of man.
+
+C. Finally, and most important, arthropods may be transmitters and
+disseminators of disease. In this capacity they may function in one of
+three ways; as _simple carriers_, as _direct inoculators_, or as
+_essential hosts_ of disease germs.
+
+As simple carriers, they may, in a wholly incidental manner, transport
+from the diseased to the healthy, or from filth to food, pathogenic
+germs which cling to their bodies or appendages. Such, for instance, is
+the relation of the house-fly to the dissemination of typhoid.
+
+As direct inoculators, biting or piercing species may take up from a
+diseased man or animal, germs which, clinging to the mouth parts, are
+inoculated directly into the blood of the insect's next victim. It it
+thus that horse-flies may occasionally transmit anthrax. Similarly,
+species of spiders and other forms which are ordinarily perfectly
+harmless, may accidentally convey and inoculate pyogenic bacteria.
+
+It is as essential hosts of disease germs that arthropods play their
+most important role. In such cases an essential part of the life cycle
+of the pathogenic organism is undergone in the insect. In other words,
+without the arthropod host the disease-producing organism cannot
+complete its development. As illustrations may be cited the relation of
+the Anopheles mosquito to the malarial parasite, and the relation of the
+cattle tick to Texas fever.
+
+A little consideration will show that this is the most important of the
+group. Typhoid fever is carried by water or by contaminated milk, and in
+various other ways, as well as by the house-fly. Kill all the
+house-flies and typhoid would still exist. On the other hand, malaria is
+carried only by the mosquito, because an essential part of the
+development of the malarial parasite is undergone in this insect.
+Exterminate all of the mosquitoes of certain species and the
+dissemination of human malaria is absolutely prevented.
+
+Once an arthropod becomes an essential host for a given parasite it may
+disseminate infection in three different ways:
+
+1. By infecting man or animals who ingest it. It is thus, for example,
+that man, dog, or cat, becomes infected with the double-pored dog
+tapeworm, _Dipylidium caninum_. The cysticercoid stage occurs in the
+dog louse, or in the dog or cat fleas, and by accidentally ingesting the
+infested insect the vertebrate becomes infested. Similarly, _Hymenolepis
+diminuta_, a common tapeworm of rats and mice, and occasional in man,
+undergoes part of its life cycle in various meal-infesting insects, and
+is accidentally taken up by its definitive host. It is very probable
+that man becomes infested with _Dracunculus (Filaria) medinensis_
+through swallowing in drinking water, the crustacean, _Cyclops_,
+containing the larvae of this worm.
+
+2. By infecting man or animals on whose skin or mucous membranes the
+insect host may be crushed or may deposit its excrement. The pathogenic
+organism may then actively penetrate, or may be inoculated by
+scratching. The causative organism of typhus fever is thus transmitted
+by the body louse.
+
+3. By direct inoculation by its bite, the insect host may transfer the
+parasite which has undergone development within it. The malarial
+parasite is thus transferred by mosquitoes; the Texas fever parasite by
+cattle ticks.
+
+
+
+
+CHAPTER II.
+
+ARTHROPODS WHICH ARE DIRECTLY POISONOUS
+
+
+Of all the myriads of insects and related forms, a very few are of
+direct use to man, some few others have forced his approbation on
+account of their wonderful beauty, but the great hordes of them are
+loathed or regarded as directly dangerous. As a matter of fact, only a
+very small number are in the slightest degree poisonous to man or to the
+higher animals. The result is that entomologists and lovers of nature,
+intent upon dissipating the foolish dread of insects, are sometimes
+inclined to go to the extreme of discrediting all statements of serious
+injury from the bites or stings of any species.
+
+Nevertheless, it must not be overlooked that poisonous forms do exist,
+and they must receive attention in a consideration of the ways in which
+arthropods may affect the health of man. Moreover, it must be recognized
+that "what is one man's meat, is another man's poison," and that in
+considering the possibilities of injury we must not ignore individual
+idiosyncrasies. Just as certain individuals may be poisoned by what, for
+others, are common articles of food, so some persons may be abnormally
+susceptible to insect poison. Thus, the poison of a bee sting may be of
+varying severity, but there are individuals who are made seriously sick
+by a single sting, regardless of the point of entry. Some individuals
+scarcely notice a mosquito bite, others find it very painful, and so
+illustrations of this difference in individuals might be multiplied.
+
+In considering the poisonous arthropods, we shall take them up by
+groups. The reader who is unacquainted with the systematic relationship
+of insects and their allies is referred to Chapter XII. No attempt will
+be made to make the lists under the various headings exhaustive, but
+typical forms will be discussed.
+
+
+ARANEIDA OR SPIDERS
+
+Of all the arthropods there are none which are more universally feared
+than are the spiders. It is commonly supposed that the majority, if not
+all the species are poisonous and that they are aggressive enemies of
+man and the higher animals, as well as of lower forms.
+
+That they really secrete a poison may be readily inferred from the
+effect of their bite upon insects and other small forms. Moreover, the
+presence of definite and well-developed poison glands can easily be
+shown. They occur as a pair of pouches (fig. 1) lying within the
+cephalothorax and connected by a delicate duct with a pore on the claw
+of the chelicera, or so-called "mandible" on the convex surface of the
+claw in such a position that it is not plugged and closed by the flesh
+of the victim.
+
+[Illustration: 1. Head of a spider showing poison gland (_c_) and its
+relation to the chelicera (_a_).]
+
+The glands may be demonstrated by slowly and carefully twisting off a
+chelicera and pushing aside the stumps of muscles at its base. By
+exercising care, the chitinous wall of the chelicera and its claw may be
+broken away and the duct traced from the gland to its outlet. The inner
+lining of the sac is constituted by a highly developed glandular
+epithelium, supported by a basement membrane of connective tissue and
+covered by a muscular layer, (fig. 2). The muscles, which are striated,
+are spirally arranged (fig. 1), and are doubtless under control of the
+spider, so that the amount of poison to be injected into a wound may be
+varied.
+
+[Illustration: 2. Section through a venom gland of Latrodectus
+13-guttatus showing the peritoneal, muscular and epithelial layers.
+After Bordas.]
+
+The poison itself, according to Kobert (1901), is a clear, colorless
+fluid, of oily consistency, acid reaction, and very bitter taste. After
+the spider has bitten two or three times, its supply is exhausted and
+therefore, as in the case of snakes, the poison of the bite decreases
+quickly with use, until it is null. To what extent the content of the
+poison sacs may contain blood serum or, at least, active principles of
+serum, in addition to a specific poison formed by the poison glands
+themselves, Kobert regards as an open question. He believes that the
+acid part of the poison, if really present, is formed by the glands and
+that, in the case of some spiders, the ferment-like, or better, active
+toxine, comes from the blood.
+
+[Illustration: 3. Chelicera of a spider.]
+
+But there is a wide difference between a poison which may kill an insect
+and one which is harmful to men. Certain it is that there is no lack of
+popular belief and newspaper records of fatal cases, but the evidence
+regarding the possibility of fatal or even very serious results for man
+is most contradictory. For some years, we have attempted to trace the
+more circumstantial newspaper accounts, which have come to our notice,
+of injury by North American species. The results have served, mainly, to
+emphasize the straits to which reporters are sometimes driven when there
+is a dearth of news. The accounts are usually vague and lacking in any
+definite clue for locating the supposed victim. In the comparatively few
+cases where the patient, or his physician, could be located, there was
+either no claim that the injury was due to spider venom, or there was no
+evidence to support the belief. Rarely, there was evidence that a
+secondary blood poisoning, such as might be brought about by the prick
+of a pin, or by any mechanical injury, had followed the bite of a
+spider. Such instances have no bearing on the question of the venomous
+nature of these forms.
+
+[Illustration: 4. The Italian tarantula (Lycosa tarantula). After
+Kobert.]
+
+The extreme to which unreasonable fear of the bites of spiders
+influenced the popular mind was evidenced by the accepted explanation of
+the remarkable dancing mania, or tarantism, of Italy during the Middle
+Ages. This was a nervous disorder, supposed to be due to the bite of a
+spider, the European tarantula (fig. 4), though it was also, at times,
+attributed to the bite of the scorpion. In its typical form, it was
+characterized by so great a sensibility to music that under its
+influence the victims indulged in the wildest and most frenzied dancing,
+until they sank to the ground utterly exhausted and almost lifeless. The
+profuse perspiring resulting from these exertions was supposed to be the
+only efficacious remedy for the disease. Certain forms of music were
+regarded as of especial value in treating this tarantism, and hence the
+name of "tarantella" was applied to them. Our frontispiece, taken from
+Athanasius Kircher's _Magnes sive de Arte Magnetica_, 1643 ed.,
+represents the most commonly implicated spider and illustrates some of
+what Fabre has aptly designated as "medical choreography."
+
+The disease was, in reality, a form of hysteria, spreading by sympathy
+until whole communities were involved, and was paralleled by the
+outbreaks of the so-called St. Vitus's or St. John's dance, which swept
+Germany at about the same time (fig. 5). The evidence that the spider
+was the cause of the first is about as conclusive as is that of the
+demoniacal origin of the latter. The true explanation of the outbreaks
+is doubtless to be found in the depleted physical and mental condition
+of the people, resulting from the wars and the frightful plagues which
+devastated all Europe previous to, and during these times. An
+interesting discussion of these aspects of the question is to be found
+in Hecker.
+
+[Illustration: 5. Dancing mania. Illustration from Johann Ludwig
+Gottfried's Chronik. 1632.]
+
+So gross has been the exaggeration and so baseless the popular fear
+regarding spiders that entomologists have been inclined to discredit all
+accounts of serious injury from their bites. Not only have the most
+circumstantial of newspaper accounts proved to be without foundation but
+there are on record a number of cases where the bite of many of the
+commoner species have been intentionally provoked and where the effect
+has been insignificant. Some years ago the senior author personally
+experimented with a number of the largest of our northern species, and
+with unexpected results. The first surprise was that the spiders were
+very unwilling to bite and that it required a considerable effort to get
+them to attempt to do so. In the second place, most of those
+experimented with were unable to pierce the skin of the palm or the back
+of the hand, but had to be applied to the thin skin between the fingers
+before they were able to draw blood. Unfortunately, no special attempt
+was made to determine, at the time, the species experimented with, but
+among them were _Theridion tepidariorum_, _Miranda aurantia_
+(_Argiopa_), _Metargiope trifasciata_, _Marxia stellata_, _Aranea
+trifolium_, _Misumena vatia_, and _Agelena naevia_. In no case was the
+bite more severe than a pin prick and though in some cases the sensation
+seemed to last longer, it was probably due to the fact that the mind was
+intent upon the experiment.
+
+[Illustration: 6. An American tarantula (Eurypelma hentzii). Natural
+size. After Comstock.]
+
+Similar experiments were carried out by Blackwell (1855), who believed
+that in the case of insects bitten, death did not result any more
+promptly than it would have from a purely mechanical injury of equal
+extent. He was inclined to regard all accounts of serious injury to man
+as baseless. The question cannot be so summarily dismissed, and we shall
+now consider some of the groups which have been more explicitly
+implicated.
+
+
+THE TARANTULAS.--In popular usage, the term "tarantula" is loosely
+applied to any one of a number of large spiders. The famous tarantulas
+of southern Europe, whose bites were supposed to cause the dancing
+mania, were Lycosidae, or wolf-spiders. Though various species of this
+group were doubtless so designated, the one which seems to have been
+most implicated was _Lycosa tarantula_ (L.), (fig. 4). On the other
+hand, in this country, though there are many Lycosidae, the term
+"tarantula" has been applied to members of the superfamily Avicularoidea
+(fig. 6), including the bird-spiders.
+
+Of the Old World Lycosidae there is no doubt that several species were
+implicated as the supposed cause of the tarantism. In fact, as we have
+already noted, the blame was sometimes attached to a scorpion. However,
+there seems to be no doubt that most of the accounts refer to the spider
+known as _Lycosa tarantula_.
+
+There is no need to enter into further details here regarding the
+supposed virulence of these forms, popular and the older medical
+literature abound in circumstantial accounts of the terrible effects of
+the bite. Fortunately, there is direct experimental evidence which bears
+on the question.
+
+Fabre induced a common south European wolf-spider, _Lycosa narbonensis_,
+to bite the leg of a young sparrow, ready to leave the nest. The leg
+seemed paralyzed as a result of the bite, and though the bird seemed
+lively and clamored for food the next day, on the third day it died. A
+mole, bitten on the nose, succumbed after thirty-six hours. From these
+experiments Fabre seemed justified in his conclusion that the bite of
+this spider is not an accident which man can afford to treat lightly.
+Unfortunately, there is nothing in the experiments, or in the symptoms
+detailed, to exclude the probability that the death of the animals was
+the result of secondary infection.
+
+As far back as 1693, as we learn from the valuable account of Kobert,
+(1901), the Italian physician, Sanguinetti allowed himself to be bitten
+on the arm by two tarantulas, in the presence of witnesses. The
+sensation was equivalent to that from an ant or a mosquito bite and
+there were no other phenomena the first day. On the second day the wound
+was inflamed and there was slight ulceration. It is clear that these
+later symptoms were due to a secondary infection. These experiments have
+been repeated by various observers, among whom may be mentioned Leon
+Dufour, Josef Erker and Heinzel, and with the similar conclusion that
+the bite of the Italian tarantula ordinarily causes no severe symptoms.
+In this conclusion, Kobert, though firmly convinced of the poisonous
+nature of some spiders, coincides. He also believes that striking
+symptoms may be simulated or artificially induced by patients in order
+to attract interest, or because they have been assured that the bite,
+under all circumstances, caused tarantism.
+
+The so-called Russian tarantula, _Trochosa singoriensis_ (fig. 7), is
+much larger than the Italian species, and is much feared. Kobert carried
+out a series of careful experiments with this species and his results
+have such an important bearing on the question of the venomous nature of
+the tarantula that we quote his summary. Experimenting first on nearly a
+hundred living specimens of _Trochosa singoriensis_ from Crimea he says
+that:
+
+"The tarantulas, no matter how often they were placed on the skin,
+handled, and irritated, could not be induced to bite either myself, the
+janitor, or the ordinary experimental animals. The objection that the
+tarantulas were weak and indifferent cannot stand, for as soon as I
+placed two of them on the shaved skin of a rabbit, instead of an attack
+on the animal, there began a furious battle between the two spiders,
+which did not cease until one of the two was killed."
+
+[Illustration: 7. Trochosa singoriensis. After Kobert.]
+
+"Since the spiders would not bite, I carefully ground up the fresh
+animals in physiological salt solution, preparing an extract which must
+have contained, in solution, all of the poisonous substance of their
+bodies. While in the case of _Latrodectus_, as we shall see, less than
+one specimen sufficed to yield an active extract, I have injected the
+filtered extract of six fresh Russian tarantulas, of which each one was
+much heavier than an average _Latrodectus_, subcutaneously and into the
+jugular vein of various cats without the animals dying or showing any
+special symptoms. On the basis of my experiments I can therefore only
+say that the quantity of the poison soluble in physiological salt
+solution, even when the spiders are perfectly fresh and well nourished,
+is very insignificant. That the poison of the Russian tarantula is not
+soluble in physiological salt solution, is exceedingly improbable.
+Moreover, I have prepared alcoholic extracts and was unable to find them
+active. Since the Russian spider exceeds the Italian in size and in
+intensity of the bite, it seems very improbable to me that the
+pharmacological test of the Italian tarantula would yield essentially
+other results than those from the Russian species."
+
+To the AVICULAROIDEA belong the largest and most formidable appearing of
+the spiders and it is not strange that in the New World they have fallen
+heir to the bad reputation, as well as to the name of the tarantula of
+Europe. In this country they occur only in the South or in the far West,
+but occasionally living specimens are brought to our northern ports in
+shipments of bananas and other tropical produce, and are the source of
+much alarm. It should be mentioned, however, that the large spider most
+frequently found under such circumstances is not a tarantula at all, but
+one of the Heteropodidae, or giant crab-spiders, (fig. 8).
+
+[Illustration: 8. The giant crab-spider or banana spider (Heteropoda
+venatoria). Natural size. After Comstock.]
+
+In spite of their prominence and the fear which they arouse there are
+few accurate data regarding these American tarantulas. It has often been
+shown experimentally that they can kill small birds and mammals, though
+it is doubtful if these form the normal prey of any of the species, as
+has been claimed. There is no question but that the mere mechanical
+injury which they may inflict, and the consequent chances of secondary
+infection, justify, in part, their bad reputation. In addition to the
+injury from their bite, it is claimed that the body hairs of several of
+the South American species are readily detached and are urticating.
+
+Recently, Phisalix (1912) has made a study of the physiological effects
+of the venom of two Avicularoidea, _Phormictopus carcerides_ Pocock,
+from Haiti and _Cteniza sauvagei_ Rossi, from Corsica. The glands were
+removed aseptically and ground up with fine, sterilized sand in
+distilled water. The resultant liquid was somewhat viscid, colorless,
+and feebly alkaline. Injected into sparrows and mice the extract of
+_Phormictopus_ proved very actively poisonous, that from a single spider
+being sufficient to kill ten sparrows or twenty mice. It manifested
+itself first and, above all, as a narcotic, slightly lowering the
+temperature and paralyzing the respiration. Muscular and cardiac
+weakening, loss of general sensibility, and the disappearance of
+reflexes did not occur until near the end. The extract from _Cteniza_
+was less active and, curiously enough, the comparative effect on
+sparrows and on mice was just reversed.
+
+
+SPIDERS OF THE GENUS LATRODECTUS.--While most of the popular accounts of
+evil effects from the bites of spiders will not stand investigation, it
+is a significant fact that, the world over, the best authenticated
+records refer to a group of small and comparatively insignificant
+spiders belonging to the genus _Latrodectus_, of the family Theridiidae.
+The dread "Malmigniatte" of Corsica and South Europe, the "Karakurte" of
+southeastern Russia, the "Katipo" of New Zealand, the "Mena-vodi" and
+"Vancoho" of Madagascar, and our own _Latrodectus mactans_, all belong
+to this genus, and concerning all of these the most circumstantial
+accounts of their venomous nature are given. These accounts are not mere
+fantastic stories by uneducated natives but in many cases are reports
+from thoroughly trained medical men.
+
+The symptoms produced are general, rather than local. As summarized by
+Kobert (1901) from a study of twenty-two cases treated in 1888, in the
+Kherson (Russia) Government Hospital and Berislaw (Kherson) District
+Hospital the typical case, aside from complications, exhibits the
+following symptoms. The victim suddenly feels the bite, like the sting
+of a bee. Swelling of the barely reddened spot seldom follows. The
+shooting pains, which quickly set in, are not manifested at the point of
+injury but localized at the joints of the lower limb and in the region
+of the hip. The severity of the pain forces the victim to the hospital,
+in spite of the fact that they otherwise have a great abhorrence of it.
+The patient is unable to reach the hospital afoot, or, at least, not
+without help, for there is usually inability to walk. The patient, even
+if he has ridden, reaches the hospital covered with cold sweat and
+continues to perspire for a considerable period. His expression
+indicates great suffering. The respiration may be somewhat dyspnoeic,
+and a feeling of oppression in the region of the heart is common. There
+is great aversion to solid food, but increasing thirst for milk and tea.
+Retention of urine, and constipation occur. Cathartics and, at night,
+strong narcotics are desired. Warm baths give great relief. After three
+days, there is marked improvement and usually the patient is dismissed
+after the fifth. This summary of symptoms agrees well with other
+trustworthy records.
+
+It would seem, then, that Riley and Howard (1889), who discussed a
+number of accounts in the entomological literature, were fully justified
+in their statement that "It must be admitted that certain spiders of the
+genus _Latrodectus_ have the power to inflict poisonous bites, which may
+(probably exceptionally and depending upon exceptional conditions) bring
+about the death of a human being."
+
+And yet, until recently the evidence bearing on the question has been
+most conflicting. The eminent arachnologist, Lucas, (1843) states that
+he himself, had been repeatedly bitten by the Malmigniatte without any
+bad effects. Dr. Marx, in 1890, gave before the Entomological Society of
+Washington, an account of a series of experiments to determine whether
+the bite of _Latrodectus mactans_ is poisonous or not. He described the
+poison glands as remarkably small[A] and stated that he had introduced
+the poison in various ways into guinea-pigs and rabbits without
+obtaining any satisfactory results. Obviously, carefully conducted
+experiments with the supposed venom were needed and fortunately they
+have been carried out in the greatest detail by Kobert (1901).
+
+This investigator pointed out that there were two factors which might
+account for the discrepancies in the earlier experiments. In the first
+place, the poison of spiders, as of snakes, might be so exhausted after
+two or three bites that further bites, following directly, might be
+without visible effect. Secondly, the application of the poison by means
+of the bite, is exceedingly inexact, since even after the most careful
+selection of the point of application, the poison might in one instance
+enter a little vein or lymph vessel, and in another case fail to do so.
+Besides, there would always remain an incalculable and very large amount
+externally, in the nonabsorptive epithelium. While all of these factors
+enter into the question of the effect of the bite in specific instances,
+they must be as nearly as possible obviated in considering the question
+of whether the spiders really secrete a venom harmful to man.
+
+Kobert therefore sought to prepare extracts which would contain the
+active principles of the poison and which could be injected in definite
+quantities directly into the blood of the experimental animal. For this
+purpose various parts of the spiders were rubbed up in a mortar with
+distilled water, or physiological salt solution, allowed to stand for an
+hour, filtered, and then carefully washed, by adding water drop by drop
+for twenty-four hours. The filtrate and the wash-water were then united,
+well mixed and, if necessary, cleared by centrifuging or by exposure to
+cold. The mixture was again filtered, measured, and used, in part, for
+injection and, in part, for the determination of the organic materials.
+
+Such an extract was prepared from the cephalothoraces of eight dried
+specimens of the Russian _Latrodectus_ and three cubic centimeters of
+this, containing 4.29 mg. of organic material, were injected into the
+jugular vein of a cat weighing 2450 grams. The previously very active
+animal was paralyzed and lay in whatever position it was placed. The
+sensibility of the skin of the extremities and the rump was so reduced
+that there was no reaction from cutting or sticking. There quickly
+followed dyspnoea, convulsions, paralysis of the respiratory muscles
+and of the heart. In twenty-eight minutes the cat was dead, after having
+exhibited exactly the symptoms observed in severe cases of poisoning of
+man from the bite of this spider.
+
+These experiments were continued on cats, dogs, guinea pigs and various
+other animals. Not only extracts from the cephalothorax, but from other
+parts of the body, from newly hatched spiders, and from the eggs were
+used and all showed a similar virulence. Every effort was made to avoid
+sources of error and the experiments, conducted by such a recognized
+authority in the field of toxicology, must be accepted as conclusively
+showing that this spider and, presumably, other species of the genus
+_Latrodectus_ against which the clinical evidence is quite parallel,
+possess a poison which paralyzes the heart and central nervous system,
+with or without preliminary stimulus of the motor center. If the
+quantity of the poison which comes into direct contact with the blood is
+large, there may occur haemolysis and thrombosis of the vessels.
+
+On the other hand, check experiments were carried out, using similar
+extracts of many common European spiders of the genera _Tegenaria_,
+_Drassus_, _Agelena_, _Eucharia_ and _Argyroneta_, as well as the
+Russian tarantula, _Lycosa singoriensis_. In no other case was the
+effect on experimental animals comparable to the _Latrodectus_ extract.
+
+Kobert concludes that in its chemical nature the poison is neither an
+alkaloid, nor a glycoside, nor an acid, but a toxalbumen, or poisonous
+enzyme which is very similar to certain other animal poisons, notably
+that of the scorpion.
+
+[Illustration: 9. Latrodectus mactans; (_a_) female, x3; (_b_) venter
+of female; (_c_) dorsum of male. After Comstock.]
+
+The genus _Latrodectus_ is represented in the United States by at least
+two species, _L. mactans_ and _L. geometricus_. Concerning _L. mactans_
+there are very circumstantial accounts of serious injury and even death
+in man[B]. _Latrodectus mactans_ is coal black, marked with red or
+yellow or both. It has eight eyes, which are dissimilar in color and
+are distinctly in front of the middle of the thorax, the lateral eyes of
+each side widely separate. The tarsus of the fourth pair of legs has a
+number of curved setae in a single series. It has on the ventral side of
+its abdomen an hour-glass shaped spot. The full-grown female is about
+half an inch in length. Its globose abdomen is usually marked with one
+or more red spots dorsally along the middle line. The male is about half
+as long but has in addition to the dorsal spots, four pairs of stripes
+along the sides. Immature females resemble the male in coloring (fig.
+9).
+
+Regarding the distribution of _Latrodectus mactans_, Comstock states
+that: "Although it is essentially a Southern species, it occurs in
+Indiana, Ohio, Pennsylvania, New Hampshire, and doubtless other of the
+Northern States." _L. geometricus_ has been reported from California.
+
+
+OTHER VENOMOUS SPIDERS--While conclusive evidence regarding the venomous
+nature of spiders is meager and relates almost wholly to that of the
+genus _Latrodectus_, the group is a large one and we are not justified
+in dismissing arbitrarily, all accounts of injury from their bites.
+Several species stand out as especially needing more detailed
+investigation.
+
+_Chiracanthium nutrix_ is a common European species of the family
+Clubionidae, concerning which there is much conflicting testimony. Among
+the reports are two by distinguished scientists whose accounts of
+personal experiences cannot be ignored. A. Forel allowed a spider of
+this species to bite him and not only was the pain extreme, but the
+general symptoms were so severe that he had to be helped to his house.
+The distinguished arachnologist, Bertkau reports that he, himself, was
+bitten and that an extreme, burning pain spread almost instantaneously
+over the arm and into the breast. There were slight chills the same day
+and throbbing pain at the wound lasted for days. While this particular
+species is not found in the United States, there are two other
+representatives of the genus and it is possible that they possess the
+same properties. We are unaware of any direct experimental work on the
+poison.
+
+_Epeira diadema_, of Europe, belongs to a wholly different group, that
+of the orb-weavers, but has long been reputed venomous. Kobert was able
+to prepare from it an extract whose effects were very similar to that
+prepared from _Latrodectus_, though feebler in its action. Under
+ordinary circumstances this spider is unable to pierce the skin of man
+and though Kobert's results seem conclusive, the spider is little to be
+feared.
+
+_Phidippus audax_ (_P. tripunctatus_) is one of our largest Attids, or
+jumping spiders. The late Dr. O. Lugger describes a case of severe
+poisoning from the bite of this spider and though details are lacking,
+it is quite possible that this and other large species of the same
+group, which stalk their prey, may possess a more active poison than
+that of web-building species.
+
+
+SUMMARY--It is clearly established that our common spiders are not to be
+feared and that the stories regarding their virulence are almost wholly
+without foundation. On the other hand, the chances of secondary
+infection from the bites of some of the more powerful species are not to
+be ignored.
+
+Probably all species possess a toxin secreted by the poison gland,
+virulent for insects and other normal prey of the spiders, but with
+little or no effect on man.
+
+There are a very few species, notably of the genus _Latrodectus_, and
+possibly including the European _Chiracanthium nutrix_ and _Epeira
+diadema_, which possess, in addition, a toxalbumen derived from the
+general body tissue, which is of great virulence and may even cause
+death in man and the higher animals.
+
+[Illustration: 10. A whip-scorpion (Mastigoproctus giganteus). Half
+natural size. After Comstock.]
+
+
+THE PEDIPALPIDA OR WHIP-SCORPIONS
+
+The tailed whip-scorpions, belonging to the family Thelyphonidae, are
+represented in the United States by the giant whip-scorpion
+_Mastigoproctus giganteus_ (fig. 10), which is common in Florida, Texas
+and some other parts of the South. In Florida, it is locally known as
+the "grampus" or "mule-killer" and is very greatly feared. There is no
+evidence that these fears have any foundation, and Dr. Marx states that
+there is neither a poison gland nor a pore in the claw of the
+chelicera.
+
+
+THE SCORPIONIDA, OR TRUE SCORPIONS
+
+The true scorpions are widely distributed throughout warm countries and
+everywhere bear an evil reputation. According to Comstock (1912), about
+a score of species occur in the Southern United States. These are
+comparatively small forms but in the tropics members of this group may
+reach a length of seven or eight inches. They are pre-eminently
+predaceous forms, which lie hidden during the day and seek their prey by
+night.
+
+[Illustration: 11. A true scorpion. After Comstock.]
+
+The scorpions (fig. 11) possess large pedipalpi, terminated by strongly
+developed claws, or chelae. They may be distinguished from all other
+Arachnids by the fact that the distinctly segmented abdomen is divided
+into a broad basal region of seven segments and a terminal, slender,
+tail-like division of five distinct segments.
+
+The last segment of the abdomen, or telson, terminates in a
+ventrally-directed, sharp spine, and contains a pair of highly developed
+poison glands. These glands open by two small pores near the tip of the
+spine. Most of the species when running carry the tip of the abdomen
+bent upward over the back, and the prey, caught and held by the
+pedipalpi, is stung by inserting the spine of the telson and allowing it
+to remain for a time in the wound.
+
+The glands themselves have been studied in _Prionurus citrinus_ by
+Wilson (1904). He found that each gland is covered by a sheet of muscle
+on its mesal and dorsal aspects, which may be described as the
+_compressor muscle_. The muscle of each side is inserted by its edge
+along the ventral inner surface of the chitinous wall of the telson,
+close to the middle line, and by a broader insertion laterally. A layer
+of fine connective tissue completely envelops each gland and forms the
+basis upon which the secreting cells rest. The secreting epithelium is
+columnar; and apparently of three different types of cells.
+
+1. The most numerous have the appearance of mucous cells, resembling the
+goblet cells of columnar mucous membranes. The nucleus, surrounded by a
+small quantity of protoplasm staining with haematoxylin, lies close to
+the base of the cell.
+
+2. Cells present in considerable numbers, the peripheral portions of
+which are filled with very numerous fine granules, staining with acid
+dyes such as methyl orange.
+
+3. Cells few in number, filled with very large granules, or irregular
+masses of a substance staining with haematoxylin.
+
+The poison, according to Kobert (1893), is a limpid, acid-reacting
+fluid, soluble in water but insoluble in absolute alcohol and ether.
+There are few data relative to its chemical nature. Wilson (1901) states
+that a common Egyptian species, _Buthus quinquestriatus_, has a specific
+gravity of 1.092, and contains 20.3% of solids and 8.4% ash.
+
+The venom of different species appears to differ not only quantitatively
+but qualitatively. The effects of the bite of the smaller species of the
+Southern United States may be painful but there is no satisfactory
+evidence that it is ever fatal. On the other hand, certain tropical
+species are exceedingly virulent and cases of death of man from the bite
+are common.
+
+In the case of _Buthus quinquestriatus_, Wilson (1904) found the
+symptoms in animals to be hypersecretion, salivation and lachrymation,
+especially marked, convulsions followed by prolonged muscular spasm;
+death from asphyxia. The temperature shows a slight, rarely
+considerable, rise. Rapid and considerable increase of blood-pressure
+(observed in dogs) is followed by a gradual fall with slowing of the
+heart-beat. The coagulability of the blood is not affected.
+
+An interesting phase of Wilson's work was the experiments on desert
+mammals. The condition under which these animals exist must frequently
+bring them in contact with scorpions, and he found that they possess a
+degree of immunity to the venom sufficient at least to protect them from
+the fatal effects of the sting.
+
+As far as concerns its effect on man, Wilson found that much depended
+upon the age. As high as 60 per cent of the cases of children under
+five, resulted fatally. Caroroz (1865), states that in a Mexican state
+of 15,000 inhabitants, the scorpions were so abundant and so much feared
+that the authorities offered a bounty for their destruction. A result
+was a large number of fatalities, over two hundred per year. Most of the
+victims were children who had attempted to collect the scorpions.
+
+The treatment usually employed in the case of bites by the more
+poisonous forms is similar to that for the bite of venomous snakes.
+First, a tight ligature is applied above the wound so as to stop the
+flow of blood and lymph from that region. The wound is then freely
+excised and treated with a strong solution of permanganate of potash, or
+with lead and opium lotion.
+
+In recent years there have been many attempts to prepare an antivenom,
+or antiserum comparable to what has been used so effectively in the case
+of snake bites. The most promising of these is that of Todd (1909),
+produced by the immunization of suitable animals. This antivenom proved
+capable of neutralizing the venom when mixed _in vitro_ and also acts
+both prophylactically and curatively in animals. Employed curatively in
+man, it appears to have a very marked effect on the intense pain
+following the sting, and the evidence so far indicates that its prompt
+use greatly reduces the chance of fatal results.
+
+
+THE SOLPUGIDA, OR SOLPUGIDS
+
+The SOLPUGIDA are peculiar spider-like forms which are distinguished
+from nearly all other arachnids by the fact that they possess no true
+cephalothorax, the last two leg-bearing segments being distinct,
+resembling those of the abdomen in this respect. The first pair of legs
+is not used in locomotion but seemingly functions as a second pair of
+pedipalpi. Figure 12 illustrates the striking peculiarities of the
+group. They are primarily desert forms and occur in the warm zones of
+all countries. Of the two hundred or more species, Comstock lists twelve
+as occurring in our fauna. These occur primarily in the southwest.
+
+[Illustration: 12. A solpugid (Eremobates cinerea). After Comstock.]
+
+The Solpugida have long borne a bad reputation and, regarding virulence,
+have been classed with the scorpions. Among the effects of their bites
+have been described painful swelling, gangrene, loss of speech, cramps,
+delirium, unconsciousness and even death. Opposed to the numerous loose
+accounts of poisoning, there are a number of careful records by
+physicians and zoologists which indicate clearly that the effects are
+local and though they may be severe, they show not the slightest symptom
+of direct poisoning.
+
+More important in the consideration of the question is the fact that
+there are neither poison glands nor pores in the fangs for the exit of
+any poisonous secretion. This is the testimony of a number of prominent
+zoologists, among whom is Dr. A. Walter, who wrote to Kobert at length
+on the subject and whose conclusions are presented by him.
+
+However, it should be noted that the fangs are very powerful and are
+used in such a manner that they may inflict especially severe wounds.
+Thus, there may be more opportunity for secondary infection than is
+usual in the case of insect wounds.
+
+The treatment of the bite of the Solpugida is, therefore, a matter of
+preventing infection. The wound should be allowed to bleed freely and
+then washed out with a 1:3000 solution of corrosive sublimate, and, if
+severe, a wet dressing of this should be applied. If infection takes
+place, it should be treated in the usual manner, regardless of its
+origin.
+
+
+THE ACARINA, OR MITES AND TICKS
+
+A number of the parasitic Acarina evidently secrete a specific poison,
+presumably carried by the saliva, but in most cases its effect on man is
+insignificant. There is an abundant literature dealing with the
+poisonous effect of the bite of these forms, especially the ticks, but
+until recently it has been confused by failure to recognize that various
+species may transmit diseases of man, rather than produce injury through
+direct poisoning. We shall therefore discuss the Acarina more especially
+in subsequent chapters, dealing with parasitism and with disease
+transmission.
+
+Nevertheless, after the evidence is sifted, there can be no doubt that
+the bites of certain ticks may occasionally be followed by a direct
+poisoning, which may be either local or general in its effects. Nuttall
+(1908) was unable to determine the cause of the toxic effect, for, in
+_Argas persicus_, the species most often implicated, he failed to get
+the slightest local or general effect on experimental animals, from the
+injection of an emulsion prepared by crushing three of the ticks.
+
+It seems clearly established that the bite of certain ticks may cause a
+temporary paralysis, or even complete paralysis, involving the organs of
+respiration or the heart, and causing death. In 1912, Dr. I. U. Temple,
+of Pendleton, Oregon, reported several cases of what he called "acute
+ascending paralysis" associated with the occurrence of ticks on the head
+or the back of the neck. A typical severe case was that of a six year
+old child, who had retired in her usual normal health. The following
+morning upon arising she was unable to stand on her feet. She exhibited
+paralysis extending to the knees, slight temperature, no pain, sensory
+nerves normal, motor nerves completely paralyzed, reflexes absent. The
+following day the paralysis had extended to the upper limbs, and before
+night of the third day the nerves of the throat (hypoglossal) were
+affected. The thorax and larynx were involved, breathing was labored,
+she was unable to swallow liquids, phonation was impossible and she
+could only make low, guttural sounds. At this stage, two ticks, fully
+distended with blood, were found over the junction of the spinal column
+with the occipital bones in the hollow depression. They were removed by
+the application of undiluted creoline. Though the child's life was
+despaired of, by the following morning she was very much improved. By
+evening she was able to speak. The paralysis gradually receded,
+remaining longest in the feet, and at the end of one week the patient
+was able to go home.
+
+There was some doubt as to the exact species of tick implicated in the
+cases which Dr. Temple reported, although the evidence pointed strongly
+to _Dermacentor venustus_.[C] Somewhat later, Hadwen (1913) reported
+that "tick paralysis" occurs in British Columbia, where it affects not
+only man, but sheep and probably other animals. It is caused by the
+bites of _Dermacentor venustus_ and was experimentally produced in lambs
+and a dog (Hadwen and Nuttall, 1913). It is only when the tick begins to
+engorge or feed rapidly, some days after it has become attached, that
+its saliva produces pathogenic effects.
+
+Ulceration following tick bite is not uncommon. In many of the instances
+it is due to the file-like hypostome, with its recurved teeth, being
+left in the wound when the tick is forcibly pulled off.
+
+
+THE MYRIAPODA, OR CENTIPEDES AND MILLIPEDES
+
+The old class, Myriapoda includes the DIPLOPODA, or millipedes, and the
+CHILOPODA, or centipedes. The present tendency is to raise these groups
+to the rank of classes.
+
+
+The Diplopoda
+
+The DIPLOPODA, or millipedes (fig. 13), are characterized by the
+presence of two pairs of legs to a segment. The largest of our local
+myriapods belong to this group. They live in moist places, feeding
+primarily on decaying vegetable matter, though a few species
+occasionally attack growing plants.
+
+[Illustration: 13. A millipede. After Comstock.]
+
+The millipedes are inoffensive and harmless. _Julus terrestris_, and
+related species, when irritated pour out over the entire body a
+yellowish secretion which escapes from cutaneous glands. It is volatile,
+with a pungent odor, and Phisalix (1900) has shown that it is an active
+poison when injected into the blood of experimental animals. This,
+however, does not entitle them to be considered as poisonous arthropods,
+in the sense of this chapter, any more than the toad can be considered
+poisonous to man because it secretes a venom from its cutaneous glands.
+
+
+The Chilopoda
+
+[Illustration: 14. Two common centipedes.
+
+(_a_) Lithobius forficatus. After Comstock.
+
+(_b_) Scutigera forceps. Natural size; after Howard.]
+
+The CHILOPODA, or centipedes (fig. 14), unlike the millipedes, are
+predaceous forms, and possess well developed poison glands for killing
+their prey. These glands are at the base of the first pair of legs
+(fig. 15), which are bent forward so as to be used in holding their
+prey. The legs terminate in a powerful claw, at the tip of which is the
+outlet of the poison glands.
+
+The poison is a limpid, homogeneous, slightly acid fluid, which
+precipitates in distilled water. Briot (1904) extracted it from the
+glands of _Scolopendra morsitans_, a species common in central France,
+and found that it was actively venomous for the ordinary experimental
+animals. A rabbit of two kilograms weight received an injection of three
+cubic centimeters in the vein of the ear and died in a minute. A white
+rat, weighing forty-eight grams, received one and a half cubic
+centimeters in the hind leg. There was an almost immediate paralysis of
+the leg and marked necrosis of the tissues.
+
+[Illustration: 15. Mandible of Scolopendra cingulata showing venom
+gland. After Dubosq.]
+
+As for the effect on man, there is little foundation for the fear with
+which centipedes are regarded. Our native species produce, at most,
+local symptoms,--sometimes severe local pain and swelling,--but there is
+no authentic record of fatal results. In the tropics, some of the
+species attain a large size, _Scolopendra gigantea_ reaching a length of
+nearly a foot. These forms are justly feared, and there is good evidence
+that death sometimes, though rarely, results from their bite.
+
+One of the most careful accounts of death from the sting of the scorpion
+is that of Linnell, (1914), which relates to a comparatively small
+Malayan species, unfortunately undetermined. The patient, a coolie, aged
+twenty, was admitted to a hospital after having been stung two days
+previously on the left heel. For cure, the other coolies had made him
+eat the head of the scorpion. On admission, the patient complained of
+"things creeping all over the body". Temp. 102.8^o. On the fourth day he
+had paralysis of the legs, and on the fifth day motor paralysis to the
+umbilicus, sensation being unaltered. On the sixth day there was
+retention of the urine and on the ninth day (first test after third day)
+sugar was present. On the thirteenth day the patient became comatose,
+but could be roused to eat and drink. The temperature on the following
+day fell below 95^o and the patient was still comatose. Death fifteenth
+day.
+
+Examination of the spinal (lumbar) cord showed acute disseminated
+myelitis. In one part there was an acute destruction of the anterior
+horn and an infiltration of round cells. In another portion Clarke's
+column had been destroyed. The perivascular sheaths were crowded with
+small round cells and the meninges were congested. Some of the cells of
+the anterior horn were swollen and the nuclei eccentric; chromatolysis
+had occurred in many of them.
+
+As for treatment, Castellani and Chalmers (1910), recommend bathing the
+part well with a solution of ammonia (one in five, or one in ten). After
+bathing, apply a dressing of the same alkali or, if there is much
+swelling and redness, an ice-bag. If necessary, hypodermic injections of
+morphine may be given to relieve the pain. At a later period
+fomentations may be required to reduce the local inflammation.
+
+
+THE HEXAPODA OR TRUE INSECTS
+
+There are a number of HEXAPODA, or true insects, which are, in one way
+or another, poisonous to man. These belong primarily to the orders
+Hemiptera, or true bugs; Lepidoptera, or butterflies and moths (larval
+forms); Diptera, or flies; Coleoptera, or beetles; and Hymenoptera, or
+ants, bees, and wasps. There are various ways in which they may be
+poisonous.
+
+1. _Piercing_ or _biting_ forms may inject an irritating or poisonous
+saliva into the wound caused by their mouth-parts.
+
+2. _Stinging forms_ may inject a poison, from glands at the caudal end
+of the abdomen, into wounds produced by a specially modified ovipositer,
+the _sting_.
+
+3. _Nettling_ properties may be possessed by the hairs of the insect.
+
+4. _Vescicating_, or _poisonous blood plasma_, or _body fluids_ are
+known to exist in a large number of species and may, under exceptional
+circumstances, affect man.
+
+For convenience of discussion, we shall consider poisonous insects under
+these various headings. In this, as in the preceding discussion, no
+attempt will be made to give an exhaustive list of the poisonous forms.
+Typical instances will be selected and these will be chosen largely from
+North American species.
+
+
+PIERCING OR BITING INSECTS POISONOUS TO MAN
+
+
+HEMIPTERA
+
+Several families of the true bugs include forms which, while normally
+inoffensive, are capable of inflicting painful wounds on man. In these,
+as in all of the Hemiptera, the mouth-parts are modified to form an
+organ for piercing and sucking. This is well shown by the accompanying
+illustration (fig. 16).
+
+The upper lip, or _labrum_, is much reduced and immovable, the lower
+lip, or _labium_, is elongated to form a jointed sheath, within which
+the lance-like mandibles and maxillae are enclosed. The mandibles are
+more or less deeply serrate, depending on the species concerned.
+
+[Illustration: 16. Beak of hemipteron.]
+
+The poison is elaborated by the salivary glands, excepting, possibly, in
+_Belostoma_ where Locy is inclined to believe that it is secreted by the
+maxillary glands. The salivary glands of the Hemiptera have been the
+subject of much study but the most recent, comprehensive work has been
+done by Bugnion and Popoff, (1908 and 1910) to whose text the reader is
+referred for details.
+
+The Hemiptera have two pairs of salivary glands: the _primary gland_, of
+which the efferent duct leads to the salivary syringe, and the
+_accessory gland_, of which the very long and flexuous duct empties into
+the primary duct at its point of insertion. Thus, when one observes the
+isolated primary gland it appears as though it had efferent ducts
+inserted at the same point. In _Nepa_ and the _Fulgoridae_ there are two
+accessory glands and therefore apparently three ducts at the same point
+on the primary gland. The _ensemble_ differs greatly in appearance in
+different species but we shall show here Bugnion and Popoff's figure of
+the apparatus of _Notonecta maculata_, a species capable of inflicting a
+painful bite on man (fig. 17).
+
+[Illustration: 17. Salivary glands of Notonecta maculata. After Bugnion
+and Popoff.]
+
+[Illustration: 18. Pharyngeal syringe or salivary pump of Fulgora
+maculata. After Bugnion and Popoff.]
+
+[Illustration: 19. Heteroptera, (_a_) Melanolestes picipes; (_b_)
+Notonecta undulata; (_c_, _d_) Aradus robustus (_c_) adult, (_d_) nymph,
+much enlarged; (_e_) Arilus cristatus; (_f_) Belostoma americana; (_g_)
+Nabis (Coriscus) subcoleoptratus, enlarged; (_h_) Cimex lectularius,
+(_i_) Oeciacus vicarius, much enlarged; (_j_) Lyctocoris fitchii, much
+enlarged. After Lugger.]
+
+Accessory to the salivary apparatus there is on the ventral side of the
+head, underneath the pharynx, a peculiar organ which the Germans have
+called the "Wanzenspritze," or syringe. The accompanying figure of the
+structure in _Fulgora maculata_ (fig. 18) shows its relation to the
+ducts of the salivary glands and to the beak. It is made up of a
+dilatation forming the body of the pump, in which there is a chitinous
+piston. Attached to the piston is a strong retractor muscle. The
+function of the salivary pump is to suck up the saliva from the salivary
+ducts and to force it out through the beak.
+
+Of the Hemiptera reported as attacking man, we shall consider briefly
+the forms most frequently noted.
+
+
+The NOTONECTIDAE, or _back swimmers_, (fig. 19_b_) are small, aquatic
+bugs that differ from all others in that they always swim on their
+backs. They are predaceous; feeding on insects and other small forms.
+When handled carelessly they are able to inflict a painful bite, which
+is sometimes as severe as the sting of a bee. In fact, they are known in
+Germany as "Wasserbienen."
+
+
+The BELOSTOMATIDAE, or _giant water bugs_, (fig. 19_f_) include the
+largest living Hemiptera. They are attracted to lights and on account of
+the large numbers which swarm about the electric street lamps in some
+localities they have received the popular name "electric light bugs."
+Our largest representatives in the northern United States belong to the
+two genera _Belostoma_ and _Banacus_, distinguished from each other by
+the fact that _Belostoma_ has a groove on the under side of the femur of
+the front leg, for the reception of the tibia.
+
+The salivary glands of Belostoma were figured by Leidy (1847) and later
+were studied in more detail by Locy (1884). There are two pairs of the
+glands, those of one pair being long and extending back as far as the
+beginning of the abdomen, while the others are about one-fourth as long.
+They lie on either side of the oesophagus. On each side of the
+oesophagus there is a slender tube with a sigmoid swelling which may
+serve as a poison reservoir. In addition to this salivary system, there
+is a pair of very prominent glands on the ventral side of the head,
+opening just above the base of the beak. These Locy has called the
+"cephalic glands" and he suggests that they are the source of the
+poison. They are the homologues of the maxillary glands described for
+other Hemiptera, and it is by no means clear that they are concerned
+with the production of venom. It seems more probable that in
+_Belostoma_, as in other Hemiptera, it is produced by the salivary
+glands, though the question is an open one.
+
+The Belostomatidae feed not only on insects, but on small frogs, fish,
+salamanders and the like. Matheson (1907) has recorded the killing of a
+good-sized bird by _Belostoma americana_. A woodpecker, or flicker, was
+heard to utter cries of distress, and fluttered and fell from a tree. On
+examination it was found that a bug of this species had inserted its
+beak into the back part of the skull and was apparently busily engaged
+in sucking the blood or brains of the bird. Various species of
+_Belostoma_ have been cited as causing painful bites in man. We can
+testify from personal experience that the bite of _Belostoma americana_
+may almost immediately cause severe, shooting pains that may extend
+throughout the arm and that they may be felt for several days.
+
+[Illustration: 20. Reduvius (Opsicoetus) personatus. (x2).]
+
+Relief from the pain may be obtained by the use of dilute ammonia, or a
+menthol ointment. In the not uncommon case of secondary infection the
+usual treatment for that should be adopted.
+
+[Illustration: 21. (_a_) Reduvius personatus, nymph. Photograph by M. V.
+S.]
+
+The REDUVIIDAE, or _assassin-bugs_ are capable of inflicting very painful
+wounds, as most collectors of Hemiptera know to their sorrow. Some
+species are frequently to be found in houses and outhouses and Dr.
+Howard suggests that many of the stories of painful spider bites relate
+to the attack of these forms.
+
+[Illustration: 21. (_b_) Reduvius personatus, adult (x2) Photograph by
+M. V. S.]
+
+An interesting psychological study was afforded in the summer of 1899,
+by the "kissing-bug" scare which swept over the country. It was reported
+in the daily papers that a new and deadly bug had made its appearance,
+which had the unpleasant habit of choosing the lips or cheeks for its
+point of attack on man. So widespread were the stories regarding this
+supposedly new insect that station entomologists all over the country
+began to receive suspected specimens for identification. At Cornell
+there were received, among others, specimens of stone-flies, may-flies
+and even small moths, with inquiries as to whether they were
+"kissing-bugs."
+
+[Illustration: 22. Rasahus biguttatus. (x2). After Howard.]
+
+Dr. L. O. Howard has shown that the scare had its origin in newspaper
+reports of some instances of bites by either _Melanolestes picipes_
+(fig. 19a) or _Opsicoetes personatus_ (fig. 20), in the vicinity of
+Washington, D. C. He then discusses in considerable detail the more
+prominent of the Reduviidae which, with greater or less frequency pierce
+the skin of human beings. These are _Opsicoetes personatus_,
+_Melanolestes picipes_, _Coriscus subcoleoptratus_ (fig. 19_g_),
+_Rasahus thoracicus_, _Rasahus biguttatus_ (fig. 22), _Conorhinus
+sanguisugus_ (fig. 71), and _Melanolestes abdominalis_ (fig. 23).
+
+[Illustration: 23. Melanolestes abdominalis (x2). After Marlatt.]
+
+One of the most interesting of these species is _Reduvius personatus_,
+(= _Opsicoetus personatus_), which is popularly known as the "masked
+bed-bug hunter." It owes this name to the fact that the immature nymphs
+(fig. 21) have their bodies and legs completely covered by dust and
+lint, and that they are supposed to prey upon bed-bugs. LeConte is
+quoted by Howard as stating that "This species is remarkable for the
+intense pain caused by its bite. I do not know whether it ever willingly
+plunges its rostrum into any person, but when caught, or unskilfully
+handled it always stings. In this case the pain is almost equal to the
+bite of a snake, and the swelling and irritation which result from it
+will sometimes last for a week."
+
+A species which very commonly attacks man is _Conorhinus sanguisugus_,
+the so-called "big bed-bug" of the south and southern United States. It
+is frequently found in houses and is known to inflict an exceedingly
+painful bite. As in the case of a number of other predaceous Hemiptera,
+the salivary glands of these forms are highly developed. The effect of
+the bite on their prey and, as Marlatt has pointed out, the constant and
+uniform character of the symptoms in nearly all cases of bites in man,
+clearly indicate that their saliva contains a specific substance. No
+satisfactory studies of the secretions have been made. On the other
+hand, Dr. Howard is doubtless right in maintaining that the very serious
+results which sometimes follow the bite are due to the introduction of
+extraneous poison germs. This is borne out by the symptoms of most of
+the cases cited in literature and also by the fact that treatment with
+corrosive sublimate, locally applied to the wound, has yielded favorable
+results.
+
+
+OTHER HEMIPTERA REPORTED AS POISONOUS TO MAN--A large number of other
+Hemiptera have been reported as attacking man. Of these, there are
+several species of Lygaeidae, Coreidae, and Capsidae. Of the
+latter, _Lygus pratensis_, the tarnished plant-bug, is reported by
+Professor Crosby as sucking blood. _Orthotylus flavosparsus_ is another
+Capsid which has been implicated. _Empoasca mali_ and _Platymetopius
+acutus_ of the Jassidae have also been reported as having similar
+habits.
+
+Whenever the periodical cicada or "seventeen-year locust" becomes
+abundant, the newspapers contain accounts of serious results from its
+bites. The senior author has made scores of attempts to induce this
+species to bite and only once successfully. At that time the bite was in
+no wise more severe than a pin-prick. A student in our department
+reports a similar experience. There is no case on record which bears
+evidence of being worthy of any credence, whatsoever.
+
+Under the heading of poisonous Hemiptera we might consider the bed-bugs
+and the lice. These will be discussed later, as parasites and as
+carriers of disease, and therefore need only be mentioned here.
+
+
+DIPTERA
+
+Several species of blood-sucking Diptera undoubtedly secrete a saliva
+possessing poisonous properties. Chief among these are the Culicidae, or
+mosquitoes, and the Simuliidae, or black-flies. As we shall consider
+these forms in detail under the heading of parasitic species and
+insects transmitting disease, we shall discuss here only the poison of
+the mosquitoes.
+
+It is well known that mosquitoes, when they bite, inject into the wound
+a minute quantity of poison. The effect of this varies according to the
+species of mosquito and also depends very much on the susceptibility of
+the individual. Soon after the bite a sensation of itching is noticed
+and often a wheal, or eminence, is produced on the skin, which may
+increase to a considerable swelling. The scratching which is induced may
+cause a secondary infection and thus lead to serious results. Some
+people seem to acquire an immunity against the poison.
+
+The purpose of this irritating fluid may be, as Reaumur suggested, to
+prevent the coagulation of the blood and thus not only to cause it to
+flow freely when the insect bites but to prevent its rapid coagulation
+in the stomach. Obviously, it is not developed as a protective fluid,
+and its presence subjects the group to the additional handicap of the
+vengeance of man.
+
+[Illustration: 24. Diagram of a longitudinal section of a mosquito.]
+
+As to the origin of the poison, there has been little question, until
+recent years, that it was a secretion from the salivary glands.
+Macloskie (1888) showed that each gland is subdivided into three lobes,
+the middle of which differs from the others in having evenly granulated
+contents and staining more deeply than the others (fig. 24). This middle
+lobe he regarded as the source of the poison. Bruck, (1911), by the use
+of water, glycerine, chloroform, and other fluids, extracted from the
+bodies of a large number of mosquitoes a toxine which he calls
+_culicin_. This he assumes comes from the salivary glands. Animal
+experimentation showed that this extract possessed hemolytic powers.
+Inoculated into the experimenter's own skin it produced lesions which
+behaved exactly as do those of mosquito bites.
+
+Similarly, most writers on the subject have concurred with the view that
+the salivary glands are the source of the poison. However, recent work,
+especially that of Nuttall and Shipley (1903), and Schaudinn (1904), has
+shown that the evidence is by no means conclusive. Nuttall dissected out
+six sets (thirty-six acini) of glands from freshly killed _Culex
+pipiens_ and placed them in a drop of salt solution. The drop was
+allowed to dry, it being thought that the salt crystals would facilitate
+the grinding up of the glands with the end of a small glass rod, this
+being done under microscopic control. After grinding up, a small drop of
+water was added of the size of the original drop of saline, and an equal
+volume of human blood taken from the clean finger-tip was quickly mixed
+therewith, and the whole drawn up into a capillary tube. Clotting was
+not prevented and no hemolysis occurred. Salivary gland emulsion added
+to a dilute suspension of corpuscles did not lead to hemolysis. This
+experiment was repeated a number of times, with slight modification, but
+with similar results. The data obtained from the series "do not support
+the hypothesis that the salivary glands, at any rate in _Culex pipiens_,
+contain a substance which prevents coagulation."
+
+Much more detailed, and the more important experiments made along this
+line, are those of Schaudinn (1904). The results of these experiments
+were published in connection with a technical paper on the alternation
+of generations and of hosts in _Trypanosoma_ and _Spirochaeta_, and for
+this reason seem to have largely escaped the notice of entomologists.
+They are so suggestive that we shall refer to them in some detail.
+
+Schaudinn observed that the three oesophageal diverticula (commonly,
+but incorrectly, known as the "sucking stomach") (fig. 24) usually
+contain large bubbles of gas and in addition, he always found yeast
+cells. On the ground of numerous observations, Schaudinn was convinced
+that these yeast plants are normal and constant commensals of the
+insect. He regarded them as the cause of the gas bubbles to be found in
+diverticula. It was found that as the insect fed, from time to time the
+abdomen underwent convulsive contractions which resulted in the emptying
+of the oesophageal diverticula and the salivary glands through blood
+pressure.
+
+In order to test the supposed toxic action of the salivary glands,
+Schaudinn repeatedly introduced them under his skin and that of his
+assistant, in a drop of salt solution, and never obtained a suggestion
+of the irritation following a bite of the insect, even though the glands
+were carefully rubbed to fragments after their implantation. Like
+Nuttall, he failed to get satisfactory evidence that the secretion of
+the salivary glands retarded coagulation of the blood.
+
+He then carefully removed the oesophageal diverticula with their
+content of yeast and introduced them into an opening in the skin of the
+hand. Within a few seconds there was noticeable the characteristic
+itching irritation of the mosquito bite; and in a short time there
+appeared reddening and typical swelling. This was usually much more
+severe than after the usual mosquito bite, and the swelling persisted
+and itched longer. This was because by the ordinary bite of the mosquito
+most of the yeast cells are again sucked up, while in these experiments
+they remained in the wound. These experiments were repeated a number of
+times on himself, his assistant and others, and always with the same
+result. From them Schaudinn decided that the poisonous action of the
+mosquito bite is caused by an enzyme from a commensal fungus. These
+conclusions have not, as yet, been satisfactorily tested.
+
+Relief from the effect of the mosquito bite may be obtained by bathing
+the swellings with weak ammonia or, according to Howard, by using moist
+soap. The latter is to be rubbed gently on the puncture and is said to
+speedily allay the irritation. Howard also quotes from the _Journal of
+Tropical Medicine and Hygiene_ to the effect that a few drops of a
+solution of thirty to forty grains of iodine to an ounce of saponated
+petroleum rubbed into the mosquito bite, or wasp sting, allay the pain
+instantaneously.
+
+Methods of mosquito control will be discussed later, in considering
+these insects as parasites and as carriers of disease.
+
+
+STINGING INSECTS
+
+The stinging insects all belong to the order HYMENOPTERA. In a number of
+families of this group the ovipositor is modified to form a sting and is
+connected with poison-secreting glands. We shall consider the apparatus
+of the honey-bee and then make briefer reference to that of other forms.
+
+
+APIS MELLIFICA, THE HONEY BEE--The sting of the worker honey-bee is
+situated within a so-called sting chamber at the end of the abdomen.
+This chamber is produced by the infolding of the greatly reduced and
+modified eighth, ninth and tenth abdominal segments into the seventh.[D]
+From it the dart-like sting can be quickly exserted.
+
+The sting (fig. 25) is made up of a central shaft, ventro-laterad of
+which are the paired _lancets_, or darts, which are provided with sharp,
+recurved teeth. Still further laterad lie the paired whitish,
+finger-like _sting palpi_. Comparative morphological as well as
+embryological studies have clearly established that these three parts
+correspond to the three pairs of gonopophyses of the ovipositor of more
+generalized insects.
+
+[Illustration: 25. Sting of a honey bee. _Psn Sc_, base of acid poison
+gland; _B Gl_, alkaline poison gland; _Stn Plp_, sting palpi; _Sh B_,
+bulb of sting; _Sh A_, basal arm; _Lct_, lancets or darts; _Sh s_, shaft
+of sting. Modified from Snodgrass.]
+
+[Illustration: 26. Poison apparatus of a honey bee. Modified from
+Snodgrass.]
+
+An examination of the internal structures (fig. 26) reveals two distinct
+types of poison glands, the acid-secreting and the alkaline-secreting
+glands, and a prominent poison reservoir. In addition, there is a small
+pair of accessory structures which have been called lubricating glands,
+on account of the supposed function of their product. The acid-secreting
+gland empties into the distal end of the poison reservoir which in turn
+pours the secretion into the muscular bulb-like enlargement at the base
+of the shaft. The alkaline secreting gland empties into the bulb ventrad
+of the narrow neck of the reservoir.
+
+The poison is usually referred to as formic acid. That it is not so
+easily explained has been repeatedly shown and is evidenced by the
+presence of the two types of glands. Carlet maintains that the product
+of either gland is in itself innocent,--it is only when they are
+combined that the toxic properties appear.
+
+The most detailed study of the poison of the honey-bee is that of Josef
+Langer (1897), who in the course of his work used some 25,000 bees.
+Various methods of obtaining the active poison for experimental purposes
+were used. For obtaining the pure secretion, bees were held in the
+fingers and compressed until the sting was exserted, when a clear drop
+of the poison was visible at its tip. This was then taken up in a
+capillary tube or dilute solutions obtained by dipping the tip of the
+sting into a definite amount of distilled water.
+
+An aqueous solution of the poison was more readily obtained by pulling
+out the sting and poison sacs by means of forceps, and grinding them up
+in water. The somewhat clouded fluid was then filtered one or more
+times. For obtaining still greater quantities, advantage was taken of
+the fact that while alcohol coagulates the poison, the active principle
+remains soluble in water. Hence the stings with the annexed glands where
+collected in 96 per cent alcohol, after filtering off of the alcohol
+were dried at 40^o C., then rubbed to a fine powder and this was
+repeatedly extracted with water. Through filtering of this aqueous
+extract there was obtained a yellowish-brown fluid which produced the
+typical reactions, according to concentration of the poison.
+
+The freshly expelled drop of poison is limpid, of distinct acid
+reaction, tastes bitter and has a delicate aromatic odor. On
+evaporation, it leaves a sticky residue, which at 100 degrees becomes
+fissured, and suggests dried gum arabic. The poison is readily soluble
+in water and possesses a specific gravity of 1.1313. On drying at room
+temperature, it leaves a residue of 30 per cent, which has not lost in
+poisonous action or in solubility. In spite of extended experiments,
+Langer was unable to determine the nature of the active principle. He
+showed that it was not, as had been supposed, an albuminous body, but
+rather an organic base.
+
+The pure poison, or the two per cent aqueous solution, placed on the
+uninjured skin showed absolutely no irritating effect, though it
+produced a marked reaction on the mucus membrane of the nose or eye. A
+single drop of one-tenth per cent aqueous solution of the poison brought
+about a typical irritation in the conjunctiva of the rabbit's eye. On
+the other hand, the application of a drop of the poison, or its
+solution, to the slightest break in the skin, or by means of a needle
+piercing the skin, produced typical effects. There is produced a local
+necrosis, in the neighborhood of which there is infiltration of
+lymphocytes, oedema, and hyperaemia.
+
+The effect of the sting on man (fig. 27) is usually transitory but there
+are some individuals who are made sick for hours, by a single sting.
+Much depends, too, on the place struck. It is a common experience that
+an angry bee will attempt to reach the eye of its victim and a sting on
+the lid may result in severe and prolonged swelling. In the case of a
+man stung on the cheek, Legiehn observed complete aphonia and a breaking
+out of red blotches all over the body. A sting on the tongue has been
+known to cause such collateral oedema as to endanger life through
+suffocation. Cases of death of man from the attacks of bees are rare but
+are not unknown. Such results are usually from a number of stings but,
+rarely, death has been known to follow a single sting, entering a blood
+vessel of a particularly susceptible individual.
+
+[Illustration: Effect of bee stings. After Root.]
+
+It is clearly established that partial immunity from the effects of the
+poison may be acquired. By repeated injections of the venom, mice have
+been rendered capable of bearing doses that certainly would have killed
+them at first. It is a well-known fact that most bee-keepers become
+gradually hardened to the stings, so that the irritation and the
+swelling become less and less. Some individuals have found this immunity
+a temporary one, to be reacquired each season. A striking case of
+acquired immunity is related by the Roots in their "A B C and X Y Z of
+Bee Culture." The evidence in the case is so clear that it should be
+made more widely available and hence we quote it here.
+
+A young man who was determined to become a bee-keeper, was so
+susceptible to the poison that he was most seriously affected by a
+single sting, his body breaking out with red blotches, breathing growing
+difficult, and his heart action being painfully accelerated. "We finally
+suggested taking a live bee and pressing it on the back of his hand
+until it merely pierced his skin with the sting, then immediately
+brushing off both bee and sting. This was done and since no serious
+effect followed, it was repeated inside of four or five days. This was
+continued for some three or four weeks, when the patient began to have a
+sort of itching sensation all over his body. The hypodermic injections
+of bee-sting poison were then discontinued. At the end of a month they
+were repeated at intervals of four or five days. Again, after two or
+three weeks the itching sensation came on, but it was less pronounced.
+The patient was given a rest of about a month, when the doses were
+repeated as before." By this course of treatment the young man became so
+thoroughly immunized that neither unpleasant results nor swelling
+followed the attacks of the insects and he is able to handle bees with
+the same freedom that any experienced bee-keeper does.
+
+In an interesting article in the _Entomological News_ for November,
+1914, J. H. Lovell calls attention to the fact that "There has been a
+widespread belief among apiarists that a beekeeper will receive more
+stings when dressed in black than when wearing white clothing. A large
+amount of evidence has been published in the various bee journals
+showing beyond question that honey-bees under certain conditions
+discriminate against black. A few instances may be cited in
+illustration. Of a flock of twelve chickens running in a bee-yard seven
+black ones were stung to death, while five light colored ones escaped
+uninjured. A white dog ran among the bee-hives without attracting much
+attention, while at the same time a black dog was furiously assailed by
+the bees. Mr. J. D. Byer, a prominent Canadian beekeeper, relates that a
+black and white cow, tethered about forty feet from an apiary, was one
+afternoon attacked and badly stung by bees. On examination it was found
+that the black spots had five or six stings to one on the white. All
+noticed this fact, although no one was able to offer any explanation. A
+white horse is in much less danger of being stung, when driven near an
+apiary, than a black one. It has, indeed, been observed repeatedly that
+domestic animals of all kinds, if wholly or partially black, are much
+more liable to be attacked by bees, if they wander among the hives, than
+those which are entirely white."
+
+In order to test the matter experimentally, the following series of
+experiments was performed. In the language of the investigator:
+
+"On a clear, warm day in August I dressed wholly in white with the
+exception of a black veil. Midway on the sleeve of my right arm there
+was sewed a band of black cloth ten inches wide. I then entered the
+bee-yard and, removing the cover from one of the hives, lifted a piece
+of comb with both hands and gently shook it. Instantly many of the bees
+flew to the black band, which they continued to attack as long as they
+were disturbed. Not a single bee attempted to sting the left sleeve,
+which was of course entirely white, and very few even alighted upon it."
+
+"This experiment was repeated a second, third and fourth time; in each
+instance with similar results. I estimated the number of bees on the
+band of black cloth at various moments was from thirty to forty; it was
+evident from their behavior that they were extremely irritable. To the
+left white sleeve and other portions of my clothing they paid very
+little attention; but the black veil was very frequently attacked."
+
+"A few days later the experiments were repeated, but the band of black
+cloth, ten inches wide, was sewed around my left arm instead of around
+the right arm as before. When the bees were disturbed, after the hive
+cover had been removed, they fiercely attacked the band of black cloth
+as in the previous experiences; but the right white sleeve and the white
+suit were scarcely noticed. At one time a part of the black cloth was
+almost literally covered with furiously stinging bees, and the black
+veil was assailed by hundreds. The bees behaved in a similar manner when
+a second hive on the opposite side of the apiary was opened."
+
+"A white veil which had been procured for this purpose, was next
+substituted for the black veil. The result was most surprising, for,
+whereas in the previous experiments hundreds of bees had attacked the
+black veil, so few flew against the white veil as to cause me no
+inconvenience. Undoubtedly beekeepers will find it greatly to their
+advantage to wear white clothing when working among their colonies of
+bees and manipulating the frames of the hives."
+
+When a honey-bee stings, the tip of the abdomen, with the entire sting
+apparatus, is torn off and remains in the wound. Here the muscles
+continue to contract, for some minutes, forcing the barbs deeper and
+deeper into the skin, and forcing out additional poison from the
+reservoir.
+
+Treatment, therefore, first consists in removing the sting without
+squeezing out additional poison. This is accomplished by lifting and
+scraping it out with a knife-blade or the fingernail instead of grasping
+and pulling it out. Local application of alkalines, such as weak
+ammonia, are often recommended on the assumption that the poison is an
+acid to be neutralized on this manner, but these are of little or no
+avail. They should certainly not be rubbed in, as that would only
+accelerate the absorption of the poison. The use of cloths wrung out in
+hot water and applied as hot as can be borne, affords much relief in the
+case of severe stings. The application of wet clay, or of the end of a
+freshly cut potato is sometimes helpful.
+
+In extreme cases, where there is great susceptibility, or where there
+may have been many stings, a physician should be called. He may find
+strychnine injections or other treatment necessary, if general symptoms
+develop.
+
+[Illustration: 28. The poison apparatus of Formica. Wheeler, after
+Forel.]
+
+
+OTHER STINGING FORMS--Of the five thousand, or more, species of bees,
+most possess a sting and poison apparatus and some of the larger forms
+are capable of inflicting a much more painful sting than that of the
+common honey-bee. In fact, some, like the bumble bees, possess the
+advantage that they do not lose the sting from once using it, but are
+capable of driving it in repeatedly. In the tropics there are found many
+species of stingless bees but these are noted for their united efforts
+to drive away intruders by biting. Certain species possess a very
+irritating saliva which they inject into the wounds.
+
+The ants are not ordinarily regarded as worthy of consideration under
+the heading of "stinging insects" but as a matter of fact, most of them
+possess well developed stings and some of them, especially in the
+tropics, are very justly feared. Even those which lack the sting possess
+well-developed poison glands and the parts of the entire stinging
+apparatus, in so far as it is developed in the various species, may
+readily be homologized with those of the honey-bee.
+
+The ants lacking a sting are those of the subfamily CAMPONOTINAE, which
+includes the largest of our local species. It is an interesting fact
+that some of these species possess the largest poison glands and
+reservoir (fig. 28) and it is found that when they attack an enemy they
+bring the tip of the abdomen forward and spray the poison in such a way
+that it is introduced into the wound made by the powerful mandibles.
+
+[Illustration: 29. A harmless, but much feared larva, the "tomato worm."
+Natural size. Photograph by M. V. S.]
+
+More feared than any of the other Hymenoptera are the hornets and wasps.
+Of these there are many species, some of which attain a large size and
+are truly formidable. Phisalix (1897), has made a study of the venom of
+the common hornet and finds that, like the poison of the honey-bee, it
+is neither an albuminoid nor an alkaloid. Its toxic properties are
+destroyed at 120^o C. Phisalix also says that the venom is soluble in
+alcohol. If this be true, it differs in this respect from that of the
+bee. An interesting phase of the work of Phisalix is that several of her
+experiments go to show that the venom of hornets acts as a vaccine
+against that of vipers.
+
+
+NETTLING INSECTS
+
+So far, we have considered insects which possess poison glands connected
+with the mouth-parts or a special sting and which actively inject their
+poison into man. There remain to be considered those insects which
+possess poisonous hairs or body fluids which, under favorable
+circumstances, may act as poisons. To the first of these belong
+primarily the larvae of certain Lepidoptera.
+
+
+LEPIDOPTERA
+
+[Illustration: 30. Another innocent but much maligned caterpillar, the
+larva of the Regal moth. Photograph by M. V. S.]
+
+When we consider the reputedly poisonous larvae of moths and butterflies,
+one of the first things to impress us is that we cannot judge by mere
+appearance. Various species of Sphingid, or hawk-moth larvae, bear at the
+end of the body a chitinous horn, which is often referred to as a
+"sting" and regarded as capable of inflicting dangerous wounds. It would
+seem unnecessary to refer to this absurd belief if it were not that each
+summer the newspapers contain supposed accounts of injury from the
+"tomato worm" (fig. 29) and others of this group. The grotesque, spiny
+larva (fig. 30) of one of our largest moths, _Citheronia regalis_ is
+much feared though perfectly harmless, and similar instances could be
+multiplied.
+
+[Illustration: 31. The flannel moth (Lagoa crispata). (_a_) Poisonous
+larva.]
+
+[Illustration: 31. (_b_) Adult. Enlarged. Photographs by M. V. S.]
+
+But if the larvae are often misjudged on account of their ferocious
+appearance, the reverse may be true. A group of most innocent looking
+and attractive caterpillars is that of the flannel-moth larvae, of which
+_Lagoa crispata_ may be taken as an example. Its larva (fig. 31) has a
+very short and thick body, which is fleshy and completely covered and
+hidden by long silken hairs of a tawny or brown color, giving a convex
+form to the upper side. Interspersed among these long hairs are
+numerous short spines connected with underlying hypodermal poison
+glands. These hairs are capable of producing a marked nettling effect
+when they come in contact with the skin. This species is found in our
+Atlantic and Southern States. Satisfactory studies of its poisonous
+hairs and their glands have not yet been made.
+
+[Illustration: 32 The poisonous saddle back caterpillar. Empretia
+(Sibine) stimulea. Photograph by M. V. S.]
+
+[Illustration: 33_a_. Io moth larvae on willow. Photograph by M. V. S.]
+
+_Sibine stimulea (Empretia stimulea)_, or the saddle-back caterpillar
+(fig. 32), is another which possesses nettling hairs. This species
+belongs to the group of Eucleidae, or slug caterpillars. It can be
+readily recognized by its flattened form, lateral, bristling spines and
+by the large green patch on the back resembling a saddle-cloth, while
+the saddle is represented by an oval, purplish-brown spot. The small
+spines are venomous and affect some persons very painfully. The larva
+feeds on the leaves of a large variety of forest trees and also on
+cherry, plum, and even corn leaves. It is to be found throughout the
+Eastern and Southern United States.
+
+[Illustration: 33_b_. Io moth. Full grown larva. Photograph by M. V. S.]
+
+[Illustration: 34. Io moth. Adult. Photograph by M. V. S.]
+
+_Automeris io_ is the best known of the nettling caterpillars. It is the
+larva of the Io moth, one of the Saturniidae. The mature caterpillar,
+(fig. 33), which reaches a length of two and one-half inches, is of a
+beautiful pale green with sublateral stripes of cream and red color and
+a few black spines among the green ones. The green radiating spines give
+the body a mossy appearance. They are tipped with a slender chitinous
+hair whose tip is readily broken off in the skin and whose poisonous
+content causes great irritation. Some individuals are very susceptible
+to the poison, while others are able to handle the larvae freely without
+any discomfort. The larvae feed on a wide range of food plants. They are
+most commonly encountered on corn and on willow, because of the
+opportunities for coming in contact with them.
+
+[Illustration: 35. Larva of brown-tail moth. (Natural size). Photograph
+by M. V. S.]
+
+The larvae of the brown-tail moth (_Euproctis chrysorrhoea_) (fig. 35
+and 36), where they occur in this country, are, on account of their
+great numbers, the most serious of all poisonous caterpillars. It is not
+necessary here, to go into details regarding the introduction of this
+species from Europe into the New England States. This is all available
+in the literature from the United States Bureau of Entomology and from
+that of the various states which are fighting the species. Suffice to
+say, there is every prospect that the pest will continue to spread
+throughout the Eastern United States and Canada and that wherever it
+goes it will prove a direct pest to man as well as to his plants.
+
+Very soon after the introduction of the species there occurred in the
+region where it had gained a foothold, a mysterious dermatitis of man.
+The breaking out which usually occurred on the neck or other exposed
+part of the body was always accompanied by an intense itching. It was
+soon found that this dermatitis was caused by certain short, barbed
+hairs of the brown-tail caterpillars and that not only the caterpillars
+but their cocoons and even the adult female moths might harbor these
+nettling hairs and thus give rise to the irritation. In many cases the
+hairs were wafted to clothing on the line and when this was worn it
+might cause the same trouble. Still worse, it was found that very
+serious internal injury was often caused by breathing or swallowing the
+poisonous hairs.
+
+[Illustration: 36. Browntail moths. One male and two females. Photograph
+by M. V. S.]
+
+The earlier studies seemed to indicate that the irritation was purely
+mechanical in origin, the result of the minute barbed hairs working into
+the skin in large numbers. Subsequently, however, Dr. Tyzzer (1907)
+demonstrated beyond question that the trouble was due to a poison
+contained in the hairs. In the first place, it is only the peculiar
+short barbed hairs which will produce the dermatitis when rubbed on the
+skin, although most of the other hairs are sharply barbed. Moreover, it
+was found that in various ways the nettling properties could be
+destroyed without modifying the structure of the hairs. This was
+accomplished by baking for one hour at 110^o C, by warming to 60^o C in
+distilled water, or by soaking in one per cent. or in one-tenth per
+cent. of potassium hydrate or sodium hydrate. The most significant part
+of his work was the demonstration of the fact that if the nettling
+hairs are mingled with blood, they immediately produce a change in the
+red corpuscles. These at once become coarsely crenated, and the roleaux
+are broken up in the vicinity of the hair (fig. 37_b_). The corpuscles
+decrease in size, the coarse crenations are transformed into slender
+spines which rapidly disappear, leaving the corpuscles in the form of
+spheres, the light refraction of which contrasts them sharply with the
+normal corpuscles. The reaction always begins at the basal sharp point
+of the hair. It could not be produced by purely mechanical means, such
+as the mingling of minute particles of glass wool, the barbed hairs of a
+tussock moth, or the other coarser hairs of the brown-tail, with the
+blood.
+
+[Illustration: 37. (_a_) Ordinary hairs and three poison hairs of
+subdorsal and lateral tubercles of the larva of the browntail moth.
+Drawing by Miss Kephart.]
+
+The question of the source of the poison has been studied in our
+laboratory by Miss Cornelia Kephart. She first confirmed Dr. Tyzzer's
+general results and then studied carefully fixed specimens of the larvae
+to determine the distribution of the hairs and their relation to the
+underlying tissues.
+
+[Illustration: 37. (_b_) Effect of the poison on the blood corpuscles of
+man. After Tyzzer.]
+
+The poison hairs (fig. 37), are found on the subdorsal and lateral
+tubercles (fig. 38), in bunches of from three to twelve on the minute
+papillae with which the tubercles are thickly covered. The underlying
+hypodermis is very greatly thickened, the cells being three or four
+times the length of the ordinary hypodermal cells and being closely
+crowded together. Instead of a pore canal through the cuticula for each
+individual hair, there is a single pore for each papillae on a tubercle,
+all the hairs of the papilla being connected with the underlying cells
+through the same pore canal, (figs. 39 and 40).
+
+[Illustration: 38. Cross section of the larva of the browntail moth
+showing the tubercles bearing the poison hairs. Drawing by Miss
+Kephart.]
+
+The hypodermis of this region is of two distinct types of cells. First,
+there is a group of slender fusiform cells, one for each poison hair on
+the papilla, which are the trichogen, or hair-formative cells. They are
+crowded to one side and towards the basement membrane by a series of
+much larger, and more prominent cells (fig. 40), of which there is a
+single one for each papilla. These larger cells have a granular
+protoplasm with large nuclei and are obviously actively secreting. They
+are so characteristic in appearance as to leave no question but that
+they are the true poison glands.
+
+[Illustration: 39. Epithelium underlying poison hairs of the larva of
+the browntail moth. Drawing by Miss Kephart.]
+
+Poisonous larvae of many other species have been reported from Europe and
+especially from the tropics but the above-mentioned species are the more
+important of those occurring in the United States and will serve as
+types. It should be noted in this connection that through some curious
+misunderstanding Goeldi (1913) has featured the larva of _Orgyia
+leucostigma_, the white-marked tussock moth, as the most important of
+the poisonous caterpillars of this country. Though there are occasional
+reports of irritation from its hairs such cases are rare and there is no
+evidence that there is any poison present. Indeed, subcutaneous
+implantation of the hairs leads to no poisoning, but merely to temporary
+irritation.
+
+[Illustration: 40. Same as figure 39, on larger scale.]
+
+Occasionally, the hairs of certain species of caterpillars find
+lodgement in the conjunctiva, cornea, or iris of the eye of man and give
+rise to the condition known as _opthalmia nodosa_. The essential feature
+of this trouble is a nodular conjunctivitis which simulates tuberculosis
+of the conjunctiva and hence has been called _pseudo-tubercular_. It may
+be distinguished microscopically by the presence of the hairs.
+
+[Illustration: 41. (_a_) Nodular conjunctivitis in the eye of a child.
+De Schweinitz and Shumway.]
+
+Numerous cases of opthalmia nodosa are on record. Of those from this
+country, one of the most interesting is reported by de Schweinitz and
+Shumway (1904). It is that of a child of fifteen years whose eye had
+become inflamed owing to the presence of some foreign body. Downward and
+inward on the bulbar conjunctiva were a number of flattened,
+grayish-yellow nodules, between which was a marked congestion of the
+conjunctival and episcleral vessels (fig. 41_a_). Twenty-seven nodules
+could be differentiated, those directly in the center of the collection
+being somewhat confluent and assuming a crescentic and circular
+appearance. The nodules were excised and, on sectioning, were found to
+be composed of a layer of spindle cells and round cells, outside of
+which the tissue was condensed into a capsule. The interior consisted of
+epithelioid cells, between which was a considerable intercellular
+substance. Directly in the center of a certain number of nodules was
+found the section of a hair (fig. 41_b_). The evidence indicated that
+the injury had resulted from playing with caterpillars of one of the
+Arctiid moths, _Spilosoma virginica_. Other reported cases have been
+caused by the hairs of larvae of _Lasiocampa rubi_, _L. pini_,
+_Porthetria dispar_, _Psilura monacha_ and _Cnethocampa processionea_.
+
+[Illustration: 41_b_. Section through one of the nodules showing the
+caterpillar hair. De Schweinitz and Shumway.]
+
+
+RELIEF FROM POISONING BY NETTLING LARVAE--The irritation from nettling
+larvae is often severe and, especially in regions where the brown-tail
+abounds, inquiries as to treatment arise. In general, it may be said
+that cooling lotions afford relief, and that scratching, with the
+possibilities of secondary infection, should be avoided, in so far as
+possible.
+
+Among the remedies usually at hand, weak solutions of ammonia, or a
+paste of ordinary baking soda are helpful. Castellani and Chalmers
+recommend cleaning away the hairs by bathing the region with an alkaline
+lotion, such as two per cent solution of bicarbonate of soda, and then
+applying an ointment of ichthyol (10%).
+
+In the brown-tail district, there are many proprietary remedies of which
+the best ones are essentially the following, as recommended by Kirkland
+(1907):
+
+    Carbolic acid  1/2 drachm.
+    Zinc oxide     1/2 oz.
+    Lime water       8 oz.
+
+Shake thoroughly and rub well into the affected parts.
+
+In some cases, and especially where there is danger of secondary
+infection, the use of a weak solution of creoline (one teaspoonful to a
+quart of water), is to be advised.
+
+
+VESCICATING INSECTS AND THOSE POSSESSING OTHER POISONS IN THEIR BLOOD
+PLASMA
+
+We have seen that certain forms, for example, the poisonous spiders, not
+only secrete a toxine in their poison glands, but that such a substance
+may be extracted from other parts of their body, or even their eggs.
+There are many insects which likewise possess a poisonous blood plasma.
+Such forms have been well designated by Taschenberg as _cryptotoxic_
+([Greek: kryptos] = hidden). We shall consider a few representative
+forms.
+
+[Illustration: 42_a_. Blister beetle.]
+
+[Illustration: 42_b_. An American blister beetle. Meloe angusticollis.
+Photograph by M. V. S.]
+
+
+THE BLISTER BEETLES--Foremost among the cryptotoxic insects are the
+_Meloidae_ or "blister beetles," to which the well-known "Spanish fly"
+(fig. 42_a_), formerly very generally used in medical practice, belongs.
+The vescicating property is due to the presence in the blood plasma of a
+peculiar, volatile, crystalline substance known as _cantharidin_, which
+is especially abundant in the reproductive organs of the beetle.
+According to Kobert, the amount of this varies in different species from
+.4 or .5% to 2.57% of the dry weight of the beetle.
+
+While blister beetles have been especially used for external
+application, they are also at times used internally as a stimulant and a
+diuretic. The powder or extract was formerly much in vogue as an
+aphrodisiac, and formed the essential constituent of various philters,
+or "love powders". It is now known that its effects on the reproductive
+organs appear primarily after the kidneys have been affected to such an
+extent as to endanger life, and that many cases of fatal poison have
+been due to its ignorant use.
+
+There are many cases on record of poisoning and death due to internal
+use, and in some instances from merely external application. There are
+not rarely cases of poisoning of cattle from feeding on herbage bearing
+a large number of the beetles and authentic cases are known of human
+beings who have been poisoned by eating the flesh of such cattle. Kobert
+states that the beetles are not poisonous to birds but that the flesh of
+birds which have fed on them is poisonous to man, and that if the flesh
+of chickens or frogs which have fed on the cantharidin be fed to cats it
+causes in them the same symptoms as does the cantharidin.
+
+Treatment of cases of cantharidin poison is a matter for a skilled
+physician. Until he can be obtained, emetics should be administered and
+these should be followed by white of egg in water. Oils should be
+avoided, as they hasten the absorption of the poison.
+
+
+OTHER CRYPTOTOXIC INSECTS--Though the blister beetles are the best known
+of the insects with poisonous blood plasma, various others have been
+reported and we shall refer to a few of the best authenticated.
+
+One of the most famous is the Chrysomelid beetle, _Diamphidia simplex_,
+the body fluids of whose larvae are used by certain South African bushmen
+as an arrow poison. Its action is due to the presence of a toxalbumin
+which exerts a haemolytic action on the blood, and produces inflammation
+of the subcutaneous connective tissue and mucous membranes. Death
+results from general paralysis. Krause (1907) has surmised that the
+active principle may be a bacterial toxin arising from decomposition of
+the tissues of the larva, but he presents no support of this view and it
+is opposed by all the available evidence.
+
+In China, a bug, _Heuchis sanguinea_, belonging to the family Cicadidae,
+is used like the Meloidae, to produce blistering, and often causes
+poisoning. It has been assumed that its vescicating properties are due
+to cantharidin, but the presence of this substance has not been
+demonstrated.
+
+Certain Aphididae contain a strongly irritating substance which produces,
+not merely on mucous membranes but on outer skin, a characteristic
+inflammation.
+
+It has been frequently reported that the larvae of the European cabbage
+butterfly, _Pieris brassicae_, accidentally eaten by cows, horses, ducks,
+and other domestic animals, cause severe colic, attempts to vomit,
+paralysis of the hind legs, salivation, and stomatitis. On _postmortem_
+there are to be found haemorrhagic gastro-enteritis, splenitis, and
+nephritis. Kobert has recently investigated the subject and has found a
+poisonous substance in the blood of not only the larvae but also the
+pupae.
+
+
+FOOTNOTES:
+
+[A] This is diametrically opposed to the findings of Bordas (1905) in
+the case of the European _Latrodectus 13-guttatus_, whose glands are
+"much larger than those of other spiders." From a considerable
+comparative study, we should also unhesitatingly make this statement
+regarding the glands of our American species, _L. mactans_.
+
+[B] Dr. E. H. Coleman (Kellogg, 1915) has demonstrated its virulence by
+a series of experiments comparable with those of Kobert.
+
+[C] According to Stiles, the species occurring in the Northwest which is
+commonly identified as _D. venustus_ should be called _D. andersoni_
+(see footnote, chapter 12).
+
+[D] It should be remembered that in all the higher Hymenoptera the first
+abdominal segment is fused with the thorax and that what is apparently
+the sixth segment is, in reality, the seventh.
+
+
+
+
+CHAPTER III
+
+PARASITIC ARTHROPODA AFFECTING MAN
+
+
+The relation of insects to man as simple parasites has long been
+studied, and until very recent years the bulk of the literature of
+medical entomology referred to this phase of the subject. This is now
+completely overshadowed by the fact that so many of these parasitic
+forms are more than simple parasites, they are transmitters of other
+microscopic parasites which are pathogenic to man. Yet the importance of
+insects as parasites still remains and must be considered in a
+discussion of the relation of insects to the health of man. In taking up
+the subject we shall first consider some general features of the
+phenomenon of animal parasitism.
+
+Parasitism is an adaptation which has originated very often among living
+organisms and in widely separated groups. It would seem simple to define
+what is meant by a "parasite" but, in reality, the term is not easily
+limited. It is often stated that a parasite is "An organism which lives
+at the expense of another," but this definition is applicable to a
+predatory species or, in its broadest sense, to all organisms. For our
+purpose we may say with Braun: "A parasite is an organism which, for the
+purpose of obtaining food, takes up its abode, temporarily or
+permanently, on or within another living organism".
+
+Thus, parasitism is a phase of the broad biological phenomenon of
+_symbiosis_, or living together of organisms. It is distinguished from
+_mutualism_, or symbiosis in the narrow sense, by the fact that only one
+party to the arrangement obtains any advantage, while the other is to a
+greater or less extent injured.
+
+Of parasites we may distinguish on the basis of their location on or in
+the host, _ecto-parasites_, which live outside of the body; and
+_endo-parasites_, which live within the body. On account of their method
+of breathing the parasitic arthropods belong almost exclusively to the
+first of these groups.
+
+On the basis of relation to their host, we find _temporary parasites_,
+those which seek the host only occasionally, to obtain food; and the
+_stationary_ or _permanent_ parasites which, at least during certain
+stages, do not leave their host.
+
+_Facultative parasites_ are forms which are not normally parasitic, but
+which, when accidentally ingested, or otherwise brought into the body,
+are able to exist for a greater or less period of time in their unusual
+environment. These are generally called in the medical literature
+"pseudoparasites" but the term is an unfortunate one.
+
+We shall now take up the different groups of arthropods, discussing the
+more important of the parasitic forms attacking man. The systematic
+relationship of these forms, and key for determining important species
+will be found in Chapter XII.
+
+
+ACARINA OR MITES
+
+The ACARINA, or _mites_, form a fairly natural group of arachnids,
+characterized, in general, by a sac-like, unsegmented body which is
+generally fused with the cephalothorax. The mouth-parts have been united
+to form a beak or rostrum.
+
+The representatives of this group undergo a marked metamorphosis.
+Commonly, the larvae on hatching from the egg, possess but three pairs of
+legs, and hence are called _hexapod larvae_. After a molt, they transform
+into nymphs which, like the adult, have four pairs of legs and are
+called _octopod nymphs_. These after a period of growth, molt one or
+more times and, acquiring external sexual organs, become adult.
+
+Most of the mites are free-living, but there are many parasitic species
+and as these have originated in widely separated families, the Acarina
+form an especially favorable group for study of the origin of
+parasitism. Such a study has been made by Ewing (1911), who has reached
+the following conclusions:
+
+"We have strong evidence indicating that the parasitic habit has
+originated independently at least eleven times in the phylogeny of the
+Ararina. Among the zoophagous parasites, the parasitic habit has been
+developed from three different types of free-living Acarina: (a)
+predaceous forms, (b) scavengers, (c) forms living upon the juices of
+plants."
+
+Ewing also showed that among the living forms of Acarina we can trace
+out all the stages of advancing parasitism, semiparasitism, facultative
+parasitism, even to the fixed and permanent type, and finally to
+endoparasitism.
+
+Of the many parasitic forms, there are several species which are serious
+parasites of man and we shall consider the more important of these.
+Infestation by mites is technically known as _acariasis_.
+
+[Illustration: 43. Effect of the harvest mites on the skin of man.
+Photograph by J. C. Bradley.]
+
+
+The Trombidiidae, or Harvest Mites
+
+In many parts of this country it is impossible for a visitor to go into
+the fields and, particularly, into berry patches and among tall weeds
+and grass in the summer or early fall without being affected by an
+intolerable itching, which is followed, later, by a breaking out of
+wheals, or papules, surrounded by a bright red or violaceous aureola,
+(fig. 43). It is often regarded as a urticaria or eczema, produced by
+change of climate, an error in diet, or some condition of general
+health.
+
+Sooner or later, the victim finds that it is due to none of these, but
+to the attacks of an almost microscopic red mite, usually called
+"jigger" or "chigger" in this country. As the term "chigger" is applied
+to one of the true fleas, _Dermatophilus penetrans_, of the tropics,
+these forms are more correctly known as "harvest mites." Natives of an
+infested region may be so immune or accustomed to its attacks as to be
+unaware of its presence, though such immunity is by no means possessed
+by all who have been long exposed to the annoyance.
+
+[Illustration: 44. Harvest mites. (Larvae of Trombidium). After C. V.
+Riley.]
+
+The harvest mites, or chiggers, attacking man are larval forms,
+possessing three pairs of legs (fig. 44). Their systematic position was
+at first unknown and they were classed under a special genus _Leptus_, a
+name which is very commonly still retained in the medical literature. It
+is now known that they are the larval forms of various species of the
+genus _Trombidium_, a group of predaceous forms, the adults of which
+feed primarily on insects and their eggs. In this country the species
+best known are those to be found late in summer, as larvae at the base of
+the wings of houseflies or grasshoppers.
+
+There is much uncertainty as to the species of the larvae attacking man
+but it is clear that several are implicated. Bruyant has shown that in
+France the larvae _Trombidium inapinatum_ and _Trombidium holosericeum_
+are those most frequently found. The habit of attacking man is abnormal
+and the larvae die after entering the skin. Normally they are parasitic
+on various insects.
+
+Most recent writers agree that, on man, they do not bore into the skin,
+as is generally supposed, but enter a hair follicle or sebaceous gland
+and from the bottom of this, pierce the cutis with their elongate
+hypopharynx. According to Braun, there arises about the inserted
+hypopharynx a fibrous secretion--the so-called "beak" which is, in
+reality, a product of the host. Dr. J. C. Bradley, however, has made
+careful observations on their method of attack, and he assures us that
+the mite ordinarily remains for a long time feeding on the surface of
+the skin, where it produces the erythema above described. During this
+time it is not buried in the skin but is able to retreat rapidly into it
+through a hair follicle or sweat gland. The irritation from the mites
+ceases after a few days, but not infrequently the intolerable itching
+leads to so much scratching that secondary infection follows.
+
+Relief from the irritation may be afforded by taking a warm salt bath as
+soon as possible after exposure or by killing the mites by application
+of benzine, sulphur ointment or carbolized vaseline. When they are few
+in number, they can be picked out with a sterile needle.
+
+Much may be done in the way of warding off their attacks by wearing
+gaiters or close-woven stockings extending from ankle to the knee. Still
+more efficacious is the sprinkling of flowers of sulphur in the
+stockings and the underclothes from a little above the knee, down. The
+writers have known this to make it possible for persons who were
+especially susceptible to work with perfect comfort in badly infested
+regions. Powdered naphthalene is successfully used in the same way and
+as Chittenden (1906) points out, is a safeguard against various forms of
+man-infesting tropical insect pests.
+
+The question of the destruction of the mites in the field is sometimes
+an important one, and under some conditions, is feasible. Chittenden
+states that much can be accomplished by keeping the grass, weeds, and
+useless herbage mowed closely, so as to expose the mites to the sun. He
+believes that in some cases good may be done by dusting the grass and
+other plants, after cutting, with flowers of sulphur or by spraying with
+dilute kerosene emulsion in which sulphur has been mixed. More recently
+(1914) he calls attention to the value of cattle, and more especially
+sheep, in destroying the pests by tramping on them and by keeping the
+grass and herbage closely cropped.
+
+
+IXODOIDEA OR TICKS
+
+Until recently, the ticks attracted comparatively little attention from
+entomologists. Since their importance as carriers of disease has been
+established, interest in the group has been enormously stimulated and
+now they rank second only to the mosquitoes in the amount of detailed
+study that has been devoted to them.
+
+[Illustration: 45_a_. Argus persicus. Capitulum of male. After Nuttall
+and Warburton.]
+
+The ticks are the largest of the Acarina. They are characterized by the
+fact that the hypostome, or "tongue" (fig. 45) is large and file-like,
+roughened by sharp teeth. They possess a breathing pore on each side of
+the body, above the third or fourth coxae (fig. 45_b_).
+
+[Illustration: 45_b_. Left spiracle of nymph of _Argas persicus_. After
+Nuttall and Warburton.]
+
+There are two distinct families of the IXODOIDEA, differing greatly in
+structure, life-history and habits. These are the ARGASIDAE and the
+IXODIDAE. We shall follow Nuttall (1908) in characterizing these two
+families and in pointing out their biological differences, and shall
+discuss briefly the more important species which attack man. The
+consideration of the ticks as carriers of disease will be reserved for a
+later chapter.
+
+
+Argasidae
+
+In the ticks belonging to the family ARGASIDAE, there is comparatively
+little sexual dimorphism, while this is very marked in the Ixodidae. The
+capitulum, or so-called "head" is ventral, instead of terminal; the
+palpi are leg-like, with the segments subequal; the scutum, or dorsal
+shield, is absent; eyes, when present, are lateral, on supracoxal folds.
+The spiracles are very small; coxae unarmed; tarsi without ventral
+spurs, and the pulvilli are absent or rudimentary.
+
+In habits and life history the Argasidae present striking
+characteristics. In the first place, they are long-lived, a factor which
+counts for much in the maintenance of the species. They are intermittent
+feeders, being comparable with the bed-bug in this respect. There are
+two or more nymphal stages, and they may molt after attaining maturity.
+The female lays comparatively few eggs in several small batches.
+
+Nuttall (1911) concludes that "The Argasidae represent the relatively
+primitive type of ticks because they are less constantly parasitic than
+are the Ixodidae. Their nymphs and adults are rapid feeders and chiefly
+infest the habitat of their hosts. * * * Owing to the Argasidae infesting
+the habitats of their hosts, their resistance to prolonged starvation
+and their rapid feeding habits, they do not need to bring forth a large
+progeny, because there is less loss of life in the various stages, as
+compared with the Ixodidae, prior to their attaining maturity."
+
+[Illustration: 46. Argus persicus. Dorsal and ventral aspects. (x4).
+After Hassell.]
+
+Of the Argasidae, we have in the United States, several species which
+have been reported as attacking man.
+
+_Argas persicus_, the famous "Miana bug" (fig. 46), is a very widely
+distributed species, being reported from Europe, Asia, Africa, and
+Australia. It is everywhere preeminently a parasite of fowls. According
+to Nuttall it is specifically identical with _Argas americanus_ Packard
+or _Argas miniatus_ Koch, which is commonly found on fowls in the United
+States, in the South and Southwest. Its habits are comparable to those
+of the bed-bug. It feeds intermittently, primarily at night, and instead
+of remaining on its host, it then retreats to cracks and crevices.
+Hunter and Hooker (1908) record that they have found the larva to remain
+attached for five or eight days before dropping. Unlike the Ixodidae, the
+adults oviposit frequently.
+
+[Illustration: 47. Otiobius (Ornithodoros) megnini, head of nymph. After
+Stiles.]
+
+[Illustration: 48. Otiobius (Ornithodoros) megnini, male. (_a_) dorsal,
+(_b_) ventral aspect. After Nuttall and Warburton.]
+
+The most remarkable feature of the biology of this species is the great
+longevity, especially of the adult. Hunter and Hooker report keeping
+larvae confined in summer in pill boxes immediately after hatching for
+about two months while under similar conditions those of the Ixodid,
+_Boophilus annulatus_ lived for but two or three days. Many writers have
+recorded keeping adults for long periods without food. We have kept
+specimens in a tin box for over a year and a half and at the end of that
+time a number were still alive. Laboulliene kept unfed adults for over
+three years. In view of the effectiveness of sulphur in warding off the
+attacks of Trombidiidae, it is astonishing to find that Lounsbury has
+kept adults of _Argas persicus_ for three months in a box nearly filled
+with flowers of sulphur, with no apparent effect on them.
+
+We have already called attention to the occasional serious effects of
+the bites of this species. While such reports have been frequently
+discredited there can be no doubt that they have foundation in fact. The
+readiness with which this tick attacks man, and the extent to which old
+huts may be infested makes it especially troublesome.
+
+_Otiobius (Ornithodoros) megnini_, the "spinose ear-tick" (figs. 47,
+48), first described from Mexico, as occurring in the ears of horses, is
+a common species in our Southwestern States and is recorded by Banks as
+occurring as far north as Iowa.
+
+The species is remarkable for the great difference between the spiny
+nymph stage and the adult. The life history has been worked out by
+Hooker (1908). Seed ticks, having gained entrance to the ear, attach
+deeply down in the folds, engorge, and in about five days, molt; as
+nymphs with their spinose body they appear entirely unlike the larvae. As
+nymphs they continue feeding sometimes for months. Finally the nymph
+leaves the host, molts to form the unspined adult, and without further
+feeding is fertilized and commences oviposition.
+
+The common name is due to the fact that in the young stage the ticks
+occur in the ear of their hosts, usually horses or cattle. Not
+uncommonly it has been reported as occurring in the ear of man and
+causing very severe pain. Stiles recommends that it be removed by
+pouring some bland oil into the ear.
+
+Banks (1908) reports three species of _Ornithodoros_--_O. turicata_,
+_coriaceus_ and _talaje_--as occurring in the United States. All of these
+attack man and are capable of inflicting very painful bites.
+
+
+Ixodidae
+
+The ticks belonging to the family IXODIDAE (figs. 49 and 50) exhibit a
+marked sexual dimorphism. The capitulum is anterior, terminal, instead
+of ventral as in the Argasidae; the palpi are relatively rigid (except in
+the subfamily Ixodinae), with rudimentary fourth segment; scutum present;
+eyes, when present, dorsal, on side of scutum. The spiracles are
+generally large, situated well behind the fourth coxae; coxae generally
+with spurs; pulvilli always present.
+
+In habits and life history the typical Ixodidae differ greatly from
+the Argasidae. They are relatively short-lived, though some recent
+work indicates that their longevity has been considerably
+under-estimated. Typically, they are permanent feeders, remaining on the
+host, or hosts, during the greater part of their life. They molt twice
+only, on leaving the larval and the nymphal stages. The adult female
+deposits a single, large batch of eggs. Contrasting the habits of the
+Ixodidae to those of the Argasidae, Nuttall (1911) emphasizes that
+the Ixodidae are more highly specialized parasites. "The majority are
+parasitic on hosts having no fixed habitat and consequently all stages,
+as a rule, occur upon the host."
+
+[Illustration: 49. Ixodes ricinus; male, ventral aspect. After Braun and
+Luehe.]
+
+As mere parasites of man, apart from their power to transmit disease,
+the Ixodidae are much less important than the Argasidae. Many are
+reported as occasionally attacking man and of these the following native
+species may be mentioned.
+
+[Illustration: 50. Ixodes ricinus, var. scapularis, female. Capitulum
+and scutum; ventral aspect of capitulum; coxae; tarsus 4; spiracle;
+genital and anal grooves. After Nuttall and Warburton.]
+
+_Ixodes ricinus_, the European castor bean tick (figs. 49, 50), is a
+species which has been often reported from this country but Banks (1908)
+has shown that, though it does occur, practically all of the records
+apply to _Ixodes scapularis_ or _Ixodes cookei_. In Europe, _Ixodes
+ricinus_ is very abundant and very commonly attacks man. At the point
+of penetration of the hypostome there is more or less inflammation but
+serious injury does not occur unless there have been introduced
+pathogenic bacteria or, unless the tick has been abruptly removed,
+leaving the capitulum in the wound. Under the latter circumstances,
+there may be an abscess formed about the foreign body and occasionally,
+serious results have followed. Under certain conditions the tick, in
+various stages, may penetrate under the skin and produce a tumor, within
+which it may survive for a considerable period of time.
+
+_Ixodes cookei_ is given by Banks as "common on mammals in the Eastern
+States as far west as the Rockies." It is said to affect man severely.
+
+_Amblyomma americanum_, (fig. 158c), the "lone star tick," is widely
+distributed in the United States. Its common name is derived from the
+single silvery spot on the scutum of the female. Hunter and Hooker
+regard this species as, next to _Boophilus annulatus_, the most
+important tick in the United States. Though more common on cattle, it
+appears to attack mammals generally, and "in portions of Louisiana and
+Texas it becomes a pest of considerable importance to moss gatherers and
+other persons who spend much time in the forests."
+
+_Amblyomma cajennense_, noted as a pest of man in central and tropical
+America, is reported from various places in the south and southwestern
+United States.
+
+_Dermacentor variabilis_ is a common dog tick of the eastern United
+States. It frequently attacks man, but the direct effects of its bite
+are negligible.
+
+The "Rocky Mountain spotted fever tick" (_Dermacentor andersoni_
+according to Stiles, _D. venustus_ according to Banks) is, from the
+viewpoint of its effects on man, the most important of the ticks of the
+United States. This is because, as has been clearly established, it
+transmits the so-called "spotted fever" of man in our northwestern
+states. This phase of the subject will be discussed later and it need
+merely be mentioned here, that this species has been reported as causing
+painful injuries by its bites. Dr. Stiles states that he has seen cases
+of rather severe lymphangitis and various sores and swellings developing
+from this cause. In one case, of an individual bitten near the elbow,
+the arm became very much swollen and the patient was confined in bed for
+several days. The so-called tick paralysis produced by this species is
+discussed in a preceding chapter.
+
+There are many other records of various species of ticks attacking man,
+but the above-mentioned will serve as typical and it is not necessary to
+enter into greater detail.
+
+
+TREATMENT OF TICK BITES--When a tick attaches to man the first thing to
+be done is to remove it without leaving the hypostome in the wound to
+fester and bring about secondary effects. This is best accomplished by
+applying to the tick's body some substance which will cause it to more
+readily loosen its hold. Gasoline or petroleum, oil or vaseline will
+serve. For removing the spinose ear-tick, Stiles recommends pouring some
+bland oil into the ear. Others have used effectively a pledget of cotton
+soaked in chloroform.
+
+In general, the treatment recommended by Wellman for the bites of
+_Ornithodoros moubata_ will prove helpful. It consists of prolonged
+bathing in very hot water, followed by the application of a strong
+solution of bicarbonate of soda, which is allowed to dry upon the skin.
+He states that this treatment is comforting. For severe itching he
+advises smearing the bites with vaseline, which is slightly impregnated
+with camphor or menthol. Medical aid should be sought when complications
+arise.
+
+The DERMANYSSIDAE are Gamasid mites which differ from others of the group
+in that they are parasitic on vertebrates. None of the species normally
+attack man, but certain of them, especially the poultry mite, may be
+accidental annoyances.
+
+[Illustration: 51. Dermanyssus gallinae, female. After Delafond.]
+
+_Dermanyssus gallinae_ (fig. 51), the red mite of poultry, is an
+exceedingly common and widespread parasite of fowls. During the day it
+lives in cracks and crevices of poultry houses, under supports of
+roosts, and in litter of the food and nests, coming out at night to
+feed. They often attack people working in poultry houses or handling
+and plucking infested fowls. They may cause an intense pruritis, but
+they do not produce a true dermatosis, for they do not find conditions
+favorable for multiplication on the skin of man.
+
+
+Tarsonemidae
+
+The representatives of the family TARSONEMIDAE are minute mites, with the
+body divided into cephalothorax and abdomen. There is marked sexual
+dimorphism. The females possess stigmata at the anterior part of the
+body, at the base of the rostrum, and differ from all other mites in
+having on each side, a prominent clavate organ between the first and
+second legs. The larva, when it exists, is hexapodous and resembles the
+adult. A number of the species are true parasites on insects, while
+others attack plants. Several of them may be accidental parasites of
+man.
+
+[Illustration: 52. Pediculoides ventricosus, female. After Webster.]
+
+[Illustration: 53. Pediculoides ventricosus, gravid female. (x80).
+After Webster.]
+
+_Pediculoides ventricosus_ (fig. 52 and 53) is, of all the
+Tarsonemidae reported, the one which has proved most troublesome to
+man. It is a predaceous species which attacks a large number of insects
+but which has most commonly been met with by man through its fondness
+for certain grain-infesting insects, notably the Angoumois grain moth,
+_Sitotroga cerealella_, and the wheat straw-worm, _Isosoma grande_. In
+recent years it has attracted much attention in the United States and
+its distribution and habits have been the object of detailed study by
+Webster (1901).
+
+[Illustration: 54. Pediculoides ventricosus, male. After Braun.]
+
+There is a very striking sexual dimorphism in this species. The
+non-gravid female is elongate, about 200u by 70u (fig. 52), with the
+abdomen slightly striated longitudinally. The gravid female (fig. 53)
+has the abdomen enormously swollen, so that it is from twenty to a
+hundred times greater than the rest of the body. The species is
+viviparous and the larvae undergo their entire growth in the body of the
+mother. They emerge as sexually mature males and females which soon
+pair. The male (fig. 54) is much smaller, reaching a length of only 320u
+but is relatively broad, 80u, and angular. Its abdomen is very greatly
+reduced.
+
+As far back as 1850 it was noted as causing serious outbreaks of
+peculiar dermatitis among men handling infested grain. For some time the
+true source of the difficulty was unknown and it was even believed that
+the grain had been poisoned. Webster has shown that in this country (and
+probably in Europe as well) its attacks have been mistaken for those of
+the red bugs or "chiggers" (larval Trombiidae). More recently a number of
+outbreaks of a mysterious "skin disease" were traced to the use of straw
+mattresses, which were found to be swarming with these almost
+microscopic forms which had turned their attentions to the occupants of
+the beds. Other cases cited were those of farmers running wheat through
+a fanning mill, and of thrashers engaged in feeding unthrashed grain
+into the cylinder of the machine.
+
+[Illustration: 55. Lesions produced by the attacks of Pediculoides
+ventricosus. After Webster.]
+
+The medical aspects of the question have been studied especially by
+Schamberg and Goldberger and from the latter's summary (1910) we derive
+the following data. Within twelve to sixteen hours after exposure,
+itching appears and in severe cases, especially where exposure is
+continued night after night by sleeping on an infested bed, the itching
+may become almost intolerable. Simultaneously, there appears an eruption
+which characteristically consists of wheals surrounded by a vesicle
+(fig. 55). The vesicle as a rule does not exceed a pin head in size but
+may become as large as a pea. Its contents rapidly become turbid and in
+a few hours it is converted into a pustule. The eruption is most
+abundant on the trunk, slight on the face and extremities and almost
+absent on the feet and hands. In severe cases there may be
+constitutional disturbances marked, at the outset, by chilliness,
+nausea, and vomiting, followed for a few days by a slight elevation of
+temperature, with the appearance of albumin in the urine. In some cases
+the eruption may simulate that of chicken-pox or small-pox.
+
+Treatment for the purpose of killing the mites is hardly necessary as
+they attach feebly to the surface and are readily brushed off by
+friction of the clothes. "Antipruritic treatment is always called for;
+warm, mildly alkaline baths or some soothing ointment, such as zinc
+oxide will be found to fulfil this indication." Of course, reinfestation
+must be guarded against, by discarding, or thoroughly fumigating
+infested mattresses, or by avoiding other sources. Goldberger suggests
+that farm laborers who must work with infested wheat or straw might
+protect themselves by anointing the body freely with some bland oil or
+grease, followed by a change of clothes and bath as soon as their work
+is done. We are not aware of any experiments to determine the effect of
+flowers of sulphur, but their efficiency in the case of "red bugs"
+suggests that they are worth a trial against _Pediculoides_.
+
+Various species of TYROGLYPHIDAE (fig. 150_f_) may abound on dried fruits
+and other products and attacking persons handling them, may cause a
+severe dermatitis, comparable to that described above for _Pediculoides
+ventricosus_. Many instances of their occurrence as such temporary
+ectoparasites are on record. Thus, workers who handle vanilla pods are
+subject to a severe dermatitis, known as vanillism, which is due to the
+attacks of _Tyroglyphus siro_, or a closely related species. The
+so-called "grocer's itch" is similarly caused by mites infesting various
+products. Castellani has shown that in Ceylon, workers employed in the
+copra mills, where dried cocoanut is ground up for export, are much
+annoyed by mites, which produce the so-called "copra itch." The skin of
+the hands, arms and legs, and sometimes of the whole body, except the
+face, is covered by fairly numerous, very pruriginous papules, often
+covered by small, bloody crusts due to scratching. The condition is
+readily mistaken for scabies. It is due to the attacks of _Tyroglyphus
+longior castellanii_ which occur in enormous numbers in some samples of
+the copra.
+
+
+Sarcoptidae
+
+The SARCOPTIDAE are minute whitish mites, semi-globular in shape, with a
+delicate transversely striated cuticula. They lack eyes and tracheae. The
+mouth-parts are fused at the base to form a cone which is usually
+designated as the head. The legs are short and stout, and composed of
+five segments. The tarsi may or may not possess a claw and may terminate
+in a pedunculated sucker, or simple long bristle, or both. The presence
+or absence of these structures and their distribution are much used in
+classification. The mites live on or under the skin of mammals and
+birds, where they produce the disease known as scabies, mange, or itch.
+Several species of the Sarcoptidae attack man but the most important of
+these, and the one pre-eminent as the "itch mite" is _Sarcoptes
+scabiei_.
+
+The female of _Sarcoptes scabiei_, of man, is oval and yellowish white;
+the male more rounded and of a somewhat reddish tinge, and much smaller.
+The body is marked by transverse striae which are partly interrupted on
+the back. There are transverse rows of scales, or pointed spines, and
+scattered bristles on the dorsum.
+
+[Illustration: 56_a_. Sarcoptes scabiei, male. (x100). After
+Furstenberg.]
+
+The male (fig. 56) which is from 200-240u in length, and 150-200u in
+breadth, possesses pedunculated suckers on each pair of legs except the
+third, which bears, instead, a long bristle. The female (fig. 56)
+300-450u in length and 250-350u in breadth, has the pedunculated suckers
+on the first and second pairs of legs, only, the third and fourth
+terminating in bristles.
+
+[Illustration: 56_b_. Sarcoptes scabiei, female. (x100.) After
+Furstenberg.]
+
+The mite lives in irregular galleries from a few millimeters to several
+centimeters in length, which it excavates in the epidermis (fig. 57). It
+works especially where the skin is thin, such as between the fingers, in
+the bend of the elbows and knees, and in the groin, but it is by no
+means restricted to these localities. The female, alone, tunnels into
+the skin; the males remain under the superficial epidermal scales, and
+seldom are found, as they die soon after mating.
+
+As she burrows into the skin the female deposits her eggs, which measure
+about 150 x 100u. Furstenberg says that each deposits an average of
+twenty-two to twenty-four eggs, though Gudden reports a single burrow as
+containing fifty-one. From these there develop after about seven days,
+the hexapod larvae. These molt on the sixteenth day to form an octopod
+nymph, which molts again the twenty-first day. At the end of the fourth
+week the nymphs molt to form the sexually mature males and the so-called
+pubescent females. These pair, the males die, and the females again cast
+their skin, and become the oviparous females. Thus the life cycle is
+completed in about twenty-eight days.
+
+The external temperature exercises a great influence on the development
+of the mites and thus, during the winter, the areas of infestation not
+only do not spread, but they become restricted. As soon as the
+temperature rises, the mites increase and the infestation becomes much
+more extensive.
+
+[Illustration: 57. Sarcoptes scabiei. Diagrammatic representation of the
+course in the skin of man.]
+
+In considering the possible sources of infestation, and the chances of
+reinfestation after treatment, the question of the ability of the mite
+to live apart from its host is a very important one. Unfortunately there
+are few reliable data on this subject. Gerlach found that, exposed in
+the dry, warm air of a room they became very inactive within twenty-four
+hours, that after two days they showed only slight movement, and that
+after three or four days they could not be revived by moisture and
+warming. The important fact was brought out that in moist air, in folded
+soiled underwear, they survived as long as ten days. Bourguignon found
+that under the most favorable conditions the mites of _Sarcoptes scabiei
+equi_ would live for sixteen days.
+
+The disease designated the "itch" or "scabies," in man has been known
+from time immemorial, but until within less than a hundred years it was
+almost universally attributed to malnutrition, errors of diet, or "bad
+blood." This was in spite of the fact that the mite was known to Mouffet
+and that Bonomo had figured both the adult and the egg and had declared
+the mite the sole cause of the disease. In 1834 the Corsican medical
+student, Francis Renucci, demonstrated the mite before a clinic in Saint
+Louis Hospital in Paris and soon thereafter there followed detailed
+studies of the life history of the various itch mites of man and
+animals.
+
+[Illustration: 58. Scabies on the hand. From portfolio of Dermochromes
+by permission of Rebman & Co., of New York. Publishers.]
+
+The disease is a cosmopolitan one, being exceedingly abundant in some
+localities. Its spread is much favored where large numbers of people are
+crowded together under insanitary conditions and hence it increases
+greatly during wars and is widely disseminated and abundant immediately
+afterwards. Though more commonly to be met with among the lower classes,
+it not infrequently appears among those of the most cleanly, careful
+habits, and it is such cases that are most liable to wrong diagnosis by
+the physician.
+
+Infection occurs solely through the passage, direct or indirect, of the
+young fertilized females to the skin of a healthy individual. The adult,
+oviparous females do not quit their galleries and hence do not serve to
+spread the disease. The young females move about more or less at night
+and thus the principal source of infestation is through sleeping in the
+same bed with an infested person, or indirectly through bedclothes, or
+even towels or clothing. Diurnal infestation through contact or clothing
+is exceptional. Many cases are known of the disease being contracted
+from animals suffering from scabies, or mange.
+
+When a person is exposed to infestation, the trouble manifests itself
+after eight or ten days, though there usually elapses a period of twenty
+to thirty days before there is a suspicion of anything serious. The
+first symptom is an intense itching which increases when the patient is
+in bed. When the point of irritation is examined the galleries may
+usually be seen as characteristic sinuous lines, at first whitish in
+color but soon becoming blackish because of the contained eggs and
+excrement. The galleries, which may not be very distinct in some cases,
+may measure as much as four centimeters in length. Little vesicles, of
+the size of a pin head are produced by the secretions of the feeding
+mite; they are firm, and projecting, and contain a limpid fluid. Figures
+58 and 59 show the typical appearance of scabies on the hands, while
+figure 60 shows a severe general infestation. The intolerable itching
+induces scratching and through this various complications may arise. The
+lesions are not normally found on the face and scalp, and are rare on
+the back.
+
+[Illustration: 59. Scabies on the hand. After Duhring.]
+
+[Illustration: 60. Generalized infection of Scabies. After Morrow.]
+
+Formerly, scabies was considered a very serious disease, for its cause
+and method of treatment were unknown, and potentially it may continue
+indefinitely. Generation after generation of the mites may develop and
+finally their number become so great that the general health of the
+individual is seriously affected. Now that the true cause of the disease
+is known, it is easily controlled.
+
+Treatment usually consists in softening the skin by friction with soap
+and warm water, followed by a warm bath, and then applying some
+substance to kill the mites. Stiles gives the following directions,
+modified from Bourguignon's, as "a rather radical guide, to be modified
+according to facilities and according to the delicacy of the skin or
+condition of the patient":
+
+1. The patient, stripped naked, is energetically rubbed all over (except
+the head) for twenty minutes, with green soap and warm water. 2. He is
+then placed in a warm bath for thirty minutes, during which time the
+rubbing is continued. 3. The parasiticide is next rubbed in for twenty
+minutes and is allowed to remain on the body for four or five hours; in
+the meantime the patient's clothes are sterilized, to kill the eggs or
+mites attached to them. 4. A final bath is taken to remove the
+parasiticide.
+
+The parasiticide usually relied on is the officinal sulphur ointment of
+the United States pharmacopoeia. When infestation is severe it is
+necessary to repeat treatment after three or four days in order to kill
+mites which have hatched from the eggs.
+
+The above treatment is too severe for some individuals and may, of
+itself, produce a troublesome dermatitis. We have seen cases where the
+treatment was persisted in and aggravated the condition because it was
+supposed to be due to the parasite. For delicate-skinned patients the
+use of balsam of Peru is very satisfactory, and usually causes no
+irritation whatever. Of course, sources of reinfection should be
+carefully guarded against.
+
+_Sarcoptes scabiei crustosae_, which is a distinct variety, if not
+species, of the human itch mite, is the cause of so-called Norwegian
+itch. This disease is very contagious, and is much more resistant than
+the ordinary scabies. Unlike the latter, it may occur on the face and
+scalp.
+
+_Sarcoptes scabiei_ not only attacks man but also occurs on a large
+number of mammals. Many species, based on choice of host, and minute
+differences in size and secondary characters, have been established, but
+most students of the subject relegate these to varietal rank. Many of
+them readily attack man, but they have become sufficiently adapted to
+their normal host so that they are usually less persistent on man.
+
+_Notoedres cati_ (usually known as _Sarcoptes minor_) is a species of
+itch mites which produce an often fatal disease of cats. The body is
+rounded and it is considerably smaller than _Sarcoptes scabiei_, the
+female (fig. 61) measuring 215-230u long and 165-175u wide; the males
+145-150u by 120-125u. The most important character separating
+_Notoedres_ from _Sarcoptes_ is the position of the anus, which is
+dorsal instead of terminal. The mite readily transfers to man but does
+not persist, the infestation usually disappearing spontaneously in about
+two weeks. Infested cats are very difficult to cure, unless treatment is
+begun at the very inception of the outbreak, and under ordinary
+circumstances it is better to kill them promptly, to avoid spread of the
+disease to children and others who may be exposed.
+
+[Illustration: 61. Notoedres cati, male and female. After Railliet.]
+
+
+Demodecidae
+
+The DEMODECIDAE are small, elongate, vermiform mites which live in the
+hair follicles of mammals. The family characteristics will be brought
+out in the discussion of the species infesting man, _Demodex
+folliculorum_.
+
+[Illustration: 62. Demodex folliculorum. (x200) After Blanchard.]
+
+_Demodex folliculorum_ (fig. 62) is to be found very commonly in the
+hair follicles and sebaceous glands of man. It is vermiform in
+appearance, and with the elongate abdomen transversely striated so as to
+give it the appearance of segmentation. The female is 380-400u long by
+45u; the male 300u by 40u. The three-jointed legs, eight in number, are
+reduced to mere stubs in the adult. The larval form is hexopod. These
+mites thus show in their form a striking adaptation to their
+environment. In the sebaceous glands and hair follicles they lie with
+their heads down (fig. 63). Usually there are only a few in a gland, but
+Gruby has counted as many as two hundred.
+
+[Illustration: 63. Demodex folliculorum. Section through skin showing
+the mites in situ. Magnification of Nos. 1, 2, 6 and 7, x150; Nos, 3,
+4, 5, x450. After Megnin.]
+
+The frequency with which they occur in man is surprising. According to
+European statistics they are found in 50 per cent to 60 per cent or even
+more. Gruby found them in forty out of sixty persons examined. These
+figures are very commonly quoted, but reliable data for the United
+States seem to be lacking. Our studies indicate that it is very much
+less common in this country than is generally assumed.
+
+The Demodex in man does not, as a rule, cause the slightest
+inconvenience to its host. It is often stated that they give rise to
+comedons or "black-heads" but there is no clear evidence that they are
+ever implicated. Certain it is that they are not the usual cause. A
+variety of the same, or a very closely related species of _Demodex_, on
+the dog gives rise to the very resistant and often fatal follicular
+mange.
+
+
+HEXAPODA OR TRUE INSECTS
+
+The HEXAPODA, or true insects, are characterized by the fact that the
+adult possesses three pairs of legs. The body is distinctly segmented
+and is divided into head, thorax, and abdomen.
+
+The mouth-parts in a generalized form, consist of an upper lip, or
+_labrum_, which is a part of the head capsule, and a central unpaired
+_hypopharynx_, two _mandibles_, two _maxillae_ and a lower lip, or
+_labium_, made up of the fused pair of second maxillae. These parts may
+be greatly modified, dependent upon whether they are used for biting,
+sucking, piercing and sucking, or a combination of biting and sucking.
+
+Roughly speaking, insects may be grouped into those which undergo
+_complete metamorphosis_ and those which have _incomplete
+metamorphosis_. They are said to undergo complete metamorphosis when the
+young form, as it leaves the egg, bears no resemblance to the adult. For
+example, the maggot changes to a quiescent pupa and from this emerges
+the winged active fly. They undergo incomplete metamorphosis, when the
+young insect, as it leaves the egg, resembles the adult to a greater or
+less extent, and after undergoing a certain number of molts becomes
+sexually mature.
+
+Representatives of several orders have been reported as accidental or
+faculative parasites of man, but the true parasites are restricted to
+four orders. These are the Siphunculata; the Hemiptera, the Diptera and
+the Siphonaptera.
+
+
+SIPHUNCULATA
+
+The order SIPHUNCULATA was established by Meinert to include the true
+sucking lice. These are small wingless insects, with reduced
+mouth-parts, adapted for sucking; thorax apparently a single piece due
+to indistinct separation of its three segments: the compound eyes
+reduced to a single ommatidium on each side. The short, powerful legs
+are terminated by a single long claw. Metamorphosis incomplete.
+
+There has been a great deal of discussion regarding the structure of the
+mouth-parts, and the relationships of the sucking lice, and the
+questions cannot yet be regarded as settled. The conflicting views are
+well represented by Cholodkovsky (1904 and 1905) and by Enderlein
+(1904).
+
+[Illustration: 64. Pediculus showing the blind sac (_b_) containing the
+mouth parts (_a_) beneath the alimentary canal (_p_). After Pawlowsky.]
+
+Following Graber, it is generally stated that the mouth-parts consist of
+a short tube furnished with hooks in front, which constitutes the lower
+lip, and that within this is a delicate sucking tube derived from the
+fusion of the labrum and the mandibles. Opposed to this, Cholodkovsky
+and, more recently, Pawlowsky, (1906), have shown that the piercing
+apparatus lies in a blind sac under the pharynx and opening into the
+mouth cavity (fig. 64). It does not form a true tube but a furrow with
+its open surface uppermost. Eysell has shown that, in addition, there is
+a pair of chitinous rods which he regards as the homologues of the
+maxillae.
+
+When the louse feeds, it everts the anterior part of the mouth cavity,
+with its circle of hooks. The latter serve for anchoring the bug, and
+the piercing apparatus is then pushed out.
+
+[Illustration: 65. Pediculus humanus, ventral aspect of male. (x10)]
+
+Most writers have classed the sucking lice as a sub-order of the
+Hemiptera, but the more recent anatomical and developmental studies
+render this grouping untenable. An important fact, bearing on the
+question, is that, as shown by Gross, (1905), the structure of the
+ovaries is radically different from that of the Hemiptera.
+
+Lice infestation and its effects are known medically as _pediculosis_.
+Though their continued presence is the result of the grossest neglect
+and filthiness, the original infestation may be innocently obtained and
+by people of the most careful habits.
+
+Three species commonly attack man. Strangely enough, there are very few
+accurate data regarding their life history.
+
+_Pediculus humanus_ (fig. 65), the head louse, is the most widely
+distributed. It is usually referred to in medical literature as
+_Pediculus capitis_, but the Linnean specific name has priority. In
+color it is of a pale gray, blackish on the margins. It is claimed by
+some authors that the color varies according to the color of the skin of
+the host. The abdomen is composed of seven distinct segments, bearing
+spiracles laterally. There is considerable variation in size. The males
+average 1.8 mm. and the females 2.7 mm. in length.
+
+The eggs, fifty to sixty in number, stick firmly to the hairs of the
+host and are known as nits. They are large and conspicuous, especially
+on dark hair and are provided with an operculum, or cap, at the free
+end, where the nymphs emerge. They hatch in about six days and about the
+eighteenth day the young lice are sexually mature.
+
+[Illustration: 66. Pediculosis of the head. The illustration shows the
+characteristic indications of the presence of lice, viz: the occipital
+eczema gluing the hairs together, the swollen cervical glands, and the
+porrigo, or eruption of contagious pustules upon the neck. After Fox.]
+
+The head lice live by preference on the scalp of their host but
+occasionally they are found on the eyelashes and beard, or in the pubic
+region. They may also occur elsewhere on the body. The penetration of
+the rostrum into the skin and the discharge of an irritating saliva
+produce a severe itching, accompanied by the formation of an eczema-like
+eruption (fig. 66). When the infestation is severe, the discharge from
+the pustules mats down the hair, and scabs are formed, under which the
+insects swarm. "If allowed to run, a regular carapace may form, called
+_trichoma_, and the head exudes a foetid odor. Various low plants may
+grow in the trichoma, the whole being known as _plica
+palonica_."--Stiles.
+
+Sources of infestation are various. School children may obtain the lice
+from seatmates, by wearing the hats or caps of infested mates, or by the
+use, in common, of brushes and combs. They may be obtained from infested
+beds or sleeper berths. Stiles reports an instance in which a large
+number of girls in a fashionable boarding school developed lousiness a
+short time after traveling in a sleeping car.
+
+Treatment is simple, for the parasites may readily be controlled by
+cleanliness and washing the head with a two per cent solution of
+carbolic acid or even kerosene. The latter is better used mixed with
+equal parts of olive oil, to avoid irritation. The treatment should be
+applied at night and followed the next morning by a shampoo with soap
+and warm water. It is necessary to repeat the operation in a few days.
+Xylol, used pure, or with the addition of five per cent of vaseline, is
+also very efficacious. Of course, the patient must be cautioned to stay
+away from a lighted lamp or fire while using either the kerosene or
+xylol. While these treatments will kill the eggs or nits, they will not
+remove them from the hairs. Pusey recommends repeated washings with
+vinegar or 25 per cent of acetic acid in water, for the purpose of
+loosening and removing the nits.
+
+Treatment of severe infestations in females is often troublesome on
+account of long hair. For such cases the following method recommended by
+Whitfield (1912) is especially applicable:
+
+The patient is laid on her back on the bed with her head over the edge,
+and beneath the head is placed a basin on a chair so that the hair lies
+in the basin. A solution of 1 in 40 carbolic acid is then poured over
+the hair into the basin and sluiced backwards and forwards until the
+whole of the hair is thoroughly soaked with it. It is especially
+necessary that care should be taken to secure thorough saturation of the
+hair over the ears and at the nape of the neck, since these parts are
+not only the sites of predilection of the parasites but they are apt to
+escape the solution. This sluicing is carried out for ten minutes by the
+clock. At the end of ten minutes the hair is lifted from the basin and
+allowed to drain, but is not dried or even thoroughly wrung out. The
+whole head is then swathed with a thick towel or better, a large piece
+of common house flannel, which is fastened up to form a sort of turban,
+and is allowed to remain thus for an hour. It can then be washed or
+simply allowed to dry, as the carbolic quickly disperses. At the end of
+this period every pediculus and what is better, every ovum is dead and
+no relapse will occur unless there is exposure to fresh contagion.
+Whitfield states that there seem to be no disadvantages in this method,
+which he has used for years. He has never seen carboluria result from
+it, but would advise first cutting the hair of children under five years
+of age.
+
+_Pediculus corporis_ (= _P. vestimenti_) the body louse, is larger than
+the preceding species, the female measuring 3.3 mm., and the male 3 mm.
+in length. The color is a dirty white, or grayish. _P. corporis_ has
+been regarded by some authorities as merely a variety of _P. humanus_
+but Piaget maintains there are good characters separating the two
+species.
+
+The body louse lives in the folds and seams of the clothing of its host,
+passing to the skin only when it wishes to feed. Brumpt states that he
+has found enormous numbers of them in the collars of glass-ware or
+grains worn by certain naked tribes in Africa.
+
+Exact data regarding the life-history of this species have been
+supplied, in part, by the work of Warburton (1910), cited by Nuttall. He
+found that _Pediculus corporis_ lives longer than _P. humanus_ under
+adverse conditions. This is doubtless due to its living habitually on
+the clothing, whereas _humanus_ lives upon the head, where it has more
+frequent opportunities of feeding. He reared a single female upon his
+own person, keeping the louse enclosed in a cotton-plugged tube with a
+particle of cloth to which it could cling. The tube was kept next to his
+body, thus simulating the natural conditions of warmth and moisture
+under which the lice thrive. The specimen was fed twice daily, while it
+clung to the cloth upon which it rested. Under these conditions she
+lived for one month. Copulation commenced five days after the female had
+hatched and was repeated a number of times, sexual union lasting for
+hours. The female laid one hundred and twenty-four eggs within
+twenty-five days.
+
+The eggs hatched after eight days, under favorable conditions, such as
+those under which the female was kept. They did not hatch in the cold.
+Eggs kept near the person during the day and hung in clothing by the
+bedside at night, during the winter, in a cold room, did not hatch until
+the thirty-fifth day. When the nymphs emerge from the eggs, they feed at
+once, if given a chance to do so. They are prone to scatter about the
+person and abandon the fragment of cloth to which the adult clings.
+
+The adult stage is reached on the eleventh day, after three molts, about
+four days apart. Adults enter into copulation about the fifth day and as
+the eggs require eight days for development, the total cycle, under
+favorable conditions, is about twenty-four days. Warburton's data differ
+considerably from those commonly quoted and serve to emphasize the
+necessity for detailed studies of some of the commonest of parasitic
+insects.
+
+Body lice are voracious feeders, producing by their bites and the
+irritating saliva which they inject, rosy elevations and papules which
+become covered with a brownish crust. The intense itching provokes
+scratching, and characteristic white scars (fig. 67) surrounded by
+brownish pigment (fig. 68) are formed. The skin may become thickened and
+take on a bronze tinge. This melanoderma is especially marked in the
+region between the shoulders but it may become generalized, a prominent
+characteristic of "vagabond's disease." According to Dubre and Beille,
+this melanoderma is due to a toxic substance secreted by the lice, which
+indirectly provokes the formation of pigment.
+
+[Illustration: 67. Pediculosis in man caused by the body louse. After
+Morrow.]
+
+Control measures, in the case of the body louse, consist in boiling or
+steaming the clothes or in some cases, sterilizing by dry heat. The
+dermatitis may be relieved by the use of zinc-oxide ointment, to which
+Pusey recommends that there be added, on account of their parasiticidal
+properties, sulphur and balsam of Peru, equal parts, 15 to 30 grains to
+the ounce.
+
+_Phthirius pubis_ (= _P. inguinalis_), the pubic louse, or so-called
+"crab louse," differs greatly from the preceding in appearance. It is
+characterized by its relatively short head which fits into a broad
+depression in the thorax. The latter is broad and flat and merges into
+the abdomen. The first pair of legs is slender and terminated by a
+straight claw. The second and third pairs of legs are thicker and are
+provided with powerful claws fitted for clinging to hairs. The females
+(fig. 69) measure 1.5 to 2 mm. in length by 1.5 mm. in breadth. The male
+averages a little over half as large. The eggs, or nits, are fixed at
+the base of the hairs. Only a few, ten to fifteen are deposited by a
+single female, and they hatch in about a week's time. The young lice
+mature in two weeks.
+
+The pubic louse usually infests the hairs of the pubis and the perineal
+region. It may pass to the arm pits or even to the beard or moustache.
+Rarely, it occurs on the eyelids, and it has even been found, in a very
+few instances, occurring in all stages, on the scalp. Infestation may be
+contracted from beds or even from badly infested persons in a crowd. We
+have seen several cases which undoubtedly were due to the use of public
+water closets. It produces papular eruption and an intense pruritis.
+When abundant, there occurs a grayish discoloration of the skin which
+Duguet has shown is due to a poisonous saliva injected by the louse, as
+is the melanoderma caused by the body louse.
+
+[Illustration: 68. Melanoderma caused by the body louse. From Portfolio
+of Dermochromes, by permission of Rebman & Co., New York, Publishers.]
+
+The pubic louse may be exterminated by the measures recommended for the
+head louse, or by the use of officinal mercurial ointment.
+
+[Illustration: 69. Phthirius pubis. Ventral aspect of female. (x12).]
+
+
+HEMIPTERA
+
+Several species of HEMIPTERA-HETEROPTERA are habitual parasites of man,
+and others occur as occasional or accidental parasites. Of all these,
+the most important and widespread are the bed-bugs, belonging to the
+genus _Cimex_ (= _Acanthia_).
+
+
+THE BED-BUGS--The bed-bugs are characterized by a much flattened oval
+body, with the short, broad head unconstricted behind, and fitting into
+the strongly excavated anterior margin of the thorax. The compound eyes
+are prominent, simple eyes lacking. Antennae four-jointed, the first
+segment short, the second long and thick, and the third and fourth
+slender. The tarsi are short and three segmented.
+
+It is often assumed in the literature of the subject that there is but a
+single species of _Cimex_ attacking man, but several such species are to
+be recognized. These are distinguishable by the characters given in
+Chapter XII. We shall consider especially _Cimex lectularius_, the most
+common and widespread species.
+
+_Cimex lectularius_ (= _Acanthia lectularia_, _Clinocoris
+lectularius_), is one of the most cosmopolitan of human parasites but,
+like the lice, it has been comparatively little studied until recent
+years, when the possibility that it may be concerned with the
+transmission of various diseases has awakened interest in the details of
+its life-history and habits.
+
+[Illustration: 70. Cimex lectularius adult and eggs. Photograph by M. V.
+S.]
+
+The adult insect (fig. 70) is 4-5 mm. long by 3 mm. broad, reddish brown
+in color, with the beak and body appendages lighter in color. The short,
+broad and somewhat rectangular head has no neck-like constriction but
+fits into the broadly semilunar prothorax. The four segmented labium or
+proboscis encloses the lancet-like maxillae and mandibles. The distal
+of the four antennal segments is slightly club-shaped. The prothorax is
+characteristic of the species, being deeply incised anteriorly and with
+its thin lateral margins somewhat turned up. The mesothorax is
+triangular, with the apex posteriorly, and bears the greatly atrophied
+first pair of wings. There is no trace of the metathoracic pair. The
+greatly flattened abdomen has eight visible segments, though in reality
+the first is greatly reduced and has been disregarded by most writers.
+The body is densely covered with short bristles and hairs, the former
+being peculiarly saber-shaped structures sharply toothed at the apex and
+along the convex side (fig. 159_b_).
+
+The peculiar disagreeable odor of the adult bed-bug is due to the
+secretion of the stink glands which lie on the inner surface of the
+mesosternum and open by a pair of orifices in front of the metacoxae,
+near the middle line. In the nymphs, the thoracic glands are not
+developed but in the abdomen there are to be found three unpaired dorsal
+stink glands, which persist until the fifth molt, when they become
+atrophied and replaced by the thoracic glands. The nymphal glands occupy
+the median dorsal portion of the abdomen, opening by paired pores at the
+anterior margin of the fourth, fifth and sixth segments. The secretion
+is a clear, oily, volatile fluid, strongly acid in reaction. Similar
+glands are to be found in most of the Hemiptera-Heteroptera and their
+secretion is doubtless protective, through being disagreeable to the
+birds. In the bed-bug, as Marlatt points out, "it is probably an
+illustration of a very common phenomenon among animals, i.e., the
+persistence of a characteristic which is no longer of any special value
+to the possessor." In fact, its possession is a distinct disadvantage to
+the bed-bug, as the odor frequently reveals the presence of the bugs,
+before they are seen.
+
+The eggs of the bed-bug (fig. 70) are pearly white, oval in outline,
+about a millimeter long, and possess a small operculum or cap at one
+end, which is pushed off when the young hatches. They are laid
+intermittently, for a long period, in cracks and crevices of beds and
+furniture, under seams of mattresses, under loose wall paper, and
+similar places of concealment of the adult bugs. Girault (1905) observed
+a well-fed female deposit one hundred and eleven eggs during the
+sixty-one days that she was kept in captivity. She had apparently
+deposited some of her eggs before being captured.
+
+The eggs hatch in six to ten days, the newly emerged nymphs being about
+1.5 mm. in length and of a pale yellowish white color. They grow slowly,
+molting five times. At the last molt the mesathoracic wing pads appear,
+characteristic of the adult. The total length of the nymphal stage
+varies greatly, depending upon conditions of food supply, temperature
+and possibly other factors. Marlatt (1907) found under most favorable
+conditions a period averaging eight days between molting which, added to
+an equal egg period, gave a total of about seven weeks from egg to adult
+insect. Girault (1912) found the postembryonic period as low as
+twenty-nine days and as high as seventy days under apparently similar
+and normal conditions of food supply. Under optimum and normal
+conditions of food supply, beginning August 27, the average nymphal life
+was 69.9 days; average number of meals 8.75 and the molts 5. Under
+conditions allowing about half the normal food supply the average
+nymphal life was from 116.9 to 139 days. Nymphs starved from birth lived
+up to 42 days. We have kept unfed nymphs, of the first stage, alive in a
+bottle for 75 days. The interesting fact was brought out that under
+these conditions of minimum food supply there were sometimes six molts
+instead of the normal number.
+
+The adults are remarkable for their longevity, a factor which is of
+importance in considering the spread of the insect and methods of
+control. Dufour (1833) (not De Geer, as often stated) kept specimens for
+a year, in a closed vial, without food. This ability, coupled with their
+willingness to feed upon mice, bats, and other small mammals, and even
+upon birds, accounts for the long periods that deserted houses and camps
+may remain infested. There is no evidence that under such conditions
+they are able to subsist on the starch of the wall paper, juices of
+moistened wood, or the moisture in the accumulations of dust, as is
+often stated.
+
+There are three or four generations a year, as Girault's breeding
+experiments have conclusively shown. He found that the bed-bug does not
+hibernate where the conditions are such as to allow it to breed and that
+breeding is continuous unless interrupted by the lack of food or, during
+the winter, by low temperature.
+
+Bed-bugs ordinarily crawl from their hiding places and attack the face
+and neck or uncovered parts of the legs and arms of their victims. If
+undisturbed, they will feed to repletion. We have found that the young
+nymph would glut itself in about six minutes, though some individuals
+fed continuously for nine minutes, while the adult required ten to
+fifteen minutes for a full meal. When gorged, it quickly retreats to a
+crack or crevice to digest its meal, a process which requires two or
+three days. The effect of the bite depends very greatly on the
+susceptibility of the individual attacked. Some persons are so little
+affected that they may be wholly ignorant of the presence of a large
+number of bugs. Usually the bite produces a small hard swelling, or
+wheal, whitish in color. It may even be accompanied by an edema and a
+disagreeable inflammation, and in such susceptible individuals the
+restlessness and loss of sleep due to the presence of the insects may be
+a matter of considerable importance. Stiles (1907) records the case of a
+young man who underwent treatment for neurasthenia, the diagnosis being
+agreed upon by several prominent physicians; all symptoms promptly
+disappeared, however, immediately following a thorough fumigation of
+his rooms, where nearly a pint of bed-bugs were collected.
+
+It is natural to suppose that an insect which throughout its whole life
+is in such intimate relationship with man should play an important role
+in the transmission of disease. Yet comparatively little is definitely
+known regarding the importance of the bed-bug in this respect. It has
+been shown that it is capable of transmitting the bubonic plague, and
+South American trypanosomiasis. Nuttall succeeded in transmitting
+European relapsing fever from mouse to mouse by its bite. It has been
+claimed that Oriental sore, tuberculosis, and even syphilis may be so
+carried. These phases of the subject will be considered later.
+
+The sources of infestation are many, and the invasion of a house is not
+necessarily due to neglect, though the continued presence of the pests
+is quite another matter. In apartments and closely placed houses they
+are known to invade new quarters by migration. They are frequently to be
+met with in boat and sleeper berths, and even the plush seats of day
+coaches, whence a nucleus may be carried in baggage to residences. They
+may be brought in the laundry or in clothes of servants.
+
+Usually they are a great scourge in frontier settlements and it is
+generally believed that they live in nature under the bark of trees, in
+lumber, and under similar conditions. This belief is founded upon the
+common occurrence of bugs resembling the bed-bug, in such places. As a
+matter of fact, they are no relation to bed-bugs but belong to
+plant-feeding forms alone (fig. 19 _c_, _d_).
+
+It is also often stated that bed-bugs live in poultry houses, in
+swallows nests, and on bats, and that it is from these sources that they
+gain access to dwellings. These bugs are specifically distinct from the
+true bed-bug, but any of them may, rarely, invade houses. Moreover,
+chicken houses are sometimes thoroughly infested with the true _Cimex
+lectularius_.
+
+Control measures consist in the use of iron bedsteads and the reduction
+of hiding places for the bugs. If the infestation is slight they may be
+exterminated by a vigilant and systematic hunt, and by squirting
+gasoline or alcohol into cracks and crevices of the beds, and furniture.
+Fumigation must be resorted to in more general infestations.
+
+The simplest and safest method of fumigation is by the use of flowers of
+sulphur at the rate of two pounds to each one thousand cubic feet of
+room space. The sulphur should be placed in a pan, a well made in the
+top of the pile and a little alcohol poured in, to facilitate burning.
+The whole should be placed in a larger pan and surrounded by water so as
+to avoid all danger of fire. Windows should be tightly closed, beds,
+closets and drawers opened, and bedding spread out over chairs in order
+to expose them fully to the fumes. As metal is tarnished by the sulphur
+fumes, ornaments, clocks, instruments, and the like should be removed.
+When all is ready the sulphur should be fired, the room tightly closed
+and left for twelve to twenty-four hours. Still more efficient in large
+houses, or where many hiding places favor the bugs, is fumigation with
+hydrocyanic acid gas. This is a deadly poison and must be used under
+rigid precautions. Through the courtesy of Professor Herrick, who has
+had much experience with this method, we give in the Appendix, the clear
+and detailed directions taken from his bulletin on "Household Insects."
+
+Fumigation with formaldehyde gas, either from the liquid or "solid"
+formalin, so efficient in the case of contagious diseases, is useless
+against bed-bugs and most other insects.
+
+
+OTHER BED-BUGS--_Cimex hemipterus_ (= _C. rotundatus_) is a tropical and
+subtropical species, occurring in both the old and new world. Patton and
+Cragg state that it is distributed throughout India, Burma, Assam, the
+Malay Peninsula, Aden, the Island of Mauritius, Reunion, St. Vincent and
+Porto Rico. "It is widely distributed in Africa, and is probably the
+common species associated there with man." Brumpt also records it for
+Cuba, the Antilles, Brazil, and Venezuela.
+
+This species, which is sometimes called the Indian bed-bug, differs from
+_C. lectularius_ in being darker and in having a more elongate abdomen.
+The head also is shorter and narrower, and the prothorax has rounded
+borders.
+
+It has the same habits and practically the same life cycle as _Cimex
+lectularius_. Mackie, in India, has found that it is capable of
+transmitting the Asiatic type of recurrent fever. Roger suggested that
+it was also capable of transmitting Kala-azar and Patton has described
+in detail the developmental stages of _Leishmania_, the causative
+organism of Kala-azar, in the stomach of this bug, but Brumpt declares
+that the forms described are those of a common, non-pathogenic
+flagellate to be found in the bug, and have nothing to do with the
+human disease. Brumpt has shown experimentally that _Cimex hemipterus_
+may transmit _Trypanosoma cruzi_ in its excrement.
+
+_Cimex boueti_, occurring in French Guinea, is another species attacking
+man. Its habits and general life history are the same as for the above
+species. It is 3 to 4.5 mm. in length, has vestigial elytra, and much
+elongated antennae and legs. The extended hind legs are about as long as
+the body.
+
+_Cimex columbarius_, a widely distributed species normally living in
+poultry houses and dove cotes, _C. inodorus_, infesting poultry in
+Mexico, _C. hirundinis_, occurring in the nests of swallows in Europe
+and _Oeciacus vicarius_ (fig. 19i) occurring in swallows' nests in this
+country, are species which occasionally infest houses and attack man.
+
+[Illustration: 71. Conorhinus sanguisugus.]
+
+_Conorhinus sanguisugus_, the cone-nosed bed-bug. We have seen in our
+consideration of poisonous insects, that various species of Reduviid
+bugs readily attack man. Certain of these are nocturnal and are so
+commonly found in houses that they have gained the name, of "big
+bed-bugs." The most noted of these, in the United States, is _Conorhinus
+sanguisugus_ (fig. 71), which is widely distributed in our Southern
+States.
+
+Like its near relatives, _Conorhinus sanguisugus_ is carnivorous in
+habit and feeds upon insects as well as upon mammalian and human blood.
+It is reported as often occurring in poultry houses and as attacking
+horses in barns. The life history has been worked out in considerable
+detail by Marlatt, (1902), from whose account we extract the following.
+
+[Illustration: 72. Beak of Conorhinus sanguisugus. After Marlatt.]
+
+The eggs are white, changing to yellow and pink before hatching. The
+young hatch within twenty days and there are four nymphal stages. In all
+these stages the insect is active and predaceous, the mouth-parts (fig.
+72) being powerfully developed. The eggs are normally deposited, and the
+early stages are undoubtedly passed, out of doors, the food of the
+immature forms being other insects. Immature specimens are rarely found
+indoors. It winters both in the partly grown and adult stage, often
+under the bark of trees or in any similar protection, and only in its
+nocturnal spring and early summer flights does it attack men. Marlatt
+states that this insect seems to be decidedly on the increase in the
+region which it particularly infests,--the plains region from Texas
+northward and westward. In California a closely related species of
+similar habits is known locally as the "monitor bug."
+
+The effect of the bite of the giant bed-bug on man is often very severe,
+a poisonous saliva apparently being injected into the wound. We have
+discussed this phase of the subject more fully under the head of
+poisonous insects.
+
+_Conorhinus megistus_ is a Brazilian species very commonly attacking
+man, and of special interest since Chagas has shown that it is the
+carrier of a trypanosomiasis of man. Its habits and life history have
+been studied in detail by Neiva, (1910).
+
+This species is now pre-eminently a household insect, depositing its
+eggs in cracks and crevices in houses, though this is a relatively
+recent adaptation. The nymphs emerge in from twenty to forty days,
+depending upon the temperature. There are five nymphal stages, and as in
+the case of true bed-bugs, the duration of these is very greatly
+influenced by the availability of food and by temperature. Neiva reckons
+the entire life cycle, from egg to egg, as requiring a minimum of three
+hundred and twenty-four days.
+
+The nymphs begin to suck blood in three to five days after hatching.
+They usually feed at night and in the dark, attacking especially the
+face of sleeping individuals. The bite occasions but little pain. The
+immature insects live in cracks and crevices in houses and invade the
+beds which are in contact with walls, but the adults are active flyers
+and attack people sleeping in hammocks. The males as well as the females
+are blood suckers.
+
+Like many blood-sucking forms, _Conorhinus megistus_ can endure for long
+periods without food. Neiva received a female specimen which had been
+for fifty-seven days alive in a tightly closed box. They rarely feed on
+two consecutive days, even on small quantities of blood, and were never
+seen to feed on three consecutive days.
+
+Methods of control consist in screening against the adult bugs, and the
+elimination of crevices and such hiding places of the nymphs. Where the
+infestation is considerable, fumigation with sulphur is advisable.
+
+
+PARASITIC DIPTERA OR FLIES
+
+Of the DIPTERA or two-winged flies, many species occasionally attack
+man. Of these, a few are outstanding pests, many of them may also serve
+to disseminate disease, a phase of our subject which will be considered
+later. We shall now consider the most important of the group from the
+viewpoint of their direct attacks on man.
+
+
+Psychodidae or Moth-Flies
+
+The PSYCHODIDAE or Moth-flies, include a few species which attack man,
+and at least one species, _Phlebotomus papatasii_, is known to transmit
+the so-called "three-day fever" of man. Another species is supposed to
+be the vector of Peruvian verruga.
+
+The family is made up of small, sometimes very small, nematocerous
+Diptera, which are densely covered with hairs, giving them a moth-like
+appearance. The wings are relatively large, oval or lanceolate in shape,
+and when at rest are held in a sloping manner over the abdomen, or are
+held horizontally in such a way as to give the insect a triangular
+outline. Not only is the moth-like appearance characteristic, but the
+venation of the wings (fig. 163, d) is very peculiar and, according to
+Comstock, presents an extremely generalized form. All of the
+longitudinal veins separate near the base of the wing except veins R_2
+and R_3 and veins M_1 and M_2. Cross veins are wanting in most cases.
+
+Comparatively little is known regarding the life-history and habits of
+the Psychodidae, but one genus, _Phlebotomus_, contains minute,
+blood-sucking species, commonly known as sand-flies. The family is
+divided into two subfamilies, the PSYCHODINAE and the PHLEBOTOMINAE.
+The second of these, the PHLEBOTOMINAE, is of interest to us.
+
+
+THE PHLEBOTOMINAE--The Phlebotominae differ from the Psychodinae
+in that the radical sector branches well out into the wing rather than
+at the base of the wing. They are usually less hairy than the
+Psychodinae. The ovipositor is hidden and less strongly chitinized.
+The species attacking man belong to the genus _Phlebotomus_, small forms
+with relatively large, hairy wings which are held upright, and with
+elongate proboscis. The mandibles and maxillae are serrated and fitted
+for biting.
+
+According to Miss Summers (1913) there are twenty-nine known species of
+the genus _Phlebotomus_, five European, eleven Asiatic, seven African
+and six American. One species only, _Phlebotomus vexator_, has been
+reported for the United States. This was described by Coquillett,
+(1907), from species taken on Plummer's Island, Maryland. It measures
+only 1.5 mm. in length. As it is very probable that this species is much
+more widely distributed, and that other species of these minute flies
+will be found to occur in our fauna, we quote Coquillett's description.
+
+_Phlebotomus vexator_, Coq.: Yellow, the mesonotum brown, hairs chiefly
+brown; legs in certain lights appear brown, but are covered with a white
+tomentum; wings hyaline, unmarked; the first vein (R_1) terminates
+opposite one-fifth of the length of the first submarginal cell (cell
+R_2); this cell is slightly over twice as long as its petiole; terminal,
+horny portion of male claspers slender, bearing many long hairs; the
+apex terminated by two curved spines which are more than one-half as
+long as the preceding part, and just in front of these are two similar
+spines, while near the middle of the length of this portion is a fifth
+spine similar to the others. Length 1.5 mm.
+
+The life-history of the Phlebotomus flies has been best worked out for
+the European _Phlebotomus papatasii_ and we shall briefly summarize the
+account of Doerr and Russ (1913) based primarily on work on this
+species. The European Phlebotomus flies appear at the beginning of the
+warm season, a few weeks after the cessation of the heavy rains and
+storms of springtime. They gradually become more abundant until they
+reach their first maximum, which in Italy is near the end of July
+(Grassi). They then become scarcer but reach a second maximum in
+September. At the beginning of winter they vanish completely,
+hibernating individuals not being found.
+
+After fertilization there is a period of eight to ten days before
+oviposition. The eggs are then deposited, the majority in a single mass
+covered by a slimy secretion from the sebaceous glands. The larvae emerge
+in fourteen to twenty days. There is uncertainty as to the length of
+larval life, specimens kept in captivity remaining fifty or more days
+without transforming. Growth may be much more rapid in nature. The larvae
+do not live in fluid media but in moist detritus in dark places. Marett
+believes that they live chiefly on the excrement of pill-bugs (Oniscidae)
+and lizards. Pupation always occurs during the night. The remnants of
+the larval skin remain attached to the last two segments of the
+quiescent pupa and serve to attach it to the stone on which it lives.
+The pupal stage lasts eleven to sixteen days, the adult escaping at
+night.
+
+Only the females suck blood. They attack not only man but all
+warm-blooded animals and, according to recent workers, also cold-blooded
+forms, such as frogs, lizards, and larvae. Indeed, Townsend (1914)
+believes that there is an intimate relation between _Phlebotomus_ and
+lizards, or other reptiles the world over. The Phlebotomus passes the
+daylight hours within the darkened recesses of the loose stone walls and
+piles of rock in order to escape wind and strong light. Lizards inhabit
+the same places, and the flies, always ready to suck blood in the
+absence of light and wind, have been found more prone to suck reptilian
+than mammalian blood.
+
+On hot summer nights, when the wind is not stirring, the Phlebotomus
+flies, or sand-flies, as they are popularly called, invade houses and
+sleeping rooms in swarms and attack the inmates. As soon as light begins
+to break the flies either escape to the breeding places, or cool, dark
+places protected from the wind, or a part of them remain in the rooms,
+hiding behind pictures, under garments, and in similar places. Wherever
+the Phlebotomus flies occur they are an intolerable nuisance. On account
+of their small size they can easily pass through the meshes of ordinary
+screens and mosquito curtains. They attack silently and inflict a very
+painful, stinging bite, followed by itching. The ankles, dorsum of the
+feet, wrists, inner elbow, knee joint and similar places are favorite
+places of attack, possibly on account of their more delicate skin.
+
+Special interest has been attracted to these little pests in recent
+years, since it has been shown that they transmit the European
+"pappatici fever" or "three day fever." More recently yet, it appears
+that they are the carriers of the virus of the Peruvian "verruga." This
+phase of the subject will be discussed later.
+
+Control measures have not been worked out. As Newstead says, "In
+consideration of the facts which have so far been brought to light
+regarding the economy of Phlebotomus, it is clearly evident that the
+task of suppressing these insects is an almost insurmountable one. Had
+we to deal with insects as large and as accessible as mosquitoes, the
+adoption of prophylactic measures would be comparatively easy, but owing
+to the extremely minute size and almost flea-like habits of the adult
+insects, and the enormous area over which the breeding-places may occur,
+we are faced with a problem which is most difficult of solution." For
+these reasons, Newstead considers that the only really prophylactic
+measures which can at present be taken, are those which are considered
+as precautionary against the bites of the insects.
+
+Of repellents, he cites as one of the best a salve composed of the
+following:
+
+  Ol. Anisi                                                    3 grs.
+  Ol. Eucalypti                                                3 grs.
+  Ol. Terebenth                                                3 grs.
+  Unq. Acid Borac.
+
+Of sprays he recommends as the least objectionable and at the same time
+one of the most effective, formalin. "The dark portions and angles of
+sleeping apartments should be sprayed with a one per cent. solution of
+this substance every day during the season in which the flies are
+prevalent. A fine spraying apparatus is necessary for its application
+and an excessive amount must not be applied. It is considered an
+excellent plan also to spray the mosquito curtains regularly every day
+towards sunset; nets thus treated are claimed to repel the attacks of
+these insects." This effectiveness of formalin is very surprising for,
+as we have seen, it is almost wholly ineffective against bed-bugs,
+mosquitoes, house flies and other insects, where it has been tried.
+
+A measure which promises to be very effective, where it can be adopted,
+is the use of electric fans so placed as to produce a current of air in
+the direction of the windows of sleeping apartments. On account of the
+inability of the Phlebotomus flies to withstand even slight breezes, it
+seems very probable that they would be unable to enter a room so
+protected.
+
+
+Culicidae or Mosquitoes
+
+From the medical viewpoint, probably the most interesting and important
+of the blood-sucking insects are the mosquitoes. Certainly this is true
+of temperate zones, such as those of the United States. The result is
+that no other group of insects has aroused such widespread interest, or
+has been subjected to more detailed study than have the mosquitoes,
+since their role as carriers of disease was made known. There is an
+enormous literature dealing with the group, but fortunately for the
+general student, this has been well summarized by a number of workers.
+The most important and helpful of the general works are those of Howard
+(1901), Smith (1904), Blanchard (1905), Mitchell (1907), and especially
+of Howard, Dyar, and Knab, whose magnificent monograph is still in
+course of publication.
+
+Aside from their importance as carriers of disease, mosquitoes are
+notorious as pests of man, and the earlier literature on the group is
+largely devoted to references to their enormous numbers and their
+blood-thirstiness in certain regions. They are to be found in all parts
+of the world, from the equator to the Arctic and Antarctic regions.
+Linnaeus, in the "Flora Lapponica," according to Howard, Dyar and Knab,
+"dwells at some length upon the great abundance of mosquitoes in Lapland
+and the torments they inflicted upon man and beast. He states that he
+believes that nowhere else on earth are they found in such abundance and
+he compares their numbers to the dust of the earth. Even in the open,
+you cannot draw your breath without having your mouth and nostrils
+filled with them; and ointments of tar and cream or of fish grease are
+scarcely sufficient to protect even the case-hardened cuticle of the
+Laplander from their bite. Even in their cabins, the natives cannot take
+a mouthful of food or lie down to sleep unless they are fumigated almost
+to suffocation." In some parts of the Northwestern and Southwestern
+United States it is necessary to protect horses working in the fields by
+the use of sheets or burlaps, against the ferocious attacks of these
+insects. It is a surprising fact that even in the dry deserts of the
+western United States they sometimes occur in enormous numbers.
+
+Until comparatively recent years, but few species of mosquitoes were
+known and most of the statements regarding their life-history were based
+upon the classic work of Reaumur (1738) on the biology of the rain
+barrel mosquito, _Culex pipiens_. In 1896, Dr. Howard refers to
+twenty-one species in the United States, now over fifty are known;
+Giles, in 1900, gives a total of two hundred and forty-two for the world
+fauna, now over seven hundred species are known. We have found eighteen
+species at Ithaca, N. Y.
+
+All of the known species of mosquitoes are aquatic in the larval stage,
+but in their life-histories and habits such great differences occur that
+we now know that it is not possible to select any one species as typical
+of the group. For our present purpose we shall first discuss the general
+characteristics and structure of mosquitoes, and shall then give the
+life-history of a common species, following this by a brief
+consideration of some of the more striking departures from what have
+been supposed to be the typical condition.
+
+The CULICIDAE are slender, nematocerous Diptera with narrow wings,
+antennae plumose in the males, and usually with the proboscis much longer
+than the head, slender, firm and adapted for piercing in the female.
+The most characteristic feature is that the margins of the wings and, in
+most cases, the wing veins possess a fringe of scale-like hairs. These
+may also cover in part, or entirely, the head, thorax, abdomen and legs.
+The females, only, suck blood.
+
+On account of the importance of the group in this country and the
+desirability of the student being able to determine material in various
+stages, we show in the accompanying figures the characters most used in
+classification.
+
+The larvae (fig. 73) are elongate, with the head and thorax sharply
+distinct. The larval antennae are prominent, consisting of a single
+cylindrical and sometimes curved segment. The outer third is often
+narrower and bears at its base a fan-shaped tuft of hairs, the
+arrangement and abundance of which is of systematic importance. About
+the mouth are the so-called rotary mouth brushes, dense masses of long
+hairs borne by the labrum and having the function of sweeping food into
+the mouth. The form and arrangement of thoracic, abdominal, and anal
+tufts of hair vary in different species and present characteristics of
+value. On either side of the eighth abdominal segment is a patch of
+scales varying greatly in arrangement and number and of much value in
+separating species. Respiration is by means of tracheae which open at the
+apex of the so-called anal siphon, when it is present. In addition,
+there are also one or two pairs of tracheal gills which vary much in
+appearance in different species. On the ventral side of the anal siphon
+is a double row of flattened, toothed spines whose number and shape are
+likewise of some value in separating species. They constitute the comb
+or pecten.
+
+[Illustration: 73. Culex larva showing details of external structure.]
+
+The pupa (fig. 139, b) unlike that of most insects, is active, though it
+takes no food. The head and thorax are not distinctly separated, but the
+slender flexible abdomen in sharply marked off. The antennae,
+mouth-parts, legs, and wings of the future adult are now external, but
+enclosed in chitinous cases. On the upper surface, near the base of the
+wings are two trumpets, or breathing tubes, for the pupal spiracles are
+towards the anterior end instead of at the caudal end, as in the larva.
+At the tip of the abdomen is a pair of large chitinous swimming paddles.
+
+As illustrative of the life cycle of a mosquito we shall discuss the
+development of a common house mosquito, _Culex pipiens_, often referred
+to in the Northern United States as the rain barrel mosquito. Its life
+cycle is often given as typical for the entire group, but, as we have
+already emphasized, no one species can serve this purpose.
+
+The adults of _Culex pipiens_ hibernate throughout the winter in
+cellars, buildings, hollow trees, or similar dark shelters. Early in the
+spring they emerge and deposit their eggs in a raft-like mass. The
+number of eggs in a single mass is in the neighborhood of two hundred,
+recorded counts varying considerably. A single female may deposit
+several masses during her life time. The duration of the egg stage is
+dependent upon temperature. In the warm summer time the larvae may emerge
+within a day. The larvae undergo four molts and under optimum conditions
+may transform into pupae in about a week's time. Under the same favorable
+conditions, the pupal stage may be completed in a day's time. The total
+life cycle of _Culex pipiens_, under optimum conditions, may thus be
+completed in a week to ten days. This period may be considerably
+extended under less favorable conditions of temperature and food supply.
+
+_Culex pipiens_ breeds continuously throughout the summer, developing in
+rain barrels, horse troughs, tin cans, or indeed in any standing water
+about houses, which lasts for a week or more. The catch basins of sewers
+furnish an abundant supply of the pests under some conditions. Such
+places, the tin gutters on residences, and all possible breeding places
+must be considered in attempts to exterminate this species.
+
+Other species of mosquitoes may exhibit radical departures from _Culex
+pipiens_ in life-history and habits. To control them it is essential
+that the biological details be thoroughly worked out for, as Howard,
+Dyar, and Knab have emphasized, "much useless labor and expense can be
+avoided by an accurate knowledge of the habits of the species." For a
+critical discussion of the known facts the reader is referred to their
+monograph. We shall confine ourselves to a few illustrations.
+
+The majority of mosquitoes in temperate climates hibernate in the egg
+stage, hatching in the spring or even mild winter days in water from
+melting snow. It is such single-brooded species which appear in
+astounding numbers in the far North. Similarly, in dry regions the eggs
+may stand thorough dessication, and yet hatch out with great promptness
+when submerged by the rains. "Another provision to insure the species
+against destruction in such a case, exists in the fact * * * that not
+all the eggs hatch, a part of them lying over until again submerged by
+subsequent rains." In temperate North America, a few species pass the
+winter in the larval state. An interesting illustration of this is
+afforded by _Wyeomia smithii_, whose larvae live in pitcher plants and
+are to be found on the coldest winter days imbedded in the solid ice.
+Late in the spring, the adults emerge and produce several broods during
+the summer.
+
+In the United States, one of the most important facts which has been
+brought out by the intensive studies of recent years is that certain
+species are migratory and that they can travel long distances and become
+an intolerable pest many miles from their breeding places. This was
+forcibly emphasized in Dr. Smith's work in New Jersey, when he found
+that migratory mosquitoes, developing in the salt marshes along the
+coast, are the dominant species largely responsible for the fame of the
+New Jersey mosquito. The species concerned are _Aedes sollicitans_, _A.
+cantator_ and _A. taeniorhynchus_. Dr. Smith decided that the first of
+these might migrate at least forty miles inland. It is obvious that
+where such species are the dominant pest, local control measures are a
+useless waste of time and money. Such migratory habits are rare,
+however, and it is probable that the majority of mosquitoes do not fly
+any great distance from their breeding places.
+
+While mosquitoes are thought of primarily as a pest of man, there are
+many species which have never been known to feed upon human or mammalian
+blood, no matter how favorable the opportunity. According to Howard,
+Dyar, and Knab, this is true of _Culex territans_, one of the common
+mosquitoes in the summer months in the Northern United States. There are
+some species, probably many, in which the females, like the males, are
+plant feeders. In experimental work, both sexes are often kept alive for
+long periods by feeding them upon ripe banana, dried fig, raisins, and
+the like, and in spite of sweeping assertions that mosquitoes must have
+a meal of blood in order to stimulate the ovaries to development, some
+of the common blood-sucking species, notably _Culex pipiens_, have been
+bred repeatedly without opportunity to feed upon blood.
+
+The effect of the bite varies greatly with different species and depends
+upon the susceptibility of the individual bitten. Some persons are
+driven almost frantic by the attacks of the pests when their companions
+seem almost unconscious of any inconvenience. Usually, irritation and
+some degree of inflammation appear shortly following the bite. Not
+infrequently a hardened wheal or even a nodule forms, and sometimes
+scratching leads to secondary infection and serious results.
+
+The source of the poison is usually supposed to be the salivary glands
+of the insect. As we have already pointed out, (p. 34), Macloskie
+believed that one lobe of the gland, on each side, was specialized for
+forming the poison, while a radically different view is that of
+Schaudinn, who believed that the irritation is due to the expelled
+contents of the oesophageal diverticula, which contain a gas and a
+peculiar type of fungi or bacteria. In numerous attempts, Schaudinn was
+unable to produce any irritation by applying the triturated salivary
+glands to a wound, but obtained the typical result when he used the
+isolated diverticula.
+
+The irritation of the bite may be relieved to some extent by using
+ammonia water, a one per cent. alcoholic solution of menthol, or
+preparations of cresol, or carbolic acid. Dr. Howard recommends rubbing
+the bite gently with a piece of moist toilet soap. Castellani and
+Chalmers recommend cleansing inflamed bites with one in forty carbolic
+lotion, followed by dressing with boracic ointment. Of course,
+scratching should be avoided as much as possible.
+
+Repellents of various kinds are used, for warding off the attacks of the
+insects. We have often used a mixture of equal parts of oil of
+pennyroyal and kerosene, applied to the hands and face. Oil of
+citronella is much used and is less objectionable to some persons. A
+recommended formula is, oil of citronella one ounce, spirits of camphor
+one ounce, oil of cedar one-half ounce. A last resort would seem to be
+the following mixture recommended by Howard, Dyar, and Knab for use by
+hunters and fishermen in badly infested regions, against mosquitoes and
+blackflies.
+
+Take 2-1/4 lbs. of mutton tallow and strain it. While still hot add 1/2
+lb. black tar (Canadian tar). Stir thoroughly and pour into the
+receptacle in which it is to be contained. When nearly cool stir in
+three ounces of oil of citronella and 1-1/4 oz. of pennyroyal.
+
+At night the surest protection is a good bed net. There are many types
+of these in use, but in order to be serviceable and at the same time
+comfortable it should be roomy and hung in such a way as to be stretched
+tightly in every direction. We prefer one suspended from a broad, square
+frame, supported by a right-angled standard which is fastened to the
+head of the bed. It must be absolutely free from rents or holes and
+tucked in securely under the mattress or it will serve merely as a
+convenient cage to retain mosquitoes which gain an entrance. While such
+nets are a convenience in any mosquito ridden community, they are
+essential in regions where disease-carrying species abound. Screening of
+doors, windows and porches, against the pests is so commonly practiced
+in this country that its importance and convenience need hardly be
+urged.
+
+Destruction of mosquitoes and prevention of breeding are of fundamental
+importance. Such measures demand first, as we have seen, the correct
+determination of the species which is to be dealt with, and a knowledge
+of its life-history and habits. If it prove to be one of the migratory
+forms, it is beyond mere local effort and becomes a problem demanding
+careful organization and state control. An excellent illustration of the
+importance and effectiveness of work along these lines is afforded by
+that in New Jersey, begun by the late Dr. John B. Smith and being pushed
+with vigor by his successor, Dr. Headlee.
+
+In any case, there is necessity for community action. Even near the
+coast, where the migratory species are dominant, there are the local
+species which demand attention and which cannot be reached by any
+measures directed against the species of the salt marshes. The most
+important of local measures consist in the destruction of breeding
+places by filling or draining ponds and pools, clearing up of more
+temporary breeding places, such as cans, pails, water barrels and the
+like. Under conditions where complete drainage of swamps is
+impracticable or undesirable, judicious dredging may result in a pool or
+series of steep-sided pools deep enough to maintain a supply of fish,
+which will keep down the mosquito larvae. Where water receptacles are
+needed for storage of rain water, they should be protected by careful
+screening or a film of kerosene over the top of the water, renewed every
+two weeks or so, so as to prevent mosquitoes from depositing their eggs.
+When kerosene is used, Water drawn from the bottom of the receptacle
+will not be contaminated by it to any injurious extent. Where ponds
+cannot be drained much good will be accomplished by spraying kerosene
+oil on the surface of the water, or by the introduction of fish which
+will feed on the larvae.
+
+Detailed consideration of the most efficient measures for controlling
+mosquitoes is to be found in Dr. Howard's Bulletin No. 88 of the Bureau
+of Entomology, "Preventive and remedial work against mosquitoes" or, in
+more summarized form, in Farmers' Bulletin No. 444. One of these should
+be obtained by any person interested in the problems of mosquito control
+and public health.
+
+[Illustration: 74. Mouth parts of Simulium. After Grunberg.]
+
+
+The Simuliidae, or Black Flies
+
+The SIMULIIDAE, or black flies, are small, dark, or black flies, with a
+stout body and a hump-back appearance. The antennae are short but
+eleven-segmented, the wings broad, without scales or hairs, and with the
+anterior veins stout but the others very weak. The mouth-parts (fig. 74)
+are fitted for biting.
+
+The larvae of the Simuliidae (fig. 75) are aquatic and, unlike those of
+mosquitoes, require a well aerated, or swiftly running water. Here they
+attach to stones, logs, or vegetation and feed upon various
+micro-organisms. They pupate in silken cocoons open at the top. Detailed
+life-histories have not been worked out for most of the species. We
+shall consider as typical that of _Simulium pictipes_, an inoffensive
+species widely distributed in the Eastern United States, which has been
+studied especially at Ithaca, N.Y. (Johannsen, 1903).
+
+[Illustration: 75. Larva of Simulium, (x8). After Garman.]
+
+The eggs are deposited in a compact yellowish layer on the surface of
+rock, on the brinks of falls and rapids where the water is flowing
+swiftly. They are elongate ellipsoidal in shape, about .4 by .18 mm. As
+myriads of females deposit in the same place the egg patches may be
+conspicuous coatings of a foot or much more in diameter. When first laid
+they are enveloped in a yellowish white slime, which becomes darker,
+until finally it becomes black just before the emerging of the larvae.
+The egg stage lasts a week.
+
+The larvae (fig. 75) are black, soft skinned, somewhat cylindrical in
+shape, enlarged at both ends and attenuated in the middle. The posterior
+half is much stouter than the anterior part and almost club-shaped. The
+head bears two large fan-shaped organs which aid in procuring food.
+Respiration is accomplished by means of three so-called blood gills
+which are pushed out from the dorsal part of the rectum. The larvae occur
+in enormous numbers, in moss-like patches. If removed from their natural
+habitat and placed in quiet water they die within three or four hours.
+Fastened to the rock by means of a disk-like sucker at the caudal end of
+the body, they ordinarily assume an erect position. They move about on
+the surface of the rocks, to a limited extent, with a looping gait
+similar to that of a measuring worm, and a web is secreted which
+prevents their being washed away by the swiftly flowing water. They feed
+chiefly upon algae and diatoms.
+
+The complete larval stage during the summer months occupies about four
+weeks, varying somewhat with the temperature and velocity of the water.
+At the end of this period they spin from cephalic glands, boot-shaped
+silken cocoons within which they pupate. The cocoon when spun is firmly
+attached to the rock and also to adjacent cocoons. Clustered
+continuously over a large area and sometimes one above another, they
+form a compact, carpet-like covering on the rocks, the reddish-brown
+color of which is easily distinguishable from the jet-black appearance
+of the larvae. The pupal stage lasts about three weeks. The adult fly,
+surrounded by a bubble of air, quickly rises to the surface of the water
+and escapes. The adults (fig. 76) are apparently short lived and thus
+the entire life cycle, from egg to egg is completed in approximately
+eight weeks.
+
+[Illustration: 76. Simulium venustum, (x8). After Garman.]
+
+In the case of _Simulium pictipes_ at Ithaca, N. Y., the first brood of
+adults emerges early in May and successive generations are produced
+throughout the summer and early autumn. This species winters in the
+larval condition. Most of the other species of _Simulium_ which have
+been studied seem to be single brooded.
+
+While _Simulium pictipes_ does not attack man, there are a number of the
+species which are blood-sucking and in some regions they are a veritable
+scourge. In recent years the greatest interest in the group has been
+aroused by Sambon's hypothesis that they transmit pellagra from man to
+man. This has not been established, and, indeed, seems very doubtful,
+but the importance of these insects as pests and the possibility that
+they may carry disease make it urgent that detailed life-histories of
+the hominoxious species be worked out.
+
+As pests a vivid account of their attacks is in Agassiz's "Lake
+Superior" (p. 61), quoted by Forbes (1912).
+
+"Neither the love of the picturesque, however, nor the interests of
+science, could tempt us into the woods, so terrible were the black
+flies. This pest of flies which all the way hither had confined our
+ramblings on shore pretty closely to the rocks and the beach, and had
+been growing constantly worse, here reached its climax. Although
+detained nearly two days, * * * we could only sit with folded hands, or
+employ ourselves in arranging specimens, and such other operations as
+could be pursued in camp, and under the protection of a 'smudge.' One,
+whom scientific ardor tempted a little way up the river in a canoe,
+after water plants, came back a frightful spectacle, with blood-red
+rings round his eyes, his face bloody, and covered with punctures. The
+next morning his head and neck were swollen as if from an attack of
+erysipelas."
+
+There are even well authenticated accounts on record of death of humans
+from the attacks of large swarms of these gnats. In some regions, and
+especially in the Mississippi Valley in this country, certain species of
+black flies have been the cause of enormous losses to farmers and
+stockmen, through their attacks on poultry and domestic animals. C. V.
+Riley states that in 1874 the loss occasioned in one county in Tennessee
+was estimated at $500,000.
+
+The measures of prevention and protection against these insects have
+been well summarized by Forbes (1912). They are of two kinds: "the use
+of repellents intended to drive away the winged flies, and measures for
+the local destruction of the aquatic larvae. The repellents used are
+either smudges, or surface applications made to keep the flies from
+biting. The black-fly will not endure a dense smoke, and the well-known
+mosquito smudge seems to be ordinarily sufficient for the protection of
+man. In the South, leather, cloth, and other materials which will make
+the densest and most stifling smoke, are often preserved for this use in
+the spring. Smudges are built in pastures for the protection of stock,
+and are kept burning before the doors of barns and stables. As the
+black-flies do not readily enter a dark room, light is excluded from
+stables as much as possible during the gnat season. If teams must be
+used in the open field while gnats are abroad, they may be protected
+against the attacks of the gnats by applying cotton-seed oil or axle
+grease to the surface, especially to the less hairy parts of the
+animals, at least twice a day. A mixture of oil and tar and, indeed,
+several other preventives, are of practical use in badly infested
+regions; but no definite test or exact comparison has been made with any
+them in a way to give a record of the precise results."
+
+"It is easy to drive the flies from houses or tents by burning pyrethrum
+powder inside; this either kills the flies or stupifies them so that
+they do not bite for some time thereafter." * * * "Oil of tar is
+commonly applied to the exposed parts of the body for the purpose of
+repelling the insects, and this preparation is supplied by the Hudson
+Bay Company to its employees. Minnesota fishermen frequently grease
+their faces and hands with a mixture of kerosene and mutton tallow for
+the same purpose." We have found a mixture of equal parts of kerosene
+and oil of pennyroyal efficient.
+
+Under most circumstances very little can be done to destroy this insect
+in its early stage, but occasionally conditions are such that a
+larvicide can be used effectively. Weed (1904), and Sanderson (1910)
+both report excellent results from the use of phinotas oil, a
+proprietary compound. The first-mentioned also found that in some places
+the larvae could be removed by sweeping them loose in masses with stiff
+stable brooms and then catching them downstream on wire netting
+stretched in the water.
+
+
+Chironomidae or Midges
+
+The flies of this family, commonly known as midges, resemble mosquitoes
+in form and size but are usually more delicate, and the wing-veins,
+though sometimes hairy, are not fringed with scales. The venation is
+simpler than in the mosquitoes and the veins are usually less distinct.
+
+These midges, especially in spring or autumn, are often seen in immense
+swarms arising like smoke over swamps and producing a humming noise
+which can be heard for a considerable distance. At these seasons they
+are frequently to be found upon the windows of dwellings, where they are
+often mistaken for mosquitoes.
+
+The larvae are worm-like, but vary somewhat in form in the different
+genera. Most of them are aquatic, but a few live in the earth, in
+manure, decaying wood, under bark, or in the sap of trees, especially in
+the sap which collects in wounds.
+
+[Illustration: 77. Culicoides guttipennis; (_a_) adult, (x15); (_b_)
+head of same; (_c_) larva; (_d_) head; (_e_) pupa. After Pratt.]
+
+Of the many species of CHIRONOMIDAE, (over eight hundred known), the vast
+majority are inoffensive. The sub-family Ceratopogoninae, however, forms
+an exception, for some of the members of this group, known as sandflies,
+or punkies, suck blood and are particularly troublesome in the
+mountains, along streams, and at the seashore. Most of these have been
+classed under the genus _Ceratopogon_, but the group has been broken up
+into a number of genera and _Ceratopogon_, in the strict sense, is not
+known to contain any species which sucks the blood of vertebrates.
+
+THE CERATOPOGONINAE--The Ceratopogoninae are among the smallest of the
+Diptera, many of them being hardly a millimeter long and some not even
+so large. They are Chironomidae in which the thorax is not prolonged over
+the head. The antennae are filiform with fourteen (rarely thirteen)
+segments in both sexes, those of the male being brush-like. The basal
+segment is enlarged, the last segment never longer than the two
+preceding combined, while the last five are sub-equal to, or longer than
+the preceding segment. The legs are relatively stouter than in the other
+Chironomidae. The following three genera of this subfamily are best known
+as blood suckers in this country.
+
+Of the genus _Culicoides_ there are many species occurring in various
+parts of the world. A number are known to bite man and animals and it is
+probable that all are capable of inflicting injury. In some localities
+they are called punkies, in others, sand-flies, a name sometimes also
+applied to the species of _Simulium_ and _Phlebotomus_. Owing to their
+very small size they are known by some tribes of Indians as No-see-ums.
+The larvae are found in ponds, pools, water standing in hollow tree
+stumps, and the like. Though probably living chiefly in fresh water, we
+have found a species occurring in salt water. The larvae are small,
+slender, legless, worm-like creatures (fig. 77_c_) with small brown head
+and twelve body segments. The pupae (fig. 77_e_) are slender, more
+swollen at the anterior end and terminating in a forked process. They
+float nearly motionless in a vertical position, the respiratory tubes in
+contact with the surface film. The adults are all small, rarely
+exceeding 2-1/4 mm. in length. The wings are more or less covered with
+erect setulae or hairs and in many species variously spotted and marked
+with iridescent blotches. The antennae have fourteen segments, the palpi
+usually five. The wing venation and mouth-parts are shown in figures 77
+and 78. Of the twenty or more species of this genus occurring in the
+United States the following are known to bite: _C. cinctus_, _C.
+guttipennis_, _C. sanguisuga_, _C. stellifer_, _C. variipennis_, _C.
+unicolor_.
+
+[Illustration: 78. Culicoides guttipennis; mouth parts of adult. After
+Pratt.]
+
+One of the most widely distributed and commonest species in the Eastern
+States is _C. guttipennis_ (fig. 77a). It is black with brown legs, a
+whitish ring before the apex of each femur and both ends of each tibia;
+tarsi yellow, knobs of halteres yellow. Mesonotum opaque, brown, two
+vittae in the middle, enlarging into a large spot on the posterior half,
+also a curved row of three spots in front of each wing, and the narrow
+lateral margins, light gray pruinose. Wings nearly wholly covered with
+brown hairs, gray, with markings as shown in the figure. Length one mm.
+
+_Johannseniella_ Will. is a wide-spread genus related to the foregoing.
+Its mouth-parts are well adapted for piercing and it is said to be a
+persistent blood sucker, particularly in Greenland. This genus is
+distinguished from _Culicoides_ by its bare wings, the venation (fig.
+163, c), and the longer tarsal claws. There are over twenty North
+American species.
+
+[Illustration: 79. Chrysops univittatus, (x4). After Osborn.]
+
+In the Southwestern United States, _Tersesthes torrens_ Towns. occurs, a
+little gnat which annoys horses, and perhaps man also, by its bite. It
+is related to _Culicoides_ but differs in the number of antennal
+segments and in its wing venation (fig. 163, e). The fly measures but
+two mm. in length and is blackish in color. The antennae of the female
+have thirteen segments, the palpi but three, of which the second is
+enlarged and swollen.
+
+
+Tabanidae or Horse-Flies
+
+The TABANIDAE,--horse-flies, ear-flies, and deer-flies,--are well-known
+pests of cattle and horses and are often extremely annoying to man. The
+characteristics of the family and of the principal North American genera
+are given in the keys of Chapter XII. There are over 2500 recorded
+species. As in the mosquitoes, the females alone are blood suckers. The
+males are flower feeders or live on plant juices. This is apparently
+true also of the females of some of the genera.
+
+The eggs are deposited in masses on water plants or grasses and sedges
+growing in marshy or wet ground. Those of a common species of _Tabanus_
+are illustrated in figure 80, _a_. They are placed in masses of several
+hundred, light colored when first deposited but turning black. In a week
+or so the cylindrical larvae, tapering at both ends (fig. 80, _b_),
+escape to the water, or damp earth, and lead an active, carnivorous
+life, feeding mainly on insect larvae, and worms. In the forms which have
+been best studied the larval life is a long one, lasting for months or
+even for more than a year. Until recently, little was known concerning
+the life-histories of this group, but the studies of Hart (1895), and
+Hine (1903 +) have added greatly to the knowledge concerning North
+American forms.
+
+Many of the species attack man with avidity and are able to inflict
+painful bites, which may smart for hours. In some instances the wound is
+so considerable that blood will continue to flow after the fly has left.
+We have seen several cases of secondary infection following such bites.
+
+[Illustration: 80. (_a_) Eggs of Tabanus. Photograph by J. T. Lloyd.]
+
+[Illustration: 80. (_b_) Larva of Tabanus. Photograph by M. V. S.]
+
+The horse-flies have been definitely convicted of transferring the
+trypanosome of surra from diseased to healthy animals and there is good
+evidence that they transfer anthrax. The possibility of their being
+important agents in the conveyal of human diseases should not be
+overlooked. Indeed, Leiper has recently determined that a species of
+_Chrysops_ transfers the blood parasite _Filaria diurna_.
+
+
+Leptidae or Snipe-Flies
+
+The family LEPTIDAE is made up of moderate or large sized flies,
+predaceous in habit. They are sufficiently characterized in the keys of
+Chapter XII. Four blood-sucking species belonging to three genera have
+been reported. Of these _Symphoromyia pachyceras_ is a western species.
+Dr. J. C. Bradley, from personal experience, reports it as a vicious
+biter.
+
+[Illustration: 80. (_c_) Mouth parts of Tabanus. After Grunberg.]
+
+
+Oestridae or Bot-flies
+
+To the family OESTRIDAE belong the bot and warble-flies so frequently
+injurious to animals. The adults are large, or of medium size, heavy
+bodied, rather hairy, and usually resemble bees in appearance.
+
+The larvae live parasitically in various parts of the body of mammals,
+such as the stomach (horse bot-fly), the subcutaneous connective tissue
+(warble-fly of cattle), or the nasal passage (sheep bot-fly or head
+maggot).
+
+There are on record many cases of the occurrence of the larvae of
+Oestridae as occasional parasites of man. A number of these have been
+collected and reviewed in a thesis by Mme. Petrovskaia (1910). The
+majority of them relate to the following species.
+
+_Gastrophilus haemorrhoidalis_, the red tailed bot-fly, is one of the
+species whose larvae are most commonly found in the stomach of the horse.
+Schoch (1877) cites the case of a woman who suffered from a severe case
+of chronic catarrh of the stomach, and who vomited, and also passed from
+the anus, larvae which apparently belonged to this species. Such cases
+are exceedingly rare but instances of subcutaneous infestation are
+fairly numerous. In the latter type these larvae are sometimes the cause
+of the peculiar "creeping myasis." This is characterized at its
+beginning by a very painful swelling which gradually migrates, producing
+a narrow raised line four to twenty-five millimeters broad. When the
+larva is mature, sometimes after several months, it becomes stationary
+and a tumor is formed which opens and discharges the larva along with
+pus and serum.
+
+_Gastrophilus equi_ is the most widespread and common of the horse
+bot-flies. Portschinsky reports it as commonly causing subcutaneous
+myasis of man in Russia.
+
+_Hypoderma bovis_ (= _Oestrus bovis_), and _Hypoderma lineata_ are the
+so-called warble-flies of cattle. The latter species is the more common
+in North America but Dr. C. G. Hewitt has recently shown that _H. bovis_
+also occurs. Though warbles are very common in cattle in this country,
+the adult flies are very rarely seen. They are about half an inch in
+length, very hairy, dark, and closely resemble common honey-bees.
+
+They deposit their eggs on the hairs of cattle and the animals in
+licking themselves take in the young larvae. These pass out through the
+walls of the oesophagus and migrate through the tissues of the animal,
+to finally settle down in the subcutaneous tissue of the back. The
+possibility of their entering directly through the skin, especially in
+case of infestation of man, is not absolutely precluded, although it is
+doubtful.
+
+For both species of _Hypoderma_ there are numerous cases on record of
+their occurrence in man. Hamilton (1893) saw a boy, six years of age,
+who had been suffering for some months from the glands on one side of
+his neck being swollen and from a fetid ulceration around the back teeth
+of the lower jaw of the same side. Three months' treatment was of no
+avail and the end seemed near; one day a white object, which was seen to
+move, was observed in the ulcer at the root of the tongue, and on being
+extracted was recognized as a full grown larva of _Hypoderma_. It was of
+usual tawny color, about half an inch long when contracted, about one
+third that thickness, and quite lively. The case resulted fatally. The
+boy had been on a dairy farm the previous fall, where probably the egg
+(or larva) was in some way taken into his mouth, and the larva found
+between the base of the tongue and the jaw suitable tissue in which to
+develop.
+
+Topsent (1901) reports a case of "creeping myasis" caused by _H.
+lineata_ in the skin of the neck and shoulders of a girl eight years of
+age. The larva travelled a distance of nearly six and a half inches. The
+little patient suffered excruciating pain in the place occupied by the
+larva.
+
+_Hypoderma diana_ infests deer, and has been known to occur in man.
+
+_Oestris ovis_, the sheep bot-fly, or head maggot, is widely distributed
+in all parts of the world. In mid-summer the flies deposit living
+maggots in the nostrils of sheep. These larvae promptly pass up the nasal
+passages into the frontal and maxillary sinuses, where they feed on the
+mucous to be found there. In their migrations they cause great
+irritation to their host, and when present in numbers may cause vertigo,
+paroxysms, and even death. Portschinsky in an important monograph on
+this species, has discussed in detail its relation to man. He shows that
+it is not uncommon for the fly to attack man and that the minute living
+larvae are deposited in the eyes, nostrils, lips, or mouth. A typical
+case in which the larvae were deposited in the eye was described by a
+German oculist Kayser, in 1905. A woman brought her six year old
+daughter to him and said that the day before, about noontime, a flying
+insect struck the eye of the child and that since then she had felt a
+pain which increased towards evening. In the morning the pain ceased but
+the eye was very red. She was examined at about noon, at which time she
+was quiet and felt no pain. She was not sensitive to light, and the only
+thing noticed was a slight congestion and accumulation of secretion in
+the corner of the right eye. A careful examination of the eye disclosed
+small, active, white larvae that crawled out from the folds of the
+conjunctiva and then back and disappeared. Five of these larvae were
+removed and although an uncomfortable feeling persisted for a while, the
+eye became normal in about three weeks.
+
+Some of the other recorded cases have not resulted so favorably, for the
+eyesight has been seriously affected or even lost.
+
+According to Edmund and Etienne Sergent (1907), myasis caused by the
+larvae of _Oestris ovis_ is very common among the shepherds in Algeria.
+The natives say that the fly deposits its larvae quickly, while on the
+wing, without pause. The greatest pain is caused when these larvae
+establish themselves in the nasal cavities. They then produce severe
+frontal headaches, making sleep impossible. This is accompanied by
+continuous secretion from the nasal cavities and itching pains in the
+sinuses. If the larvae happen to get into the mouth, the throat becomes
+inflamed, swallowing is painful, and sometimes vomiting results. The
+diseased condition may last for from three to ten days or in the case of
+nasal infection, longer, but recovery always follows. The natives remove
+the larvae from the eye mechanically by means of a small rag. When the
+nose is infested, tobacco fumigations are applied, and in case of throat
+infestation gargles of pepper, onion, or garlic extracts are used.
+
+_Rhinoestrus nasalis_, the Russian gad-fly, parasitizes the
+nasopharyngeal region of the horse. According to Portschinsky, it not
+infrequently attacks man and then, in all the known cases deposits its
+larvae in the eye, only. This is generally done while the person is
+quiet, but not during sleep. The fly strikes without stopping and
+deposits its larva instantaneously. Immediately after, the victim
+experiences lancinating pains which without intermission increase in
+violence. There is an intense conjunctivitis and if the larvae are not
+removed promptly the envelopes of the eye are gradually destroyed and
+the organ lost.
+
+[Illustration: 81. Larvae of Dermatobia cyaniventris. After Blanchard.]
+
+[Illustration: 82. Young larva of Dermatobia cyaniventris. After
+Surcouf.]
+
+_Dermatobia cyaniventris_--This fly (fig. 83) is widely distributed
+throughout tropical America, and in its larval stage is well known as a
+parasite of man. The larvae (figs. 81 and 82) which are known as the "ver
+macaque," "torcel," "ver moyocuil" or by several other local names,
+enter the skin and give rise to a boil-like swelling, open at the top,
+and comparable with the swelling produced by the warble fly larvae, in
+cattle. They cause itching and occasional excruciating pain. When
+mature, nearly an inch in length, they voluntarily leave their host,
+drop to the ground and complete their development. The adult female is
+about 12 mm. in length. The face is yellow, the frons black with a
+grayish bloom; antennae yellow, the third segment four times as long as
+the second, the arista pectinate. The thorax is bluish black with
+grayish bloom; the abdomen depressed, brilliant metallescent blue with
+violet tinge. The legs are yellowish, the squamae and wings brownish.
+
+The different types of larvae represented in figure 81 were formerly
+supposed to belong to different species but Blanchard regards them as
+merely various stages of the same species. It is only very recently that
+the early stage and the method by which man becomes infested were made
+known.
+
+[Illustration: 83. Dermatobia cyaniventris (x1-3/4). After Manson.]
+
+[Illustration: 84. Mosquito carrying eggs of Dermatobia cyaniventris.
+After Surcouf.]
+
+About 1900, Blanchard observed the presence of packets of large-sized
+eggs under the abdomen of certain mosquitoes from Central America; and
+in 1910, Dr. Morales, of Costa Rica, declared that the Dermatobia
+deposited its eggs directly under the abdomen of the mosquito and that
+they were thus carried to vertebrates. Dr. Nunez Tovar observed the
+mosquito carriers of the eggs and placing larvae from this source on
+animals, produced typical tumors and reared the adult flies. It remained
+for Surcouf (1913) to work out the full details. He found that the
+Dermatobia deposits its eggs in packets covered by a very viscid
+substance, on leaves. These become attached to mosquitoes of the species
+_Janthinosoma lutzi_ (fig. 84) which walk over the leaves. The eggs
+which adhere to the abdomen, remain attached and are thus transported.
+The embryo develops, but the young larva (fig. 82) remains in the egg
+until it has opportunity to drop upon a vertebrate fed upon by the
+mosquito.
+
+
+Muscidae
+
+The following MUSCIDAE, characterized elsewhere, deserve special mention
+under our present grouping of parasitic species. Other important species
+will be considered as facultative parasites.
+
+_Stomoxys calcitrans_, the stable-fly, or the biting house-fly, is often
+confused with _Musca domestica_ and therefore is discussed especially in
+our consideration of the latter species as an accidental carrier of
+disease. Its possible relation to the spread of infantile paralysis is
+also considered later.
+
+The _tsetse flies_, belonging to the genus _Glossina_, are African
+species of blood-sucking Muscidae which have attracted much attention
+because of their role in transmitting various trypanosome diseases of
+man and animals. They are characterized in Chapter XII and are also
+discussed in connection with the diseases which they convey.
+
+_Chrysomyia macellaria_, (= _Compsomyia_), the "screw worm"-fly is one
+of the most important species of flies directly affecting man, in North
+America. It is not normally parasitic, however, and hence will be
+considered with other facultative parasites in Chapter IV.
+
+[Illustration: 85. Larva of Auchmeromyia luteola. After Graham-Smith.]
+
+[Illustration: 86. Auchmeromyia luteola (x4). After Graham-Smith.]
+
+_Auchmeromyia luteola_, the Congo floor maggot. This is a muscid of
+grewsome habits, which has a wide distribution throughout Africa. The
+fly (fig. 86) deposits its eggs on the ground of the huts of the
+natives. The whitish larvae (fig. 85) on hatching are slightly flattened
+ventrally, and each segment bears posteriorly three foot-pads
+transversely arranged. At night the larvae find their way into the low
+beds or couches of the natives and suck their blood. The adult flies do
+not bite man and, as far as known, the larvae do not play any role in the
+transmission of sleeping sickness or other diseases.
+
+This habit of blood-sucking by muscid larvae is usually referred to as
+peculiar to _Auchmeromyia luteola_ but it should be noted that the larvae
+of _Protocalliphora_ frequent the nests of birds and feed upon the
+young. Mr. A. F. Coutant has studied especially the life-history and
+habits of _P. azurea_, whose larvae he found attacking young crows at
+Ithaca, N.Y. He was unable to induce the larvae to feed on man.
+
+[Illustration: 87. Cordylobia anthropophaga (x3). After Fulleborn.]
+
+[Illustration: 88. Larva of Cordylobia anthropophaga. After Blanchard.]
+
+_Cordylobia anthropophaga_, (_Ochromyia anthropophaga_), or Tumbu-fly
+(fig. 87) is an African species whose larvae affect man much as do those
+of _Dermatobia cyniventris_, of Central and South America. The larva
+(fig. 88), which is known as "ver du Cayor" because it was first
+observed in Cayor, in Senegambia, develops in the skin of man and of
+various animals, such as dogs, cats, and monkeys. It is about 12 mm. in
+length, and of the form of the larvae of other muscids. Upon the
+intermediate segments are minute, brownish recurved spines which give to
+the larva its characteristic appearance. The life-history is not
+satisfactorily worked out, but Fuller (1914), after reviewing the
+evidence believes that, as a rule, it deposits its young in the sleeping
+places of man and animals, whether such be a bed, a board, the floor, or
+the bare ground. In the case of babies, the maggots may be deposited on
+the scalp. The minute maggots bore their way painlessly into the skin.
+As many as forty parasites have been found in one individual and one
+author has reported finding more than three hundred in a spaniel puppy.
+Though their attacks are at times extremely painful, it is seldom that
+any serious results follow.
+
+
+THE SIPHONAPTERA OR FLEAS
+
+The SIPHONAPTERA, or fleas (fig. 89) are wingless insects, with highly
+chitinized and laterally compressed bodies. The mouth-parts are formed
+for piercing and sucking. Compound eyes are lacking but some species
+possess ocelli. The metamorphosis is complete.
+
+This group of parasites, concerning which little was known until
+recently, has assumed a very great importance since it was learned that
+fleas are the carriers of bubonic plague. Now over four hundred species
+are known. Of these, several species commonly attack man. The most
+common hominoxious species are _Pulex irritans_, _Xenopsylla cheopis_,
+_Ctenocephalus canis_, _Ctenocephalus felis_, _Ceratophyllus fasciatus_
+and _Dermatophilus penetrans_, but many others will feed readily on
+human blood if occasion arises.
+
+[Illustration: 89. Xenopsylla cheopis, male (x25). After Jordan and
+Rothschild.]
+
+We shall treat in this place of the general biology and habits of the
+hominoxious forms and reserve for the systematic section the discussion
+of the characteristics of the different genera.
+
+The most common fleas infesting houses in the Eastern United States are
+the cosmopolitan dog and cat fleas, _Ctenocephalus canis_ (fig. 90) and
+_C. felis_. Their life cycles will serve as typical. These two species
+have until recently been considered as one, under the name _Pulex
+serraticeps_. See figure 92.
+
+[Illustration: 90. Dog flea (x15). After Howard.]
+
+The eggs are oval, slightly translucent or pearly white, and measure
+about .5 mm. in their long diameter. They are deposited loosely in the
+hairs of the host and readily drop off as the animal moves around.
+Howard found that these eggs hatch in one to two days. The larvae are
+elongate, legless, white, worm-like creatures. They are exceedingly
+active, and avoid the light in every way possible. They cast their first
+skin in from three to seven days and their second in from three to four
+days. They commenced spinning in from seven to fourteen days after
+hatching and the imago appeared five days later. Thus in summer, at
+Washington, the entire life cycle may be completed in about two weeks.
+(cf. fig. 91, 92).
+
+Strickland's (1914) studies on the biology of the rat flea,
+_Ceratophyllus fasciatus_, have so important a general bearing that we
+shall cite them in considerable detail.
+
+[Illustration: 91. Larva of Xenopsylla cheopis. After Bacot and
+Ridewood.]
+
+He found, to begin with, that there is a marked inherent range in the
+rate of development. Thus, of a batch of seventy-three eggs, all laid in
+the same day and kept together under the same conditions, one hatched in
+ten days; four in eleven days; twenty-five in twelve days; thirty-one in
+thirteen days; ten in fourteen days; one in fifteen days; and one in
+sixteen days. Within these limits the duration of the egg period seems
+to depend mainly on the degree of humidity. The incubation period is
+never abnormally prolonged as in the case of lice, (Warburton) and
+varying conditions of temperature and humidity have practically no
+effect on the percentage of eggs which ultimately hatch.
+
+The same investigator found that the most favorable condition for the
+larva is a low temperature, combined with a high degree of humidity; and
+that the presence of rubbish in which the larva may bury itself is
+essential to its successful development. When larvae are placed in a
+bottle containing either wood-wool soiled by excrement, or with feathers
+or filter paper covered with dried blood they will thrive readily and
+pupate. They seem to have no choice between dried blood and powdered rat
+feces for food, and also feed readily on flea excrement. They possess
+the curious habit of always devouring their molted skins.
+
+[Illustration: 92. Head and pronotum of (_a_) dog flea; (_b_) of cat
+flea; (_c_) of hen flea. After Rothschild. (_d_) Nycteridiphilus
+(Ischnopsyllus) hexactenus. After Oudemans.]
+
+An important part of Strickland's experiments dealt with the question of
+duration of the pupal stage under the influence of temperature and with
+the longevity and habits of the adult. In October, he placed a batch of
+freshly formed cocoons in a small dish that was kept near a white rat in
+a deep glass jar in the laboratory. Two months later one small and
+feeble flea had emerged, but no more until February, four months after
+the beginning of the experiment. Eight cocoons were then dissected and
+seven more found to contain the imago fully formed but in a resting
+state. The remainder of the batch was then placed at 70^o F. for one
+night, near a white rat. The next day all the cocoons were empty and the
+fleas were found on the white rat.
+
+Thus, temperature greatly influences the duration of the pupal period,
+which in _Ceratophyllus fasciatus_ averages seventeen days. Moreover,
+when metamorphosis is complete a low temperature will cause the imago to
+remain within the cocoon.
+
+Sexually mature and ovipositing fleas, he fed at intervals and kept
+alive for two months, when the experiment was discontinued. In the
+presence of rubbish in which they could bury themselves, unfed rat fleas
+were kept alive for many months, whereas in the absence of any such
+substratum they rarely lived a month. In the former case, it was found
+that the length of life is influenced to some degree by the temperature
+and humidity. In an experiment carried out at 70^o F. and 45 per cent
+humidity, the fleas did not live for more than four months, while in an
+experiment at 60^o F. and 70 per cent humidity they lived for at least
+seventeen months. There was no indication that fleas kept under these
+conditions sucked moisture from surrounding objects, and those kept in
+bell jars, with an extract of flea-rubbish on filter paper, did not live
+any longer than those which were not so supplied.
+
+Curiously enough, although the rat is the normal host of _Ceratophyllus
+fasciatus_, it was found that when given the choice these fleas would
+feed upon man in preference to rats. However, none of the fleas laid
+eggs unless they fed on rat blood.
+
+The experiments of Strickland on copulation and oviposition in the rat
+flea showed that fleas do not copulate until they are sexually mature
+and that, at least in the case of _Ceratophyllus fasciatus_, the
+reproductive organs are imperfectly developed for some time (more than a
+week) after emerging from the pupa. When mature, copulation takes place
+soon after the fleas have fed on their true host--the rat--but not if
+they have fed on a facultative host only, such as man. Copulation is
+always followed by oviposition within a very short time.
+
+The effect of the rat's blood on the female with regard to egg-laying,
+Strickland concludes, is stimulating rather than nutritive, as fleas
+that were without food for many months were observed to lay eggs
+immediately after one feed. Similarly, the male requires the stimulus of
+a meal of rat's blood before it displays any copulatory activity.
+
+Mitzmain (1910) has described in detail the act of biting on man, as
+observed in the squirrel flea, _Ceratophyllus acutus_. "The flea when
+permitted to walk freely on the arm selects a suitable hairy space where
+it ceases abruptly in its locomotion, takes a firm hold with the tarsi,
+projects its proboscis, and prepares to puncture the skin. A puncture is
+drilled by the pricking epipharynx, the saw-tooth mandibles
+supplementing the movement by lacerating the cavity formed. The two
+organs of the rostrum work alternately, the middle piece boring, while
+the two lateral elements execute a sawing movement. The mandibles, owing
+to their basal attachments, are, as is expressed by the advisory
+committee on plague investigations in India (_Journal of Hygiene_, vol.
+6, No. 4, p. 499), 'capable of independent action, sliding up and down
+but maintaining their relative positions and preserving the lumen of the
+aspiratory channel.' The labium doubles back, the V-shaped groove of
+this organ guiding the mandibles on either side."
+
+"The action of the proboscis is executed with a forward movement of the
+head and a lateral and downward thrust of the entire body. As the
+mouth-parts are sharply inserted, the abdomen rises simultaneously. The
+hind and middle legs are elevated, resembling oars. The forelegs are
+doubled under the thorax, the tibia and tarsi resting firmly on the
+epidermis serve as a support for the body during the feeding. The
+maxillary palpi are retracted beneath the head and thorax. The labium
+continues to bend, at first acting as a sheath for the sawing mandibles,
+and as these are more deeply inserted, it bends beneath the head with
+the elasticity of a bow, forcing the mandibles into the wound until the
+maxillae are embedded in the skin of the victim. When the proboscis is
+fully inserted, the abdomen ceases for a time its lateral swinging."
+
+"The acute pain of biting is first felt when the mandibles have not
+quite penetrated and subsequently during each distinct movement of the
+abdomen. The swinging of the abdomen gradually ceases as it becomes
+filled with blood. The sting of the biting gradually becomes duller and
+less sensitive as feeding progresses. The movements of the elevated
+abdomen grow noticeably feebler as the downward thrusts of the springy
+bow-like labium becomes less frequent."
+
+"As the feeding process advances one can discern through the translucent
+walls of the abdomen a constant flow of blood, caudally from the
+pharynx, accompanied by a peristaltic movement. The end of the meal is
+signified in an abrupt manner. The flea shakes its entire body, and
+gradually withdraws its proboscis by lowering the abdomen and legs and
+violently twisting the head."
+
+"When starved for several days the feeding of the rat fleas is conducted
+in a rather vigorous manner. As soon as the proboscis is buried to the
+full length the abdomen is raised and there ensues a gradual lateral
+swaying motion, increasing the altitude of the raised end of the abdomen
+until it assumes the perpendicular. The flea is observed at this point
+to gain a better foothold by advancing the fore tarsi, and then,
+gradually doubling back the abdomen, it turns with extreme agility,
+nearly touching with its dorsal side the skin of the hand upon which it
+is feeding. Meanwhile, the hungry parasite feeds ravenously."
+
+"It is interesting to note the peculiar nervous action which the rodent
+fleas exhibit immediately when the feeding process is completed or when
+disturbed during the biting. Even while the rostrum is inserted to the
+fullest the parasite shakes its head spasmodically; in a twinkling the
+mouth is withdrawn and then the flea hops away."
+
+A habit of fleas which we shall see is of significance in considering
+their agency in the spread of bubonic plague, is that of ejecting blood
+from the anus as they feed.
+
+Fleas are famous for their jumping powers, and in control measures it is
+of importance to determine their ability along this line. It is often
+stated that they can jump about four inches, or, according to the Indian
+Plague Commission _Xenopsylla cheopis_ cannot hop farther than five
+inches. Mitzmain (1910) conducted some careful experiments in which he
+found that the human flea, _Pulex irritans_, was able to jump as far as
+thirteen inches on a horizontal plane. The mean average of five
+specimens permitted to jump at will was seven and three-tenths inches.
+The same species was observed to jump perpendicularly to a height of at
+least seven and three-fourths inches. Other species were not able to
+equal this record.
+
+The effect of the bite of fleas on man varies considerably according to
+the individual susceptibility. According to Patton and Cragg, this was
+borne out in a curious manner by the experiments of Chick and Martin.
+"In these, eight human hosts were tried; in seven, little or no
+irritation was produced, while in one quite severe inflammation was set
+up around each bite." Of two individuals, equally accustomed to the
+insects, going into an infested room, one may be literally tormented by
+them while the other will not notice them. Indeed it is not altogether
+a question of susceptibility, for fleas seem to have a special
+predilection for certain individuals. The typical itching wheals
+produced by the bites are sometimes followed, especially after
+scratching, by inflammatory papules.
+
+The itching can be relieved by the use of lotions of carbolic acid (2-3
+per cent), camphor, menthol lotion, or carbolated vaseline. If forced to
+sleep in an infested room, protection from attacks can be in a large
+measure gained by sprinkling pyrethrum, bubach, or California insect
+powder between the sheets. The use of camphor, menthol, or oil of
+eucalyptus, or oil of pennyroyal is also said to afford protection to a
+certain extent.
+
+In the Eastern United States the occurrence of fleas as household pests
+is usually due to infested cats and dogs which have the run of the
+house. We have seen that the eggs are not attached to the host but drop
+to the floor when they are laid. Verrill, cited by Osborn, states that
+on one occasion he was able to collect fully a teaspoonful of eggs from
+the dress of a lady in whose lap a half-grown kitten had been held for a
+short time. Patton and Cragg record seeing the inside of a hat in which
+a kitten had spent the night, so covered with flea eggs that it looked
+"as if it had been sprinkled with sugar from a sifter." It is no wonder
+that houses in which pets live become overrun with the fleas.
+
+One of the first control measures, then, consists in keeping such
+animals out of the house or in rigorously keeping them free from fleas.
+The latter can best be accomplished by the use of strong tar soap or
+Armour's "Flesope," which may be obtained from most druggists. The use
+of a three per cent solution of creolin, approximately four teaspoonfuls
+to a quart of warm water, has also been recommended. While this is
+satisfactory in the case of dogs, it is liable to sicken cats, who will
+lick their fur in an effort to dry themselves. Howard recommends
+thoroughly rubbing into the fur a quantity of pyrethrum powder. This
+partially stupifies the fleas which should be promptly swept up and
+burned.
+
+He also recommends providing a rug for the dog or cat to sleep on and
+giving this rug a frequent shaking and brushing, afterwards sweeping up
+and burning the dust thus removed.
+
+Since the larvae of fleas are very susceptible to exposure, the use of
+bare floors, with few rugs, instead of carpets or matting, is to be
+recommended. Thorough sweeping, so as to allow no accumulation of dust
+in cracks and crevices will prove efficient. If a house is once
+infested it may be necessary to thoroughly scrub the floors with hot
+soapsuds, or to spray them with gasoline. If the latter method is
+adopted, care must be taken to avoid the possibility of fire.
+
+To clear a house of fleas Skinner recommends the use of flake
+naphthalene. In a badly infested house he took one room at a time,
+scattering on the floor five pounds of flake naphthalene, and closed it
+for twenty-four hours. It proved to be a perfect and effectual remedy
+and very inexpensive, as the naphthalene could be swept up and
+transferred to other rooms. Dr. Skinner adds, "so far as I am concerned,
+the flea question is solved and if I have further trouble I know the
+remedy. I intend to keep the dog and cat."
+
+The late Professor Slingerland very effectively used hydrocyanic acid
+gas fumigation in exterminating fleas in houses. In one case, where
+failure was reported, he found on investigation that the house had
+become thoroughly reinfested from pet cats, which had been left
+untreated. Fumigation with sulphur is likewise efficient.
+
+The fact that adult fleas are usually to be found on the floor, when not
+on their hosts, was ingeniously taken advantage of by Professor S. H.
+Gage in ridding an animal room at Cornell University of the pests. He
+swathed the legs of a janitor with sticky fly-paper and had him walk
+back and forth in the room. Large numbers of the fleas were collected in
+this manner.
+
+In some parts of the southern United States hogs are commonly infested
+and in turn infest sheds, barns and even houses. Mr. H. E. Vick informs
+us that it is a common practice to turn sheep into barn-lots and sheds
+in the spring of the year to collect in their wool, the fleas which
+abound in these places after the hogs have been turned out.
+
+It is a common belief that adult fleas are attracted to fresh meat and
+that advantage of this can be taken in trapping them. Various workers,
+notably Mitzman (1910), have shown that there is no basis for such a
+belief.
+
+
+THE TRUE CHIGGERS--The chigoes, or true chiggers, are the most
+completely parasitic of any of the fleas. Of the dozen or more known
+species, one commonly attacks man. This is _Dermatophilus penetrans_,
+more commonly known as _Sarcopsylla penetrans_ or _Pulex penetrans_.
+
+This species occurs in Mexico, the West Indies, Central and South
+America. There are no authentic records of its occurrence in the United
+States although, as Baker has pointed out, there is no reason why it
+should not become established in Florida and Texas. It is usually
+believed that Brazil was its original home. Sometime about the middle of
+the nineteenth century it was introduced into West Africa and has spread
+across that continent.
+
+The males and the immature females of _Dermatophilus penetrans_ (fig.
+93) closely resemble those of other fleas. They are very active little
+brown insects about 1-1.2 mm. in size, which live in the dust of native
+huts and stables, and in dry, sandy soil. In such places they often
+occur in enormous numbers and become a veritable plague.
+
+[Illustration: 93. Dermatophilus penetrans. Much enlarged. After
+Karsten.]
+
+They attack not only man but various animals. According to Castellani
+and Chalmers, "Perhaps the most noted feature is the way in which it
+attacks pigs. On the Gold Coast it appeared to be largely kept in
+existence by these animals. It is very easily captured in the free state
+by taking a little pig with a pale abdomen, and placing it on its back
+on the ground on which infected pigs are living. After watching a few
+moments, a black speck will appear on the pig's abdomen, and quickly
+another and another. These black specks are jiggers which can easily be
+transferred to a test tube. On examination they will be found to be
+males and females in about equal numbers."
+
+Both the males and females suck blood. That which characterizes this
+species as distinguished from other fleas attacking man is that when the
+impregnated female attacks she burrows into the skin and there swells
+until in a few days she has the size and appearance of a small pea (fig.
+94). Where they are abundant, hundreds of the pests may attack a single
+individual (fig. 95). Here they lie with the apex of the abdomen
+blocking the opening. According to Fulleborn (1908) they do not
+penetrate beneath the epidermis. The eggs are not laid in the flesh of
+the victim, as is sometimes stated, but are expelled through this
+opening. The female then dies, withers and falls away or is expelled by
+ulceration. According to Brumpt, she first quits the skin and then,
+falling to the ground, deposits her eggs. The subsequent development in
+so far as known, is like that of other fleas.
+
+[Illustration: 94. Dermatophilus penetrans, gravid female. After
+Moniez.]
+
+[Illustration: 95. Chiggers in the sole of foot of man. Manson's
+Tropical Diseases. Permission of Cassell and Co.]
+
+The chigoe usually enters between the toes, the skin about the roots of
+the nails, or the soles of the feet, although it may attack other parts
+of the body. Mense records the occurrence in folds of the epidermis, as
+in the neighborhood of the anus. They give rise to irritation and unless
+promptly and aseptically removed there often occurs pus formation and
+the development of a more or less serious abscess. Gangrene and even
+tetanus may ensue.
+
+Treatment consists in the careful removal of the insect, an operation
+more easily accomplished a day or two after its entrance, than at first,
+when it is unswollen. The ulcerated point should then be treated with
+weak carbolic acid, or tincture of iodine, or dusted thoroughly with an
+antiseptic powder.
+
+[Illustration: 96. Echidnophaga gallinacea.]
+
+[Illustration: 97. Echidnophaga gallinacea infesting head of chicken.
+After Enderlein.]
+
+Castellani and Chalmers recommend as prophylactic measures, keeping the
+house clean and keeping pigs, poultry, and cattle away therefrom. "High
+boots should be used, and especial care should be taken not to go to a
+ground floor bathroom with bare feet. The feet, especially the toes, and
+under the nails, should be carefully examined every morning to see if
+any black dots can be discovered, when the jigger should be at once
+removed, and in this way suppuration will be prevented. It is
+advisable, also, to sprinkle the floors with carbolic lotion, Jeyes'
+fluid, or with pyrethrum powder, or with a strong infusion of native
+tobacco, as recommended by Law and Castellani."
+
+_Echidnophaga gallinacea_ (fig. 96) is a widely distributed Hectopsyllid
+attacking poultry (fig. 97). It occurs in the Southern and Southwestern
+United States and has been occasionally reported as attacking man,
+especially children. It is less highly specialized than _Dermatophilus
+penetrans_, and does not ordinarily cause serious trouble in man.
+
+
+
+
+CHAPTER IV
+
+ACCIDENTAL OR FACULTATIVE PARASITES
+
+
+In addition to the many species of Arthropods which are normally
+parasitic on man and animals, there is a considerable number of those
+which may be classed as _accidental_ or _facultative_ parasites.
+
+Accidental or facultative parasites are species which are normally
+free-living, but which are able to exist as parasites when accidentally
+introduced into the body of man or other animal. A wide range of forms
+is included under this grouping.
+
+
+ACARINA
+
+A considerable number of mites have been reported as accidental or even
+normal, endoparasites of man, but the authentic cases are comparatively
+few.
+
+In considering such reports it is well to keep in mind von Siebold's
+warning that in view of the universal distribution of mites one should
+be on his guard. In vessels in which animal and other organic fluids and
+moist substances gradually dry out, mites are very abundantly found. If
+such vessels are used without very careful preliminary cleaning, for the
+reception of evacuations of the sick, or for the reception of parts
+removed from the body, such things may be readily contaminated by mites,
+which have no other relation whatever to them.
+
+Nevertheless, there is no doubt but that certain mites, normally
+free-living, have occurred as accidental parasites of man. Of these the
+most commonly met with is _Tyroglyphus siro_, the cheese-mite.
+
+_Tyroglyphus siro_ is a small mite of a whitish color. The male measures
+about 500u long by 250u wide, the female slightly larger. They live in
+cheese of almost any kind, especially such as is a little decayed. "The
+individuals gather together in winter in groups or heaps in the hollows
+and chinks of the cheese and there remain motionless. As soon as the
+temperature rises a little, they gnaw away at the cheese and reduce it
+to a powder. The powder is composed of excrement having the appearance
+of little grayish microscopic balls; eggs, old and new, cracked and
+empty; larvae, nymphs, and perfect mites, cast skins and fragments of
+cheese, to which must be added numerous spores of microscopic
+fungi."--Murray.
+
+_Tyroglyphus siro_, and related species, have been found many times in
+human feces, under conditions which preclude the explanation that the
+contamination occurred outside of the body. They have been supposed to
+be the cause of dysentery, or diarrhoea, and it is probable that the
+_Acarus dysenteriae_ of Linnaeus, and Latreille, was this species.
+However, there is little evidence that the mites cause any noteworthy
+symptoms, even when taken into the body in large numbers.
+
+_Histiogaster spermaticus_ (fig. 152) is a Tyroglyphid mite which was
+reported by Trouessart (1902) as having been found in a cyst in the
+groin, adherent to the testis. When the cyst was punctured, it yielded
+about two ounces of opalescent fluid containing spermatozoa and numerous
+mites in all stages of development. The evidence indicated that a
+fecundated female mite had been introduced into the urethra by means of
+an unclean catheter. Though Trouessart reported the case as that of a
+Sarcoptid, Banks places the genus _Histiogaster_ with the Tyroglyphidae.
+He states that our species feeds on the oyster-shell bark louse,
+possibly only after the latter is dead, and that in England a species
+feeds within decaying reeds.
+
+_Nephrophages sanguinarius_ is a peculiarly-shaped, angular mite which
+was found by Miyake and Scriba (1893) for eight successive days in the
+urine of a Japanese suffering from fibrinuria. Males, .117 mm. long by
+.079 mm. wide, females .36 mm. by. 12 mm., and eggs were found both in
+the spontaneously emitted urine and in that drawn by means of a
+catheter. All the mites found were dead. The describers regarded this
+mite as a true endoparasite, but it is more probable that it should be
+classed as an accidental parasite.
+
+
+MYRIAPODA
+
+There are on record a number of cases of myriapods occurring as
+accidental parasites of man. The subject has been treated in detail by
+Blanchard (1898 and 1902), who discussed forty cases. Since then at
+least eight additions have been made to the list.
+
+Neveau-Lamaire (1908) lists thirteen species implicated, representing
+eight different genera. Of the _Chilognatha_ there are three, _Julus
+terrestris_, _J. londinensis_ and _Polydesmus complanatus_. The
+remainder are _Chilopoda_, namely, _Lithobius forficatus_, _L.
+malenops_, _Geophilus carpophagus_, _G. electricus_, _G. similis_, _G.
+cephalicus_, _Scutigera coleoptrata_, _Himantarium gervaisi_,
+_Chaetechelyne vesuviana_ and _Stigmatogaster subterraneus_.
+
+The majority of the cases relate to infestation of the nasal fossae, or
+the frontal sinus, but intestinal infestation also occurs and there is
+one recorded case of the presence of a species in _Julus_ (fig. 13) in
+the auditory canal of a child.
+
+In the nose, the myriapods have been known to live for months and
+according to some records, even for years. The symptoms caused by their
+presence are inflammation, with or without increased flow of mucus,
+itching, more or less intense headache, and at times general symptoms
+such as vertigo, delirium, convulsions, and the like. These symptoms
+disappear suddenly when the parasites are expelled.
+
+In the intestine of man, myriapods give rise to obscure symptoms
+suggestive of infestation by parasitic worms. In a case reported by
+Verdun and Bruyant (1912), a child twenty months of age had been
+affected for fifteen days by digestive disturbances characterized by
+loss of appetite, nausea and vomiting. The latter had been particularly
+pronounced for three days, when there was discovered in the midst of the
+material expelled a living myriapod of the species _Chaetechelyne
+vesuviana_. Anthelminthics had been administered without result. In some
+of the other cases, the administration of such drugs had resulted in the
+expulsion of the parasite through the anus.
+
+One of the extreme cases on record is that reported by Shipley (1914).
+Specimens of _Geophilus gorizensis_ (= _G. subterraneus_) "were vomited
+and passed by a woman of 68 years of age. Some of the centipedes emerged
+through the patient's nose, and it must be mentioned that she was also
+suffering from a round worm. One of her doctors was of the opinion that
+the centipedes were certainly breeding inside the lady's intestines, and
+as many as seven or eight, sometimes more, were daily leaving the
+alimentary canal."
+
+"According to her attendant's statements those centipedes had left the
+body in some hundreds during a period of twelve or eighteen months.
+Their presence produced vomiting and some haematemesis, and treatment
+with thymol, male-fern and turpentine had no effect in removing the
+creatures."
+
+The clinical details, as supplied by Dr. Theodore Thompson were as
+follows:
+
+"Examined by me July, 1912, her tongue was dry and glazed. There was
+bleeding taking place from the nose and I saw a living centipede she had
+just extracted from her nostril. Her heart, lungs and abdomen appeared
+normal. She was not very wasted, and did not think she had lost much
+flesh, nor was there any marked degree of anemia."
+
+Shipley gives the following reasons for believing it impossible that
+these centipedes could have multiplied in the patient's intestine. "The
+breeding habits of the genus _Geophilus_ are peculiar, and ill adapted
+for reproducing in such a habitat. The male builds a small web or nest,
+in which he places his sperm, and the female fertilizes herself from
+this nest or web, and when the eggs are fertilized they are again laid
+in a nest or web in which they incubate and in two or three weeks hatch
+out. The young _Geophilus_ differ but very little from the adult, except
+in size. It is just possible, but improbable, that a clutch of eggs had
+been swallowed by the host when eating some vegetables or fruit, but
+against this is the fact that the _Geophilus_ does not lay its eggs upon
+vegetables or fruit, but upon dry wood or earth. The egg-shell is very
+tough and if the eggs had been swallowed the egg-shells could certainly
+have been detected if the dejecta were examined. The specimens of the
+centipede showed very little signs of being digested, and it is almost
+impossible to reconcile the story of the patient with what one knows of
+the habits of the centipedes."
+
+In none of the observed cases have there been any clear indications as
+to the manner of infestation. It is possible that the myriapods have
+been taken up in uncooked fruit or vegetables.
+
+
+LEPIDOPTEROUS LARVAE
+
+SCHOLECIASIS--Hope (1837) brought together six records of infestation of
+man by lepidopterous larvae and proposed to apply the name scholeciasis
+to this type of parasitism. The clearest case was that of a young boy
+who had repeatedly eaten raw cabbage and who vomited larvae of the
+cabbage butterfly, _Pieris brassicae_. Such cases are extremely rare, and
+there are few reliable data relative to the subject. In this connection
+it may be noted that Spuler (1906) has described a moth whose larvae live
+as ectoparasites of the sloth.
+
+
+COLEOPTERA
+
+CANTHARIASIS--By this term Hope designated instances of accidental
+parasitism by the larvae or adults of beetles. Reports of such cases
+are usually scouted by parasitologists but there seems no good basis for
+wholly rejecting them. Cobbold refers to a half dozen cases of
+accidental parasitism by the larvae of _Blaps mortisaga_. In one of
+these cases upwards of 1200 larvae and several perfect insects were
+said to have been passed _per annum_. French (1905) reports the case of
+a man who for a considerable period voided adult living beetles of the
+species _Nitidula bipustulata_. Most of the other cases on record relate
+to the larvae of _Dermestidae_ (larder beetles _et al._) or
+_Tenebrionidae_ (meal infesting species). Infestation probably occurs
+through eating raw or imperfectly cooked foods containing eggs or minute
+larvae of these insects.
+
+[Illustration: 98. Larva of Piophila casei. Caudal aspect of larva.
+Posterior stigmata.]
+
+Brumpt cites a curious case of accidental parasitism by a coleopterous
+larva belonging to the genus _Necrobia_. This larva was extracted from a
+small tumor, several millimeters long, on the surface of the conjunctiva
+of the eye. The larvae of this genus ordinarily live in decomposing flesh
+and cadavers.
+
+
+DIPTEROUS LARVAE
+
+[Illustration: 99. Piophila casei. After Graham-Smith.]
+
+MYASIS--By this term (spelled also myiasis, and myiosis), is meant
+parasitism by dipterous larvae. Such parasitism may be normal, as in the
+cases already described under the heading parasitic Diptera, or it may
+be facultative, due to free-living larvae being accidentally introduced
+into wounds or the body-cavities of man. Of this latter type, there is a
+multitude of cases on record, relating to comparatively few species. The
+literature of the subject, like that relating to facultative parasitism
+in general, is unsatisfactory, for most of the determinations of species
+have been very loose. Indeed, so little has been known regarding the
+characteristics of the larvae concerned that in many instances they could
+not be exactly determined. Fortunately, several workers have undertaken
+comparative studies along this line. The most comprehensive publication
+is that of Banks (1912), entitled "The structure of certain dipterous
+larvae, with particular reference to those in human food."
+
+Without attempting an exhaustive list, we shall discuss here the more
+important species of Diptera whose larvae are known to cause myasis,
+either external or internal. The following key will serve to determine
+those most likely to be encountered. The writers would be glad to
+examine specimens not readily identifiable, if accompanied by exact data
+relative to occurrence.
+
+_a._ Body more or less flattened, depressed; broadest in the middle,
+    each segment with dorsal, lateral, and ventral fleshy processes, of
+    which the laterals, at least, are more or less spiniferous (fig.
+    101). _Fannia_ (= _Homalomyia_).
+
+  In _F. canicularis_ the dorsal processes are nearly as long as the
+      laterals; in _F. scalaris_ the dorsal processes are short spinose
+      tubercles.
+
+_aa._ Body cylindrical, or slender conical tapering toward the head;
+    without fleshy lateral processes (fig. 105).
+
+_b._ With the posterior stigmata at the end of shorter or longer
+    tubercles, or if not placed upon tubercles, then not in pit; usually
+    without a "marginal button" and without a chitinous ring surrounding
+    the three slits; the slits narrowly or broadly oval, not bent (fig.
+    171 i). _Acalyptrate muscidae_ and some species of
+    _Anthomyiidae_. To this group belong the cheese skipper (_Piophila
+    casei_, figs. 98, 99), the pomace-fly (_Drosophila ampelophila_),
+    the apple maggot (_Rhagoletis pomonella_), the cherry fruit fly
+    (_Rhagoletis cingulata_), the small dung fly (_Sepsis violacea_,
+    fig. 170), the beet leaf-miner (_Pegomyia vicina_, fig. 171 i), the
+    cabbage, bean and onion maggots (_Phorbia_ spp.) et. al.
+
+_bb._ Posterior stigmata of various forms, if the slits are narrowly
+    oval (fig. 171) then they are surrounded by a chitin ring which may
+    be open ventro-mesally.
+
+_c._ Integument leathery and usually strongly spinulose; larvae
+    hypodermatic or endoparasitic. Bot flies (fig. 171, f, g,
+    k).--_Oestridae_
+
+_cc._ Integument not leathery and (except in _Protocalliphora_) spinulae
+    restricted to transverse patches near the incisures of the segments.
+
+_d._ The stigmal plates in a pit; the lip-like margin of the pit with a
+    number of fleshy tubercles; chitin ring of the stigma not complete;
+    open ventro-mesally, button absent (fig. 171 e). Flesh
+    flies.--_Sarcophaga_
+
+_dd._ Stigmata not in a pit.
+
+_e._ The chitin ring open ventra-mesally; button absent (fig. 171 c).
+    Screw-worm fly. _Chrysomyia_
+
+_ee._ The chitin ring closed.
+
+_f._ Slits of the posterior stigmata straight; marginal "button" present
+    (fig. 171 b); two distinct mouth hooks, fleshy tubercles around the
+    anal area. _Phormia_ (fig. 171 f), _Lucilia_ and _Calliphora_ (fig.
+    172, a, b), _Protocalliphora_ (fig. 171, j), _Cynomyia_ (fig. 171,
+    a). Blow flies, bluebottle flies. _Calliphorinae_
+
+_ff._ Slits of the posterior stigmata sinuous or bent. Subfamily
+    Muscinae.
+
+_g._ Slits of the posterior stigmata bent; usually two mouth hooks.
+    _Muscina stabulans_ (fig. 171, l), _Muscina similis_, _Myiospila
+    meditabunda_ (fig. 172, i), and some of the higher _Anthomyiidae_.
+
+_gg._ Slits of the posterior stigmata sinuous; mouth hooks usually
+    consolidated into one. The house-fly (_Musca domestica_ fig. 171,
+    d), the stable fly (_Stomoxys calcitrans_), the horn fly (_Lyperosia
+    irritans_), _Pyrellia_, _Pseudopyrellia_, _Morellia_, _Mesembrina_.
+    _Polietes_, et. al. (fig. 172 in part).
+
+_Eristalis_--The larvae of _Eristalis_ are the so-called rat-tailed
+maggots, which develop in foul water. In a few instances these larvae
+have been known to pass through the human alimentary canal uninjured.
+Hall and Muir (1913) report the case of a boy five years of age, who had
+been ailing for ten weeks and who was under treatment for indigestion
+and chronic constipation. For some time he had vomited everything he
+ate. On administration of a vermifuge he voided one of the rat-tailed
+maggots of _Eristalis_. He admitted having drunk water from a ditch full
+of all manner of rotting matter. It was doubtless through this that he
+became infested. It is worth noting that the above described symptoms
+may have been due to other organisms or substances in the filthy water.
+
+_Piophila casei_, the cheese-fly (fig. 99), deposits its eggs not only
+in old cheeses, but on ham, bacon, and other fats. The larvae (fig. 98)
+are the well-known cheese skippers, which sometimes occur in great
+abundance on certain kinds of cheese. Indeed, some people have a
+comfortable theory that such infested cheese is especially good. Such
+being the case, it is small wonder that this species has been repeatedly
+reported as causing intestinal myasis. Thebault (1901) describes the
+case of a girl who, shortly after consuming a large piece of badly
+infested cheese, became ill and experienced severe pains in the region
+of the navel. Later these extended through the entire alimentary canal,
+the excrement was mixed with blood and she suffered from vertigo and
+severe headaches. During the four following days the girl felt no
+change, although the excretion of the blood gradually diminished and
+stopped. On the fourth day she voided two half-digested larvae and,
+later, seven or eight, of which two were alive and moving.
+
+That these symptoms may be directly attributed to the larvae, or
+"skippers," has been abundantly shown by experimental evidence.
+Portschinsky cites the case of a dog fed on cheese containing the larvae.
+The animal suffered much pain and its excrement contained blood. On
+_post mortem_ it was found that the small intestine throughout almost
+its entire length was marked by bloody bruises. The papillae on these
+places were destroyed, although the walls were not entirely perforated.
+In the appendix were found two or three dead larvae. Alessandri (1910)
+has likewise shown that the larvae cause intestinal lesions.
+
+According to Graham-Smith, Austen (1912) has recorded a case of myasis
+of the nose, attended with a profuse watery discharge of several weeks
+duration and pain, due to the larvae of _Piophila casei_.
+
+
+ANTHYOMYIIDAE--The characteristic larvae of two species of _Fannia_ (=
+_Homalomyia_ or _Anthomyia_, in part) (fig. 101) are the most commonly
+reported of dipterous larvae causing intestinal myasis. Hewitt (1912) has
+presented a valuable study of the bionomics and of the larvae of these
+flies, a type of what is needed for all the species concerned in myasis.
+We have seen two cases of their having been passed in stools, without
+having caused any special symptoms. In other instances their presence in
+the alimentary canal has given rise to symptoms vaguely described as
+those of tapeworm infestation, or helminthiasis. More specifically, they
+have been described as causing vertigo, severe headache, nausea and
+vomiting, severe abdominal pains, and in some instances, bloody
+diarrhoea.
+
+[Illustration: 100. Fannia canicularis (x4). After Graham-Smith.]
+
+One of the most striking cases is that reported by Blankmeyer (1914), of
+a woman whose illness began fourteen years previously with nausea and
+vomiting. After several months of illness she began passing larvae and
+was compelled to resort to enemas. Three years previous to the report,
+she noticed frequent shooting pains in the rectal region and at times
+abdominal tenderness was marked. There was much mucus in the stools and
+she "experienced the sensation of larvae crawling in the intestine."
+Occipital headaches were marked, with remissions, and constipation
+became chronic. The appetite was variable, there was a bad taste in the
+mouth, tongue furred and ridged, and red at the edges. Her complexion
+was sallow, and general nervousness was marked. As treatment, there were
+given doses of magnesium sulphate before breakfast and at 4 P. M., with
+five grain doses of salol four times a day. The customary parasiticides
+yielded no marked benefit. At the time of the report the patient passed
+from four to fifty larvae per day, and was showing some signs of
+improvement. The nausea had disappeared, her nervousness was less
+evident, and there was a slight gain in weight.
+
+The case was complicated by various other disorders, but the symptoms
+given above seem to be in large part attributable to the myasis. There
+is nothing in the case to justify the assumption that larvae were
+continuously present, for years. It seems more reasonable to suppose
+that something in the habits of the patient favored repeated
+infestation. Nevertheless, a study of the various cases of intestinal
+myasis caused by these and other species of dipterous larvae seems to
+indicate that the normal life cycle may be considerably prolonged under
+the unusual conditions.
+
+The best authenticated cases of myasis of the urinary passage have been
+due to larvae of _Fannia_. Chevril (1909) collected and described twenty
+cases, of which seven seemed beyond doubt. One of these was that of a
+woman of fifty-five who suffered from albuminuria, and urinated with
+much difficulty, and finally passed thirty to forty larvae of _Fannia
+canicularis_.
+
+It is probable that infestation usually occurs through eating partially
+decayed fruit or vegetables on which the flies have deposited their
+eggs. Wellman points out that the flies may deposit their eggs in or
+about the anus of persons using outside privies and Hewitt believes that
+this latter method of infection is probably the common one in the case
+of infants belonging to careless mothers. "Such infants are sometimes
+left about in an exposed and not very clean condition, in consequence of
+which flies are readily attracted to them and deposit their eggs."
+
+[Illustration: 101. Larva of Fannia scalaris.]
+
+
+MUSCINAE--The larvae of the common house-fly, _Musca domestica_, are
+occasionally recorded as having been passed with the feces or vomit of
+man. While such cases may occur, it is probable that in most instances
+similar appearing larvae of other insects have been mistakenly
+identified.
+
+_Muscina stabulans_ is regarded by Portschinsky (1913) as responsible
+for many of the cases of intestinal myasis attributed to other species.
+He records the case of a peasant who suffered from pains in the lower
+part of the breast and intestines, and whose stools were mixed with
+blood. From November until March he had felt particularly ill, being
+troubled with nausea and vomiting in addition to the pain in his
+intestines. In March, his physician prescribed injections of a
+concentrated solution of tannin, which resulted in the expulsion of
+fifty living larvae of _Muscina stabulans_. Thereafter the patient felt
+much better, although he suffered from intestinal catarrh in a less
+severe form.
+
+[Illustration: 102 Muscina stabulans (x4). After Graham-Smith.]
+
+
+CALLIPHORINAE--Closely related to the Sarcophagidae are the
+_Calliphorinae_, to which group belong many of the so-called "blue
+bottle" flies. Their larvae feed upon dead animals, and upon fresh and
+cooked meat. Those of _Protocalliphora_, already mentioned, are
+ectoparasitic on living nestling birds. Larva of _Lucilia_, we have
+taken from tumors on living turtles. To this sub-family belongs also
+_Auchmeromyia luteola_, the Congo floor maggot. Some of these, and at
+least the last mentioned, are confirmed, rather than faculative
+parasites. Various species of Calliphorinae are occasionally met with as
+facultative parasites of man.
+
+[Illustration: 103. Lucilia caesar, (x3). After Howard.]
+
+_Chrysomyia macellaria_, the screw worm fly (fig. 107), is the fly which
+is responsible for the most serious cases of human myasis in the United
+States. It is widely distributed in the United States but is especially
+abundant in the south. While the larvae breed in decaying matter in
+general, they so commonly breed in the living flesh of animals that they
+merit rank as true parasites. The females are attracted to open wounds
+of all kinds on cattle and other animals and quickly deposit large
+numbers of eggs. Animals which have been recently castrated, dehorned,
+or branded, injured by barbed wire, or even by the attacks of ticks are
+promptly attacked in the regions where the fly abounds. Even the navel
+of young calves or discharges from the vulva of cows may attract the
+insect.
+
+[Illustration: 104. Calliphora erythrocephala, (x6). After
+Graham-Smith.]
+
+Not infrequently the fly attacks man, being attracted by an offensive
+breath, a chronic catarrh, or a purulent discharge from the ears. Most
+common are the cases where the eggs are deposited in the nostrils. The
+larvae, which are hatched in a day or two, are provided with strong
+spines and proceed to bore into the tissues of the nose, even down into
+or through the bone, into the frontal sinus, the pharynx, larynx, and
+neighboring parts.
+
+Osborn (1896) quotes a number of detailed accounts of the attacks of the
+_Chrysomyia_ on man. A vivid picture of the symptomology of rhinal
+myasis caused by the larvae of this fly is given by Castellani and
+Chalmers: "Some couple of days after a person suffering from a chronic
+catarrh, foul breath, or ozaena, has slept in the open or has been
+attacked by a fly when riding or driving,--_i.e._, when the hands are
+engaged--signs of severe catarrh appear, accompanied with inordinate
+sneezing and severe pain over the root of the nose or the frontal bone.
+Quickly the nose becomes swollen, and later the face also may swell,
+while examination of the nose may show the presence of the larvae. Left
+untreated, the patient rapidly becomes worse, and pus and blood are
+discharged from the nose, from which an offensive odor issues. Cough
+appears as well as fever, and often some delirium. If the patient lives
+long enough, the septum of the nose may fall in, the soft and hard
+palates may be pierced, the wall of the pharynx may be destroyed. By
+this time, however, the course of the disease will have become quite
+evident by the larvae dropping out of the nose, and if the patient
+continues to live all the larvae may come away naturally."
+
+For treatment of rhinal myasis these writers recommend douching the nose
+with chloroform water or a solution of chloroform in sweet milk (10-20
+per cent), followed by douches of mild antiseptics. Surgical treatment
+may be necessary.
+
+[Illustration: 105. Larva of a flesh fly (Sarcophaga). Caudal aspect.
+Anterior stigmata. Pharyngeal skeleton.]
+
+
+SARCOPHAGIDAE--The larvae (fig. 105) of flies of this family usually
+feed upon meats, but have been found in cheese, oleomargerine, pickled
+herring, dead and living insects, cow dung and human feces. Certain
+species are parasitic in insects. Higgins (1890) reported an instance of
+"hundreds" of larvae of _Sarcophaga_ being vomited by a child eighteen
+months of age. There was no doubt as to their origin for they were
+voided while the physician was in the room. There are many other reports
+of their occurrence in the alimentary canal. We have recorded elsewhere
+(Riley, 1906) a case in which some ten or twelve larvae of
+_Sarcophaga_ were found feeding on the diseased tissues of a malignant
+tumor. The tumor, a melanotic sarcoma, was about the size of a small
+walnut, and located in the small of the back of an elderly lady.
+Although they had irritated and caused a slight haemorrhage, neither the
+patient nor others of the family knew of their presence. Any discomfort
+which they had caused had been attributed to the sarcomatous growth. The
+infestation occurred in mid-summer. It is probable that the adult was
+attracted by the odor of the discharges and deposited the living maggots
+upon the diseased tissues.
+
+[Illustration: 106. A flesh fly (Sarcophaga), (x4). After Graham-Smith.]
+
+According to Kuchenmeister, _Sarcophaga carnaria_ (fig. 106), attracted
+by the odor, deposits its eggs and larvae in the vagina of girls and
+women when they lie naked in hot summer days upon dirty clothes, or when
+they have a discharge from the vagina. In malignant inflammations of the
+eyes the larvae even nestle under the eyelids and in Egypt, for example,
+produce a very serious addition to the effects of small-pox upon the
+cornea, as according to Pruner, in such cases perforation of the cornea
+usually takes place.
+
+[Illustration: 107. Chrysomyia macellaria, (x3).]
+
+_Wohlfartia magnifica_ is another Sarcophagid which commonly infests man
+in the regions where it is abundant. It is found in all Europe but is
+especially common in Russia, where Portschinsky has devoted much
+attention to its ravages. It deposits living larvae in wounds, the nasal
+fossae, the ears and the eyes, causing injuries even more revolting than
+those described for _Chrysomyia_.
+
+
+
+
+CHAPTER V
+
+ARTHROPODS AS SIMPLE CARRIERS OF DISEASE
+
+
+The fact that certain arthropods are poisonous, or may affect the health
+of man as direct parasites has always received attention in the medical
+literature. We come now to the more modern aspect of our subject,--the
+consideration of insects and other arthropods as transmitters and
+disseminators of disease.
+
+The simplest way in which arthropods may function in this capacity is as
+_simple carriers_ of pathogenic organisms. It is conceivable that any
+insect which has access to, and comes in contact with such organisms and
+then passes to the food, or drink, or to the body of man, may in a
+wholly accidental and incidental manner convey infection. That this
+occurs is abundantly proved by the work of recent years. We shall
+consider as typical the case against the house-fly, which has attracted
+so much attention, both popular and scientific. The excellent general
+treatises of Hewitt (1910), Howard (1911), and Graham-Smith (1913), and
+the flood of bulletins and popular literature render it unnecessary to
+consider the topic in any great detail.
+
+
+THE HOUSE-FLY AS A CARRIER OF DISEASE
+
+Up to the past decade the house-fly has usually been regarded as a mere
+pest. Repeatedly, however, it had been suggested that it might
+disseminate disease. We have seen that as far back as the sixteenth
+century, Mercurialis suggested that it was the agent in the spread of
+bubonic plague, and in 1658, Kircher reiterated this view. In 1871,
+Leidy expressed the opinion that flies were probably a means of
+communicating contagious diseases to a greater degree than was generally
+suspected. From what he had observed regarding gangrene in hospitals, he
+thought flies should be carefully excluded from wounds. In the same
+year, the editor of the _London Lancet_, referring to the belief that
+they play a useful role in purifying the air said, "Far from looking
+upon them as dipterous angels dancing attendance on Hygeia, regard them
+rather in the light of winged sponges spreading hither and thither to
+carry out the foul behests of Contagion."
+
+These suggestions attracted little attention from medical men, for it is
+only within very recent years that the charges have been supported by
+direct evidence. Before considering this evidence, it is necessary that
+we define what is meant by "house-fly" and that we then consider the
+life-history of the insect.
+
+There are many flies which are occasionally to be found in houses, but
+according to various counts, from 95 per cent to 99 per cent of these in
+warm weather in the Eastern United States belong to the one species
+_Musca domestica_ (fig. 108). This is the dominant house-fly the world
+over and is the one which merits the name. It has been well
+characterized by Schiner (1864), whose description has been freely
+translated by Hewitt, as follows:
+
+"Frons of male occupying a fourth part of the breadth of the head.
+Frontal stripe of female narrow in front, so broad behind that it
+entirely fills up the width of the frons. The dorsal region of the
+thorax dusty grey in color with four equally broad longitudinal stripes.
+Scutellum gray with black sides. The light regions of the abdomen
+yellowish, transparent, the darkest parts at least at the base of the
+ventral side yellow. The last segment and a dorsal line blackish brown.
+Seen from behind and against the light, the whole abdomen shimmering
+yellow, and only on each side of the dorsal line on each segment a dull
+transverse band. The lower part of the face silky yellow, shot with
+blackish brown. Median stripe velvety black. Antennae brown. Palpi black.
+Legs blackish brown. Wings tinged with pale gray with yellowish base.
+The female has a broad velvety back, often reddishly shimmering frontal
+stripe, which is not broader at the anterior end than at the bases of
+the antennae, but become so very much broader above that the light
+dustiness of the sides is entirely obliterated. The abdomen gradually
+becoming darker. The shimmering areas on the separate segments generally
+brownish. All the other parts are the same as in the male."
+
+The other species of flies found in houses in the Eastern United States
+which are frequently mistaken for the house or typhoid fly may readily
+be distinguished by the characters of the following key:
+
+_a._ Apical cell (R_5) of the wide wing open, i.e., the bounding veins
+    parallel or divergent (fig. 100). Their larvae are flattened, the
+    intermediate body segments each fringed with fleshy, more or less
+    spinose, processes. _Fannia_
+
+  b. Male with the sides of the second and third abdominal segments
+      translucent yellowish. The larva with three pairs of nearly equal
+      spiniferous appendages on each segment, arranged in a
+      longitudinal series and in addition two pairs of series of smaller
+      processes (fig. 100) _F. canicularis_
+
+  bb. Male with blackish abdomen, middle tibia with a tubercle beyond
+      the middle. The larva with spiniferous appendages of which the
+      dorsal and ventral series are short, the lateral series long and
+      feathered (fig. 101) _F. scalaris_
+
+aa. Apical cell (R) of the wing more or less narrowed in the margin; i.
+    e., the bounding veins more or less converging (fig. 108).
+
+  b. The mouth-parts produced and pointed, fitted for piercing.
+
+    c. Palpi much shorter than the proboscis; a brownish gray fly, its
+        thorax with three rather broad whitish stripes; on each border
+        of the middle stripe and on the mesal borders of the lateral
+        stripes is a blackish brown line. Abdomen yellowish brown; on
+        the second, third and fourth segments are three brown spots
+        which may be faint or even absent. The larvae live in dung. The
+        stable-fly (fig. 110) _Stomoxys calcitrans_
+
+    cc. Palpi nearly as long as the proboscis. Smaller species than the
+        house-fly. The horn-fly (fig. 167) _Haematobia irritans_
+
+  bb. Mouth-parts blunt, fitted for lapping.
+
+    c. Thorax, particularly on the sides and near the base of the wings
+        with soft golden yellow hairs among the bristles. This fly is
+        often found in the house in very early spring or even in the
+        winter. The cluster-fly, _Pollenia rudis_
+
+    cc. Thorax without golden yellow hairs among the bristles.
+
+      d. The last segment of the vein M with an abrupt angle. (fig.
+          108). The larvae live in manure, etc. House-fly, _Musca
+          domestica_
+
+      dd. The last segment of vein M with a broad, gentle curve (fig.
+          102).
+
+        e. Eyes microscopically hairy; each abdominal segment with two
+            spots. Larvae in dung. _Myiospila meditabunda_
+
+        ee. Eyes bare; abdomen gray and brown marbled. _Muscina_
+
+          f. With black legs and palpi. _M. assimilis_
+
+          ff. With legs more or less yellowish; palpi yellow. Larvae in
+              decaying vegetable substances, dung, etc. _M. stabulans_
+
+It is almost universally believed that the adults of _Musca domestica_
+hibernate, remaining dormant throughout the winter in attics, around
+chimneys, and in sheltered but cold situations. This belief has been
+challenged by Skinner (1913), who maintains that all the adult flies die
+off during the fall and early winter and that the species is carried
+over in the pupal stage, and in no other way. The cluster-fly, _Pollenia
+rudis_, undoubtedly does hibernate in attics and similar situations and
+is often mistaken for the house-fly. In so far as concerns _Musca
+domestica_, the important question as to hibernation in the adult stage
+is an open one. Many observations by one of the writers (Johannsen) tend
+to confirm Dr. Skinner's conclusion, in so far as it applies to
+conditions in the latitude of New York State. Opposed, is the fact that
+various experimenters, notably Hewitt (1910) and Jepson (1909) wholly
+failed to carry pupae through the winter.
+
+[Illustration: 108. The house or typhoid fly (Musca domestica (x4)).
+After Howard.]
+
+The house-fly breeds by preference in horse manure. Indeed, Dr. Howard,
+whose extensive studies of the species especially qualify him for
+expressing an opinion on the subject, has estimated that under ordinary
+city and town conditions, more than ninety per cent of the flies present
+in houses have come from horse stables or their vicinity. They are not
+limited to such localities, by any means, for it has been found that
+they would develop in almost any fermenting organic substance. Thus,
+they have been bred from pig, chicken, and cow manure, dirty waste
+paper, decaying vegetation, decaying meat, slaughter-house refuse,
+sawdust-sweepings, and many other sources. A fact which makes them
+especially dangerous as disease-carriers is that they breed readily in
+human excrement.
+
+The eggs are pure white, elongate ovoid, somewhat broader at the
+anterior end. They measure about one millimeter (1-25 inch) in length.
+They are deposited in small, irregular clusters, one hundred and twenty
+to one hundred and fifty from a single fly. A female may deposit as many
+as four batches in her life time. The eggs hatch in from eight to
+twenty-four hours.
+
+The newly hatched larva, or maggot (fig. 108), measures about two
+millimeters (1-12 inch) in length. It is pointed at the head end and
+blunt at the opposite end, where the spiracular openings are borne. It
+grows rapidly, molts three times and reaches maturity in from six to
+seven days, under favorable conditions.
+
+The pupal stage, like that of related flies, is passed in the old larval
+skin which, instead of being molted, becomes contracted and heavily
+chitinized, forming the so-called _puparium_ (fig. 108). The pupal stage
+may be completed in from three to six days.
+
+Thus during the warm summer months a generation of flies may be produced
+in ten to twelve days. Hewitt at Manchester, England, found the minimum
+to be eight days but states that larvae bred in the open air in horse
+manure which had an average daily temperature of 22.5^o C., occupied
+fourteen to twenty days in their development, according to the air
+temperature.
+
+After emergence, a period of time must elapse before the fly is capable
+of depositing eggs. This period has been tuned the _preoviposition_
+period. Unfortunately we have few exact data regarding this period.
+Hewitt found that the flies became sexually mature in ten to fourteen
+days after their emergence from the pupal state and four days after
+copulation they began to deposit their eggs; in other words the
+preoviposition stage was fourteen days or longer. Griffith (1908) found
+this period to be ten days. Dr. Howard believes that the time "must
+surely be shorter, and perhaps much shorter, under midsummer conditions,
+and in the freedom of the open air." He emphasizes that the point is of
+great practical importance, since it is during this period that the
+trapping and other methods of destroying the adult flies, will prove
+most useful.
+
+Howard estimates that there may be nine generations of flies a year
+under outdoor conditions in places comparable in climate to Washington.
+The number may be considerably increased in warmer climates.
+
+The rate at which flies may increase under favorable conditions is
+astounding. Various writers have given estimates of the numbers of flies
+which may develop as the progeny of a single individual, providing all
+the eggs and all the individual flies survived. Thus, Howard estimates
+that from a single female, depositing one hundred and twenty eggs on
+April 15th, there may be by September 10th, 5,598,720,000,000 adults.
+Fortunately, living forms do not produce in any such mathematical manner
+and the chief value of the figures is to illustrate the enormous
+struggle for existence which is constantly taking place in nature.
+
+Flies may travel for a considerable distance to reach food and shelter,
+though normally they pass to dwellings and other sources of food supply
+in the immediate neighborhood of their breeding places. Copeman, Howlett
+and Merriman (1911) marked flies by shaking them in a bag containing
+colored chalk. Such flies were repeatedly recovered at distances of
+eight to one thousand yards and even at a distance of seventeen hundred
+yards, nearly a mile.
+
+Hindle and Merriman (1914) continued these experiments on a large scale
+at Cambridge, England. They "do not think it likely that, as a rule,
+flies travel more than a quarter of a mile in thickly-housed areas." In
+one case a single fly was recovered at a distance of 770 yards but a
+part of this distance was across open fen-land. The surprising fact was
+brought out that flies tend to travel either _against_ or across the
+wind. The actual direction followed may be determined either directly by
+the action of the wind (positive anemotropism), or indirectly owing to
+the flies being attracted by any odor that it may convey from a source
+of food. They conclude that it is likely that the chief conditions
+favoring the disposal of flies are fine weather and a warm temperature.
+The nature of the locality is another considerable factor. Hodge (1913)
+has shown that when aided by the wind they may fly to much greater
+distances over the water. He reports that at Cleveland, Ohio, the cribs
+of the water works, situated a mile and a quarter, five miles, and six
+miles out in Lake Erie are invaded by a regular plague of flies when the
+wind blows from the city. Investigation showed that there was absolutely
+nothing of any kind in which flies could breed on the crib.
+
+The omnivorous habits of the house-fly are matters of everyday
+observation. From our view point, it is sufficient to emphasize that
+from feeding on excrement, on sputum, on open sores, or on putrifying
+matter, the flies may pass to the food or milk upon the table or to
+healthy mucous membranes, or uncontaminated wounds. There is nothing in
+its appearance to tell whether the fly that comes blithely to sup with
+you is merely unclean, or whether it has just finished feeding upon
+dejecta teeming with typhoid bacilli.
+
+[Illustration: 100. Pulvillus of foot of house-fly, showing glandular
+hairs.]
+
+The method of feeding of the house-fly has an important bearing on the
+question of its ability to transmit pathogenic organisms. Graham-Smith
+(1910) has shown that when feeding, flies frequently moisten soluble
+substances with "vomit" which is regurgitated from the crop. This is, of
+course, loaded with bacteria from previous food. When not sucked up
+again these drops of liquid dry, and produce round marks with an opaque
+center and rim and an intervening less opaque area. Fly-specks, then,
+consist of both vomit spots and feces. Graham-Smith shows a photograph
+of a cupboard window where, on an area six inches square, there were
+counted eleven hundred and two vomit marks and nine fecal deposits.
+
+From a bacteriologist's viewpoint a discussion of the possibility of a
+fly's carrying bacteria would seem superfluous. Any exposed object,
+animate or inanimate, is contaminated by bacteria and will transfer them
+if brought into contact with suitable culture media, whether such
+substance be food, or drink, open wounds, or the sterile culture media
+of the laboratory. A needle point may convey enough germs to produce
+disease. Much more readily may the house-fly with its covering of hairs
+and its sponge-like pulvilli (fig. 109) pick up and transfer bits of
+filth and other contaminated material.
+
+For popular instruction this inevitable transfer of germs by the
+house-fly is strikingly demonstrated by the oft copied illustration of
+the tracks of a fly on a sterile culture plate. Two plates of gelatine
+or, better, agar medium are prepared. Over one of these a fly (with
+wings clipped) is allowed to walk, the other is kept as a check. Both
+are put aside at room temperature, to be examined after twenty-four to
+forty-eight hours. At the end of that time, the check plate is as clear
+as ever, the one which the fly has walked is dotted with colonies of
+bacteria and fungi. The value in the experiment consists in emphasizing
+that by this method we merely render visible what is constantly
+occurring in nature.
+
+A comparable experiment which we use in our elementary laboratory work
+is to take three samples of _clean_ (preferably, sterile) fresh milk in
+sterile bottles. One of them is plugged with a pledget of cotton, into
+the second is dropped a fly from the laboratory and into the third is
+dropped a fly which has been caught feeding upon garbage or other filth.
+After a minute or two the flies are removed and the vials plugged as was
+number one. The three are then set aside at room temperature. When
+examined after twenty-four hours the milk in the first vial is either
+still sweet or has a "clean" sour odor; that of the remaining two is
+very different, for it has a putrid odor, which is usually more
+pronounced in the case of sample number three.
+
+Several workers have carried out experiments to determine the number of
+bacteria carried by flies under natural conditions. One of the most
+extended and best known of these is the series by Esten and Mason
+(1908). These workers caught flies from various sources in a sterilized
+net, placed them in a sterile bottle and poured over them a known
+quantity of sterilized water, in which they were shaken so as to wash
+the bacteria from their bodies. They found the number of bacteria on a
+single fly to range from 550 to 6,600,000. Early in the fly season the
+numbers of bacteria on flies are comparatively small, while later the
+numbers are comparatively very large. The place where flies live also
+determines largely the numbers that they carry. The lowest number, 550,
+was from a fly caught in the bacteriological laboratory, the highest
+number, 6,600,000 was the average from eighteen swill-barrel flies.
+Torrey (1912) made examination of "wild" flies from a tenement house
+district of New York City. He found "that the surface contamination of
+these 'wild' flies may vary from 570 to 4,400,000 bacteria per insect,
+and the intestinal bacterial content from 16,000 to 28,000,000."
+
+Less well known in this country is the work of Cox, Lewis, and Glynn
+(1912). They examined over four hundred and fifty naturally infected
+house-flies in Liverpool during September and early October. Instead of
+washing the flies they were allowed to swim on the surface of sterile
+water for five, fifteen, or thirty minutes, thus giving natural
+conditions, where infection occurs from vomit and dejecta of the flies,
+as well as from their bodies. They found, as might be expected, that
+flies from either insanitary or congested areas of the city contain far
+more bacteria than those from the more sanitary, less congested, or
+suburban areas. The number of aerobic bacteria from the former varied
+from 800,000 to 500,000,000 per fly and from the latter from 21,000 to
+100,000. The number of intestinal forms conveyed by flies from
+insanitary or congested areas was from 10,000 to 333,000,000 as compared
+with from 100 to 10,000 carried by flies from the more sanitary areas.
+
+Pathogenic bacteria and those allied to the food poisoning group were
+only obtained from the congested or moderately congested areas and not
+from the suburban areas, where the chances of infestation were less.
+
+The interesting fact was brought out that flies caught in milk shops
+apparently carry and obtain more bacteria than those from other shops
+with exposed food in a similar neighborhood. The writers explained this
+as probably due to the fact that milk when accessible, especially during
+the summer months, is suitable culture medium for bacteria, and the
+flies first inoculate the milk and later reinoculate themselves, and
+then more of the milk, so establishing a vicious circle.
+
+They conclude that in cities where food is plentiful flies rarely
+migrate from the locality in which they are bred, and consequently the
+number of bacteria which they carry depends upon the general standard
+of cleanliness in that locality. Flies caught in a street of modern,
+fairly high class, workmen's dwellings forming a sanitary oasis in the
+midst of a slum area, carried far less bacteria than those caught in the
+adjacent neighborhood.
+
+Thus, as the amount of dirt carried by flies in any particular locality,
+measured in the terms of bacteria, bears a definite relation to the
+habits of the people and to the state of the streets, it demonstrates
+the necessity of efficient municipal and domestic cleanliness, if the
+food of the inhabitants is to escape pollution, not only with harmless
+but also with occasional pathogenic bacteria.
+
+The above cited work is of a general nature, but, especially in recent
+years, many attempts have been made to determine more specifically the
+ability of flies to transmit pathogenic organisms. The critical reviews
+of Nuttall and Jepson (1909), Howard (1911), and Graham-Smith (1913)
+should be consulted by the student of the subject. We can only cite here
+a few of the more striking experiments.
+
+Celli (1888) fed flies on pure cultures of _Bacillus typhosus_ and
+declared that he was able to recover these organisms from the intestinal
+contents and excrement.
+
+Firth and Horrocks (1902), cited by Nuttall and Jepson, "kept _Musca
+domestica_ (also bluebottles) in a large box measuring 4 x 3 x 3 feet,
+with one side made of glass. They were fed on material contaminated with
+cultures of _B. typhosus_. Agar plates, litmus, glucose broth and a
+sheet of clean paper were at the same time exposed in the box. After a
+few days the plates and broth were removed and incubated with a positive
+result." Graham-Smith (1910) "carried out experiments with large numbers
+of flies kept in gauze cages and fed for eight hours on emulsions of _B.
+typhosus_ in syrup. After that time the infested syrup was removed and
+the flies were fed on plain syrup. _B. typhosus_ was isolated up to 48
+hours (but not later) from emulsions of their feces and from plates over
+which they walked."
+
+Several other workers, notably Hamilton (1903), Ficker (1903),
+Bertarelli (1910) Faichnie (1909), and Cochrane (1912), have isolated
+_B. typhosus_ from "wild" flies, naturally infected. The papers of
+Faichnie and of Cochrane we have not seen, but they are quoted in
+_extenso_ by Graham-Smith (1913).
+
+On the whole, the evidence is conclusive that typhoid germs not only may
+be accidentally carried on the bodies of house-flies but may pass
+through their bodies and be scattered in a viable condition in the feces
+of the fly for at least two days after feeding. Similar, results have
+been reached in experiments with cholera, tuberculosis and yaws, the
+last-mentioned being a spirochaete disease. Darling (1913) has shown that
+murrina, a trypanosome disease of horses and mules in the Canal zone is
+transmitted by house-flies which feed upon excoriated patches of
+diseased animals and then pass to cuts and galls of healthy animals.
+
+Since it is clear that flies are abundantly able to disseminate viable
+pathogenic bacteria, it is important to consider whether they have
+access to such organisms in nature. A consideration of the method of
+spread of typhoid will serve to illustrate the way in which flies may
+play an important role.
+
+Typhoid fever is a specific disease caused by _Bacillus typhosus_, and
+by it alone. The causative organism is to be found in the excrement and
+urine of patients suffering from the disease. More than that, it is
+often present in the dejecta for days, weeks, or even months and years,
+after the individual has recovered from the disease. Individuals so
+infested are known as "typhoid carriers" and they, together with those
+suffering from mild cases, or "walking typhoid," are a constant menace
+to the health of the community in which they are found.
+
+Human excrement is greedily visited by flies, both for feeding and for
+ovipositing. The discharges of typhoid patients, or of chronic
+"carriers," when passed in the open, in box privies, or camp latrines,
+or the like, serve to contaminate myriads of the insects which may then
+spread the germ to human food and drink. Other intestinal diseases may
+be similarly spread. There is abundant epidaemiological evidence that
+infantile diarrhoea, dysentery, and cholera may be so spread.
+
+Stiles and Keister (1913) have shown that spores of _Lamblia
+intestinalis_, a flagellate protozoan living in the human intestine, may
+be carried by house-flies. Though this species is not normally
+pathogenic, one or more species of _Entamoeba_ are the cause of a type
+of a highly fatal tropical dysentery. Concerning it, and another
+protozoan parasite of man, they say, "If flies can carry _Lamblia_
+spores measuring 10 to 7u, and bacteria that are much smaller, and
+particles of lime that are much larger, there is no ground to assume
+that flies may not carry _Entamoeba_ and _Trichomonas_ spores."
+
+Tuberculosis is one of the diseases which it is quite conceivable may be
+carried occasionally. The sputum of tubercular patients is very
+attractive to flies, and various workers, notably Graham-Smith, have
+found that _Musca domestica_ may distribute the bacillus for several
+days after feeding on infected material.
+
+A type of purulent opthalmia which is very prevalent in Egypt is often
+said to be carried by flies. Nuttall and Jepson (1909) consider that the
+evidence regarding the spread of this disease by flies is conclusive and
+that the possibility of gonorrhoeal secretions being likewise conveyed
+cannot be denied.
+
+Many studies have been published, showing a marked agreement between the
+occurrence of typhoid and other intestinal diseases and the prevalence
+of house-flies. The most clear-cut of these are the studies of the Army
+Commission appointed to investigate the cause of epidemics of enteric
+fever in the volunteer camps in the Southern United States during the
+Spanish-American War. Though their findings as presented by Vaughan
+(1909), have been quoted very many times, they are so germane to our
+discussion that they will bear repetition:
+
+"Flies swarmed over infected fecal matter in the pits and fed upon the
+food prepared for the soldiers in the mess tents. In some instances
+where lime had recently been sprinkled over the contents of the pits,
+flies with their feet whitened with lime were seen walking over the
+food." Under such conditions it is no wonder that "These pests had
+inflicted greater loss upon American soldiers than the arms of Spain."
+
+Similar conditions prevailed in South Africa during the Boer War. Seamon
+believes that very much of the success of the Japanese in their fight
+against Russia was due to the rigid precautions taken to prevent the
+spread of disease by these insects and other means.
+
+Veeder has pointed out that the characteristics of a typical fly-borne
+epidemic of typhoid are that it occurs in little neighborhood epidemics,
+extending by short leaps from house to house, without regard to water
+supply or anything else in common. It tends to follow the direction of
+prevailing winds (cf. the conclusions of Hindle and Merriman). It occurs
+during warm weather. Of course, when the epidemic is once well under
+way, other factors enter into its spread.
+
+In general, flies may be said to be the chief agency in the spread of
+typhoid in villages and camps. In cities with modern sewer systems they
+are less important, though even under the best of such conditions, they
+are important factors. Howard has emphasized that in such cities there
+are still many uncared-for box privies and that, in addition, the
+deposition of feces overnight in uncared-for waste lots and alleys is
+common.
+
+Not only unicellular organisms, such as bacteria and protozoa, but also
+the eggs, embryos and larvae of parasitic worms have been found to be
+transported by house-flies. Ransom (1911) has found that _Habronema
+muscae_, a nematode worm often found in adult flies, is the immature
+stage of a parasite occurring in the stomach of the horse. The eggs or
+embryos passing out with the feces of the horse, are taken up by fly
+larvae and carried over to the imago stage.
+
+Grassi (1883), Stiles (1889), Calandruccio (1906), and especially Nicoll
+(1911), have been the chief investigators of the ability of house-flies
+to carry the ova and embryos of human intestinal parasites. Graham-Smith
+(1913) summarizes the work along this line as follows:
+
+"It is evident from the investigations that have been quoted that
+house-flies and other species are greatly attracted to the ova of
+parasitic worms contained in feces and other materials, and make great
+efforts to ingest them. Unless the ova are too large they often succeed,
+and the eggs are deposited uninjured in their feces, in some cases up to
+the third day at least. The eggs may also be carried on their legs or
+bodies. Under suitable conditions, food and fluids may be contaminated
+with the eggs of various parasitic worms by flies, and in one case
+infection of the human subject has been observed. Feces containing
+tape-worm segments may continue to be a source of infection for as long
+as a fortnight. Up to the present, however, there is no evidence to show
+what part flies play in the dissemination of parasitic worms under
+natural conditions."
+
+Enough has been said to show that the house-fly must be dealt with as a
+direct menace to public health. Control measures are not merely matters
+of convenience but are of vital importance.
+
+Under present conditions the speedy elimination of the house-fly is
+impossible and the first thing to be considered is methods of protecting
+food and drink from contamination. The first of these methods is the
+thorough screening of doors and windows to prevent the entrance of
+flies. In the case of kitchen doors, the flies, attracted by odors, are
+likely to swarm onto the screen and improve the first opportunity for
+gaining an entrance. This difficulty can be largely avoided by
+screening-in the back porch and placing the screen door at one end
+rather than directly before the door.
+
+The use of sticky fly paper to catch the pests that gain entrance to the
+house is preferable to the various poisons often used. Of the latter,
+formalin (40 per cent formaldehyde) in the proportion of two
+tablespoonfuls to a pint of water is very efficient, if all other
+liquids are removed or covered, so that the flies must depend on the
+formalin for drink. The mixture is said to be made more attractive by
+the addition of sugar or milk, though we have found the plain solution
+wholly satisfactory, under proper conditions. It should be emphasized
+that this formalin mixture is not perfectly harmless, as so often
+stated. There are on record cases of severe and even fatal poisoning
+from the accidental drinking of solutions.
+
+When flies are very abundant in a room they can be most readily gotten
+rid of by fumigation with sulphur, or by the use of pure pyrethrum
+powder either burned or puffed into the air. Herrick (1913) recommends
+the following method: "At night all the doors and windows of the kitchen
+should be closed; fresh powder should be sprinkled over the stove, on
+the window ledges, tables, and in the air. In the morning flies will be
+found lying around dead or stupified. They may then be swept up and
+burned." This method has proved very efficaceous in some of the large
+dining halls in Ithaca.
+
+The writers have had little success in fumigating with the vapors of
+carbolic acid, or carbolic acid and gum camphor, although these methods
+will aid in driving flies from a darkened room.
+
+All of these methods are but makeshifts. As Howard has so well put it,
+"the truest and simplest way of attacking the fly problem is to prevent
+them from breeding, by the treatment or abolition of all places in which
+they can breed. To permit them to breed undisturbed and in countless
+numbers, and to devote all our energy to the problem of keeping them out
+of our dwellings, or to destroy them after they have once entered in
+spite of all obstacles, seems the wrong way to go about it."
+
+We have already seen that _Musca domestica_ breeds in almost any
+fermenting organic material. While it prefers horse manure, it breeds
+also in human feces, cow dung and that of other animals, and in refuse
+of many kinds. To efficiently combat the insect, these breeding places
+must be removed or must be treated in some such way as to render them
+unsuitable for the development of the larvae. Under some conditions
+individual work may prove effective, but to be truly efficient there
+must be extensive and thorough cooperative efforts.
+
+Manure, garbage, and the like should be stored in tight receptacles and
+carted away at least once a week. The manure may be carted to the fields
+and spread. Even in spread manure the larvae may continue their
+development. Howard points out that "it often happens that after a lawn
+has been heavily manured in early summer the occupants of the house will
+be pestered with flies for a time, but finding no available breeding
+place these disappear sooner or later. Another generation will not breed
+in the spread manure."
+
+Hutchinson (1914) has emphasized that the larvae of houseflies have
+deeply engrained the habit of migrating in the prepupal stage and has
+shown that this offers an important point of attack in attempts to
+control the pest. He has suggested that maggot traps might be developed
+into an efficient weapon in the warfare against the house-fly. Certain
+it is that the habit greatly simplifies the problem of treating the
+manure for the purpose of killing the larvae.
+
+There have been many attempts to find some cheap chemical which would
+destroy fly larvae in horse manure without injuring the bacteria or
+reducing the fertilizing values of the manure. The literature abounds in
+recommendations of kerosene, lime, chloride of lime, iron sulphate, and
+other substances, but none of them has met the situation. The whole
+question has been gone into thoroughly by Cook, Hutchinson and Scales
+(1914), who tested practically all of the substances which have been
+recommended. They find that by far the most effective, economical, and
+practical of the substances is borax in the commercial form in which it
+is available throughout the country.
+
+"Borax increases the water-soluble nitrogen, ammonia and alkalinity of
+manure and apparently does not permanently injure the bacterial flora.
+The application of manure treated with borax at the rate of 0.62 pound
+per eight bushels (10 cubic feet) to soil does not injure the plants
+thus far tested, although its cumulative effect, if any, has not been
+determined."
+
+As their results clearly show that the substances so often recommended
+are inferior to borax, we shall quote in detail their directions for
+treating manure so as to kill fly eggs and maggots.
+
+"Apply 0.62 pound borax or 0.75 pound calcined colemanite to every 10
+cubic feet (8 bushels) of manure immediately on its removal from the
+barn. Apply the borax particularly around the outer edges of the pile
+with a flour sifter or any fine sieve, and sprinkle two or three gallons
+of water over the borax-treated manure.
+
+"The reason for applying the borax to the fresh manure immediately after
+its removal from the stable is that the flies lay their eggs on the
+fresh manure, and borax, when it comes in contact with the eggs,
+prevents their hatching. As the maggots congregate at the outer edge of
+the pile, most of the borax should be applied there. The treatment
+should be repeated with each addition of fresh manure, but when the
+manure is kept in closed boxes, less frequent applications will be
+sufficient. When the calcined colemanite is available, it may be used at
+the rate of 0.75 pound per 10 cubic feet of manure, and is a cheaper
+means of killing the maggots. In addition to the application of borax to
+horse manure to kill fly larvae, it may be applied in the same proportion
+to other manures, as well as to refuse and garbage. Borax may also be
+applied to the floors and crevices in barns, stables, markets, etc., as
+well as to street sweepings, and water should be added as in the
+treatment of horse manure. After estimating the amount of material to be
+treated and weighing the necessary amount of borax, a measure may be
+used which will hold the proper amount, thus avoiding the subsequent
+weighings.
+
+"While it can be safely stated that no injurious action will follow the
+application of manure treated with borax at the rate of 0.62 pound for
+eight bushels, or even larger amounts in the case of some plants,
+nevertheless the borax-treated manure has not been studied in connection
+with the growth of all crops, nor has its cumulative effect been
+determined. It is therefore recommended that not more than 15 tons per
+acre of the borax-treated manure should be applied to the field. As
+truckmen use considerably more than this amount, it is suggested that
+all cars containing borax-treated manure be so marked, and that
+public-health officials stipulate in their directions for this treatment
+that not over 0.62 pound for eight bushels of manure be used, as it has
+been shown that larger amounts of borax will injure most plants. It is
+also recommended that all public-health officials and others, in
+recommending the borax treatment for killing fly eggs and maggots in
+manure, warn the public against the injurious effects of large amounts
+of borax on the growth of plants."
+
+"The amount of manure from a horse varies with the straw or other
+bedding used, but 12 or 15 bushels per week represent the approximate
+amount obtained. As borax costs from five to six cents per pound in
+100-pound lots in Washington, it will make the cost of the borax
+practically one cent per horse, per day. And if calcined colemanite is
+purchased in large shipments the cost should be considerably less."
+
+Hodge (1910) has approached the problem of fly extermination from
+another viewpoint. He believes that it is practical to trap flies out of
+doors during the preoviposition period, when they are sexually immature,
+and to destroy such numbers of them that the comparatively few which
+survive will not be able to lay eggs in sufficient numbers to make the
+next generation a nuisance. To the end of capturing them in enormous
+numbers he has devised traps to be fitted over garbage cans, into stable
+windows, and connected with the kitchen window screens. Under some
+conditions this method of attack has proved very satisfactory.
+
+One of the most important measures for preventing the spread of disease
+by flies is the abolition of the common box privy. In villages and rural
+districts this is today almost the only type to be found. It is the
+chief factor in the spread of typhoid and other intestinal diseases, as
+well as intestinal parasites. Open and exposed to myriads of flies which
+not only breed there but which feed upon the excrement, they furnish
+ideal conditions for spreading contamination. Even where efforts are
+made to cover the contents with dust, or ashes, or lime, flies may
+continue to breed unchecked. Stiles and Gardner have shown that
+house-flies buried in a screened stand-pipe forty-eight inches under
+sterile sand came to the surface. Other flies of undetermined species
+struggled up through seventy-two inches of sand.
+
+So great is the menace of the ordinary box privy that a number of
+inexpensive and simple sanitary privies have been designed for use where
+there are not modern sewer systems. Stiles and Lumsden (1911) have given
+minute directions for the construction of one of the best types, and
+their bulletin should be obtained by those interested.
+
+Another precaution which is of fundamental importance in preventing the
+spread of typhoid, is that of disinfecting all discharges from patients
+suffering with the disease. For this purpose, quick-lime is the cheapest
+and is wholly satisfactory. In chamber vessels it should be used in a
+quantity equal to that of the discharge to be treated. It should be
+allowed to act for two hours. Air-slaked lime is of no value whatever.
+Chloride of lime, carbolic acid, or formalin may be used, but are more
+expensive. Other intestinal diseases demand similar precautions.
+
+
+STOMOXYS CALCITRANS, THE STABLE-FLY--It is a popular belief that
+house-flies bite more viciously just before a rain. As a matter of
+fact, the true house-flies never bite, for their mouth-parts are not
+fitted for piercing. The basis of the misconception is the fact that a
+true biting fly, _Stomoxys calcitrans_ (fig. 110), closely resembling
+the house-fly, is frequently found in houses and may be driven in in
+greater numbers by muggy weather. From its usual habitat this fly is
+known as the "stable-fly" or, sometimes as the "biting house-fly."
+
+_Stomoxys calcitrans_ may be separated from the house-fly by the use of
+the key on p. 145. It may be more fully characterized as follows:
+
+The eyes of the male are separated by a distance equal to one-fourth of
+the diameter of the head, in the female by one-third. The frontal stripe
+is black, the cheeks and margins of the orbits silvery-white. The
+antennae are black, the arista feathered on the upper side only. The
+proboscis is black, slender, fitted for piercing and projects forward in
+front of the head. The thorax is grayish, marked by four conspicuous,
+more or less complete black longitudinal stripes; the scutellum is
+paler; the macrochaetae are black. The abdomen is gray, dorsally with
+three brown spots on the second and third segments and a median spot on
+the fourth. These spots are more pronounced in the female. The legs are
+black, the pulvilli distinct. The wings are hyaline, the vein M_{1+2}
+less sharply curved than in the house-fly, the apical cell being thus
+more widely open (cf. fig. 110). Length 7 mm.
+
+[Illustration: 110. Stomoxys calcitrans; adult, larva, puparium and
+details, (x5). After Howard.]
+
+This fly is widely distributed, being found the world over. It was
+probably introduced into the United States, but has spread to all parts
+of the country. Bishopp (1913) regards it as of much more importance as
+a pest of domestic animals in the grain belt than elsewhere in the
+United States. The life-history and habits of this species have assumed
+a new significance since it has been suggested that it may transmit the
+human diseases, infantile paralysis and pellagra. In this country, the
+most detailed study of the fly is that of Bishopp (1913) whose data
+regarding the life cycle are as follows:
+
+The eggs like those of the house-fly, are about one mm. in length. Under
+a magnifying glass they show a distinct furrow along one side. When
+placed on any moist substance they hatch in from one to three days after
+being deposited.
+
+The larva or maggots (fig. 110) have the typical shape and actions of
+most maggots of the Muscid group. They can be distinguished from those
+of the house-fly as the stigma-plates are smaller, much further apart,
+with the slits less sinuous. Development takes place fairly rapidly when
+the proper food conditions are available and the growth is completed
+within eleven to thirty or more days.
+
+The pupa (fig. 110), like that of related flies, undergoes its
+development within the contracted and hardened last larval skin, or
+puparium. This is elongate oval, slightly thicker towards the head end,
+and one-sixth to one-fourth of an inch in length. The pupal stage
+requires six to twenty days, or in cool weather considerably longer.
+
+The life-cycle of the stable-fly is therefore considerably longer than
+that of _Musca domestica_. Bishopp found that complete development might
+be undergone in nineteen days, but that the average period was somewhat
+longer, ranging from twenty-one to twenty-five days, where conditions
+are very favorable. The longest period which he observed was forty-three
+days, though his finding of full grown larvae and pupae in straw during
+the latter part of March, in Northern Texas, showed that development may
+require about three months, as he considered that these stages almost
+certainly developed from eggs deposited the previous December.
+
+The favorite breeding place, where available, seems to be straw or
+manure mixed with straw. It also breeds in great numbers in
+horse-manure, in company with _Musca domestica_.
+
+Newstead considers that in England the stable-fly hibernates in the
+pupal stage. Bishopp finds that in the southern part of the United
+States there is no true hibernation, as the adults have been found to
+emerge at various times during the winter. He believes that in the
+northern United States the winter is normally passed in the larval and
+pupal stages, and that the adults which have been observed in heated
+stables in the dead of winter were bred out in refuse within the warm
+barns and were not hibernating adults.
+
+Graham-Smith (1913) states that although the stable-fly frequents stable
+manure, it is probably not an important agent in distributing the
+organisms of intestinal diseases. Bishopp makes the important
+observation that "it has never been found breeding in human excrement
+and does not frequent malodorous places, which are so attractive to the
+house-fly. Hence it is much less likely to carry typhoid and other germs
+which may be found in such places."
+
+Questions of the possible agency of _Stomoxys calcitrans_ in the
+transmission of infantile paralysis and of pellagra, we shall consider
+later.
+
+
+OTHER ARTHROPODS WHICH MAY SERVE AS SIMPLE CARRIERS OF PATHOGENIC
+ORGANISMS--It should be again emphasized that any insect which has
+access to, and comes in contact with, pathogenic organisms and then
+passes to the food, or drink, or the body of man, may serve as a simple
+carrier of disease. In addition to the more obvious illustrations, an
+interesting one is the previously cited case of the transfer of
+_Dermatobia cyaniventris_ by a mosquito (fig. 81-84). Darling (1913) has
+shown that in the tropics, the omnipresent ants may be important factors
+in the spread of disease.
+
+
+
+
+CHAPTER VI
+
+ARTHROPODS AS DIRECT INOCULATORS OF DISEASE GERMS
+
+
+We have seen that any insect which, like the house-fly, has access to
+disease germs and then comes into contact with the food or drink of man,
+may serve to disseminate disease. Moreover, it has been clearly
+established that a contaminated insect, alighting upon wounded or
+abraded surfaces, may infect them. These are instances of mere
+accidental, mechanical transfer of pathogenic organisms.
+
+Closely related are the instances of direct inoculation of disease germs
+by insects and other arthropods. In this type, a blood-sucking species
+not only takes up the germs but, passing to a healthy individual, it
+inserts its contaminated mouth-parts and thus directly inoculates its
+victim. In other words, the disease is transferred just as blood
+poisoning may be induced by the prick of a contaminated needle, or as
+the laboratory worker may inoculate an experimental animal.
+
+Formerly, it was supposed that this method of the transfer of disease by
+arthropods was a very common one and many instances are cited in the
+earlier literature of the subject. It is, however, difficult to draw a
+sharp line between such cases and those in which, on the one hand, the
+arthropod serves as a mere passive carrier or, on the other hand, serves
+as an essential host of the pathogenic organism. More critical study of
+the subject has led to the belief that the importance of the role of
+arthropods as direct inoculators has been much overestimated.
+
+The principal reason for regarding this phase of the subject as
+relatively unimportant, is derived from a study of the habits of the
+blood-sucking species. It is found that, in general, they are
+intermittent feeders, visiting their hosts at intervals and then
+abstaining from feeding for a more or less extended period, while
+digesting their meal. In the meantime, most species of bacteria or of
+protozoan parasites with which they might have contaminated their
+mouth-parts, would have perished, through inability to withstand drying.
+
+In spite of this, it must be recognized that this method of transfer
+does occur and must be reckoned with in any consideration of the
+relations of insects to disease. We shall first cite some general
+illustrations and shall then discuss the role of fleas in the spreading
+of bubonic plague, an illustration which cannot be regarded as typical,
+since it involves more than mere passive carriage.
+
+
+SOME ILLUSTRATIONS OF DIRECT INOCULATION OF DISEASE GERMS BY ARTHROPODS
+
+In discussing poisonous arthropods, we have already emphasized that
+species which are of themselves innocuous to man, may occasionally
+introduce bacteria by their bite or sting and thus cause more or less
+severe secondary symptoms. That such cases should occur, is no more than
+is to be expected. The mouth-parts or the sting of the insect are not
+sterile and the chances of their carrying pyogenic organisms are always
+present.
+
+More strictly falling in the category of transmission of disease germs
+by direct inoculation are the instances where the insect, or related
+form, feeds upon a diseased animal and passes promptly to a healthy
+individual which it infects. Of such a nature are the following:
+
+Various species of biting flies are factors in the dissemination of
+anthrax, an infectious and usually fatal disease of animals and,
+occasionally, of man. That the bacteria with which the blood of diseased
+animals teem shortly before death might be transmitted by such insects
+has long been contended, but the evidence in support of the view has
+been unsatisfactory. Recently, Mitzmain (1914) has reported a series of
+experiments which show conclusively that the disease may be so conveyed
+by a horse-fly, _Tabanus striatus_, and by the stable-fly, _Stomoxys
+calcitrans_.
+
+Mitzmain's experiments were tried with an artificially infected guinea
+pig, which died of the disease upon the third day. The flies were
+applied two and one-half hours, to a few minutes, before the death of
+the animal. With both species the infection was successfully transferred
+to healthy guinea pigs by the direct method, in which the flies were
+interrupted while feeding on the sick animal. The evidence at hand does
+not warrant the conclusion that insect transmission is the rule in the
+case of this disease.
+
+The nagana, or tsetse-fly disease of cattle is the most virulent disease
+of domestic animals in certain parts of Africa. It is caused by a
+protozoan blood parasite, _Trypanosoma brucei_, which is conveyed to
+healthy animals by the bite of _Glossina morsitans_ and possibly other
+species of tsetse-flies. The flies remain infective for forty-eight
+hours after feeding on a diseased animal. The insect also serves as an
+essential host of the parasite.
+
+Surra, a similar trypanosomiasis affecting especially horses and mules,
+occurs in southern Asia, Malaysia, and the Philippines where the
+tsetse-flies are not to be found. It is thought to be spread by various
+species of blood-sucking flies belonging to the genera _Stomoxys_,
+_Haematobia_, and _Tabanus_. Mitzmain (1913) demonstrated that in the
+Philippines it is conveyed mechanically by _Tabanus striatus_.
+
+The sleeping sickness of man, in Africa, has also been supposed to be
+directly inoculated by one, or several, species of tsetse-flies. It is
+now known that the fly may convey the disease for a short time after
+feeding, but that there is then a latent period of from fourteen to
+twenty-one days, after which it again becomes infectious. This indicates
+that in the meantime the parasite has been undergoing some phase of its
+life-cycle and that the fly serves as an intermediate host. We shall
+therefore consider it more fully under that grouping.
+
+These are a few of the cases of direct inoculation which may be cited as
+of the simpler type. We shall next consider the role of the flea in the
+dissemination of the bubonic plague, an illustration complicated by the
+fact that the bacillus multiples within the insect and may be indirectly
+inoculated.
+
+
+THE ROLE OF FLEAS IN THE TRANSMISSION OF THE PLAGUE
+
+The plague is a specific infectious disease caused by _Bacillus pestis_.
+It occurs in several forms, of which the bubonic and the pneumonic are
+the most common. According to Wyman, 80 per cent of the human cases are
+of the bubonic type. It is a disease which, under the name of oriental
+plague, the pest, or the black death, has ravaged almost from time
+immemorial the countries of Africa, Asia, and Europe. The record of its
+ravages are almost beyond belief. In 542 A. D. it caused in one day ten
+thousand deaths in Constantinople. In the 14th century it was introduced
+from the East and prevailed throughout Armenia, Asia Minor, Egypt and
+Northern Africa and Europe. Hecker estimates that one-fourth of the
+population of Europe, or twenty-five million persons, died in the
+epidemic of that century. From then until the 17th century it was almost
+constantly present in Europe, the great plague of London, in 1665
+killing 68,596 out of a population of 460,000. Such an epidemic would
+mean for New York City a proportionate loss of over 600,000 in a single
+year. It is little wonder that in the face of such an appalling disaster
+suspicion and credulity were rife and the wildest demoralization ensued.
+
+During the 14th century the Jews were regarded as responsible for the
+disease, through poisoning wells, and were subjected to the most
+incredible persecution and torture. In Milan the visitation of 1630 was
+credited to the so-called anointers,--men who were supposed to spread
+the plague by anointing the walls with magic ointment--and the most
+horrible tortures that human ingenuity could devise were imposed on
+scores of victims, regardless of rank or of public service (fig. 112,
+a). Manzoni's great historical novel, "The Betrothed" has well pictured
+conditions in Italy during this period.
+
+[Illustration: 111. A contemporaneous engraving of the pest hospital in
+Vienna in 1679. After Peters.]
+
+In modern times the plague is confined primarily to warm climates, a
+condition which has been brought about largely through general
+improvement in sanitary conditions.
+
+At present, the hotbed of the disease is India, where there were
+1,040,429 deaths in 1904 and where in a period of fifteen years, ending
+with January 1912, there were over 15,000,000 deaths. The reported
+deaths in that country for 1913 totaled 198,875.
+
+During the winter of 1910-11 there occurred in Manchuria and North China
+a virulent epidemic of the pneumonic plague which caused the death of
+nearly 50,000 people. The question as to its origin and means of spread
+will be especially referred to later.
+
+[Illustration: 112 a. A medieval method of combating the plague. The
+persecution of the anointers in Milan in 1630. From a copy of "Il
+processi originale degli untori" in the library of Cornell University.]
+
+Until recent years, the plague had not been known to occur in the New
+World but there were outbreaks in Brazil and Hawaii in 1899, and in 1900
+there occurred the first cases in San Francisco. In California there
+were 125 cases in the period 1900-04; three cases in the next three
+years and then from May 1907 to March 1908, during the height of the
+outbreak, 170 cases. Since that time there have been only sporadic
+cases, the last case reported being in May 1914. Still more recent were
+the outbreaks in the Philippine Islands, Porto Rico, and Cuba.
+
+On June 24, 1914, there was recognized a case of human plague in New
+Orleans. The Federal Health Service immediately took charge, and
+measures for the eradication of the disease were vigorously enforced. Up
+to October 10, 1914 there had been reported 30 cases of the disease in
+man, and 181 cases of plague in rats.
+
+[Illustration: 112 b. The modern method of combating the plague. A day's
+catch of rats in the fight against plague in San Francisco. Courtesy of
+Review of Reviews.]
+
+The present-day methods of combating bubonic plague are well illustrated
+by the fight in San Francisco. Had it not been for the strenuous and
+radical anti-plague campaign directed by the United States Marine
+Hospital Service we might have had in our own country an illustration of
+what the disease can accomplish. On what newly acquired knowledge was
+this fight based?
+
+The basis was laid in 1894, when the plague bacillus was first
+discovered. All through the centuries, before and during the Christian
+era, down to 1894, the subject was enveloped in darkness and there had
+been a helpless, almost hopeless struggle in ignorance on the part of
+physicians, sanitarians, and public health officials against the ravages
+of this dread disease. Now its cause, method of propagation and means to
+prevent its spread are matters of scientific certainty.
+
+After the discovery of the causative organism, one of the first advances
+was the establishment of the identity of human plague and that of
+rodents. It had often been noted that epidemics of the human disease
+were preceded by great epizootics among rats and mice. So well
+established was this fact that with the Chinese, unusual mortality among
+these rodents was regarded as foretelling a visitation of the human
+disease. That there was more than an accidental connection between the
+two was obvious when Yersin, the discoverer of _Bacillus pestis_,
+announced that during an epidemic the rats found dead in the houses and
+in the streets almost always contain the bacillus in great abundance in
+their organs, and that many of them exhibit veritable buboes.
+
+Once it was established that the diseases were identical, the attention
+of the investigators was directed to a study of the relations between
+that of rats and of humans, and evidence accumulated to show that the
+bubonic plague was primarily a disease of rodents and that in some
+manner it was conveyed from them to man.
+
+There yet remained unexplained the method of transfer from rat to man.
+As long ago as the 16th century, Mercuralis suggested that house-flies
+were guilty of disseminating the plague but modern investigation, while
+blaming the fly for much in the way of spreading disease, show that it
+is an insignificant factor in this case.
+
+Search for blood-sucking insects which would feed on both rodents and
+man, and which might therefore be implicated, indicated that the fleas
+most nearly met the conditions. At first it was urged that rat fleas
+would not feed upon man and that the fleas ordinarily attacking man
+would not feed upon rats. More critical study of the habits of fleas
+soon showed that these objections were not well-founded. Especially
+important was the evidence that soon after the death of their host, rat
+fleas deserted its body and might then become a pest in houses where
+they had not been noticed before.
+
+Attention was directed to the fact that while feeding, fleas are in the
+habit of squirting blood from the anus and that in the case of those
+which had fed upon rats and mice dying of the plague, virulent plague
+bacilli were to be found in such blood. Liston (1905) even found, and
+subsequent investigations confirmed, that the plague bacilli multiply in
+the stomach of the insect and that thus the blood ejected was richer in
+the organisms than was that of the diseased animal. It was found that a
+film of this infected blood spread out under the body of the flea and
+that thus the bacilli might be inoculated by the bite of the insect and
+by scratching.
+
+Very recently, Bacot and Martin (1914) have paid especial attention to
+the question of the mechanism of the transmission of the plague bacilli
+by fleas. They believe that plague infested fleas regurgitate blood
+through the mouth, and that under conditions precluding the possibility
+of infection by dejecta, the disease may be thus transmitted. The
+evidence does not seem sufficient to establish that this is the chief
+method of transmission.
+
+Conclusive experimental proof that fleas transmit the disease is further
+available from a number of sources. The most extensive series of
+experiments is that of the English Plague Commission in India, which
+reported in 1906 that:
+
+On thirty occasions a healthy rat contracted plague in sequence of
+living in the neighborhood of a plague infected rat under circumstances
+which prevented the healthy rat coming in contact with either the body
+or excreta of the diseased animal.
+
+In twenty-one experiments out of thirty-eight, healthy rats living in
+flea-proof cages contracted plague when exposed to rat fleas
+(_Xenopsylla cheopis_), collected from rats dead or dying of septicaemic
+plague.
+
+Close contact of plague-infected with healthy animals, if fleas are
+excluded, does not give rise to an epizootic among the latter. As the
+huts were never cleaned out, close contact included contact with feces
+and urine of infected animals, and contact with, and eating of food
+contaminated with feces and urine of infected animals, as well as pus
+from open plague ulcers. Close contact of young, even when suckled by
+plague-infected mothers, did not give the disease to the former.
+
+If fleas are present, then the epizootic, once started, spreads from
+animal to animal, the rate of progress being in direct proportion to the
+number of fleas.
+
+Aerial infection was excluded. Thus guinea-pigs suspended in a cage two
+feet above the ground did not contract the disease, while in the same
+hut those animals allowed to run about and those placed two inches above
+the floor became infected. It had previously been found that a rat flea
+could not hop farther than about five inches.
+
+Guinea pigs and monkeys were placed in plague houses in pairs, both
+protected from soil contact infection and both equally exposed to aerial
+infection, but one surrounded with a layer of tangle-foot paper and the
+other surrounded with a layer of sand. The following observations were
+made:
+
+(_a_) Many fleas were caught in the tangle-foot, a certain proportion of
+which were found on dissection to contain in their stomachs abundant
+bacilli microscopically identical with plague bacilli. Out of
+eighty-five human fleas dissected only one contained these bacilli,
+while out of seventy-seven rat fleas twenty-three were found thus
+infected.
+
+(_b_) The animals surrounded with tangle-foot in no instance developed
+plague, while several (24 per cent) of the non-protected animals died of
+the disease.
+
+Thus, the experimental evidence that fleas transmit the plague from rat
+to rat, from rats to guinea pigs, and from rats to monkeys is
+indisputable. There is lacking direct experimental proof of its transfer
+from rodents to man but the whole chain of indirect evidence is so
+complete that there can be no doubt that such a transfer does occur so
+commonly that in the case of bubonic plague it must be regarded as the
+normal method.
+
+Rats are not the only animals naturally attacked by the plague but as
+already suggested, it occurs in various other rodents. In California the
+disease has spread from rats to ground squirrels (_Otospermophilus
+beecheyi_), a condition readily arising from the frequency of
+association of rats with the squirrels in the neighborhood of towns, and
+from the fact that the two species of fleas found on them are also found
+on rats. While the danger of the disease being conveyed from squirrels
+to man is comparatively slight, the menace in the situation is that the
+squirrels may become a more or less permanent reservoir of the disease
+and infect rats, which may come into more frequent contact with man.
+
+The tarbagan (_Arctomys bobac_), is a rodent found in North Manchuria,
+which is much prized for its fur. It is claimed that this animal is
+extremely susceptible to the plague and there is evidence to indicate
+that it was the primary source of the great outbreak of pneumonic plague
+which occurred in Manchuria and North China during the winter of
+1910-11.
+
+Of fleas, any species which attacks both rodents and man may be an agent
+in the transmission of the plague. We have seen that in India the
+species most commonly implicated is the rat flea, _Xenopsylla cheopis_,
+(= _Loemopsylla_ or _Pulex cheopis_) (fig. 89). This species has also
+been found commonly on rats in San Francisco. The cat flea,
+_Ctenocephalus felis_, the dog flea, _Ctenocephalus canis_, the human
+flea, _Pulex irritans_, the rat fleas, _Ceratophyllus fasciatus_ and
+_Ctenopsyllus musculi_ have all been shown to meet the conditions.
+
+But, however clear the evidence that fleas are the most important agent
+in the transfer of plague, it is a mistake fraught with danger to assume
+that they are the only factor in the spread of the disease. The
+causative organism is a bacillus and is not dependent upon any insect
+for the completion of its development.
+
+Therefore, any blood-sucking insect which feeds upon a plague infected
+man or animal and then passes to a healthy individual, conceivably might
+transfer the bacilli. Verjbitski (1908) has shown experimentally that
+bed-bugs may thus convey the disease. Hertzog found the bacilli in a
+head-louse, _Pediculus humanus_, taken from a child which had died from
+the plague, and McCoy found them in a louse taken from a plague-infected
+squirrel. On account of their stationary habits, the latter insects
+could be of little significance in spreading the disease.
+
+Contaminated food may also be a source of danger. While this source,
+formerly supposed to be the principal one, is now regarded as
+unimportant, there is abundant experimental evidence to show that it
+cannot be disregarded. It is believed that infection in this way can
+occur only when there is some lesion in the alimentary canal.
+
+Still more important is the proof that in pneumonic plague the patient
+is directly infective and that the disease is spread from man to man
+without any intermediary. Especially conclusive is the evidence obtained
+by Drs. Strong and Teague during the Manchurian epidemic of 1910-11.
+They found that during coughing, in pneumonic plague cases, even when
+sputum visible to the naked eye is not expelled, plague bacilli in large
+numbers may become widely disseminated into the surrounding air. By
+exposing sterile plates before patients who coughed a single time, very
+numerous colonies of the bacillus were obtained.
+
+But the great advance which has been made rests on the discovery that
+bubonic plague is in the vast majority of cases transmitted by the flea.
+The pneumonic type forms a very small percentage of the human cases and
+even with it, the evidence indicates that the original infection is
+derived from a rodent through the intermediary of the insect.
+
+So modern prophylactic measures are directed primarily against the rat
+and fleas. Ships coming from infected ports are no longer disinfected
+for the purpose of killing the plague germs, but are fumigated to
+destroy the rats and the fleas which they might harbor. When anchored at
+infected ports, ships must observe strenuous precautions to prevent the
+ingress of rats. Cargo must be inspected just before being brought on
+board, in order to insure its freedom from rats. Even lines and hawsers
+must be protected by large metal discs or funnels, for rats readily run
+along a rope to reach the ship. Once infested, the ship must be
+thoroughly fumigated, not only to avoid carrying the disease to other
+ports but to obviate an outbreak on board.
+
+When an epidemic begins, rats must be destroyed by trapping and
+poisoning. Various so-called biological poisons have not proved
+practicable. Sources of food supply should be cut off by thorough
+cleaning up, by use of rat-proof garbage cans and similar measures. Hand
+in hand with these, must go the destruction of breeding places, and the
+rat-proofing of dwellings, stables, markets, warehouses, docks and
+sewers. All these measures are expensive, and a few years ago would have
+been thought wholly impossible to put into practice but now they are
+being enforced on a large scale in every fight against the disease.
+
+Rats and other rodents are regularly caught in the danger zone and
+examined for evidence of infection, for the sequence of the epizootic
+and of the human disease is now understood. In London, rats are
+regularly trapped and poisoned in the vicinity of the principal docks,
+to guard against the introduction of infected animals in shipping.
+During the past six years infected rats have been found yearly, thirteen
+having been found in 1912. In Seattle, Washington, seven infected rats
+were found along the water front in October, 1913, and infected ground
+squirrels are still being found in connection with the anti-plague
+measures in California.
+
+The procedure during an outbreak of the human plague was well
+illustrated by the fight in San Francisco. The city was districted, and
+captured rats, after being dipped in some fluid to destroy the fleas,
+were carefully tagged to indicate their source, and were sent to the
+laboratory for examination. If an infected rat was found, the officers
+in charge of the work in the district involved were immediately notified
+by telephone, and the infected building was subjected to a thorough
+fumigation. In addition, special attention was given to all the
+territory in the four contiguous blocks.
+
+By measures such as these, this dread scourge of the human race is being
+brought under control. Incidentally, the enormous losses due to the
+direct ravages of rats are being obviated and this alone would justify
+the expenditure many times over of the money and labor involved in the
+anti-rat measures.
+
+
+
+
+CHAPTER VII
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC ORGANISMS
+
+
+We now have to consider the cases in which the arthropod acts as the
+essential host of a pathogenic organism. In other words, cases in which
+the organism, instead of being passively carried or merely accidentally
+inoculated by the bite of its carrier, or vector, is taken up and
+undergoes an essential part of its development within the arthropod.
+
+[Illustration: 113. Dipylidium caninum. The double pored tapeworm of the
+dog.]
+
+In some cases, the sexual cycle of the parasite is undergone in the
+arthropod, which then serves as the _definitive_ or _primary host_. In
+other cases, it is the asexual stage of the parasite which is undergone,
+and the arthropod then acts as the _intermediate host_. This distinction
+is often overlooked and all the cases incorrectly referred to as those
+in which the insect or other arthropod acts as intermediate host.
+
+We have already emphasized that this is the most important way in which
+insects may transmit disease, for without them the particular organisms
+concerned could never complete their development. Exterminate the
+arthropod host and the life cycle of the parasite is broken, the disease
+is exterminated.
+
+As the phenomenon of alternation of generations, as exhibited by many of
+the parasitic protozoa, is a complicated one and usually new to the
+student, we shall first take up some of the grosser cases illustrated by
+certain parasitic worms. There is the additional reason that these were
+the first cases known of arthropod transmission of pathogenic organisms.
+
+
+INSECTS AS INTERMEDIATE HOSTS OF TAPEWORMS
+
+A number of tapeworms are known to undergo their sexual stage in an
+insect or other arthropod. Of these at least two are occasional
+parasites of man.
+
+_Dipylidium caninum_ (figs. 113 and 114), more generally known as
+_Taenia cucumerina_ or _T. elliptica_, is the commonest intestinal
+parasite of pet dogs and cats. It is occasionally found as a human
+parasite, 70 per cent of the cases reported being in young children.
+
+In 1869, Melnikoff found in a dog louse, _Trichodectes canis_, some
+peculiar bodies which Leuckart identified as the larval form of this
+tapeworm. The worm is, however, much more common in dogs and cats than
+is the skin parasite, and hence it appears that the _Trichodectes_ could
+not be the only intermediate host. In 1888, Grassi found that it could
+also develop in the cat and dog fleas, _Ctenocephalus felis_ and _C.
+canis_, and in the human flea, _Pulex irritans_.
+
+[Illustration: 114. Dipylidium caninum. Rostrum evaginated and
+invaginated. After Blanchard.]
+
+[Illustration: 115. Dipylidium caninum. Immature cysticercoid. After
+Grassi and Rovelli.]
+
+The eggs, scattered among the hairs of the dog or cat, are ingested by
+the insect host and in its body cavity they develop into pyriform
+bodies, about 300u in length, almost entirely destitute of a bladder,
+but in the immature stage provided with a caudal appendage (fig. 115).
+Within the pear-shaped body (fig. 116) are the invaginated head and
+suckers of the future tapeworm. This larval form is known as a
+cysticercoid, in contradistinction to the bladder-like cysticercus of
+many other cestodes. It is often referred to in literature as
+_Cryptocystis trichodectis_ Villot.
+
+As many as fifty of the cysticercoids have been found in the body cavity
+of a single flea. When the dog takes up an infested flea or louse, by
+biting itself, or when the cat licks them up, the larvae quickly develop
+into tapeworms, reaching sexual maturity in about twenty days in the
+intestine of their host. Puppies and kittens are quickly infested when
+suckling a flea-infested mother, the developing worms having been found
+in the intestines of puppies not more than five or six days old.
+
+[Illustration: 116. Dipylidium caninum. Cysticercoid. After Villet.]
+
+Infestation of human beings occurs only through accidental ingestion of
+an infested flea. It is natural that such cases should occur largely in
+children, where they may come about in some such way as illustrated in
+the accompanying figures 117 and 118.
+
+_Hymenolepis diminuta_, very commonly living in the intestine of mice
+and rats, is also known to occur in man. Its cysticercoid develops in
+the body cavity of a surprising range of meal-infesting insects. Grassi
+and Rovelli (abstract in Ransom, 1904) found it in the larvae and adult
+of a moth, _Asopia farinalis_, in the earwig, _Anisolabis annulipes_,
+the Tenebrionid beetles _Akis spinosa_ and _Scaurus striatus_. Grassi
+considers that the lepidopter is the normal intermediate host. The
+insect takes up the eggs scattered by rats and mice. It has been
+experimentally demonstrated that man may develop the tapeworm by
+swallowing infested insects. Natural infection probably occurs by
+ingesting such insects with cereals, or imperfectly cooked foods.
+
+[Illustration: 117. One way in which Dipylidium infection in children
+may occur. After Blanchard.]
+
+_Hymenolepis lanceolata_, a parasite of geese and ducks, has been
+reported once for man. The supposed cysticercoid occurs in various small
+crustaceans of the family Cyclopidae.
+
+[Illustration: 118. The probable method by which Dipylidium infection
+usually occurs.]
+
+Several other cestode parasites of domestic animals are believed to
+develop their intermediate stage in certain arthropods. Among these may
+be mentioned:
+
+_Choanotaenia infundibulformis_, of chickens, developing in the house-fly
+(Grassi and Rovelli);
+
+_Davainea cesticillus_, of chickens, in some lepidopter or coleopter
+(Grassi and Rovelli);
+
+_Hymenolepis anatina_, _H. gracilis_, _H. sinuosa_, _H. coronula_ and
+_Fimbriaria fasciolaris_, all occurring in ducks, have been reported as
+developing in small aquatic crustaceans. In these cases, cysticercoids
+have been found which, on account of superficial characters, have been
+regarded as belonging to the several species, but direct experimental
+evidence is scant.
+
+
+ARTHROPODS AS INTERMEDIATE HOSTS OF NEMATODE WORMS
+
+
+FILARIASIS AND MOSQUITOES--A number of species of Nematode worms
+belonging to the genus _Filaria_, infest man and other vertebrates and
+in the larval condition are to be found in the blood. Such infestation
+is known as _filariasis_. The sexually mature worms are to be found in
+the blood, the lymphatics, the mesentery and subcutaneous connective
+tissue. In the cases best studied it has been found that the larval
+forms are taken up by mosquitoes and undergo a transformation before
+they can attain maturity in man.
+
+The larvae circulating in the blood are conveniently designated as
+microfilariae. In this stage they are harmless and only one species,
+_Filaria bancrofti_, appears to be of any great pathological
+significance at any stage.
+
+_Filaria bancrofti_ in its adult state, lives in the lymphatics of man.
+Though often causing no injury it has been clearly established that they
+and their eggs may cause various disorders due to stoppage of the
+lymphatic trunks (fig. 119). Manson lists among other effects, abscess,
+varicose groin glands, lymph scrotum, chyluria, and elephantiasis.
+
+The geographical distribution of this parasite is usually given as
+coextensive with that of elephantiasis, but it is by no means certain
+that it is the only cause of this disease and so actual findings of the
+parasites are necessary. Manson reports that it is "an indigenous
+parasite in almost every country throughout the tropical and subtropical
+world, as far north as Spain in Europe and Charlestown in the United
+States, and as far south as Brisbane in Australia." In some sections,
+fully 50 per cent of the natives are infested. Labredo (1910) found
+17.82 per cent infestation in Havana.
+
+[Illustration: 119. Elephantiasis in Man. From "New Sydenham Society's
+Atlas."]
+
+The larval forms of _Filaria bancrofti_ were first discovered in 1863,
+by Demarquay, in a case of chylous dropsy. They were subsequently noted
+under similar conditions, by several workers, and by Wucherer in the
+urine of twenty-eight cases of tropical chyluria, but in 1872 Lewis
+found that the blood of man was the normal habitat, and gave them the
+name _Filaria sanguinis hominis_. The adult worm was found in 1876 by
+Bancroft, and in 1877, Cobbold gave it the name _Filaria bancrofti_. It
+has since been found repeatedly in various parts of the lymphatic
+system, and its life-history has been the subject of detailed studies by
+Manson (1884), Bancroft (1899), Low (1900), Grassi and Noe (1900), Noe
+(1901) and Fulleborn (1910).
+
+The larvae as they exist in the circulating blood, exhibit a very active
+wriggling movement, without material progression. They may exist in
+enormous numbers, as many as five or six hundred swarming in a single
+drop of blood. This is the more surprising when we consider that they
+measure about 300u x 8u, that is, their width is equal to the diameter
+of the red blood corpuscle of their host and their length over
+thirty-seven times as great.
+
+Their organs are very immature and the structure obscure. When they have
+quieted down somewhat in a preparation it may be seen that at the head
+end there is a six-lipped and very delicate prepuce, enclosing a short
+"fang" which may be suddenly exserted and retracted. Completely
+enclosing the larva is a delicate sheath, which is considerably longer
+than the worm itself. To enter into further details of anatomy is beyond
+the scope of this discussion and readers interested are referred to the
+work of Manson and of Fulleborn.
+
+One of the most surprising features of the habits of these larvae is the
+periodicity which they exhibit in their occurrence in the peripheral
+blood. If a preparation be made during the day time there may be no
+evidence whatever of filarial infestation, whereas a preparation from
+the same patient taken late in the evening or during the night may be
+literally swarming with the parasites. Manson quotes Mackenzie as having
+brought out the further interesting fact that should a "filarial subject
+be made to sleep during the day and remain awake at night, the
+periodicity is reversed; that is to say, the parasites come into the
+blood during the day and disappear from it during the night." There have
+been numerous attempts to explain this peculiar phenomenon of
+periodicity but in spite of objections which have been raised, the most
+plausible remains that of Manson, who believes that it is an adaptation
+correlated with the life-habits of the liberating agent of the parasite,
+the mosquito.
+
+The next stages in the development of _Filaria nocturna_ occur in
+mosquitoes, a fact suggested almost simultaneously by Bancroft and
+Manson in 1877, and first demonstrated by the latter very soon
+thereafter. The experiments were first carried out with _Culex
+quinquefasciatus_ (= _fatigans_) as a host, but it is now known that a
+number of species of mosquitoes, both anopheline and culicine, may serve
+equally well.
+
+When the blood of an infested individual is sucked up and reaches the
+stomach of such a mosquito, the larvae, by very active movements, escape
+from their sheaths and within a very few hours actively migrate to the
+body cavity of their new host and settle down primarily in the thoracic
+muscles. There in the course of sixteen to twenty days they undergo a
+metamorphosis of which the more conspicuous features are the formation
+of a mouth, an alimentary canal and a trilobed tail. At the same time
+there is an enormous increase in size, the larvae which measured .3 mm.
+in the blood becoming 1.5 mm. in length. This developmental period may
+be somewhat shortened in some cases and on the other hand may be
+considerably extended. The controlling factor seems to be the one of
+temperature.
+
+The transformed larvae then reenter the body cavity and finally the
+majority of them reach the interior of the labium (fig. 120). A few
+enter the legs and antennae, and the abdomen, but these are wanderers
+which, it is possible, may likewise ultimately reach the labium, where
+they await the opportunity to enter their human host.
+
+It was formerly supposed that when the infested mosquito punctured the
+skin of man, the mature larvae were injected into the circulation. The
+manner in which this occurred was not obvious, for when the insect feeds
+it inserts only the stylets, the labium itself remaining on the surface
+of the skin. Fulleborn has cleared up the question by showing that at
+this time the filariae escape and, like the hookworm, actively bore into
+the skin of their new host.
+
+[Illustration: 120. Filaria in the muscles and labium of Culex. After
+Blanchard.]
+
+Once entered, they migrate to the lymphatics and there quickly become
+sexually mature. The full grown females measure 85-90 mm. in length by
+.24-.28 mm. in diameter, while the males are less than half this size,
+being about 40 mm. by .1 mm. Fecundation occurs and the females will be
+found filled with eggs in various stages of development, for they are
+normally viviparous.
+
+_Filaria philippinensis_ is reported by Ashburn and Craig (1907) as a
+common blood filaria in the Philippine Islands. As they describe it, it
+differs from _Filaria bancrofti_ primarily in that it does not exhibit
+periodicity. Its development has been found to occur in _Culex
+quinquefasciatus_, where it undergoes metamorphosis in about fourteen or
+fifteen days. There is doubt as to the species being distinct from
+_bancrofti_.
+
+Several other species occur in man and are thought to be transferred by
+various insects, among which have been mentioned Tabanidae and
+tsetse-flies, but there is no experimental proof in support of such
+conjectures.
+
+_Filaria immitis_ is a dangerous parasite of the dog, the adult worm
+living in the heart and veins of this animal. It is one of the species
+which has been clearly shown to undergo its development in the mosquito,
+particularly in _Anopheles maculipennis_ and _Aedes calopus_ (=
+Stegomyia). The larval form occurs in the peripheral blood, especially
+at night. When taken up by mosquitoes they differ from _Filaria
+bancrofti_ in that they undergo their development in the Malpighian
+tubules rather than in the thoracic muscles. In about twelve days they
+have completed their growth in the tubules, pierce the distal end, and
+pass to the labium. This species occurs primarily in China and Japan,
+but is also found in Europe and in the United States. It is an
+especially favorable species for studying the transformations in the
+mosquito.
+
+[Illustration: 121. Dracunculus medinensis; female; mouth; embryo. After
+Bastian and Leuckart.]
+
+_Filariae_ are also commonly found in birds, and in this country this is
+the most available source of laboratory material. We have found them
+locally (Ithaca, N. Y.) in the blood of over sixty per cent of all the
+crows examined, at any season of the year, and have also found them in
+English sparrows.
+
+In the crows, they often occur in enormous numbers, as many as two
+thousand having been found in a single drop of the blood of the most
+heavily infested specimen examined. For study, a small drop of blood
+should be mounted on a clean slide and the coverglass rung with vaseline
+or oil to prevent evaporation. In this way they can be kept for hours.
+
+Permanent preparations may be made by spreading out the blood in a film
+on a perfectly clean slide and staining. This is easiest done by
+touching the fresh drop of blood with the end of a second slide which is
+then held at an angle of about 45^o to the first slide and drawn over it
+without pressure. Allow the smear to dry in the air and stain in the
+usual way with haematoxylin.
+
+
+OTHER NEMATODE PARASITES OF MAN AND ANIMALS DEVELOPING IN ARTHROPODS
+
+_Dracunculus medinensis_ (fig. 121), the so-called guinea-worm, is a
+nematode parasite of man which is widely distributed in tropical Africa,
+Asia, certain parts of Brazil and is occasionally imported into North
+America.
+
+The female worm is excessively long and slender, measuring nearly three
+feet in length and not more than one-fifteenth of an inch in diameter.
+It is found in the subcutaneous connective tissue and when mature
+usually migrates to some part of the leg. Here it pierces the skin and
+there is formed a small superficial ulcer through which the larvae reach
+the exterior after bursting the body of the mother.
+
+[Illustration: 122. Cyclops, the intermediate host of Dracunculus.]
+
+Fedtschenko (1879) found that when these larvae reach the water they
+penetrate the carapace of the little crustacean, _Cyclops_ (fig. 122).
+Here they molt several times and undergo a metamorphosis. Fedtschenko,
+in Turkestan, found that these stages required about five weeks, while
+Manson who confirmed these general results, found that eight or nine
+weeks were required in the cooler climate of England.
+
+Infection of the vertebrate host probably occurs through swallowing
+infested cyclops in drinking water. Fedtschenko was unable to
+demonstrate this experimentally and objection has been raised against
+the theory, but Leiper (1907), and Strassen (1907) succeeded in
+infesting monkeys by feeding them on cyclops containing the larvae.
+
+_Habronema muscae_ is a worm which has long been known in its larval
+stage, as a parasite of the house-fly. Carter found them in 33 per cent
+of the house-flies examined in Bombay during July, 1860, and since that
+time they have been shown to be very widely distributed. Italian workers
+reported them in 12 per cent to 30 per cent of the flies examined.
+Hewitt reported finding it rarely in England. In this country it was
+first reported by Leidy who found it in about 20 per cent of the flies
+examined at Philadelphia, Pa. Since then it has been reported by several
+American workers. We have found it at Ithaca, N. Y., but have not made
+sufficient examinations to justify stating percentage. Ransom (1913)
+reports it in thirty-nine out of one hundred and thirty-seven flies, or
+28 per cent.
+
+[Illustration: 123. An Echinorhynchid, showing the spinose retractile
+proboscis.]
+
+[Illustration: 124. June beetle (Lachnosterna).]
+
+[Illustration: Larva]
+
+Until very recently the life-history of this parasite was unknown but
+the thorough work of Ransom (1911, 1913) has shown clearly that the
+adult stage occurs in the stomach of horses. The embryos, produced by
+the parent worms in the stomach of the horse, pass out with the feces
+and enter the bodies of fly larvae which are developing in the manure. In
+these they reach their final stage of larval development at about the
+time the adult flies emerge from the pupal stage. In the adult fly they
+are commonly found in the head, frequently in the proboscis, but they
+occur also in the thorax and abdomen. Infested flies are accidentally
+swallowed by horses and the parasite completes its development to
+maturity in the stomach of its definitive host.
+
+_Gigantorhynchus hirudinaceus_ (= _Echinorhynchus gigas_) is a common
+parasite of the pig and has been reported as occurring in man. The adult
+female is 20-35 cm. long and 4-9 mm. in diameter. It lacks an alimentary
+canal and is provided with a strongly spined protractile rostrum, by
+means of which it attaches to the intestinal mucosa of its host.
+
+The eggs are scattered with the feces of the host and are taken up by
+certain beetle larvae. In Europe the usual intermediate hosts are the
+larvae of the cockchafer, _Melolontha vulgaris_, or of the flower beetle,
+_Cetonia aurata_. Stiles has shown that in the United States the
+intermediate host is the larva of the June bug, _Lachnosterna_ (fig.
+124). It is probable that several of the native species serve in this
+capacity.
+
+A number of other nematode parasites of birds and mammals have been
+reported as developing in arthropods but here, as in the case of the
+cestodes, experimental proof is scant. The cases above cited are the
+better established and will serve as illustrations.
+
+
+
+
+CHAPTER VIII
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA
+
+
+MOSQUITOES AND MALARIA
+
+Under the name of malaria is included a group of morbid symptoms
+formerly supposed to be due to a miasm or bad air, but now known to be
+caused by protozoan parasites of the genus _Plasmodium_, which attack
+the red blood corpuscles. It occurs in paroxysms, each marked by a
+chill, followed by high fever and sweating. The fever is either
+intermittent or remittent.
+
+There are three principal types of the disease, due to different species
+of the parasite. They are:
+
+1. The benign-tertian, caused by _Plasmodium vivax_, which undergoes its
+schizogony or asexual cycle in the blood in forty-eight hours or even
+less. This type of the disease,--characterized by fever every two days,
+is the most wide-spread and common.
+
+2. The quartan fever is due to the presence of _Plasmodium malariae_,
+which has an asexual cycle of seventy-two hours, and therefore the fever
+recurs every three days. This type is more prevalent in temperate and
+sub-tropical regions, but appears to be rare everywhere.
+
+3. The sub-tertian "aestivo-autumnal," or "pernicious" fever is caused by
+_Plasmodium falciparum_. Schizogony usually occurs in the internal
+organs, particularly in the spleen, instead of in the peripheral
+circulation, as is the case of the tertian and quartan forms. The fever
+produced is of an irregular type and the period of schizogony has not
+been definitely determined. It is claimed by some that the variations
+are due to different species of malignant parasites.
+
+It is one of the most wide-spread of human diseases, occurring in almost
+all parts of the world, except in the polar regions and in waterless
+deserts. It is most prevalent in marshy regions.
+
+So commonplace is malaria that it causes little of the dread inspired by
+most of the epidemic diseases, and yet, as Ross says, it is perhaps the
+most important of human diseases. Figures regarding its ravages are
+astounding. Celli estimated that in Italy it caused an average annual
+mortality of fifteen thousand, representing about two million cases. In
+India alone, according to Ross (1910) "it has been officially estimated
+to cause a mean annual death-rate of five per thousand; that is, to kill
+every year, on the average, one million one hundred and thirty
+thousand." In the United States it is widespread and though being
+restricted as the country develops, it still causes enormous losses.
+During the year 1911, "in Alabama alone there were seventy thousand
+cases and seven hundred and seventy deaths." The weakening effects of
+the disease, the invasion of other diseases due to the attacks of
+malaria, are among the very serious results, but they cannot be
+estimated.
+
+Not only is there direct effect on man, but the disease has been one of
+the greatest factors in retarding the development of certain regions.
+Everywhere pioneers have had to face it, and the most fertile regions
+have, in many instances been those most fully dominated by it. Herrick
+(1903) has presented an interesting study of its effects on the
+development of the southern United States and has shown that some parts,
+which are among the most fertile in the world, are rendered practically
+uninhabitable by the ravages of malaria. Howard (1909) estimates that
+the annual money loss from the disease in the United States is not less
+than $100,000,000.
+
+It was formerly supposed that the disease was due to a miasm, to a
+noxious effluvia, or infectious matter rising in the air from swamps. In
+other words its cause was, as the name indicated "mal aria," and the
+deep seated fear of night air is based largely on the belief that this
+miasm was given off at night. Its production was thought to be favored
+by stirring of the soil, dredging operations and the like.
+
+The idea of some intimate connection between malaria and mosquitoes is
+not a new one. According to Manson, Lancisi noted that in some parts of
+Italy the peasants for centuries have believed that malaria is produced
+by the bite of mosquitoes. Celli states that one not rarely hears from
+such peasants the statement that "In such a place, there is much fever,
+because it is full of mosquitoes." Koch points out that in German East
+Africa the natives call malaria and the mosquito by the same name,
+_Mbu_. The opinion was not lacking support from medical men. Celli
+quotes passages from the writings of the Italian physician, Lancisi,
+which indicate that he favored the view in 1717.
+
+Dr. Josiah Nott is almost universally credited with having supported the
+theory, in 1848, but as we have already pointed out his work has been
+misinterpreted. The statements of Beauperthuy, (1853) were more
+explicit.
+
+The clearest early presentation of the circumstantial evidence in favor
+of the theory of mosquito transmission was that of A. F. A. King, an
+American physician, in 1883. He presented a series of epidemiological
+data and showed "how they may be explicable by the supposition that the
+mosquito is the real source of the disease, rather than the inhalation
+or cutaneous absorption of a marsh vapor." We may well give the space to
+summarizing his argument here for it has been so remarkably
+substantiated by subsequent work:
+
+1. Malaria, like mosquitoes, affects by preference low and moist
+localities, such as swamps, fens, jungles, marshes, etc.
+
+2. Malaria is hardly ever developed at a lower temperature than 60^o
+Fahr., and such a temperature is necessary for the development of the
+mosquito.
+
+3. Mosquitoes, like malaria, may both accumulate in and be obstructed by
+forests lying in the course of winds blowing from malarious localities.
+
+4. By atmospheric currents malaria and mosquitoes are alike capable of
+being transported for considerable distances.
+
+5. Malaria may be developed in previously healthy places by turning up
+the soil, as in making excavations for the foundation of houses, tracks
+for railroads, and beds for canals, because these operations afford
+breeding places for mosquitoes.
+
+6. In proportion as countries, previously malarious, are cleared up and
+thickly settled, periodical fevers disappear, because swamps and pools
+are drained so that the mosquito cannot readily find a place suitable to
+deposit her eggs.
+
+7. Malaria is most dangerous when the sun is down and the danger of
+exposure after sunset is greatly increased by the person exposed
+sleeping in the night air. Both facts are readily explicable by the
+mosquito malaria theory.
+
+8. In malarial districts the use of fire, both indoors and to those who
+sleep out, affords a comparative security against malaria, because of
+the destruction of mosquitoes.
+
+9. It is claimed that the air of cities in some way renders the poison
+innocuous, for, though a malarial disease may be raging outside, it does
+not penetrate far into the interior. We may easily conceive that
+mosquitoes, while invading cities during their nocturnal pilgrimages
+will be so far arrested by walls and houses, as well as attracted by
+lights in the suburbs, that many of them will in this way be prevented
+from penetrating "far into the interior."
+
+10. Malarial diseases and likewise mosquitoes are most prevalent toward
+the latter part of summer and in the autumn.
+
+11. Various writers have maintained that malaria is arrested by canvas
+curtains, gauze veils and mosquito nets and have recommended the rise of
+mosquito curtains, "through which malaria can seldom or never pass." It
+can hardly be conceived that these intercept marsh-air but they
+certainly do protect from mosquitoes.
+
+12. Malaria spares no age, but it affects infants much less frequently
+than adults, because young infants are usually carefully housed and
+protected from mosquito inoculation.
+
+Correlated with the miasmatic theory was the belief that some animal or
+vegetable organism which lived in marshes, produced malaria, and
+frequent searches were made for it. Salisbury (1862) thought this
+causative organism to be an alga, of the genus _Palmella_; others
+attributed it to certain fungi or bacteria.
+
+In 1880, the French physician, Laveran, working in Algeria, discovered
+an amoeboid organism in the blood of malarial patients and definitely
+established the parasitic nature of this disease. Pigmented granules had
+been noted by Meckel as long ago as 1847, in the spleen and blood of a
+patient who had died of malaria, and his observations had been
+repeatedly verified, but the granules had been regarded as degeneration
+products, and the fact that they occurred in the body of a foreign
+organism had been overlooked.
+
+Soon after the discovery of the parasites in the blood, Gerhardt (1884)
+succeeded in transferring the disease to healthy individuals by
+inoculation of malarious blood, and thus proved that it is a true
+infection. This was verified by numerous experimenters and it was found
+that inoculation with a very minute quantity of the diseased blood would
+not only produce malaria but the particular type of disease.
+
+Laveran traced out the life cycle of the malarial parasite as it occurs
+in man. The details as we now know them and as they are illustrated by
+the accompanying figure 125, are as follows:
+
+The infecting organism or _sporozoite_, is introduced into the
+circulation, penetrates a red blood corpuscle, and forms the amoeboid
+_schizont_. This lives at the expense of the corpuscle and as it
+develops there are deposited in its body scattered black or reddish
+black particles. These are generally called melanin granules, but are
+much better referred to as haemozoin, as they are not related to
+melanin. The haemozoin is the most conspicuous part of the parasite, a
+feature of advantage in diagnosing from unstained preparations.
+
+[Illustration: 125. Life cycle of the malaria parasite. Adapted from
+Leuckart's chart, by Miss Anna Stryke.]
+
+As the schizont matures, its nucleus breaks up into a number of daughter
+nuclei, each with a rounded mass of protoplasm about it, and finally the
+corpuscles are broken down and these rounded bodies are liberated in the
+plasma as _merozoites_. These merozoites infect new corpuscles and thus
+the asexual cycle is continued. The malarial paroxysm is coincident with
+sporulation.
+
+As early as Laveran's time it was known that under conditions not yet
+determined there are to be found in the blood of malarious patients
+another phase of the parasite, differing in form according to the type
+of the disease. In the pernicious type these appear as large,
+crescent-shaped organisms which have commonly been called "crescents."
+We now know that these are sexual forms.
+
+When the parasite became known there immediately arose speculations as
+to the way in which it was transferred from man to man. It was thought
+by some that in nature it occurred as a free-living amoeba, and that
+it gained access to man through being taken up with impure water.
+However, numerous attempts to infect healthy persons by having them
+drink or inhale marsh water, or by injecting it into their circulation
+resulted in failure, and influenced by Leuckart's and Melnikoff's work
+on _Dipylidium_, that of Fedtschenko on _Dracunculus_, and more
+especially by that of Manson on _Filaria_, search was made for some
+insect which might transfer the parasite.
+
+Laveran had early suggested that the role of carrier might be played by
+the mosquito, but Manson first clearly formulated the hypothesis, and it
+was largely due to his suggestions that Ross in India, undertook to
+solve the problem. With no knowledge of the form or of the appearance in
+this stage, or of the species of mosquito concerned, Ross spent almost
+two and a half years of the most arduous work in the search and finally
+in August, 1897, seventeen years after the discovery of the parasite in
+man, he obtained his first definite clue. In dissecting a
+"dappled-winged mosquito," "every cell was searched and to my intense
+disappointment nothing whatever was found, until I came to the insect's
+stomach. Here, however, just as I was about to abandon the examination,
+I saw a very delicate circular cell, apparently lying amongst the
+ordinary cells of the organ and scarcely distinguishable from them. On
+looking further, another and another similar object presented itself. I
+now focused the lens carefully on one of these, and found that it
+contained a few minute granules of some black substance, exactly like
+the pigment of the parasite of malaria. I counted altogether twelve of
+these cells in the insect."
+
+Further search showed that "the contents of the mature pigment cells did
+not consist of clear fluid but of a multitude of delicate, thread-like
+bodies which on the rupture of the parent cell, were poured into the
+body cavity of the insect. They were evidently spores."
+
+With these facts established, confirmation and extension of Ross's
+results quickly followed, from many different sources. We cannot trace
+this work in detail but will only point out that much of the credit is
+due to the Italian workers, Grassi, Bignami, and Bastianelli, and to
+Koch and Daniels.
+
+It had already been found that when fresh blood was mounted and properly
+protected against evaporation, a peculiar change occurred in these
+crescents after about half an hour's time. From certain of them there
+were pushed out long whip-like processes which moved with a very active,
+lashing movement. The parasite at this stage is known as the
+"flagellated body." Others, differing somewhat in details of structure,
+become rounded but do not give off "flagella."
+
+The American worker, MacCallum (1897), in studying bird malaria as found
+in crows, first recognized the true nature of these bodies. He regarded
+them as sexual forms and believed that the so-called flagella played the
+part of spermatozoa. Thus, the "flagellated body" is in reality a
+_microgametoblast_, producing _microgametes_, or the male sexual
+element, while the others constitute the _macrogametes_, or female
+elements.
+
+It was found that when blood containing these sexual forms was sucked up
+by an Anopheline mosquito and taken into its stomach, a microgamete
+penetrated and fertilized a macrogamete in a way analogous to what takes
+place in the fertilization of the egg in higher forms. The resultant,
+mobile organism is known as the _migratory ookinete_. In this stage the
+parasite bores through the epithelial lining of the "stomach"
+(mid-intestine) of the mosquito and becomes encysted under the muscle
+layers. Here the _oocyst_, as it is now known, matures and breaks up
+into the body cavity and finally its products come to lie in the
+salivary glands of the mosquito. Ten to twelve days are required for
+these changes, after which the mosquito is infective, capable of
+introducing the parasite with its saliva, when feeding upon a healthy
+person.
+
+Thus the malarial parasite is known to have a double cycle, an
+alternation of generations, of which the asexual stage is undergone in
+man, the sexual in certain species of mosquitoes. The mosquito is
+therefore the definitive host rather than the _intermediate_, as usually
+stated.
+
+The complicated cycle may be made clearer by the diagram of Miss Stryke
+(1912) which, by means of a double-headed mosquito (fig. 126) endeavors
+to show how infection takes place through the biting of the human
+victim, (at A), in whom asexual multiplication then takes place, and how
+the sexual stages, taken up at B in the diagram, are passed in the body
+of the mosquito.
+
+[Illustration: 126. Life cycle of the malarial parasite. After Miss Anna
+Stryke.]
+
+The experimental proof that mosquitoes of the Anopheline group are
+necessary agents in the transmission of malaria was afforded in 1900
+when two English physicians, Drs. Sambon and Low lived for the three
+most malarial months in the midst of the Roman Campagna, a region
+famous for centuries as a hot-bed of malaria. The two experimenters
+moved about freely throughout the day, exposed themselves to rains and
+all kinds of weather, drank marsh water, slept exposed to the marsh air,
+and, in short, did everything which was supposed to cause malaria,
+except that they protected themselves thoroughly from mosquito bites,
+retiring at sunset to a mosquito-proof hut. Though they took no quinine
+and all of their neighbors suffered from malaria, they were absolutely
+free from the disease.
+
+To complete the proof, mosquitoes which had fed in Rome on malarious
+patients were sent to England and allowed to bite two volunteers, one of
+them Dr. Manson's own son, who had not been otherwise exposed to the
+disease. Both of these gentlemen contracted typical cases of malaria and
+the parasites were to be found in abundance in their blood.
+
+[Illustration: 127. Eggs of Anopheles. After Howard.]
+
+Since that time there have been many practical demonstrations of the
+fact that malaria is transmitted exclusively by the bite of mosquitoes
+and that the destruction of the mosquitoes means the elimination of the
+disease.
+
+We have said that the malarial parasite is able to undergo its
+development only in certain species of mosquitoes belonging to the
+Anopheline group. It is by no means certain that all of this group even,
+are capable of acting as the definitive host of the parasites, and much
+careful experiment work is still needed along this line. In the United
+States, several species have been found to be implicated, _Anopheles
+quadrimaculatus_ and _Anopheles crucians_ being the most common. The
+characteristics of these species and the distinctions between them and
+other mosquitoes will be discussed in Chapter XII.
+
+In antimalarial work it is desirable to distinguish the anopheline
+mosquitoes from the culicine species in all stages. The following
+tabulation presents the more striking distinctions between the groups as
+represented in the United States.
+
+_Anopheles_                             _Culex, Aedes, etc_.
+
+_Eggs_: Laid singly in small            Deposited in clumps in the
+numbers upon the surface of the         form of a raft (Culex group) or
+water. Eggs lie upon their sides        deposited singly in the water or
+and float by means of lateral           on the ground in places which
+expansions (fig. 127).                  may later be submerged.
+
+_Larva_: When at rest floats in         When at rest (with few exceptions)
+a horizontal position beneath the       floats suspended in an
+surface film. No respiratory            oblique or vertical position, or
+tube but instead a flattened            more rarely nearly horizontal,
+area on the eighth abdominal            with the respiratory tube in
+segment into which the two              contact with the surface film
+spiracles open (fig. 128).              (fig. 128).
+
+_Adults_: Palpi in both sexes           Palpi short in the female, in
+nearly or quite as long as the          the male usually elongate.
+proboscis. Proboscis projecting         Proboscis projects forward at an
+forward nearly on line with the         angle with the axis of the body.
+axis of the body. When at rest          When at rest on a vertical wall
+on a vertical wall the body is          the body is usually held parallel
+usually held at an angle with the       or the tip of the abdomen inclined
+vertical (fig. 128). Wings frequently   towards the wall (fig. 128).
+spotted (fig. 130).                     Wings usually not spotted.
+
+[Illustration: 128. (_a_) Normal position of the larvae of Culex and
+Anopheles in the water. Culex, left; Anopheles, middle; Culex pupa,
+right hand figure.]
+
+These malarial-bearing species are essentially domesticated mosquitoes.
+They develop in any accumulation of water which stands for a week or
+more. Ponds, puddles, rain barrels, horse troughs, cess-pools, cans,
+even the foot-prints of animals in marshy ground may afford them
+breeding places.
+
+[Illustration: 128. (_b_) Normal position of Culex and Anopheles on the
+wall.]
+
+It is clear from what has been said regarding the life cycle of the
+malarial parasite that the mosquito is harmless if not itself diseased.
+Hence malarial-bearing species may abound in the neighborhood where
+there is no malaria, the disease being absent simply because the
+mosquitoes are uninfected. Such a locality is potentially malarious and
+needs only the introduction of a malarial patient who is exposed to the
+mosquitoes. It is found that such patients may harbor the parasites in
+their blood long after they are apparently well and thus may serve as a
+menace, just as do the so-called typhoid carriers. In some malarious
+regions as high as 80-90 per cent of the natives are such
+malaria-carriers and must be reckoned with in antimalaria measures.
+
+Based upon our present day knowledge of the life cycle of the malarial
+parasite the fight against the disease becomes primarily a problem in
+economic entomology,--it is a question of insect control, in its
+broadest interpretation.
+
+[Illustration: 129. Larva of Anopheles. After Howard.]
+
+The lines of defence and offence against the disease as outlined by
+Boyce (1909) are:
+
+  1. Measures to avoid the reservoir (man):
+
+    Segregation.
+
+    Screening of patients.
+
+  2. Measures to avoid Anopheles:
+
+    Choice of suitable locality, when possible.
+
+    Screening of houses and porches.
+
+    Sleeping under mosquito nets.
+
+  3. Measures to exterminate the Anopheles:
+
+    Use of natural enemies.
+
+    Use of culicides, oiling ponds, etc.
+
+    Drainage and scavenging to destroy breeding places.
+
+    Enforcement of penalties for harboring larvae or keeping stagnant
+      water.
+
+    Educational methods.
+
+  4. Systematic treatment with quinine to exterminate the parasites.
+
+
+MOSQUITOES AND YELLOW FEVER
+
+Yellow fever was until recently one of the most dreaded of epidemic
+diseases. It is an acute, specific and infectious disease,
+non-contagious in character but occurring in epidemics, or endemics,
+within a peculiarly limited geographical area. It is highly fatal, but
+those who recover are generally immune from subsequent attacks.
+
+It is generally regarded as an American disease, having been found by
+Cortez, in Mexico, and being confined principally to the American
+continents and islands. It also occurs in Africa and attempts have been
+made to show that it was originally an African disease but there is not
+sufficient evidence to establish this view.
+
+There have been many noted outbreaks in the United States. Boston
+suffered from it in 1691 and again in 1693; New York in 1668 and as late
+as 1856; Baltimore in 1819. In 1793 occurred the great epidemic in
+Philadelphia, with a death rate of one in ten of the population. In the
+past century it was present almost every year in some locality of our
+Southern States, New Orleans being the greatest sufferer. In the latter
+city there were 7848 deaths from the disease in 1853, 4854 in 1858, and
+4046 in 1878. The last notable outbreak was in 1905. Reed and Carroll
+(1901) estimated that during the period from 1793 to 1900 there had not
+been less than 500,000 cases in the United States.
+
+[Illustration: 130. Anopheles quadrimaculatus, male and female,
+(x3-1/2). After Howard.]
+
+As in the case of the plague, the most stringent methods of control
+proved ineffective and helplessness, almost hopelessness marked the
+great epidemics. A vivid picture of conditions is that given by Mathew
+Cary, 1793 (quoted by Kelly, 1906) in "A Short Account of the Malignant
+Fever Lately Prevalent in Philadelphia."
+
+[Illustration: 131. Anopheles punctipennis. Female, (x4). After Howard.]
+
+"The consternation of the people of Philadelphia at this period was
+carried beyond all bounds. Dismay and affright were visible in the
+countenance of almost every person. Of those who remained, many shut
+themselves in their houses and were afraid to walk the streets. * * *
+The corpses of the most respectable citizens, even those who did not die
+of the epidemic, were carried to the grave on the shafts of a chair
+(chaise), the horse driven by a negro, unattended by friends or
+relative, and without any sort of ceremony. People hastily shifted their
+course at the sight of a hearse coming toward them. Many never walked on
+the footpath, but went into the middle of the streets to avoid being
+infected by passing by houses wherein people had died. Acquaintances and
+friends avoided each other in the streets and only signified their
+regard by a cold nod. The old custom of shaking hands fell into such
+disuse that many shrunk back with affright at even the offer of the
+hand. A person with a crape, or any appearance of mourning was shunned
+like a viper. And many valued themselves highly on the skill and address
+with which they got to the windward of every person they met. Indeed, it
+is not probable that London, at the last stage of the plague, exhibited
+stronger marks of terror than were to be seen in Philadelphia from the
+24th or 25th of August until pretty late in September."
+
+[Illustration: 132. Anopheles crucians. Female (x4). After Howard.]
+
+Such was the condition in Philadelphia in 1793 and, as far as methods of
+control of the disease were concerned, there was practically no advance
+during the last century. The dominant theory was that yellow fever was
+spread by _fomites_, that is, exposed bedding, clothing, baggage, and
+the like. As late as 1898 a bulletin of the United States Marine
+Hospital Service stated:
+
+"While yellow fever is a communicable disease, it is not contagious in
+the ordinary acceptance of the term, but is spread by the infection of
+places and articles of bedding, clothing, and furniture."
+
+Based upon this theory, houses, baggage, freight, even mail, were
+disinfected, and the most rigid quarantine regulations were enforced.
+The hardships to which people of the stricken regions were subjected and
+the financial losses are incalculable. And withal, the only efficient
+check upon the disease seemed to be the heavy frosts. It was found that
+for some reason, the epidemic abated with cold weather,--a measure
+beyond human control.
+
+[Illustration: 133. Culex sollicitans. Female (x4). After Howard.]
+
+It is not strange that among the multitude of theories advanced to
+explain the cause and method of dissemination of the disease there
+should be suggestions that yellow fever was transmitted by the mosquito.
+We have seen that Beauperthuy (1855) clearly urged this theory.
+
+More detailed, and of the greatest influence in the final solution of
+the problem were the arguments of Dr. Carlos Finlay, of Havana. In 1881,
+in a paper presented before the "Real Academia de Ciencias Medicas,
+Fisicas y Naturales de la Habana," he said:
+
+"I feel convinced that any theory which attributes the origin and the
+propagation of yellow fever to atmospheric influences, to miasmatic or
+meteorological conditions, to filth, or to the neglect of general
+hygienic precautions, must be considered as utterly indefensible."
+
+He postulated the existence of a material transportable substance
+causing yellow fever,--"something tangible which requires to be conveyed
+from the sick to the healthy before the disease can be propagated" and
+after discussing the peculiarities of the spread of the disease and the
+influence of meteorological conditions, he decides that the carriers of
+the disease must be sought among insects. He continues:
+
+"On the other hand, the fact of yellow fever being characterized both
+clinically and (according to recent findings) histologically, by lesions
+of the blood vessels and by alterations of the physical and chemical
+conditions of the blood, suggested that the insect which should convey
+the infectious particles from the patient to the healthy should be
+looked for among those which drive their sting into blood vessels in
+order to suck human blood. Finally, by reason of other considerations
+which need not be stated here, I came to think that the mosquito might
+be the transmitter of yellow fever."
+
+"Assimilating the disease to small-pox and to vaccination, it occurred
+to me that in order to inoculate yellow fever it would be necessary to
+pick out the inoculable material from within the blood vessels of a
+yellow fever patient and to carry it likewise into the interior of a
+blood vessel of a person who was to be inoculated. All of which
+conditions the mosquito satisfies most admirably through its bite."
+
+In the course of his study of the problem, Finlay made detailed studies
+of the life history and habits of the common mosquitoes at Havana, and
+arrived at the conclusion that the carrier of the yellow fever was the
+_Culex mosquito_ or _Aedes calopus_, as it is now known. With this
+species he undertook direct experimental tests, and believed that he
+succeeded in transmitting the disease by the bite of infected mosquitoes
+in three cases. Unfortunately, possibility of other exposure was not
+absolutely excluded, and the experiments attracted little attention.
+
+Throughout the next twenty years Finlay continued his work on yellow
+fever, modifying his original theory somewhat as time went on. Among his
+later suggestions was that in the light of Smith's work on Texas fever,
+his theory must be "somewhat modified so as to include the important
+circumstance that the faculty of transmitting the yellow fever germ need
+not be limited to the parent insect, directly contaminated by stinging a
+yellow fever patient (or perhaps by contact with or feeding from his
+discharges), but may be likewise inherited by the next generation of
+mosquitoes issued from the contaminated parent." He believed that the
+bite of a single mosquito produced a light attack of the disease and was
+thus effective in immunizing the patient. Throughout the period, many
+apparently successful attempts to transmit the disease by mosquitoes
+were made. In the light of present day knowledge we must regard these as
+defective not only because possibility of other infection was not
+absolutely excluded but because no account was taken of the incubation
+period within the body of the mosquito.
+
+In 1900, while the American army was stationed in Cuba there occurred an
+epidemic of yellow fever and an army medical board was appointed for
+"the purpose of pursuing scientific investigations with reference to the
+acute infectious diseases prevalent on the island." This was headed by
+Walter Reed and associated with him were James Carroll, Jesse W. Lazear
+and Aristides Agramonte, the latter a Cuban immune. For a detailed
+summary of this work the lay reader cannot do better than read Dr.
+Kelly's fascinating biography "Walter Reed and Yellow Fever."
+
+Arriving at the army barracks near Havana the Commission first took up
+the study of _Bacillus icteroides_, the organism which Sanarelli, an
+Italian physician, had declared the causative agent in yellow fever.
+They were unable to isolate this bacillus either from the blood during
+life or from the blood and organs of cadavers and therefore turned their
+attention to Finlay's theory of the propagation of yellow fever by means
+of the mosquito. In this work they had the unselfish and enthusiastic
+support of Dr. Finlay himself, who not only consulted with them and
+placed his publications at their disposal, but furnished eggs from which
+their experimental mosquitoes were obtained. Inoculations of eleven
+non-immunes through the bite of infected mosquitoes were made, and of
+these, two gave positive results. The first of the two was Dr. Carroll
+who allowed himself to be bitten by a mosquito which had been caused to
+feed upon four cases of yellow fever, two of them severe and two mild.
+The first patient had been bitten twelve days before.
+
+Three days after being bitten, Dr. Carroll came down with a typical case
+of yellow fever. So severe was the attack that for three days his life
+hung in the balance. During his convalescence an incident occurred which
+showed how the theory of mosquito transmission of the disease was
+generally regarded. We quote from Dr. Kelly: "One of his nurses who came
+from Tennessee had had considerable experience with yellow fever, having
+indeed, lost her husband and several children from it. One day early in
+his illness Dr. Carroll mentioned to her that he had contracted the
+disease through the bite of a mosquito, and noticed that she looked
+surprised. Some time later, when well enough to look over the daily
+records of his condition, he found this entry: 'Says he got his illness
+through the bite of a mosquito,--delirious'."
+
+The second case was that of an American who was bitten by four
+mosquitoes, two of which had bitten severe (fatal) cases of yellow fever
+twelve days previously, one of which had bitten a severe case (second
+day) sixteen days before and one which had bitten a severe case eight
+days before. Five days later, the subject developed a well pronounced
+but mild case of the disease.
+
+In the meantime, another member of the Commission, Dr. Lazear, was
+accidentally bitten by a mosquito while collecting blood from yellow
+fever patients. Five days later he contracted a typical case which
+resulted fatally.
+
+So clear was the evidence from these preliminary experiments that the
+commission felt warranted in announcing, October 27, 1900, that, "The
+mosquito serves as the intermediate host for the parasite of yellow
+fever, and it is highly probable that the disease is only propagated
+through the bite of this insect."
+
+In order to extend the experimental evidence under conditions which
+could leave no possibility of infection from other sources, a special
+experimental sanitary station, named in honor of the deceased member of
+the Commission, was established in an open field near the town of
+Quemados, Cuba. Here there were constructed two small buildings known
+respectively as the "infected clothing building" and the "infected
+mosquito building."
+
+The infected clothing building, 14 x 20 feet in size, was purposely so
+constructed as to exclude anything like efficient ventilation, but was
+thoroughly screened to prevent the entrance of mosquitoes. Into this
+building were brought sheets, pillow-slips, blankets, etc., contaminated
+by contact with cases of yellow fever and their discharges,--many of
+them purposely soiled with a liberal quantity of black vomit, urine, and
+fecal matter from patients sick with yellow fever. Nothing could better
+serve as the fomites which were supposed to convey the dread disease.
+
+Three non-immunes unpacked these articles, giving each a thorough
+handling and shaking in order to disseminate through the air of the room
+the specific agent of the disease. They were then used in making up the
+beds which the volunteers occupied each night for a period of twenty
+days. The experiment was repeated three times, volunteers even sleeping
+in the soiled garments of yellow fever victims but in not a single case
+was there the slightest symptom of disease. The theory of the spread of
+yellow fever by fomites was completely demolished.
+
+The infected mosquito building, equal in size to its companion, was the
+antithesis as far as other features were concerned. It was so
+constructed as to give the best possible ventilation, and bedding which
+was brought into it was thoroughly sterilized. Like the infected
+clothing building it was carefully screened, but in this case it was in
+order to keep mosquitoes in it as well as to prevent entrance of others.
+Through the middle of the room ran a mosquito-proof screen.
+
+On December 5, 1900, a non-immune volunteer who had been in the
+quarantine camp for fifteen days and had had no other possible exposure,
+allowed himself to be bitten by five mosquitoes which had fed on yellow
+fever patients fifteen or more days previously. The results were fully
+confirmatory of the earlier experiments of the Commission--at the end of
+three days, nine and a half hours, the subject came down with a well
+marked case of yellow fever.
+
+In all, ten cases of experimental yellow fever, caused by the bite of
+infected mosquitoes were developed in Camp Lazear. Throughout the period
+of the disease, other non-immunes slept in the little building,
+separated from the patient only by the mosquito-proof screen, but in no
+circumstances did they suffer any ill effects.
+
+It was found that a yellow fever patient was capable of infecting
+mosquitoes only during the first three or four days after coming down
+with the disease. Moreover, after the mosquito has bitten such a
+patient, a period of at least twelve days must elapse before the insect
+is capable of transmitting the disease.
+
+Once the organism has undergone its twelve day development, the mosquito
+may remain infective for weeks. In experiments of the Commission, two of
+the mosquitoes transmitted the disease to a volunteer fifty-seven days
+after their contamination. No other volunteers presenting themselves,
+one of these mosquitoes died the sixty-ninth and one the seventy-first
+day after their original contamination, without it being determined
+whether they were still capable of transmitting the disease.
+
+So carefully carried out was this work and so conclusive were the
+results that Dr. Reed was justified in writing:
+
+"Six months ago, when we landed on this island, absolutely nothing was
+known concerning the propagation and spread of yellow fever--it was all
+an unfathomable mystery--but today the curtain has been drawn--its mode
+of propagation is established and we know that a case minus mosquitoes
+is no more dangerous than one of chills and fever."
+
+The conclusions of the Commission were fully substantiated by numerous
+workers, notably Dr. Guiteras of the Havana Board of Health, who had
+taken a lively interest in the work and whose results were made known in
+1901, and by the Brazilian and French Commission at Sao Paulo, Brazil,
+in 1903.
+
+Throughout the work of the Army Commission and down to the present time
+many fruitless efforts have been made to discover the specific organism
+of yellow fever. It was clearly established that the claims of Sanarelli
+for _Bacillus icteroides_ were without foundation. It was found, too,
+that whatever the infective agent might be it was capable of passing
+through a Berkefeld filter and thus belongs to the puzzling group of
+"filterable viruses." It was further found that the virus was destroyed
+by heating up to 55^o C for ten minutes. It is generally believed that
+the organism is a Protozoan.
+
+The question of the hereditary transmission of the yellow fever organism
+within the mosquito was left unsettled by the Army Commission, though,
+as we have seen, it was raised by Finlay. Marchoux and Simond, of the
+French Commission devoted much attention to this phase of the problem
+and basing their conclusions on one apparently positive case, they
+decided that the disease could be transmitted through the egg of an
+infected _Aedes calopus_ to the second generation and thence to man. The
+conclusion, which is of very great importance in the control of yellow
+fever, has not been verified by other workers.
+
+Once clearly established that yellow fever was transmitted solely by
+mosquitoes, the question of the characteristics, habits, and
+geographical distribution of the insect carrier became of vital
+importance.
+
+_Aedes calopus_, more commonly known as _Stegomyia fasciata_ or
+_Stegomyia calopus_ (fig. 134) is a moderate sized, rather strikingly
+marked mosquito. The general color is dark-brown or reddish-brown, but
+the thorax has a conspicuous broad, silvery-white curved line on each
+side, with two parallel median silvery lines. Between the latter there
+is a slender, broken line. The whole gives a lyre-shaped pattern to the
+thorax. The abdomen is dark with silvery-white basal bands and silvery
+white spots on each side of the abdominal segments. Legs black with
+rings of pure white at the base of the segments.
+
+Size of the female 3.3 to 5 mm.; male 3 to 4.5 mm.
+
+[Illustration: 134. The yellow fever mosquito (Aedes calopus). (x7).
+After Howard.]
+
+It is preeminently a domesticated species, being found almost
+exclusively about the habitation of man. "Its long association with man
+is shown by many of its habits. It approaches stealthily from behind. It
+retreats upon the slightest alarm. The ankles and, when one is sitting
+at a table or desk, the underside of the hands and wrists are favorable
+points of attack. It attacks silently, whereas other mosquitoes have a
+piping or humming note. The warning sound has doubtless been suppressed
+in the evolutionary process of its adaptation to man. It is extremely
+wary. It hides whenever it can, concealing itself in garments, working
+into the pockets, and under the lapels of coats, and crawling up under
+the clothes to bite the legs. In houses, it will hide in dark corners,
+under picture moldings and behind the heads of old-fashioned bedsteads.
+It will enter closets and hide in the folds of garments."--Howard.
+
+It was claimed by the French Commission, and subsequently often stated
+in discussions of the relation of the mosquito to yellow fever that the
+mature _Aedes calopus_ will bite only at night. If this were true it
+would be of the greatest importance in measures to avoid the disease.
+Unfortunately, the claim was illy founded and numerous workers have
+clearly established that the exact converse is more nearly true, this
+mosquito being pre-eminently a day species, feeding most actively in
+early morning, about sunrise, and late in the afternoon. On cloudy days
+it attacks at any time during the day. Thus there is peril in the
+doctrine that infected regions may be visited with perfect safety during
+the daytime and that measures to avoid the mosquito attack need be taken
+only at night.
+
+[Illustration: 135_a_. Aedes calopus. Pupa. After Howard.]
+
+Dr. Finlay maintained that the adult, even when starved, would not bite
+when the temperature was below 23^o C, but subsequent studies have shown
+that this statement needs modification. The French Commission, working
+at Rio de Janeiro, found that _Aedes calopus_ would bite regularly at
+temperatures between 22^o and 25^o and that the optimum temperature was
+between 27^o and 30^o C, but their experiments led them to believe that it
+would bite in nature at a temperature as low as 17^o C.
+
+The yellow fever mosquito breeds in cisterns, water barrels, pitchers
+and in the various water receptacles about the house. In our own
+Southern States it very commonly breeds in the above-ground cisterns
+which are in general use. Often the larvae (fig. 135b) are found in
+flower vases, or even in the little cups of water which are placed under
+the legs of tables to prevent their being overrun by ants. They have
+been repeatedly found breeding in the holy water font in churches. In
+short, they breed in any collection of water in close proximity to the
+dwellings or gathering places of man.
+
+The life cycle under favorable conditions is completed in from twelve to
+fifteen days. These figures are of course very dependent upon the
+temperature. The Army Commission in Cuba found that the cycle might be
+completed in as brief a period as nine and a half days. Under less
+favorable conditions it may be greatly lengthened.
+
+The adults are long lived. We have seen that during the experimental
+work in Cuba specimens were kept in captivity for sixty-nine and
+seventy-one days, respectively, and that they were proved to retain
+their infectivity for at least fifty-seven days. Dr. Guiteras
+subsequently kept an infected adult for one hundred and fifty-four days.
+
+Low temperatures have a very great effect not only on development, but
+on the activity and even life of the adults. Long before the method of
+transmission of yellow fever was discovered it was well known that the
+epidemics were brought to a close by heavy frosts, and it is now known
+that this is due to the killing of the mosquitoes which alone could
+spread the disease.
+
+[Illustration: 135_b_. Aedes calopus; larva. (x7). After Howard.]
+
+_Aedes calopus_ has a very wide distribution since, as Howard says,
+being a domestic mosquito, having a fairly long life in the adult stage,
+and having the custom of hiding itself in the most ingenious ways, it is
+particularly subject to carriage for long distances on board vessels, in
+railway trains, even packed in baggage. In general, its permanent
+distribution is from 40 degrees north latitude to 40 degrees south
+latitude (Brumpt), in a belt extending around the world. In the United
+States it breeds in most of our Southern States.
+
+Thus, as in the case of malaria, there are many places where the insect
+carrier is abundant but where yellow fever does not occur. Such, for
+instance, are Hawaii, Australia and Asia. An outbreak may occur at any
+time that a patient suffering from the disease is allowed to enter and
+become a source of infection for the mosquitoes. In this connection
+various writers have called attention to the menace from the Panama
+Canal. When it is completed, it will allow of direct passage from
+regions where yellow fever is endemic and this will greatly increase the
+possibility of its introduction into these places where it is now
+unknown. The result, with a wholly non-immune population, would be
+appalling.
+
+On the other hand, there are places wholly outside of the normal range
+of _Aedes calopus_ where the disease has raged. Such are New York,
+Boston, and even Philadelphia, which have suffered notable epidemics.
+These outbreaks have been due to the introduction of infected mosquitoes
+during the heat of summer, when they have not only conveyed the disease
+but have found conditions favorable for their multiplication. Or,
+uninfected mosquitoes have been thus accidentally brought in and
+developed in large numbers, needing then only the accidental
+introduction of cases of the disease to start an epidemic.
+
+Methods of control of various diseases have been revolutionized by the
+discovery that they were insect-borne, but in no other case has the
+change been as radical or the results as spectacular as in the case of
+yellow fever. The "shot-gun quarantine," the sufferings and horrors, the
+hopelessness of fighting absolutely blindly have given way to an
+efficient, clear-cut method of control, based upon the knowledge that
+the disease is carried from man to man solely by the mosquito, _Aedes
+calopus_. The lines of defense and offense are essentially as follows:
+
+In the first place, when a case of yellow fever occurs, stringent
+precautions must be adopted to prevent the infection of mosquitoes and
+the escape of any already infected. This means that the patient must be
+removed to a mosquito-proof room, or ward beyond reach of the insects,
+and that the infected room must be thoroughly fumigated at once, to kill
+the mosquitoes hiding within it. All cracks and openings should be
+closed with strips of paper and fumigation with burning sulphur or
+pyrethrum carefully carried out.
+
+It should be remembered that if the first case noted is that of a
+resident rather than imported, it means that the mosquito carriers
+became infected more than two weeks before the case was diagnosed, for
+as we have seen, the germ must undergo a twelve-day period of
+development within its insect host. Therefore a careful search must be
+made for mild cases which, though unrecognized, may serve as foci for
+the spread of the disease.
+
+In face of a threatened epidemic one of the most essential measures is
+to educate the citizens and to gain their complete cooperation in the
+fight along modern lines. This may be done through the schools, the
+pulpit, places of amusement, newspapers and even bulletin boards.
+
+Emphasis should be placed on the necessity of both non-immunes and
+immunes using mosquito curtains, and in all possible ways avoiding
+exposure to the mosquitoes.
+
+Then the backbone of the fight must be the anti-mosquito measures. In
+general, these involve screening and fumigating against adults, and
+control of water supply, oiling, and drainage against the larvae. The
+region involved must be districted and a thorough survey undertaken to
+locate breeding places, which must, if possible, be eradicated. If they
+are necessary for water supplies, such as casks, or cisterns, they
+should be carefully screened to prevent access of egg-laying adults.
+
+The practical results of anti-mosquito measures in the fight against
+yellow fever are well illustrated by the classic examples of the work in
+Havana, immediately following the discoveries of the Army Commission and
+by the stamping out of the New Orleans epidemic in 1905.
+
+The opportunities for an immediate practical application of the theories
+of the Army Commission in Havana were ideal. The city had always been a
+hotbed of yellow fever and was the principal source from which the
+disease was introduced year after year into our Southern States. It was
+under martial law and with a military governor who was himself a
+physician and thoroughly in sympathy with the views of the Commission,
+the rigid enforcement of the necessary regulations was possible. The
+story of the first campaign has been often told, but nowhere more
+clearly than in Dr. Reed's own account, published in the _Journal of
+Hygiene_ for 1902.
+
+Closer home was the demonstration of the efficacy of these measures in
+controlling the yellow fever outbreak in New Orleans in 1905. During the
+spring and early summer of the year the disease had, unperceived, gained
+a firm foothold in that city and when, in early July the local Board of
+Health took cognizance of its existence, it was estimated that there had
+been in the neighborhood of one hundred cases.
+
+Conditions were not as favorable as they had been under martial law in
+Havana for carrying on a rigid fight along anti-mosquito lines. The
+densely populated city was unprepared, the public had to be educated,
+and an efficient organization built up. The local authorities actively
+began a general fight against the mosquito but in spite of their best
+efforts the disease continued to spread. It was recognized that more
+rigid organization was needed and on August 12th the United States
+Public Health and Marine Hospital Service was put in absolute charge of
+the fight. Up to this time there had been one hundred and forty-two
+deaths from a total of nine hundred and thirteen cases and all of the
+conditions seemed to threaten an outbreak to exceed the memorable one of
+1878 when, as we have seen there were four thousand and forty-six
+deaths.
+
+With the hearty cooperation of the citizens,--physicians and laymen
+alike,--the fight was waged and long before frost or any near approach
+thereto the disease was stamped out,--a thing unheard of in previous
+epidemics. The total loss of life was four hundred and sixty--about 11
+per cent as great as that from the comparable epidemic of 1878. If the
+disease had been promptly recognized and combated with the energy which
+marked the fight later in the summer, the outbreak would have made
+little headway and the great proportion of these lives would have been
+saved.
+
+
+
+
+CHAPTER IX
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA (Continued)
+
+
+INSECTS AND TRYPANOSOMIASES
+
+By trypanosomiasis is meant a condition of animal parasitism, common to
+man and the lower animals, in which trypanosomes, peculiar flagellate
+protozoa, infest the blood. Depending upon the species, they may be
+harmless, producing no appreciable ill-effect, or pathogenic, giving
+rise to conditions of disease. A number of these are known to be
+transferred by insects.
+
+In order that we may consider more fully the developmental stage of
+these parasites within their insect host, it is necessary that we
+describe briefly the structure of the blood-inhabiting stage.
+
+[Illustration: 136. Trypanosoma brucei. After Bruce.]
+
+The trypanosomes are elongated, usually pointed, flagellated protozoa
+(fig. 136) in which the single flagellum, bent under the body, forms the
+outer limit of a delicate undulating membrane. It arises near one end of
+the organism from a minute centrosome-like body which is known as the
+blepheroplast, and at the opposite end extends for a greater or less
+distance as a free flagellum. Enclosing, or close beside the
+blepheroplast is the small kinetonucleus. The principal nucleus, round
+or oval in form, is situated near the center of the body. Asexual
+reproductions occurs in this stage, by longitudinal fission, the nucleus
+and the blepheroplast dividing independently of one another. From the
+blepheroplast of one of the daughter cells a new flagellum is formed.
+
+Among the pathogenic species are to be found the causative organisms of
+some of the most serious diseases of domestic animals and even of man.
+It is probable that these pathogenic species secrete a specific poison.
+The majority of them are tropical in distribution.
+
+Though we are concerned especially with the species which infest man, we
+shall first consider two of the trypanosomes of lower animals, known
+long before any of those of man had been found.
+
+
+FLEAS AND LICE AS CARRIERS OF TRYPANOSOMA LEWISI.--_Trypanosoma lewisi_,
+the first mammalian trypanosome known, is to be found in the blood of
+wild rats. Like its host, it appears to be cosmopolitan in distribution,
+having been reported from several localities in the United States,
+Brazil, Argentine, England, Germany, France, Italy, Russia, Asia and
+Africa.
+
+This species is usually regarded as non-pathogenic, but in experimental
+work, especially with white rats, heavy infestations often result
+fatally, and naturally infested specimens sometimes show evidence of
+injury. Rats which have been infested exhibit at least temporary
+immunity against new infection.
+
+_Trypanosoma lewisi_ is transmitted from rat to rat by fleas and by
+lice. Rabinowitsch and Kempner (1899) first found that healthy rats
+which were kept with infested rats, showed trypanosomes in their blood
+after about two weeks. They found the trypanosomes in the alimentary
+canal of fleas which had fed on the diseased rats. On teasing such fleas
+in physiological salt solution and inoculating them into fresh rats they
+were able to produce the infection. Finally, they showed that the fleas
+which had fed upon infested rats were able to carry the parasites to
+healthy rats. Corresponding experiments with lice were not successful.
+Prowazek (1905) found in the rat louse (_Haematopinus spinulosus_)
+organisms which he regarded as developmental stages of the _Trypanosoma
+lewisi_. He believed that the sexual cycle was undergone in this insect.
+
+Nuttall (1908) readily transmitted the trypanosomes through the agency
+of fleas, (_Ceratophyllus fasciatus_ and _Ctenopthalmus agyrtes_). He
+believes that these insects are probably the chief transmitters of the
+parasite. He was also able to transmit it from diseased to healthy rats
+through the agency of the rat louse. He was unable to trace any
+developmental stages in the louse and inclined to the opinion that
+Prowazek was deceived by the presence of extraneous flagellates such as
+are known to exist in a number of blood-sucking arthropods.
+
+Nuttall concludes that since three distinct kinds of blood-sucking
+insects are capable of transmitting _Trypanosoma lewisi_ it appears
+doubtful that this flagellate is a parasite of the invertebrate "host"
+in the sense claimed by Prowazek and other investigators.
+
+
+TSETSE-FLIES AND NAGANA--One of the greatest factors in retarding the
+development of certain regions of Africa has been the presence of a
+small fly, little larger than the common house-fly. This is the
+tsetse-fly, _Glossina morsitans_ (fig. 165) renowned on account of the
+supposed virulence of its bite for cattle, horses and other domestic
+mammals.
+
+The technical characteristics of the tsetse-flies, or Glossinas, and
+their several species, will be found in a later chapter. We need
+emphasize only that they are blood-sucking Muscidae and that, unlike the
+mosquitoes, the sexes resemble each other closely in structure of the
+mouth-parts, and in feeding habits.
+
+In 1894, Colonel David Bruce discovered that the fly was not in itself
+poisonous but that the deadly effect of its bite was due to the fact
+that it transmitted a highly pathogenic blood parasite, _Trypanosoma
+brucei_. This trypanosome Bruce had discovered in the blood of South
+African cattle suffering from a highly fatal disease known as "nagana".
+On inoculating the blood of infected cattle into horses and dogs he
+produced the disease and found the blood teeming with the causative
+organism. In the course of his work he established beyond question that
+the "nagana" and the tsetse-fly disease were identical.
+
+Tsetse-flies of the species _Glossina morsitans_, which fed upon
+diseased animals, were found capable of giving rise to the disease in
+healthy animals up to forty-eight hours after feeding. Wild tsetse-flies
+taken from an infected region to a region where they did not normally
+occur were able to transmit the disease to healthy animals. It was found
+that many of the wild animals in the tsetse-fly regions harbored
+_Trypanosoma brucei_ in their blood, though they showed no evidence of
+disease. As in the case of natives of malarial districts, these animals
+acted as reservoirs of the parasite. Non-immune animals subjected to the
+attacks of the insect carrier, quickly succumbed to the disease.
+
+A question of prime importance is as to whether the insect serves as an
+essential host of the pathogenic protozoan or whether it is a mere
+mechanical carrier. Bruce inclined to the latter view. He was unable to
+find living trypanosomes in the intestines or excrements of the fly or
+to produce the disease on the many occasions when he injected the
+excrement into healthy animals. Moreover, he had found that the
+experimental flies were infective only during the first forty-eight
+hours and that if wild flies were taken from the infected region, "kept
+without food for three days and then fed on a healthy dog, they never
+gave rise to the disease."
+
+Koch had early described what he regarded as sexual forms from the
+intestine of the fly but it remained for Kleine (1909) to experimentally
+demonstrate that a part of the life cycle of the parasite was undergone
+in the fly. Working with _Glossina palpalis_, he found that for a period
+of ten days or longer after feeding on an animal suffering from nagana
+it was non-infective, but that then it became infective and was able to
+transmit the disease for weeks thereafter. He discovered and described
+developmental stages of the parasite within the intestine of the insect.
+In other words, the tsetse-fly (in nature, _Glossina morsitans_), serves
+as an essential host, within which an important part of the life cycle
+of the parasite is undergone. These conclusions were quickly verified by
+Bruce and numerous other workers and are no longer open to question.
+Klein and Taute are even inclined to think that mechanical transmission
+plays practically no role in nature, unless the fly is interrupted while
+feeding and passes immediately to a new animal.
+
+
+TSETSE-FLIES AND SLEEPING SICKNESS OF MAN--About the beginning of the
+present century a hitherto little known disease of man began to attract
+great attention on account of its ravages in Uganda and the region of
+Victoria Nyanza in South Africa. It was slow, insiduous and absolutely
+fatal, characterized in its later stages by dullness, apathy, and
+finally absolute lethargy all day long, symptoms which gave it the name
+of "sleeping sickness."
+
+It was soon found that the disease was not a new one but that it had
+been known for over a hundred years on the west coast of Africa. Its
+introduction into Central and East Africa and its rapid spread have been
+attributed primarily to the development of the country, the formation of
+new trade routes and the free mingling of native tribes formerly
+isolated. It is estimated that in the first ten years of the present
+century there were approximately two hundred thousand deaths from the
+disease in the Uganda protectorate. In the British province Bugosa, on
+the Victoria Nyanza there were thirty thousand deaths in the period from
+1902-1905.
+
+While the disease is peculiarly African there are a number of instances
+of its accidental introduction into temperate regions. Slaves suffering
+from it were occasionally brought to America in the early part of the
+last century and cases have sometimes been imported into England. In
+none of the cases did the disease gain a foothold or spread at all to
+other individuals.
+
+In 1902 Dutton described a trypanosome, _T. gambiense_, which he and
+Forde had found the year before in the blood of a patient suffering from
+a peculiar type of fever in Gambia. In 1902-1903 Castellani found the
+same parasite in the cerebro-spinal fluid of sleeping-sickness patients
+and definitely reported it as the causative organism of the disease. His
+work soon found abundant confirmation, and it was discovered that the
+sleeping sickness was but the ultimate phase of the fever discovered by
+Dutton and Forde.
+
+When Castellani made known his discovery of the trypanosome of sleeping
+sickness, Brumpt, in France, and Sambon, in England, independently
+advanced the theory that the disease was transmitted by the tsetse-fly,
+_Glossina palpalis_. This theory was based upon the geographical
+distribution and epidemiology of the disease. Since then it has been
+abundantly verified by experimental evidence.
+
+Fortunately for the elucidation of problems relating to the methods of
+transfer of sleeping sickness, _Trypanosoma gambiense_ is pathogenic for
+many species of animals. In monkeys it produces symptoms very similar to
+those caused in man. Bruce early showed that _Glossina palpalis_ "fed on
+healthy monkeys eight, twelve, twenty-four and forty-eight hours after
+having fed on a native suffering from trypanosomiasis, invariably
+transmitted the disease. After three days the flies failed to transmit
+it." In his summary in Osler's Modern Medicine, he continues "But this
+is not the only proof that these flies can carry the infective agent. On
+the lake shore there was a large native population among whom we had
+found about one-third to be harboring trypanosomes in their blood. The
+tsetse-flies caught on this lake shore, brought to the laboratory in
+cages, and placed straightway on healthy monkeys, gave them the disease
+in every instance, and furnished a startling proof of the danger of
+loitering along the lake shore among those infected flies."
+
+As in the case of nagana, Bruce and most of the earlier investigators
+supposed the transmission of the sleeping sickness trypanosome by
+_Glossina palpalis_ to be purely mechanical. The work of Kleine (1909)
+clearly showed that for _Trypanosoma gambiense_ as well as for
+_Trypanosoma brucei_ the fly served as an essential host. Indeed, Kleine
+and many subsequent investigators are inclined to think that there is
+practically no mechanical transmission of trypanosomes from animal to
+animal by _Glossina_ in nature, and that the many successful experiments
+of the earlier investigators were due to the fact that they used wild
+flies which already harbored the transformed parasite rather than
+directly inoculated it from the blood of the diseased experimental
+animals. While the criticism is applicable to some of the work, this
+extreme view is not fully justified by the evidence at hand.
+
+Kleine states (1912) that _Glossina palpalis_ can no longer be regarded
+as the sole transmitter of sleeping sickness. Taute (1911) had shown
+that under experimental conditions _Glossina morsitans_ was capable of
+transferring the disease and Kleine calls attention to the fact that in
+German East Africa, in the district of the Rovuma River, at least a
+dozen cases of the disease have occurred recently, though only _Glossina
+morsitans_ exists in the district. It appears, however, that these cases
+are due to a different parasite, _Trypanosoma rhodesiense_. This
+species, found especially in north-east Rhodesia and in Nyassaland, is
+transferred by _Glossina morsitans_.
+
+Other workers maintain that the disease may be transmitted by various
+blood-sucking flies, or even bugs and lice which attack man. Fulleborn
+and Mayer (1907) have shown by conclusive experiments that _Aedes
+(Stegomyia) calopus_ may transmit it from one animal to another if the
+two bites immediately succeed each other.
+
+It is not possible that insects other than the tsetse-flies (and only
+certain species of these), play an important role in the transmission of
+the disease, else it would be much more wide-spread. Sambon (1908)
+pointed out that the hypothesis that is spread by _Aedes calopus_ is
+opposed by the fact that the disease never spread in the Antilles,
+though frequently imported there by West African slaves. The same
+observation would apply also to conditions in our own Southern States in
+the early part of the past century.
+
+Since _Glossina palpalis_ acts as an essential host of the parasite and
+the chief, if not the only, transmitter, the fight against sleeping
+sickness, like that against malaria and yellow fever, becomes primarily
+a problem in economic entomology. The minutest detail of the
+life-history, biology, and habits of the fly, and of its parasites and
+other natural enemies becomes of importance in attempts to eradicate the
+disease. Here we can consider only the general features of the subject.
+
+_Glossina palpalis_ lives in limited areas, where the forest and
+undergrowth is dense, along the lake shore or river banks. According to
+Hodges, the natural range from shore is under thirty yards, though the
+distance to which the flies may follow man greatly exceed this.
+
+It is a day feeder, a fact which may be taken advantage of in avoiding
+exposure to its attacks. The young are brought forth alive and
+full-grown, one every nine or ten days. Without feeding, they enter the
+ground and under favorable conditions, complete their development in a
+month or more.
+
+[Illustration: 137. Sleeping sickness concentration camp in German East
+Africa. Report of German Commission.]
+
+Methods of control of the disease must look to the prevention of
+infection of the flies, and to their avoidance and destruction. Along
+the first line, much was hoped from temporary segregation of the sick in
+regions where the fly was not found. On the assumption that the flies
+acted as carriers only during the first two or three days, it was
+supposed that even the "fly belts" would become safe within a few days
+after the sick were removed. The problem was found to be a much more
+difficult one when it was learned that after a given brief period the
+fly again became infective and remained so for an indeterminate period.
+Nevertheless, isolation of the sick is one of the most important
+measures in preventing the spread of the disease into new districts.
+Much, too, is being accomplished by moving native villages from the fly
+belts. (c.f. fig. 137.)
+
+All measures to avoid the flies should be adopted. This means locating
+and avoiding the fly belts as far as possible, careful screening of
+houses, and protection of the body against bites.
+
+Clearing the jungle along the water courses for some yards beyond the
+natural range of the fly has proved a very important measure. Castellani
+recommends that the area be one hundred yards and around a village three
+hundred yards at least.
+
+Detailed studies of the parasites and the natural enemies of the
+tsetse-fly are being undertaken and may ultimately yield valuable
+results.
+
+
+SOUTH AMERICAN TRYPANOSOMIASIS--The tsetse-flies are distinctively
+African in distribution and until recently there were no trypanosomes
+known to infest man in America. In 1909 Dr. Chagas, of Rio de Janeiro
+described a new species, _Trypanosoma cruzi_, pathogenic to man.
+
+_Trypanosoma cruzi_ is the causative organism of a disease common in
+some regions of Brazil, where it is known as "opilacao." It is
+especially to be met with in children and is characterized by extreme
+anemia, wasting, and stunted development associated with fever, and
+enlargement of the thyroid glands. The disease is transmitted by the
+bites of several species of assassin-bugs, or Reduviidae, notably by
+_Conorhinus megistus_. The evolution of the parasite within the bug has
+been studied especially by Chagas and by Brumpt. From the latter's text
+we take the following summary.
+
+The adult trypanosomes, ingested by a _Conorhinus megistus_, of any
+stage, first change into Crithidia-like forms and then those which
+remain in the stomach become ovoid and non-motile. Brumpt found these
+forms in immense numbers, in a _Conorhinus_ which had been infested
+fourteen months before. The forms which pass into the intestine quickly
+assume the _Crithidia_ form and continue to develop rapidly under this
+form. Some weeks later they evolve into the trypanosome forms,
+pathogenic for man. They then pass out with the excrement of the bug and
+infect the vertebrate host as soon as they come in contact with any
+mucous layer (buccal, ocular or rectal). More rarely they enter through
+the epidermis.
+
+Brumpt showed that the development could take place in three species;
+bed-bugs (_Cimex lectularius_, _C. hemipterus_) and in the tick
+_Ornithodoros moubata_. The evolution proceeds in the first two species
+of bed-bugs as rapidly as in Conorhinus, or even more rapidly, but they
+remain infective for a much shorter time and hence Brumpt considers that
+they play a much less important role in the spread of the disease.
+
+_Conorhinus megistus_, like related forms in our Southern States, very
+commonly frequents houses and attacks man with avidity. Chagas states
+that the bites are painless and do not leave any traces. They are
+usually inflicted on the lips, or the cheeks and thus the buccal mucosa
+of a sleeper may be soiled by the dejections of the insect and the bite
+serving as a port of entry of the virus, remain unnoticed.
+
+The possibility of some of our North American Reduviidae playing a
+similar role in the transmission of disease should not be overlooked.
+
+
+LEISHMANIOSES AND INSECTS--Closely related to the trypanosomes is a
+group of intracellular parasites which have recently been grouped by
+Ross under the genus _Leishmania_. Five species are known to affect man.
+Three of these produce local skin infestations, but two of them,
+_Leishmania donovani_ and _L. infantum_, produce serious and often fatal
+systemic diseases.
+
+The first of these, that produced by _L. donovani_, is an exceedingly
+virulent disease common in certain regions of India and China. It is
+commonly known as "Kala-azar," or "dum-dum" fever, and more technically
+as tropical leishmaniasis. Patton (1907) believes that the parasite is
+transmitted by the bed-bug _Cimex hemipterus_, and has described a
+developmental cycle similar to that which can be found in artificial
+cultures. On the other hand, Donovan was unable to confirm Patton's work
+and believes that the true intermediate host is a Reduviid bug,
+_Conorhinus rubrofasciatus_.
+
+_Leishmania infantum_ is the cause of the so-called infantile splenic
+leishmaniasis, occurring in northern Africa, Spain, Portugal, Italy, and
+possibly other parts of Europe. The parasite occurs habitually in the
+dog and is only accidentally transferred to children. Alvares and da
+Silva, in Portugal (according to Brumpt, 1913) have found that the
+excrement of a flea from a diseased dog contains flagellates, and they
+suggest that the infection may be transmitted by the accidental
+inoculation of this excrement by means of the proboscis of the flea, as
+has been thought to occur in the case of the plague. To this Brumpt
+objects that they and other workers who thought to trace the development
+of _Leishmania infantum_ were apparently misled by the presence of a
+harmless _Herpetomonas_ which infests dog fleas in all countries, even
+where the leishmaniasis is unknown.
+
+Basile (1910 and 1911) however, carried on numerous experiments
+indicating that the disease was transferred from children to dogs and
+from dog to dog by the dog flea, and was able to find in the tissues of
+the insects forms perfectly identical with those found in children and
+in dogs suffering from leishmaniasis. He also found that _Pulex
+irritans_ was capable of acting as the carrier.
+
+Of the cutaneous type of leishmaniasis, the best known is the so-called
+"Oriental sore," an ulcerative disease of the skin which is epidemic in
+many tropical and subtropical regions. The causative organism is
+_Leishmania tropica_, which occurs in the diseased tissues as bodies
+very similar to those found in the spleen in cases of Kala-azar. The
+disease is readily inoculable and there is no doubt that it may be
+transferred from the open sores to abraded surfaces of a healthy
+individual by house-flies. It is also believed by a number of
+investigators that it may be transferred and directly inoculated by
+various blood-sucking insects.
+
+
+TICKS AND DISEASES OF MAN AND ANIMALS
+
+We have seen that the way to the discoveries of the relations of
+arthropods to disease was pointed out by the work of Leuckart and
+Melnikoff on the life cycle of _Dipylidium_, and of Fedtschenko and
+Manson on that of _Filaria_. They dealt with grosser forms, belonging to
+well-recognized parasitic groups.
+
+This was long before the role of any insect as a carrier of pathogenic
+micro-organisms had been established, and before the Protozoa were
+generally regarded as of importance in the causation of disease. The
+next important step was taken in 1889 when Smith and Kilbourne
+conclusively showed that the so-called Texas fever of cattle, in the
+United States, is due to an intracorpuscular blood parasite transmitted
+exclusively by a tick. This discovery, antedating by eight years the
+work on the relation of the mosquito to malaria, had a very great
+influence on subsequent studies along these lines.
+
+While much of the recent work has dealt with the true insects, or
+hexapods, it is now known that several of the most serious diseases of
+animals, and at least two important diseases of man are tick borne.
+These belong to the types known collectively as _babesioses_ (or
+"_piroplasmoses_"), and _spirochaetoses_.
+
+The term _babesiosis_ is applied to a disease of man or animals which is
+caused by minute protozoan parasites of the genus _Babesia_, living in
+the red blood corpuscles. These parasites have usually been given the
+generic name _Piroplasma_ and hence the type of disease which they cause
+is often referred to as "_piroplasmosis_." The best known illustration
+is the disease known in this country as Texas fever of cattle.
+
+
+CATTLE TICKS AND TEXAS FEVER--The cattle disease, which in the United
+States is known as Texas fever, is a widely distributed, exceedingly
+acute disease. In Australia it is known as _redwater fever_ and in
+Europe as haemoglobinuria, due to the fact that the urine of the diseased
+animals is discolored by the breaking down of the red blood corpuscles
+infested by the parasite.
+
+In their historical discussion, Smith and Kilbourne, point out that as
+far back as 1796 it was noted that Southern cattle, in a state of
+apparent health, might spread a fatal disease among Northern herds. As
+observations accumulated, it was learned that this infection was carried
+only during the warm season of the year and in the depth of winter
+Southern cattle were harmless. Moreover, Southern cattle after remaining
+for a short time in the North lost their power to transmit the disease,
+and the same was true of cattle which had been driven for a considerable
+distance.
+
+Very significant was the fact that the infection was not communicated
+directly from the Southern to Northern cattle but that the ground over
+which the former passed was infected by them, and that the infection was
+transmitted thence to susceptible cattle _after a period of not less
+than thirty days had elapsed_.
+
+Of course a disease as striking as this, and which caused such enormous
+losses of cattle in the region invaded was fruitful in theories
+concerning its causation. The most widespread was the belief that
+pastures were infected by the saliva, urine, or manure of Southern
+cattle. There were not wanting keen observers who suggested that the
+disease was caused by ticks, but little weight was given to their view.
+
+Various workers had described bacteria which they had isolated from the
+organs of the diseased animals, but their findings could not be
+verified. In 1889, Smith and Kilbourne discovered a minute, pear-shaped
+organism (fig. 138) in the red blood corpuscles of a cow which had
+succumbed to Texas fever. On account of their shape they were given the
+generic name _Pyrososma_ and because they were usually found two in a
+corpuscle, the specific name, _bigeminum_. It is now generally accepted
+that the parasite is the same which Babes had observed the year before
+in Roumanian cattle suffering from haemoglobinuria, and should be known
+as _Babesia bovis_ (Babes).
+
+[Illustration: 138. Babesia bovis in blood corpuscles. After Calli.]
+
+[Illustration: 139. The cattle tick (Boophilus annulatus). (_a_) Female;
+(_b_) male. After Comstock.]
+
+By a series of perfectly conclusive experiments carried on near
+Washington, D.C., Smith and Kilbourne showed that this organism was
+carried from Southern cattle to non-immune animals by the so-called
+Southern cattle tick, _Boophilus annulatus_ (= _Margaropus annulatus_)
+(fig. 139).
+
+Of fourteen head of native cattle placed in a field with tick-infested
+Northern cattle all but two contracted the disease. This experiment was
+repeated with similar results. Four head of native cattle kept in a plot
+with three North Carolina cattle which had been carefully freed from
+ticks remained healthy. A second experiment the same year gave similar
+results.
+
+Still more conclusive was the experiment showing that fields which had
+not been entered by Southern cattle but which had been infected by
+mature ticks taken from such animals would produce Texas fever in native
+cattle. On September 13, 1889, several thousand ticks collected from
+cattle in North Carolina three and four days before, were scattered in a
+small field near Washington. Three out of four native animals placed in
+this field contracted the disease. The fourth animal was not examined as
+to its blood but it showed no external symptoms of the disease.
+
+[Illustration: 140. Hyalomma aegypticum. After Nuttall and Warburton.]
+
+In these earlier experiments it was believed that the cattle tick acted
+as a carrier of the disease between the Southern cattle and the _soil_
+of the Northern pastures. "It was believed that the tick obtained the
+parasite from the blood of its host and in its dissolution on the
+pasture a certain resistant spore form was set free which produced the
+disease when taken in with the food." The feeding of one animal for some
+time with grass from the most abundantly infected field, without any
+appearance of the disease, made this hypothesis untenable.
+
+In the experimental work in 1890 the astonishing fact was brought out
+that the disease was conveyed neither by infected ticks disintegrating
+nor by their directly transferring the parasite, but that it was
+conveyed by the young hatched from eggs of infected ticks. In other
+words, the disease was hereditarily transferred to ticks of the second
+generation and they alone were capable of conveying it.
+
+Thus was explained the fact that Texas fever did not appear immediately
+along the route of Southern cattle being driven to Northern markets but
+that after a certain definite period it manifested itself. It was
+conveyed by the progeny of ticks which had dropped from the Southern
+cattle and deposited their eggs on the ground.
+
+These results have been fully confirmed by workers in different parts of
+the world,--notably by Koch, in Africa, and by Pound, in Australia.
+
+The disease is apparently transmitted by _Boophilus annulatus_ alone, in
+the United States, but it, or an almost identical disease, is conveyed
+by _Ixodes hexagonus_ in Norway, _Ixodes ricinus_ in Finland and France
+and by the three species, _Boophilus decoloratus_, _Hyalomma aegypticum_
+(fig. 140 and 141), and _Haemaphysalis punctata_ in Africa.
+
+[Illustration: 141. Hyalomma aegypticum. Capitulum of female; (_a_)
+dorsal, (_b_) ventral aspect.]
+
+In spite of the detailed study which it has received, the life cycle of
+_Babesia bovis_ has not been satisfactorily worked out. The asexual
+reproduction in the blood of the vertebrate host has been described but
+the cycle in the tick is practically unknown.
+
+More successful attempts have been made to work out the life cycle of a
+related species, _Babesia canis_, which causes malignant jaundice in
+dogs in Africa and parts of Southern Europe. In this instance, also, the
+disease is transmitted by heredity to the ticks of the second
+generation. Yet the larval, or "seed ticks," from an infected female are
+not capable of conveying the disease, but only the nymphs and adults.
+Still more complicated is the condition in the case of _Babesia ovis_ of
+sheep, which Motas has shown can be conveyed solely by the adult,
+sexually mature ticks of the second generation.
+
+In _Babesia canis_, Christopher (1907) observed developmental stages in
+the tick. He found in the stomach of adult ticks, large motile
+club-shaped bodies which he considered as ookinetes. These bodies pass
+to the ovaries of the tick and enter the eggs where they become globular
+in form and probably represent an oocyst. This breaks up into a number
+of sporoblasts which enter the tissues of the developing tick and give
+rise to numerous sporozoites, which collect in the salivary glands and
+thence are transferred to the vertebrate host. A number of other species
+of _Babesia_ are known to infest vertebrates and in all the cases where
+the method has been worked out it has been found that the conveyal was
+by ticks. We shall not consider the cases more fully here, as we are
+concerned especially with the method of transfer of human diseases.
+
+
+TICKS AND ROCKY MOUNTAIN SPOTTED FEVER OF MAN--Ever since 1873 there has
+been known in Montana and Idaho a peculiar febrile disease of man, which
+has gained the name of "Rocky Mountain spotted fever." Its onset is
+marked by chills and fever which rapidly become acute. In about four to
+seven days there appears a characteristic eruption on the wrists, ankles
+or back, which quickly covers the body.
+
+McClintic (1912) states that the disease has now been reported from
+practically all of the Rocky Mountain States, including Arizona,
+California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, Washington,
+and Wyoming. "Although the disease is far more prevalent in Montana and
+Idaho than in any of the other States, its spread has assumed such
+proportions in the last decade as to call for the gravest consideration
+on the part of both the state and national health authorities. In fact,
+the disease has so spread from state to state that it has undoubtedly
+become a very serious interstate problem demanding the institution of
+measures for its control and suppression."
+
+A peculiar feature of the Rocky Mountain spotted fever is a marked
+variation in its severity in different localities. In Montana, and
+especially in the famous Bitter Root Valley, from 33 per cent to 75 per
+cent of the cases result fatally. On the other hand, the fatality does
+not exceed four per cent in Idaho.
+
+In 1902, Wilson and Chowning reported the causative organism of spotted
+fever to be a blood parasite akin to the _Babesia_ of Texas fever, and
+made the suggestion that the disease was tick-borne. The careful studies
+of Stiles (1905) failed to confirm the supposed discovery of the
+organism, and the disease is now generally classed as due to an
+invisible virus. On the other hand, the accumulated evidence has fully
+substantiated the hypothesis that it is tick-borne.
+
+According to Ricketts (1907) the experimental evidence in support of
+this hypothesis was first afforded by Dr. L. P. McCalla and Dr. H. A.
+Brereton, in 1905. These investigators transmitted the disease from man
+to man in two experiments. "The tick was obtained 'from the chest of a
+man very ill with spotted fever' and 'applied to the arm of a man who
+had been in the hospital for two months and a half, and had lost both
+feet from gangrene due to freezing.' On the eighth day the patient
+became very ill and passed through a mild course of spotted fever,
+leaving a characteristic eruption. The experiment was repeated by
+placing the tick on a woman's leg and she likewise was infected with
+spotted fever."
+
+The most detailed studies were those of the late Dr. H. T. Ricketts, and
+it was he who clearly established the tick hypothesis. In the summer of
+1906 he found that guinea pigs and monkeys are very susceptible to
+spotted fever and can readily be infected by inoculation of blood from
+patients suffering from the disease. This opened the way to experimental
+work on tick transmission. A female tick was fed upon an infected guinea
+pig for two days, removed and isolated for two days and then placed upon
+a healthy guinea pig. After an incubation period of three and a half
+days the experimental animal contracted a well-marked case of the
+disease.
+
+A similar result was obtained at the same time by King, and later in the
+season Ricketts proved that the male tick was also capable of
+transmitting the disease. He found that there was a very intimate
+relation of the virus to the tick and that the transmission must be
+regarded as biological throughout. Ticks remained infective as long as
+they lived and would feed for a period of several months. If they
+acquired the disease in the larval or nymphal stage they retained it
+during molting and were infective in the subsequent stages. In a few
+cases the larvae from an infected female were infective.
+
+The evidence indicated that the tick suffers from a relatively harmless,
+generalized infection and the virus proliferates in its body. The
+disease probably is transferred through the salivary secretion of the
+tick since inoculation experiments show that the salivary glands of the
+infected adult contain the virus.
+
+It is probable that in nature the reservoir of the virus of spotted
+fever is some one or more of the native small animals. Infected ticks
+have been found in nature, and as various wild animals are susceptible
+to the disease, it is obvious that it may exist among them unnoticed.
+Wilson and Chowning suggested that the ground squirrel plays the
+principal role.
+
+Unfortunately, much confusion exists regarding the correct name of the
+tick which normally conveys the disease. In the medical literature it is
+usually referred to as _Dermacentor occidentalis_, but students of the
+group now agree that it is specifically distinct. Banks has designated
+it as _Dermacentor venustus_ and this name is used in the publications
+of the Bureau of Entomology. On the other hand, Stiles maintains that
+the common tick of the Bitter Root Valley, and the form which has been
+collected by the authors who have worked on Rocky Mountain spotted fever
+in that region, is separable from _D. venustus_, and he has described it
+under the name of _Dermacentor andersoni_.
+
+Mayer (1911) has shown experimentally that spotted fever may be
+transmitted by several different species of ticks, notably _Dermacentor
+marginatus_, _Dermacentor variabilis_ and _Amblyomma americanum_. This
+being the case, the question of the exact systematic status of the
+species experimented upon in the Bitter Root Valley becomes less
+important, for since _Dermacentor occidentalis_, _Dermacentor venustus_
+and _Dermacentor andersoni_ all readily attack man, it is probable that
+either species would readily disseminate the disease if it should spread
+into their range.
+
+Hunter and Bishop (1911) have emphasized the fact that in the eastern
+and southern United States there occur several species which attack man,
+and any one of which might transmit the disease from animal to animal
+and from animal to man. The following species, they state, would
+probably be of principal importance in the Southern and Eastern States:
+the lone star tick (_Amblyomma americanum_); the American dog tick
+(_Dermacentor variabilis_); and the gulf-coast tick (_Amblyomma
+maculatum_). In the extreme southern portions of Texas, _Amblyomma
+cajennense_, is a common pest of man.
+
+Since the evidence all indicates that Rocky Mountain spotted fever is
+transmitted solely by the tick, and that some of the wild animals serve
+as reservoirs of the virus, it is obvious that personal prophylaxis
+consists in avoiding the ticks as fully as possible, and in quickly
+removing those which do attack. General measures along the line of tick
+eradication must be carried out if the disease is to be controlled. That
+such measures are feasible has been shown by the work which has been
+done in controlling the tick-borne Texas fever of cattle, and by such
+work as has already been done against the spotted fever tick, which
+occurs on both wild and domestic animals. Detailed consideration of
+these measures is to be found in the publications of the Public Health
+and Marine Hospital Service, and the Bureau of Entomology. Hunter and
+Bishopp give the following summarized recommendations for control or
+eradication measures in the Bitter Root Valley.
+
+(1) A campaign of education, whereby all the residents of the valley
+will be made thoroughly familiar with the feasibility of the plan of
+eradication, and with what it will mean in the development of the
+valley.
+
+(2) The obtaining of legislation to make it possible to dip or oil all
+live stock in the Bitter Root Valley.
+
+(3) The obtaining of an accurate census of the horses, cattle, sheep,
+mules, and dogs in the valley.
+
+(4) The construction of ten or more dipping vats.
+
+(5) The providing of materials to be used in the dipping mixture.
+
+(6) The organization of a corps of workers to carry on the operations.
+
+(7) The systematic dipping of the horses, cattle, sheep, and dogs of the
+valley on a definite weekly schedule from approximately March 10 to June
+9.
+
+(8) The treatment by hand of the animals in localities remote from vats,
+on the same schedule.
+
+They estimate that after three seasons' operations a very small annual
+expenditure would provide against reinfestation of the valley by the
+incoming of cattle from other places.
+
+Supplementary measures consist in the killing of wild mammals which may
+harbor the tick; systematic burning of the brush and debris on the
+mountain side; and in clearing, since the tick is seldom found on land
+under cultivation.
+
+
+
+
+CHAPTER X
+
+ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA [_Continued_]
+
+
+ARTHROPODS AND SPIROCHAETOSES OF MAN AND ANIMALS
+
+The term spirochaetoses is applied to diseases of man or animals which
+are due to protistan parasites belonging to the group of slender, spiral
+organisms known as spirochaetes.
+
+There has been much discussion concerning the relationship Of the
+spirochaetes. Formerly, they were regarded as bacteria closely related to
+the forms grouped in the genus _Spirillum_. The results of the detailed
+study which the spirochaetes have received in recent years, have led most
+of the workers to consider them as belonging to the protozoa. The merits
+of the discussion we are not concerned with here, but rather with the
+fact that a number of diseases caused by spirochaetes are
+arthropod-borne. The better known of these we shall discuss.
+
+
+AFRICAN RELAPSING FEVER OF MAN--It has long been known to the natives of
+Africa and to travelers in that country, that the bite of a certain
+tick, _Ornithodoros moubata_, may be followed by severe or even fatal
+fever of the relapsing type. Until recent years, it was supposed that
+the effect was due to some special virulence of the tick, just as nagana
+of cattle was attributed to the direct effect of the bite of the
+tsetse-fly. The disease is commonly known as "tick-fever" or by the
+various native names of the tick.
+
+In 1904, Ross and Milne, in Uganda, and Dutton and Todd on the Congo,
+discovered that the cause of the disease is a spirochaete which is
+transmitted by the tick. This organism has been designated by Novy and
+Knapp as _Spirochaeta duttoni_.
+
+_Ornithodoros moubata_ (fig. 142), the carrier of African relapsing
+fever, or "tick-fever," is widely distributed in tropical Africa, and
+occurs in great numbers in the huts of natives, in the dust, cracks and
+crevices of the dirt floors, or the walls. It feeds voraciously on man
+as well as upon birds and mammals. Like others of the _Argasidae_, it
+resembles the bed-bug in its habit of feeding primarily at night. Dutton
+and Todd observed that the larval stage is undergone in the egg and that
+the first free stage is that of the octopod nymph.
+
+[Illustration: 142. Ornithodoros moubata. (_a_) Anterior part of venter;
+(_b_) second stage nymph; (_c_) capitulum; (_d_) dorsal and (_e_)
+ventral aspect of female; (_f_) ventral aspect of nymph; (_g_) capitulum
+of nymph. After Nuttall and Warburton.]
+
+The evidence that the fever is transmitted by this tick is conclusive.
+Koch found that from five per cent to fifteen per cent, and in some
+places, fifty per cent of the ticks captured, harbored the spirochaete.
+The disease is readily transmitted to monkeys, rats, mice and other
+animals and the earlier experiments along these lines have been
+confirmed by many workers.
+
+Not only are the ticks which have fed on infected individuals capable of
+conveying the disease to healthy animals but they transmit the causative
+organism to their progeny. Thus Mollers (1907), working in Berlin,
+repeatedly infected monkeys through the bites of nymphs which had been
+bred in the laboratory from infected ticks. Still more astonishing was
+his discovery that ticks of the third generation were infective. In
+other words, if the progeny of infected ticks were fed throughout life
+on healthy animals, and on maturity deposited eggs, the nymphs which
+hatched from these eggs would still be capable of carrying the
+infection.
+
+The developmental cycle of the spirochaete within the tick has not been
+fully worked out, though the general conclusions of Leishman (1910) have
+been supported by the recent works of Balfour (1911 and 1912), and
+Hindle (1912), on the life cycle of spirochaetes affecting fowls.
+
+_Spirochaeta duttoni_ ingested by _Ornithodoros moubata_ apparently
+disappear within a few days, but Leishman believed that in reality they
+break up into minute granules which are to be found in the alimentary
+canal, the salivary glands and the Malpighian tubes of the tick. These
+granules, or "coccoid bodies," as Hindle calls them, are supposed to be
+the form in which the spirochaetes infect the new host. We shall see
+later that Marchoux and Couvy (1913) dissent wholly from this
+interpretation.
+
+According to Leishman, and Hindle, the coccoid bodies are not injected
+into the vertebrate host with the saliva of the tick, as are the
+sporozoites of malaria with that of the mosquito. Instead, they pass out
+with the excrement and secondarily gain access to the wound inflicted by
+the tick.
+
+Nuttall (1912) calls attention to the fact that the geographical
+distribution of _Ornithodoros moubata_ is far wider than our present
+records show for the distribution of the relapsing fever in man and that
+there is every reason to fear the extension of the disease. Huts where
+the ticks occur should be avoided and it should be remembered that in
+infected localities there is special danger in sleeping on the ground.
+
+
+EUROPEAN RELAPSING FEVER--There is widely distributed in Europe a type
+of relapsing fever which is caused by _Spirochaeta recurrentis_. It has
+long been supposed that this disease is spread by the bed-bug and there
+is some experimental evidence to show that it may be conveyed by these
+insects.
+
+In 1897, Tictin found that he could infect monkeys by inoculating the
+contents of bed-bugs which had fed upon a patient within forty-eight
+hours. Nuttall, in 1907, in one experiment succeeded in transmitting
+_Spirochaeta recurrentis_ from mouse to mouse by bites of bed-bugs. The
+bugs, thirty-five in number, were transferred at short intervals from
+one mouse to another, not being allowed to take a full meal on the
+first, or infected mouse.
+
+On the other hand, there is much clinical evidence to show that the
+European relapsing fever like various other types of the disease is
+transmitted from man to man by head and body lice (_Pediculus humanus_
+and _Pediculus corporis_).
+
+Interesting supplementary evidence is that of Bayon's observations
+(1912), in Moscow. "Having visited the big municipal night hospitals at
+Moscow I soon noticed that they were kept with such scrupulous
+cleanliness, disinfected so lavishly, the beds of iron, the floor
+cemented, that it was not possible for bed-bugs to thrive to any extent
+on the premises. The people sleeping there were allowed, however, to
+sleep in their own clothes. The introduction of these model homes had
+not had any effect on the incidence of relapsing fever, for the places
+were still hot-beds of the fever during winter. On the other hand,
+though I changed my rooms several times, I found bugs in every
+successive lodging, and I was told in Moscow, this can hardly be
+avoided. Yet no foreigner, or Russian of the better class, ever catches
+relapsing fever. To this may be added the fact that when I asked for
+clothes-lice and promised to pay a kopec for two, the attendants from
+the night hostel brought me next morning a small ounce bottle crammed
+with _Pediculus capitis_ (= _P. humanus_), and _Pediculus vestimentorum_
+(= _P. corporis_) collected off the sleepers. If relapsing fever were
+transmitted by bed-bugs, it would be much more disseminated than it is
+at present in Moscow."
+
+Direct experimental evidence of the agency of lice in transmitting
+relapsing fever is especially clear in the case of a type of the disease
+prevalent in parts of North Africa. We shall consider this evidence
+later.
+
+
+OTHER TYPES OF RELAPSING FEVER OF MAN--In addition to the three types of
+human relapsing fever already referred to, several others have been
+distinguished and have been attributed to distinct species of
+spirochaetes. The various spirochaetoses of man are:
+
+African, caused by _S. duttoni_; European, caused by _S. recurrentis_;
+North African, caused by _S. berbera_; East African, caused by _S.
+rossi_; East Indian, caused by _S. carteri_; North American, caused by
+_S. novyi_; South American, caused by _S. duttoni_ (?).
+
+Nuttall (1912) in his valuable resume of the subject, has emphasized
+that "in view of the morphological similarity of the supposedly
+different species of spirochaetes and their individual variations in
+virulence, we may well doubt if any of the 'species' are valid. As I
+pointed out four years ago, the various specific names given to the
+spirochaetes causing relapsing fever in man may be used merely for
+convenience _to distinguish strains or races_ of different origin. They
+cannot be regarded as valid names, in the sense of scientific
+nomenclature, for virulence and immunity reactions are not adequate
+tests of specificity."
+
+
+NORTH AFRICAN RELAPSING FEVER OF MAN--The type of human relapsing fever
+to be met with in Algeria, Tunis, and Tripoli, is due to a _Spirochaeta_
+to which does not differ morphologically from _Spirochaeta duttoni_, but
+which has been separated on biological grounds as _Spirochaeta berberi_.
+
+Experimenting with this type of disease in Algeria, Sergent and Foly
+(1910), twice succeeded in transmitting it from man to monkeys by
+inoculation of crushed body lice and in two cases obtained infection of
+human subjects who had received infected lice under their clothing and
+who slept under coverings harboring many of the lice which had fed upon
+a patient. Their results were negative with _Argas persicus_, _Cimex
+lectularius_, _Musca domestica_, _Haematopinus spinulosus_ and
+_Ceratophyllus fasciatus_. They found body lice associated with every
+case of relapsing fever which they found in Algeria.
+
+Nicolle, Blaizot, and Conseil (1912) showed that the louse did not
+transmit the parasite by its bite. Two or three hours after it has fed
+on a patient, the spirochaetes begin to break up and finally they
+disappear, so that after a day, repeated examinations fail to reveal
+them. They persist, nevertheless, in some unknown form, for if the
+observations are continued they reappear in eight to twelve days. These
+new forms are virulent, for a monkey was infected by inoculating a
+single crushed louse which had fed on infected blood fifteen days
+before.
+
+Natural infection is indirect. Those attacked by the insect scratch, and
+in this act they excoriate the skin, crush the lice and contaminate
+their fingers. The least abrasion of the skin serves for the entrance of
+the spirochaetes. Even the contact of the soiled fingers on the various
+mucosa, such as the conjunctive of the eye, is sufficient.
+
+As in the case of _Spirochaeta duttoni_, the organism is transmitted
+hereditarily in the arthropod vector. The progeny of lice which have fed
+on infected blood may themselves be infective.
+
+
+SPIROCHAETOSIS OF FOWLS--One of the best known of the spirochaetes
+transmitted by arthropods is _Spirochaeta gallinarum_, the cause of a
+very fatal disease of domestic fowls in widely separated regions of the
+world. According to Nuttall, it occurs in Southeastern Europe, Asia,
+Africa, South America and Australia.
+
+In 1903, Marchoux and Salimbeni, working in Brazil, made the first
+detailed study of the disease, and showed that the causative organism is
+transmitted from fowl to fowl by the tick _Argas persicus_. They found
+that the ticks remained infective for at least five months. Specimens
+which had fed upon diseased birds in Brazil were sent to Nuttall and he
+promptly confirmed the experiments. Since that date many investigators,
+notably Balfour and Hindle, have contributed to the elucidating of the
+life-cycle of the parasite. Since it has been worked out more fully than
+has that of any of the human spirochaetes, we present Hindle's diagram
+(fig. 143) and quote the brief summary from his preliminary paper
+(1911_b_).
+
+"Commencing with the ordinary parasite in the blood of the fowl, the
+spirochaete grows until it reaches a certain length (16-19u) and then
+divides by transverse division. This process is repeated, and is
+probably the only method of multiplication of the parasite within the
+blood. When the spirochaetes disappear from the circulation, some of them
+break up into the coccoid bodies which, however, do not usually develop
+in the fowl. When the spirochaetes are ingested by _Argas persicus_, some
+of them pass through the gut wall into the coelomic fluid. From this
+medium they bore their way into the cells of the various organs of the
+tick and there break up into a number of coccoid bodies. These
+intracellular forms multiply by ordinary fission in the cells of the
+Malpighian tubules and gonads. Some of the coccoid bodies are formed in
+the lumen of the gut and Malpighian tubules. The result is that some of
+the coccoid bodies may be present in the Malpighian secretion and
+excrement of an infected tick and when mixed with the coxal fluid may
+gain entry into another fowl by the open wound caused by the tick's
+bite. They then elongate and redevelop into ordinary spirochaetes in the
+blood of the fowl, and the cycle may be repeated."
+
+[Illustration: 143. Spirochaeta gallinarum. After Hindle.]
+
+Hindle's account is clear cut and circumstantial, and is quite in line
+with the work of Balfour, and of Leishman. Radically different is the
+interpretation of Marchoux and Couvy (1913). These investigators
+maintain that the granules localized in the Malpighian tubules in the
+larvae and, in the adult, also in the ovules and the genital ducts of the
+male and female, are not derived from spirochaetes but that they exist
+normally in many acariens. They interpret the supposed disassociation
+of the spirochaete into granules as simply the first phase, not of a
+process of multiplication, but of a degeneration ending in the death of
+the parasite. The fragmented chromatin has lost its affinity for stains,
+remaining always paler than that of the normal spirochaetes. On the other
+hand, the granules of Leishman stain energetically with all the basic
+stains.
+
+Further, according to Marchoux and Couvy, infection takes place without
+the emission of the coxal fluid and indeed, soiling of the host by the
+coxal fluid diluting the excrement is exceptional. All of the organs of
+the Argasid are invaded by the parasites, but they pass from the
+coelom into the acini of the salivary glands and collect in its
+efferent canal. The saliva serves as the vehicle of infection.
+
+Thus, the question of the life cycle of _Spirochaeta gallinarum_, and of
+spirochaetes in general, is an open one.
+
+It should be noted that _Argas persicus_, the carrier of _Spirochaeta
+gallinarum_, is a common pest of poultry in the southwestern United
+States. Though the disease has not been reported from this country,
+conditions are such that if accidentally introduced, it might do great
+damage.
+
+
+OTHER SPIROCHAETE DISEASES OF ANIMALS--About a score of other blood
+inhabiting spirochaetes have been reported as occurring in mammals, but
+little is known concerning their life-histories. One of the most
+important is _Spirochaeta theileri_ which produces a spirochaetosis of
+cattle in the Transvaal. Theiler has determined that it is transmitted
+by an Ixodid tick, _Margaropus decoloratus_.
+
+
+TYPHUS FEVER AND PEDICULIDAE
+
+Typhus is an acute, and continued fever, formerly epidemically prevalent
+in camps, hospitals, jails, and similar places where persons were
+crowded together under insanitary conditions. It is accompanied by a
+characteristic rash, which gives the disease the common name of
+"spotted" or "lenticular" fever. The causative organism is unknown.
+
+Typhus fever has not generally been supposed to occur in the United
+States, but there have been a few outbreaks and sporadic cases
+recognized. According to Anderson and Goldberger (1912_a_), it has been
+a subject of speculation among health authorities why, in spite of the
+arrival of occasional cases in this country and of many persons from
+endemic foci of the disease, typhus fever apparently does not gain a
+foothold in the United States. These same workers showed that the
+so-called Brill's disease, studied especially in New York City, is
+identical with the typhus fever of Mexico and of Europe.
+
+The conditions under which the disease occurs and under which it spreads
+most rapidly are such as to suggest that it is carried by some parasitic
+insect. On epidemiological grounds the insects most open to suspicion
+are the lice, bed-bugs and fleas.
+
+In 1909, Nicolle, Comte and Conseil, succeeded in transmitting typhus
+fever from infected to healthy monkeys by means of the body louse
+(_Pediculus corporis_). Independently of this work, Anderson and
+Goldberger had undertaken work along this line in Mexico, and in 1910
+reported two attempts to transmit the disease to monkeys by means of
+body lice. The first experiment resulted negatively, but the second
+resulted in a slight rise in temperature, and in view of later results
+it seems that this was due to infection with typhus.
+
+Shortly after, Ricketts and Wilder (1910) succeeded in transmitting the
+disease to the monkey by the bite of body lice in two experiments, the
+lice in one instance deriving their infection from a man and in another
+from the monkey. Another monkey was infected by typhus through the
+introduction of the feces and abdominal contents of infested lice into
+small incisions. Experiments with fleas and bed-bugs resulted
+negatively.
+
+Subsequently, Goldberger and Anderson (1912_b_) indicated that the head
+louse (_Pediculus humanus_) as well, may become infected with typhus. In
+an attempt to transmit typhus fever (Mexican virus) from man to monkey
+by subcutaneous injection of a saline suspension of crushed head lice,
+the monkeys developed a typical febrile reaction with subsequent
+resistance to an inoculation of virulent typhus (Mexican) blood. In one
+of the three experiments to transmit the disease from man to monkey by
+means of the bite of the head louse, the animal bitten by the presumably
+infected head lice proved resistant to two successive immunity tests
+with virulent typhus blood.
+
+In 1910, Ricketts and Wilder reported an experiment undertaken with a
+view to determining whether the young of infected lice were themselves
+infected. Young lice were reared to maturity on the bodies of typhus
+patients, so that if the eggs were susceptible to infection at any stage
+of their development, they would have every opportunity of being
+infected within the ovary. The eggs of these infected lice were
+obtained, they were incubated, and the young lice of the second
+generation were placed on a normal rhesus monkey. The experimenters were
+unable to keep the monkey under very close observation during the
+following three or four weeks, but from the fact that he proved
+resistant to a subsequent immunity test they concluded that he probably
+owed this immunity to infection by these lice of the second generation.
+
+Anderson and Goldberger (1912_b_) object that due consideration was not
+given to the possibility of a variable susceptibility of the monkey to
+typhus. Their similar experiment was "frankly negative."
+
+Prophylaxis against typhus fever is, therefore, primarily a question of
+vermin extermination. A brief article by Dr. Goldberger (1914) so
+clearly shows the practical application of his work and that of the
+other investigators of the subject, that we abstract from it the
+following account:
+
+"In general terms it may be stated that association with a case of
+typhus fever in the absence of the transmitting insect is no more
+dangerous than is association with a case of yellow fever in the absence
+of the yellow fever mosquito. Danger threatens only when the insect
+appears on the scene."
+
+"We may say, therefore, that to prevent infection of the individual it
+is necessary for him only to avoid being bitten by the louse. In theory
+this may readily be done, for we know that the body louse infests and
+attaches itself almost entirely to the body linen, and that boiling
+kills this insect and its eggs. Individual prophylaxis is based
+essentially, therefore, on the avoidance of contact with individuals
+likely to harbor lice. Practically, however, this is not always as easy
+as it may seem, especially under the conditions of such intimate
+association as is imposed by urban life. Particularly is this the case
+in places such as some of the large Mexican cities, where a large
+proportion of the population harbors this vermin. Under such
+circumstances it is well to avoid crowds or crowded places, such as
+public markets, crowded streets, or public assemblies at which the
+'peon' gathers."
+
+"Community prophylaxis efficiently and intelligently carried out is,
+from a certain point of view, probably easier and more effective in
+protecting the individual than is the individual's own effort to guard
+himself. Typhus emphasizes, perhaps better than any other disease, the
+fact that fundamentally, sanitation and health are economic problems. In
+proportion as the economic condition of the masses has improved--that
+is, in proportion as they could afford to keep clean--the notorious
+filth disease has decreased or disappeared. In localities where it still
+prevails, its further reduction or complete eradication waits on a
+further improvement in, or extension of, the improved economic status of
+those afflicted. Economic evolution is very slow process, and, while
+doing what we can to hasten it, we must take such precautions as
+existing conditions permit, looking to a reduction in or complete
+eradication of the disease."
+
+"When possible, public bath houses and public wash houses, where the
+poor may bathe and do their washings at a minimum or without cost,
+should be provided. Similar provision should be made in military and
+construction camps. Troops in the field should be given the opportunity
+as frequently as possible to wash and _scald_ or _boil_ their body
+linen."
+
+"Lodging houses, cheap boarding houses, night shelters, hospitals, jails
+and prisons, are important factors in the spread and frequently
+constitute foci of the disease. They should receive rigid sanitary
+supervision, including the enforcement of measures to free all inmates
+of such institutions of lice on admission."
+
+"So far as individual foci of the disease are concerned these should be
+dealt with by segregating and keeping under observation all exposed
+individuals for 14 days--the period of incubation--from the last
+exposure, by disinfecting (boiling or steaming) the suspected bedding,
+body linen, and clothes, for the destruction of any possible vermin that
+they may harbor, and by fumigating (with sulphur) the quarters that they
+may have occupied."
+
+"It will be noted that nothing has been said as to the disposition of
+the patient. So far as the patient is concerned, he should be removed to
+'clean' surroundings, making sure that he does not take with him any
+vermin. This may be done by bathing, treating the hair with an
+insecticide (coal oil, tincture of larkspur), and a complete change of
+body linen. Aside from this, the patient may be treated or cared for in
+a general hospital ward or in a private house, provided the sanitary
+officer is satisfied that the new surroundings to which the patient has
+been removed are 'clean,' that is, free from vermin. Indeed, it is
+reasonably safe to permit a 'clean' patient to remain in his own home if
+this is 'clean,' for, as has already been emphasized, there can be no
+spread in the absence of lice. This is a common experience in native
+families of the better class and of Europeans in Mexico City."
+
+"Similarly the sulphur fumigation above prescribed may be dispensed with
+as unnecessary in this class of cases."
+
+
+
+
+CHAPTER XI
+
+SOME POSSIBLE, BUT IMPERFECTLY ESTABLISHED CASES OF ARTHROPOD
+TRANSMISSION OF DISEASE
+
+
+INFANTILE PARALYSIS OR ACUTE ANTERIOR POLIOMYELITIS
+
+The disease usually known in this country as infantile paralysis or,
+more technically, as acute anterior poliomyelitis, is one which has
+aroused much attention in recent years.
+
+The causative organism of infantile paralysis is unknown, but it has
+been demonstrated that it belongs to the group of filterable viruses. It
+gives rise to a general infection, producing characteristic lesions in
+the central nervous system. The result of the injury to the motor nerves
+is a more or less complete paralysis of the corresponding muscle. This
+usually manifests itself in the legs and arms. The fatal cases are
+usually the result of paralysis of the muscles of respiration. Of the
+non-fatal cases about 60 per cent remain permanently crippled in varying
+degrees.
+
+Though long known, it was not until about 1890 that it was emphasized
+that the disease occurs in epidemic form. At this time Medin reported
+his observations on an epidemic of forty-three cases which occurred in
+and around Stockholm in 1887. Since then, according to Frost (1911),
+epidemics have been observed with increasing frequency in various parts
+of the world. The largest recorded epidemics have been those in Vermont,
+1894, 126 cases; Norway and Sweden, 1905, about 1,500 cases; New York
+City, 1907, about 2,500 cases. Since 1907 many epidemics have been
+reported in the United States, and especially in the Northern States
+east of the Dakotas. In 1912 there were over 300 cases of the disease in
+Buffalo, N. Y., with a mortality of somewhat over 11 per cent.
+
+In view of the sudden prominence and the alarming spread of infantile
+paralysis, there have been many attempts to determine the cause, and the
+manner in which the disease spreads and develops in epidemic form. In
+the course of these studies, the question of possible transmission by
+insects was naturally suggested.
+
+C. W. Howard and Clark (1912) presented the results of studies in this
+phase of the subject. They dealt especially with the house-fly, bedbug,
+head, and body lice, and mosquitoes. It was found that the house-fly
+(_Musca domestica_) can carry the virus of poliomyelitis in an active
+state for several days upon the surface of the body and for several
+hours within the gastro-intestinal tract. Mosquitoes and lice were found
+not to take up or maintain the virus. On the other hand, the bedbug
+(_Cimex lectularius_) was found to take the virus from the infected
+monkeys and to maintain it in a living state within the body for a
+period of seven days. This was demonstrated by grinding up in salt
+solution, insects which had fed on poliomyelitic animals and injecting
+the filtrate into a healthy monkey. The experimenters doubted that the
+bedbug is a carrier of the virus in nature.
+
+Earlier in the same year, Brues and Sheppard published the results of an
+intensive epidemiological study of the outbreak of 1911, in
+Massachusetts. Special attention had been paid to the possibility of
+insect transfer and the following conclusion was reached:
+
+"Field work during the past summer together with a consideration of the
+epidemiology of the disease so far as known, points strongly toward
+biting flies as possible carriers of the virus. It seems probable that
+the common stable-fly (_Stomoxys calcitrans_ L.) may be responsible to a
+certain extent for the spread of acute epidemic poliomyelitis, possibly
+aided by other biting flies, such as _Tabanus lineola_. No facts which
+disprove such a hypothesis have as yet been adduced, and experiments
+based upon it are now in progress."
+
+As stated by Brues (1913), especial suspicion fell upon the stable-fly
+because:
+
+1. The blood-sucking habits of the adult fly suit it for the transfer of
+virus present in the blood.
+
+2. The seasonal abundance of the fly is very closely correlated with the
+incidence of the disease, rising rapidly during the summer and reaching
+a maximum in July and August, then slowly declining in September and
+October.
+
+3. The geographical distribution of the fly is, so far as can be
+ascertained, wider, or at least co-extensive with that of poliomyelitis.
+
+4. _Stomoxys_ is distinctly more abundant under rural conditions, than
+in cities and thickly populated areas.
+
+5. While the disease spreads over districts quickly and in a rather
+erratic way, it often appears to follow along lines of travel, and it is
+known that _Stomoxys_ flies will often follow horses for long distances
+along highways.
+
+6. In a surprisingly large number of cases, it appeared probable that
+the children affected had been in the habit of frequenting places where
+_Stomoxys_ is particularly abundant, i.e., about stables, barnyards,
+etc.
+
+The experiments referred to were carried on during the summer of 1912
+and in September Dr. Rosenau announced that the disease was transferred
+by the bite of the stable-fly.
+
+A monkey infected by inoculation was exposed to the bites of upwards of
+a thousand of the _Stomoxys_ flies daily, by stretching it at full
+length and rolling it in a piece of chicken wire, and then placing it on
+the floor of the cage in which the flies were confined. The flies fed
+freely from the first, as well as later, after paralysis had set in.
+Alternating with the inoculated monkey, healthy monkeys were similarly
+introduced into the cage at intervals. New monkeys were inoculated to
+keep a supply of such infected animals and additional healthy ones were
+exposed to the flies, which fed willingly and in considerable numbers on
+each occasion. "Thus the flies were given every opportunity to obtain
+infection from the monkeys, since the animals were bitten during
+practically every stage of the disease from the time of the inoculation
+of the virus till their death following the appearance of paralysis. By
+the same arrangement the healthy monkeys were likely to be bitten by
+flies that had previously fed during the various stages of the disease
+on the infected monkeys. The flies had meanwhile enjoyed the opportunity
+of incubating the virus for periods varying from the day or two which
+usually elapses between consecutive feedings, to the two or three-week
+period for which at least some (although a very small percentage) of the
+flies lived in the cage."
+
+"In all, twelve apparently healthy monkeys of a small Japan species were
+exposed to the flies in the manner described for the infected monkeys.
+Some were placed in the cage only once or twice and others a number of
+times after varying intervals. These exposures usually lasted for about
+half an hour, but were sometimes more protracted. No results were
+apparent until two or three weeks after the experiment was well under
+way, and then in rather rapid succession six of the animals developed
+symptoms of poliomyelitis. In three, the disease appeared in a virulent
+form, resulting in death, while the other three experienced transient
+tremblings, diarrhoea, partial paralysis and recovery."--Brues, 1913.
+
+Very soon after the announcement of the results of experiments by
+Rosenau and Brues, they were apparently conclusively confirmed by
+Anderson and Frost (1912), who repeated the experiments, at Washington.
+They announced that through the bites of the _Stomoxys_ flies that had
+previously fed on infected monkeys, they had succeeded in experimentally
+infecting three healthy monkeys.
+
+The results of these experiments gained much publicity and in spite of
+the conservative manner in which they had been announced, it was widely
+proclaimed that infantile paralysis was conveyed in nature by the
+stable-fly and by it alone.
+
+Serious doubt was cast on this theory by the results of further
+experiments by Anderson and Frost, reported in May of 1913. Contrary to
+the expectations justified by their first experience, the results of all
+the later, and more extended, experiments were wholly negative. Not once
+were these investigators again able to transmit the infection of
+poliomyelitis through _Stomoxys_. They concluded that it was extremely
+doubtful that the insect was an important factor in the natural
+transmission of the disease, not only because of their series of
+negative results, "but also because recent experiments have afforded
+additional evidence of the direct transmissibility or contagiousness of
+poliomyelitis, and because epidemiological studies appear to us to
+indicate that the disease is more likely transmitted largely through
+passive human virus carriers."
+
+Soon after this, Kling and Levaditi (1913) published their detailed
+studies on acute anterior poliomyelitis. They considered that the
+experiments of Flexner and Clark (and Howard and Clark), who fed
+house-flies on emulsion of infected spinal cord, were under conditions
+so different from what could occur in nature that one could not draw
+precise conclusions from them regarding the epidemiology of the disease.
+They cited the experiments of Josefson (1912), as being under more
+reasonable conditions. He sought to determine whether the inoculation of
+monkeys with flies caught in the wards of the Hospital for Contagious
+Diseases at Stockholm, where they had been in contact with cases of
+poliomyelitis, would produce the disease. The results were completely
+negative.
+
+Kling and Lavaditi made four attempts of this kind. The flies were
+collected in places where poliomyelitics had dwelt, three, four and
+twenty-four after the beginning of the disease in the family and one,
+three, and fifteen days after the patient had left the house. These
+insects were for the greater part living and had certainly been in
+contact with the infected person. In addition, flies were used which had
+been caught in the wards of the Hospital for Contagious Diseases at
+Soderkoping, when numbers of poliomyelitics were confined there.
+Finally, to make the conditions as favorable as possible, the emulsions
+prepared from these flies were injected without previous filtering,
+since filtration often causes a weakening of the virus. In spite of
+these precautions, all their results were negative, none of the
+inoculated animals having contracted poliomyelitis. They also
+experimented with bedbugs which had fed upon infected patients at
+various stages of the disease, but the results in these cases also were
+wholly negative.
+
+Kling and Levaditi considered at length the possibility of transmission
+of the disease by _Stomoxys_. As a result of their epidemiological
+studies, they found that infantile paralysis continued to spread in
+epidemic form in the dead of winter, when these flies were very rare and
+torpid, or were even completely absent. Numerous cases developed in the
+northern part of Sweden late in October and November, long after snow
+had fallen. On account of the rarity of the Stomoxys flies during the
+period of their investigations they were unable to conduct satisfactory
+experiments. In one instance, during a severe epidemic, they found a
+number of the flies in a stable near a house inhabited by an infected
+family, though none was found in the house itself. These flies were used
+in preparing an emulsion which, after filtering, was injected into the
+peritoneal cavity of a monkey. The result was wholly negative.
+
+As for the earlier experiments, Kling and Levaditi believe if the flies
+were responsible for the transmission of the disease in the cases
+reported by Rosenau and Brues, and the first experiments of Anderson and
+Frost, it was because the virus of infantile paralysis is eliminated
+with the nasal secretions of paralyzed monkeys and the flies, becoming
+contaminated, had merely acted as accidental carriers.
+
+Still further evidence against the hypothesis of the transmission of
+acute anterior poliomyelitis by _Stomoxys calcitrans_ was brought
+forward by Sawyer and Herms (1913). Special precautions were used to
+prevent the transference of saliva or other possibly infectious material
+from the surface of one monkey to that of another, and to avoid the
+possibility of complicating the experiments by introducing other
+pathogenic organisms from wild flies, only laboratory-bred flies were
+used. In a series of seven carefully performed experiments, in which the
+conditions were varied, Sawyer and Herms were unable to transmit
+poliomyelitis from monkey to monkey through the agency of _Stomoxys_, or
+to obtain any indication that the fly is the usual agent for spreading
+the disease in nature.
+
+The evidence at hand to date indicates that acute anterior
+poliomyelitis, or infantile paralysis, is transmitted by contact with
+infected persons. Under certain conditions insects may be agents in
+spreading the disease, but their role is a subordinate one.
+
+
+Pellagra
+
+PELLAGRA is an endemic and epidemic disease characterized by a peculiar
+eruption or erythema of the skin (figs 144 and 145), digestive
+disturbances and nervous trouble. Insanity is a common result, rather
+than a precursor of the disease. The manifestations of pellagra are
+periodic and its duration indeterminate.
+
+[Illustration: 144. Pellagrous eruption on the face. After Watson.]
+
+The disease is one the very name of which was almost unknown in the
+United States until within the past decade. It has usually been regarded
+as tropical, though it occurs commonly in Italy and in various parts of
+Europe. Now it is known that it not only occurs quite generally in the
+United States but that it is spreading. Lavinder (1911) says that "There
+are certainly many thousand cases of the disease in this country, and
+the present situation must be looked upon with grave concern."
+
+It is not within the scope of this book to undertake a general
+discussion of pellagra. The subject is of such importance to every
+medical man that we cannot do better than refer to Lavinder's valuable
+precis. We can only touch briefly upon the entomological phases of the
+problems presented.
+
+The most commonly accepted theories regarding the etiology of the
+disease have attributed it to the use of Indian corn as an article of
+diet. This supposed relationship was explained either on the basis of,
+(a) insufficiency of nutriment and inappropriateness of corn as a prime
+article of food; (b) toxicity of corn or, (c) parasitism of certain
+organisms--fungi or bacteria--ingested with either sound or deteriorated
+corn.
+
+In 1905, Sambon proposed the theory of the protozoal origin of pellagra
+and in 1910 he marshalled an imposing array of objections to the theory
+that there existed any relationship between corn and the disease. He
+presented clear evidence that pellagra existed in Europe before the
+introduction of Indian corn from America, as an article of diet, and
+that its spread was not _pari passu_ with that of the use of corn. Cases
+were found in which the patients had apparently never used corn, though
+that is obviously difficult to establish. He showed that preventive
+measures based on the theory had been a failure. Finally, he believed
+that the recurrence of symptoms of the disease for successive springs,
+in patients who abstained absolutely from the use of corn, militated
+against the theory.
+
+[Illustration: 145. Pellagrous eruption on the hand. After Watson.]
+
+On the other hand, Sambon believed that the periodicity of the symptoms,
+peculiarities of distribution and seasonal incidence, and analogies of
+the symptoms to those of other parasitic diseases indicated that
+pellagra was of protozoal origin, and that it was insect-borne.
+
+The insect carriers, he believed to be one or more species of Simuliidae,
+or black-flies. In support of this he stated that _Simulium_ appears to
+effect the same topographical conditions as pellagra, that in its imago
+stage it seems to present the same seasonal incidence, that it has a
+wide geographical distribution which seems to cover that of pellagra,
+and that species of the genus are known to cause severe epizootics.
+Concluding from his studies in Italy, that pellagra was limited almost
+wholly to agricultural laborers, he pointed out that the Simulium flies
+are found only in rural districts, and as a rule do not enter towns,
+villages, or houses.
+
+[Illustration: 146. A favorite breeding place of Simulium. Ithaca, N.
+Y.]
+
+When Sambon's detailed report was published in 1910, his theory was
+seized upon everywhere by workers who were anxious to test it and who,
+in most cases, were favorably disposed towards it because of the
+wonderful progress which had been made in the understanding of other
+insect-borne diseases. In this country, the entomological aspects of the
+subject have been dealt with especially by Forbes (1912), and by King
+and Jennings, under the direction of W. D. Hunter, of the Bureau of
+Entomology, and in cooperation with the Thompson-McFadden Pellagra
+Commission of the Department of Tropical Medicine of the New York
+Post-Graduate Medical School. An important series of experiments with
+monkeys has been undertaken by S. J. Hunter, of Kansas, but
+unfortunately we have as yet no satisfactory evidence that these animals
+are susceptible to the disease--a fact which renders the whole problem
+difficult.
+
+The accumulated evidence is increasingly opposed to Sambon's hypothesis
+of the transmission of pellagra by _Simulium_. This has been so clearly
+manifested in the work of the Thompson-McFadden Commission that we quote
+here from the report by Jennings (1914):
+
+"Our studies in 1912 convinced us that there was little evidence to
+support the incrimination of any species of _Simulium_ in South Carolina
+in the transmission of pellagra. Reviewing the group as a whole, we find
+that its species are essentially "wild" and lack those habits of
+intimate association with man which would be expected in the vector of
+such a disease as pellagra. Although these flies are excessively
+abundant in some parts of their range and are moderately so in
+Spartanburg County, man is merely an incidental host, and no disposition
+whatever to seek him out or to invade his domicile seems to be
+manifested. Critically considered, it is nearer the fact that usually
+man is attacked only when he invades their habitat."
+
+"As our knowledge of pellagra accumulates, it is more and more evident
+that its origin is in some way closely associated with the domicile. The
+possibility that an insect whose association with man and his immediate
+environment is, at the best, casual and desultory, can be active in the
+causation of the disease becomes increasingly remote."
+
+"Our knowledge of the biting habits of _Simulium_ is not complete, but
+it is evident, as regards American species at least, that these are
+sometimes not constant for the same species in different localities.
+Certain species will bite man freely when opportunity offers, while
+others have never been known to attack him. To assume that the proximity
+of a _Simulium_-breeding stream necessarily implies that persons in its
+vicinity must be attacked and bitten is highly fallacious. In
+Spartanburg County attacks by _Simulium_ seems to be confined to the
+immediate vicinity of the breeding-places. Our records and observations,
+exceedingly few in number, refer almost exclusively to such locations.
+Statements regarding such attacks, secured with much care and
+discrimination from a large number of persons, including many
+pellagrins, indicate conclusively that these insects are seldom a pest
+of man in this county. A certain number of the persons questioned were
+familiar with the gnats in other localities, but the majority were
+seemingly ignorant of the existence of such flies with biting habits.
+This is especially striking, in view of the fact that the average
+distance of streams from the homes of the pellagra cases studied was
+about 200 yards, many being at a distance of less than 200 yards, and
+that 78 per cent of these streams were found to be infested by larval
+_Simulium_. Such ignorance in a large number of persons cannot be
+overlooked and indicates strongly that our belief in the negligible
+character of local attacks by _Simulium_ is well founded."
+
+"In localities infested by 'sand-flies,' mosquitoes, etc., these pests
+are always well known and the ignorance described above is very
+significant."
+
+"Such positive reports as we received nearly always referred to bites
+received in the open, along streams, etc., and observations made of
+their attack were of those on field laborers in similar situations.
+Males engaged in agricultural pursuits are almost exempt from pellagra
+in Spartanburg County. During the season of 1913, in some two or three
+instances, observations were made of the biting of _Simulium_ and some
+additional and entirely creditable reports were received. These
+observations and reports were under conditions identical with those
+referred to in the reports of 1912 and confirm the conclusions based on
+the observations of that year. I would repeat with emphasis that it is
+inconceivable that a fly of the appearance and habits of the prevalent
+species of _Simulium_ could be present in such a region, especially
+about the haunts of man and attack him with sufficient frequency and
+regularity to satisfactorily account for so active and prevalent a
+disease as pellagra without being a well-known and recognized pest."
+
+"In connection with the conditions in the Piedmont region of South
+Carolina, it may be well to cite the results of a study of those in the
+arid region of western Texas."
+
+"In May, 1913, in company with Capt. J. F. Siler of the
+Thompson-McFadden Pellagra Commission, I visited the region of which
+Midland in Midland County is the center. This region is very dry and
+totally devoid of running water for a long distance in every direction.
+The only natural source of water-supply, a few water holes and ponds,
+were visited and found to be of such a nature that the survival of
+_Simulium_, far less its propagation in them, is absolutely impossible.
+The nearest stream affording possibilities as a source of _Simulium_ is
+60 miles away, while the average distance of such possibility is not
+less than 100 miles."
+
+"Artificial sources of water-supply were also investigated carefully and
+were found to offer no opportunity for the breeding of _Simulium_."
+
+"At Midland the histories of five cases of pellagra were obtained, which
+gave clear evidence that this place or its immediate vicinity was the
+point of origin. Persons of long residence in the country were
+questioned as to the occurrence of such flies as _Simulium_ and returned
+negative answers. These included a retired cattle owner, who is a man of
+education and a keen observer, an expert veterinarian stationed in the
+country who has the cattle of the country under constant observation,
+and a practical cattle man, manager of a ranch and of wide experience.
+The latter had had experience with 'Buffalo gnats' in other localities
+(in the East) and is well acquainted with them. His close personal
+supervision of the cattle under his charge, makes it practically certain
+that he would have discovered these gnats had they been present in the
+country."
+
+"At the time the study was made, _Simulium_ was breeding and active in
+the adult state in the vicinity of Dallas, Texas, in the eastern part of
+the state. We have here a region in which cases of pellagra have
+originated, yet in which _Simulium_ does not and cannot breed."
+
+Other possible insect vectors of pellagra have been studied in great
+detail and the available evidence indicates that if _any_ insect plays a
+role in the spread of the disease, _Stomoxys calcitrans_ most nearly
+fills the conditions. This conclusion was announced by Jennings and King
+in 1912, and has been supported by their subsequent work.
+
+Yet, after all the studies of the past decade, the old belief that
+pellagra is essentially of dietary origin is gaining ground. Goldberger,
+Waring and Willets (1914) of the United States Public Health Service
+summarize their conclusions in the statement, (1) that it is dependent
+on some yet undetermined fault in a diet in which the animal or
+leguminous protein component is disproportionately large and (2) that no
+pellagra develops in those who _consume_ a mixed, well-balanced, and
+varied diet, such, for example, as that furnished by the Government to
+the enlisted men of the Army, Navy, and Marine Corps.
+
+
+Leprosy
+
+LEPROSY is a specific, infectious disease due to _Bacillus leprae_, and
+characterized by the formation of tubercular nodules, ulcerations, and
+disturbances of sensation. In spite of the long time that the disease
+has been known and the dread with which it is regarded, little is known
+concerning the method of transfer of the causative organism or the means
+by which it gains access to the human body.
+
+It is known that the bacilli are to be found in the tubercles, the scurf
+of the skin, nasal secretions, the sputum and, in fact in practically
+all the discharges of the leper. Under such conditions it is quite
+conceivable that they may be transferred in some instances from diseased
+to healthy individuals through the agency of insects and other
+arthropods. Many attempts have been made to demonstrate this method of
+spread of the disease, but with little success.
+
+Of the suggested insect carriers none seem to meet the conditions better
+than mosquitoes, and there are many suggestions in literature that these
+insects play an important role in the transmission of leprosy. The
+literature has been reviewed and important experimental evidence
+presented by Currie (1910). He found that mosquitoes feeding, under
+natural conditions, upon cases of nodular leprosy so rarely, if ever,
+imbibe the lepra bacillus that they cannot be regarded as one of the
+ordinary means of transference of this bacillus from lepers to the skin
+of healthy persons. He believes that the reason that mosquitoes that
+have fed on lepers do not contain the lepra bacillus is that when these
+insects feed they insert their proboscis directly into a blood vessel
+and thus obtain bacilli-free blood, unmixed with lymph.
+
+The same worker undertook to determine whether flies are able to
+transmit leprosy. He experimented with five species found in
+Honolulu,--_Musca domestica_, _Sarcophaga pallinervis_, _Sarcophaga
+barbata_, _Volucella obesa_ and an undetermined species of _Lucilia_.
+The experiments with _Musca domestica_ were the most detailed. From
+these experiments he concluded, first, that all of the above-named
+flies, when given an opportunity to feed upon leprous fluids, will
+contain the bacilli in their intestinal tracts and feces for several
+days after such feeding. Second, that considering the habits of these
+flies, and especially those of _Musca domestica_, it is certain that,
+given an exposed leprous ulcer, these insects will frequently convey
+immense numbers of lepra bacilli, directly or indirectly, to the skins,
+nasal mucosa, and digestive tracts of healthy persons. Additional
+evidence along this line has recently been brought forward by Honeij and
+Parker (1914), who incriminate both _Musca domestica_ and _Stomoxys
+calcitrans_. Whether or not such insect-borne bacilli are capable of
+infecting persons whose skin and mucosa are thus contaminated, Currie
+was unwilling to maintain, but he concludes that until we have more
+accurate knowledge on this point, we are justified in regarding these
+insects with grave suspicion of being one of the means of disseminating
+leprous infection.
+
+Various students of the subject have suggested that bed-bugs may be the
+carriers of leprosy and have determined the presence of acid-fast
+bacilli in the intestines of bed-bugs which had fed on leprous patients.
+Opposed to this, the careful experiments of Thompson (1913) and of
+Skelton and Parkham (1913) have been wholly negative.
+
+Borrel has recently suggested that _Demodex_, may play a role in
+spreading the infection in families. Many other insects and acariens
+have been suggested as possible vectors, but the experimental data are
+few and in no wise conclusive. The most that can be said is that it is
+quite possible that under favorable conditions the infection might be
+spread by any of the several blood-sucking forms or by house-flies.
+
+
+Verruga peruviana
+
+VERRUGA PERUVIANA is defined by Castellani and Chalmers as "a chronic,
+endemic, specific, general disorder of unknown origin, not contagious,
+but apparently inoculable, and characterized by an irregular fever
+associated with rheumatoid pains, anemia, followed by granulomatous
+swellings in the skin, mucous membranes, and organs of the body." It has
+been generally believed by medical men interested that the comparatively
+benign eruptive verruga is identical with the so-called Oroya, or
+Carrion's fever, a malignant type. This view is not supported by the
+work of Strong, Tyzzer and Brues, (1913).
+
+The disease is confined to South America and to definitely limited areas
+of those countries in which it does occur. It is especially prevalent in
+some parts of Peru.
+
+The causative organism and the method of transfer of verruga are
+unknown. Castellani and Chalmers pointed out in 1910 that the study of
+the distribution of the disease in Peru would impress one with the
+similarity to the distribution of the Rocky Mountain fever and would
+lead to the conclusion that the aetiological cause must in some way be
+associated with some blood-sucking animal, perhaps an arachnid, and that
+this is supported by the fact that the persons most prone to the
+infection are those who work in the fields.
+
+More recently, Townsend (1913), in a series of papers, has maintained
+that verruga and Carrion's disease are identical, and that they are
+transmitted to man by the bites of the Psychodid fly, _Phlebotomus
+verrucarum_. He succeeded in producing the eruptive type of the disease
+in experimental animals by injecting a physiological salt trituration of
+wild Phlebotomus flies. A cebus monkey was exposed from October so to
+November 6, by chaining him to a tree in the verruga zone, next to a
+stone wall from which the flies emerged in large numbers every night.
+Miliar eruption began to appear on the orbits November 13 and by
+November 21, there were a number of typical eruptions, with exudation on
+various parts of the body exactly like miliar eruptive sores commonly
+seen on legs of human cases.
+
+An assistant in the verruga work, George E. Nicholson, contracted the
+eruptive type of the disease, apparently as a result of being bitten by
+the Phlebotomus flies. He had slept in a verruga zone, under a tight
+net. During the night he evidently put his hands in contact with the
+net, for in the morning there were fifty-five unmistakable Phlebotomus
+bites on the backs of his hands and wrists.
+
+Townsend believes that in nature, lizards constitute the reservoir of
+the disease and that it is from them that the Phlebotomus flies receive
+the infection.
+
+
+Cancer
+
+There are not wanting suggestions that this dread disease is carried, or
+even caused, by arthropods. Borrel (1909) stated that he had found mites
+of the genus _Demodex_ in carcinoma of the face and of the mammae. He
+believed that they acted as carriers of the virus.
+
+Saul (1910) and Dahl (1910) go much further, since they attribute the
+production of the malignant growth to the presence of mites which Saul
+had found in cancers. These Dahl described as belonging to a new
+species, which he designated _Tarsonemus hominis_. These findings have
+since been confirmed by several workers. Nevertheless, the presence of
+the mite is so rare that it cannot be regarded as an important factor in
+the causation of the disease. The theory that cancer is caused by an
+external parasite is given little credence by investigators in this
+field.
+
+
+IN CONCLUSION, it should be noted that the medical and entomological
+literature of the past few years abounds in suggestions, and in
+unsupported direct statements that various other diseases are
+insect-borne. Knab (1912) has well said "Since the discovery that
+certain blood-sucking insects are the secondary hosts of pathogenic
+parasites, nearly every insect that sucks blood, whether habitually or
+occasionally, has been suspected or considered a possible transmitter of
+disease. No thought seems to have been given to the conditions and the
+characteristics of the individual species of blood-sucking insects,
+which make disease transmission possible."
+
+He points out that "in order to be a potential transmitter of human
+blood-parasites, an insect must be closely associated with man and
+normally have opportunity to suck his blood repeatedly. It is not
+sufficient that occasional specimens bite man, as, for example, is the
+case with forest mosquitoes. Although a person may be bitten by a large
+number of such mosquitoes, the chances that any of these mosquitoes
+survive to develop the parasites in question, (assuming such development
+to be possible), and then find opportunity to bite and infect another
+person, are altogether too remote. Applying this criterion, not only the
+majority of mosquitoes but many other blood-sucking insects, such as
+Tabanidae and Simuliidae, may be confidently eliminated. Moreover,
+these insects are mostly in evidence only during a brief season, so that
+we have an additional difficulty of a very long interval during which
+there could be no propagation of the disease in question." He makes an
+exception of tick-borne diseases, where the parasites are directly
+transmitted from the tick host to its offspring and where, for this
+reason, the insect remains a potential transmitter for a very long
+period. He also cites the trypanosome diseases as possible exceptions,
+since the causative organisms apparently thrive in a number of different
+vertebrate hosts and may be transmitted from cattle, or wild animals, to
+man.
+
+Knab's article should serve a valuable end in checking irresponsible
+theorizing on the subject of insect transmission of disease.
+Nevertheless, the principles which he laid down cannot be applied to the
+cases of accidental carriage of bacterial diseases, or to those of
+direct inoculation of pyogenic organisms, or of blood parasites such as
+the bacillus of anthrax, or of bubonic plague. Accumulated evidence has
+justified the conclusion that certain trypanosomes pathogenic to man are
+harbored by wild mammals, and so form an exception. Townsend believes
+that lizards constitute the natural reservoir of verruga; and it seems
+probable that field mice harbor the organism of tsutsugamushi disease.
+Such instances are likely to accumulate as our knowledge of the relation
+of arthropods to disease broadens.
+
+
+
+
+CHAPTER XII
+
+HOMINOXIOUS ARTHROPODS
+
+
+The following synoptic tables are presented in the hope that they may be
+of service in giving the reader a perspective of the relationships of
+the Arthropoda in general and enabling him to identify the more
+important species which have been found noxious to man. Though
+applicable chiefly to the arthropods found in the United States, exotic
+genera and species which are concerned in the transmission of disease
+are also included. For this reason the keys to the genera of the Muscids
+of the world are given. As will be seen, the tables embrace a number of
+groups of species which are not injurious. This was found necessary in
+order that the student might not be lead to an erroneous determination
+which would result were he to attempt to identify a species which
+heretofore had not been considered noxious, by means of a key containing
+only the noxious forms. The names printed in BOLD FACED TYPE indicate
+the hominoxious arthropods which have been most commonly mentioned in
+literature.
+
+
+CRUSTACEA
+
+Arthropods having two pairs of antennae which are sometimes modified for
+grasping, and usually with more than five pairs of legs. With but few
+exceptions they are aquatic creatures. Representatives are: Crabs,
+lobsters, shrimps, crayfish, water-fleas, and woodlice. To this class
+belongs the CYCLOPS (fig. 122) a genus of minute aquatic crustaceans of
+which at least one species harbors _Dracunculus medinensis_, the Guinea
+worm (fig. 121).
+
+
+MYRIAPODA
+
+Elongate, usually vermiform, wingless, terrestrial creatures having one
+pair of antennae, legs attached to each of the many intermediate body
+segments. This group is divided into two sections, now usually given
+class rank: the DIPLOPODA or millipedes (fig. 13), commonly known as
+thousand legs, characterized by having two pairs of legs attached to
+each intermediate body segment, and the CHILOPODA or centipedes (fig.
+14) having only one pair of legs to each body segment.
+
+
+ARACHNIDA
+
+In this class the antennae are apparently wanting, wings are never
+present, and the adults are usually provided with four pairs of legs.
+Scorpions, harvest-men, spiders, mites, etc.
+
+
+HEXAPODA (Insects)
+
+True insects have a single pair of antennae, which is rarely vestigial,
+and usually one or two pairs of wings in the adult stage. Familiar
+examples are cockroaches, crickets, grasshoppers, bugs, dragon-flies,
+butterflies, moths, mosquitoes, flies, beetles, ants, bees and wasps.
+
+
+ORDERS OF THE ARACHNIDA
+
+a. Abdomen distinctly segmented. A group of orders including scorpions,
+    (fig. 11), whip-scorpions (fig. 10), pseudo-scorpions, solpugids
+    (fig. 12) harvest-men (daddy-long-legs or harvestmen), etc.
+    ARTHROGASTRA
+
+aa. Abdomen unsegmented, though sometimes with numerous annulations
+    SPHAEROGASTRA
+
+  b. A constriction between cephalothorax and abdomen (fig. 7). True
+      Spiders ARANEIDA
+
+  bb. No deep constriction between these parts.
+
+    c. Legs usually well developed, body more or less depressed (fig.
+        49). Mites ACARINA
+
+    cc. Legs stumpy or absent, body more or less elongate or vermiform,
+        or if shorter, the species is aquatic or semi-aquatic in habit.
+
+      d. Four pairs of short legs; species inhabiting moss or water.
+          Water-bears. TARDIGRADA
+
+      dd. Two pairs of clasping organs near the mouth, instead of legs,
+          in the adult; worm-like creatures parasitic within the nasal
+          passages, lungs, etc. of mammals and reptiles (fig. 148).
+          Tongue worms. LINGUATULINA
+
+[Illustration: 148. Linguatula. (_a_) larva; (enlarged). (_b_) adult;
+(natural size).]
+
+
+ACARINA[E]
+
+a. Abdomen annulate, elongate; very minute forms, often with but four
+    legs (fig. 62). DEMODICOIDEA
+
+  b. With but four legs of five segments each. Living on plants, often
+      forming galls. ERIOPHYIDAE
+
+  bb. With eight legs, of three segments each. Living in the skin of
+      mammals. DEMODICIDAE
+
+    To this family belongs the genus DEMODEX found in the sebaceous
+        glands and hair follicles of various mammals, including man. _D.
+        phylloides_ Csokor has been found in Canada on swine, causing
+        white tubercles on the skin. _D. bovis_ Stiles has been reported
+        from the United States on cattle, upon the skin of which they
+        form swellings. D. FOLLICULORUM Simon is the species found on
+        man. See page 78.
+
+aa. Abdomen not annulate nor prolonged behind; eight legs in the adult
+    stage.
+
+  b. With a distinct spiracle upon a stigmal plate on each side of the
+      body (usually ventral) above the third or fourth coxae or a little
+      behind (fig. 50); palpi free; skin often coriaceous or leathery;
+      tarsi often with a sucker.
+
+    c. Hypostome large (fig. 50), furnished below with many recurved
+        teeth; venter with furrows, skin leathery; large forms, usually
+        parasitic. IXODOIDEA
+
+      d. Without scutum but covered by a more or less uniform leathery
+          integument; festoons absent; coxae unarmed, tarsi without
+          ventral spurs; pulvilli absent or vestigial in the adults;
+          palpi cylindrical; sexual dimorphism slight. ARGASIDAE
+
+        e. Body flattened, oval or rounded, with a distinct flattened
+            margin differing in structure from the general integument;
+            this margin gives the body a sharp edge which is not
+            entirely obliterated even when the tick is full fed.
+            Capitulum (in adults and nymphs) entirely invisible
+            dorsally, distant in the adult by about its own length from
+            the anterior border. Eyes absent. ARGUS Latr.
+
+          f. Body oblong; margin with quadrangular cells; anterior tibiae
+              and metatarsi each about three times as long as broad. On
+              poultry, southwest United States. A. PERSICUS MINIATUS
+
+            _A. brevipes_ Banks, a species with proportionately shorter
+                legs has been recorded from Arizona.
+
+          ff. With another combination of characters. About six other
+              species of _Argas_ from various parts of the world,
+              parasitic on birds and mammals.
+
+        ee. Body flattened when unfed, but usually becoming very convex
+            on distention; anterior end more or less pointed and
+            hoodlike; margin thick and not clearly defined, similar in
+            structure to the rest of the integument and generally
+            disappearing on distention; capitulum subterminal, its
+            anterior portions often visible dorsally in the adult; eyes
+            present in some species.
+
+          f. Integument pitted, without rounded tubercles; body provided
+              with many short stiff bristles; eyes absent. On horses,
+              cattle and man (fig. 48). OTIOBIUS Banks.
+
+            O. MEGNINI, a widely distributed species, is the type of
+                this genus.
+
+          ff. Integument with rounded tubercles or granules; body
+              without stiff bristles. ORNITHODOROS Koch.
+
+            g. Two pairs of eyes; tarsi IV with a prominent subterminal
+                spur above; leg I strongly roughened. On cattle and man.
+                O. CORIACEUS
+
+            gg. No eyes; no such spur on the hind tarsi.
+
+              h. Tarsi I without humps above. _O. talaje._
+
+              hh. Tarsi I with humps above.
+
+                i. Tarsi IV without distinct humps above. On hogs,
+                    cattle and man. O. TURICATA
+
+                ii. Tarsi IV with humps nearly equidistant (fig. 142).
+                    Africa. O. MOUBATA
+
+[Illustration: 149. Haemaphysalis wellingtoni. Note short palpi. After
+Nuttall and Warburton.]
+
+      dd. With scutum or shield (fig. 50); festoons usually present;
+          coxae usually armed with spurs, tarsi generally with one or two
+          ventral spurs; pulvilli present in the adults; sexual
+          dimorphism pronounced. IXODIDAE
+
+        e. With anal grooves surrounding anus in front; inornate;
+            without eyes; no posterior marginal festoons; venter of the
+            male with non-salient plates. Numerous species, 14 from the
+            United States, among them I. RICINUS (fig. 49 and 50),
+            SCAPULARIS, COOKEI, _hexagonus_, _bicornis_. IXODES Latr.
+            (including Ceratixodes).
+
+        ee. With anal groove contouring anus behind, or groove faint or
+            obsolete.
+
+          f. With short palpi (fig. 149).
+
+            g. Without eyes, inornate, with posterior marginal festoons;
+                male without ventral plates. Numerous species. _H.
+                chordeilis_ and _leporis-palustris_ from the United
+                States. _Haemaphysalis_ Koch.
+
+[Illustration: 150. Stigmal plate of Dermacentor andersoni; (_a_) of
+male, (_b_) of female. After Stiles. (_c_) Dermacentor variabilis, male;
+(_d_) Glyciphagus obesus; (_e_) Otodectes cynotis; (_f_) Tyroglyphus
+lintneri; (_g_) Tarsonemus pallidus; (_h_) anal plate and mandible of
+Liponyssus; (_c_) to (_h_) after Banks.]
+
+            gg. With eyes.
+
+              h. Anal groove distinct; posterior marginal festoons
+                  present.
+
+                i. Base of the capitulum (fig. 150c) rectangular
+                    dorsally; usually ornate. DERMACENTOR Koch.
+
+                  j. Adults with four longitudinal rows of large
+                      denticles on each half of hypostome; stigmal plate
+                      nearly circular, without dorso-lateral
+                      prolongation, goblets very large, attaining 43u to
+                      115u in diameter; not over 40 per plate, each
+                      plate surrounded by an elevated row of regularly
+                      arranged supporting cells; white rust wanting;
+                      base of capitulum distinctly broader than long,
+                      its postero-lateral angles prolonged slightly, if
+                      at all; coxae T with short spurs; trochanter I with
+                      small dorso-terminal blade. Texas, Arizona, etc.
+                      _D. nitens_
+
+[Illustration: 151. Rhipicephalus bursa, male. After Nuttall and
+Warburton.]
+
+                  jj. Adults with three longitudinal rows of large
+                      denticles on each half of hypostome; goblet cells
+                      always more than 40 per plate; whitish rust
+                      usually present.
+
+                    k. Dorso-lateral prolongation of stigmal plate small
+                        or absent; plates of the adults distinctly
+                        longer than broad; goblet cells large, usually
+                        30u to 85u in diameter, appearing as very coarse
+                        punctations on untreated specimens, but on
+                        specimens treated with caustic potash they
+                        appear very distinct in outline; base of
+                        capitulum distinctly (usually about twice)
+                        broader than long, the postero-lateral angles
+                        distinctly produced caudad; spurs of coxae I
+                        long, lateral spur slightly longer than median;
+                        trochanter I with dorso-terminal spur. _D.
+                        albipictus_, (= _variegatus_), _salmoni_,
+                        _nigrolineatus_.
+
+                    kk. Dorso-lateral prolongation of stigmal plate
+                        distinct.
+
+                      l. Body of plate distinctly longer than broad;
+                          goblet cells of medium size, usually 17.5u to
+                          35u or 40u in diameter, appearing as medium
+                          sized punctuations on untreated specimens, but
+                          on the specimens treated with caustic potash
+                          they appear very distinct in outline, which is
+                          not circular; base of capitulum usually less
+                          than twice as broad as long, the
+                          postero-lateral angles always distinctly
+                          prolonged caudad.
+
+                        m. Trochanter I with distinct dorso-subterminal
+                            retrograde sharp, digitate spur;
+                            postero-lateral angles of capitulum
+                            pronouncedly prolonged caudal, 112u to 160u
+                            long; goblet cells attain 13u to 40u in
+                            diameter; type locality California. D.
+                            OCCIDENTALIS
+
+                        mm. Trochanter I with dorso-terminal blade;
+                            postero-lateral angles of capitulum with
+                            rather short prolongations.
+
+                          n. Stigmal plate small, goblet cells not
+                              exceeding 45 in the male or 100 in the
+                              female; scutum with little rust, coxa I
+                              with short spurs, the inner distinctly
+                              shorter than the outer. _D.
+                              parumapertus-marginatus_
+
+                          nn. Stigmal plate larger; goblet cells over 70
+                              in the male and over 100 in the female;
+                              coxa I with longer spurs, inner slightly
+                              shorter than the outer; scutum with
+                              considerable rust. D. VENUSTUS[F]
+
+                      ll. Goblet cells small, rarely exceeding 17.6u,
+                          occasionally reaching 19u in diameter; on
+                          untreated specimens they appear as very fine
+                          granulations, and on specimens treated with
+                          caustic potash they may be difficult to see,
+                          but their large number can be determined from
+                          the prominent stems of the goblets; surface of
+                          outline of the goblets distinctly circular;
+                          base of the capitulum usually less than twice
+                          as broad as long, the postero-lateral angle
+                          distinctly prolonged caudad; spurs of coxae I
+                          long. _D. reticulatus_ and _electus_ (=
+                          _variabilis_?)
+
+                ii. Base of the capitulum (fig. 151) usually hexagonal
+                    (except in the male of _puchellus_); and usually
+                    inornate.
+
+                  j. No ventral plate or shield in either sex (fig.
+                      153). R. BICORNIS from the United States.
+                      RHIPICENTOR Nuttall
+
+                  jj. Males with a pair of adanal shields, and usually a
+                      pair of accessory adanal shields. Numerous
+                      species, among them _R. sanguineus_ (fig. 154) and
+                      _texanus_, the latter from the United States.
+                      _Rhipicephalus_ Koch
+
+              hh. Anal grooves faint or obsolete; no marginal festoons.
+
+                i. Short palpi; highly chitinized; unfed adults of large
+                    size; coxae conical; male with a median plate
+                    prolonged in two long spines projecting caudad;
+                    segments of leg pair IV greatly swollen (fig. 155,
+                    156). _M. winthemi_ _Margaropus_ Karsch
+
+[Illustration: 152. Monieziella (Histiogaster) emtomophaga-spermatica,
+ventral aspect, male and female. After Trouessart.]
+
+                ii. Very short palpi, ridged dorsally and laterally;
+                    slightly chitinized; unfed adults of smaller size;
+                    coxae I bifid; male with adanal and accessory adanal
+                    shields (fig. 139). B. ANNULATUS. BOOPHILUS Curtis
+
+          ff. Palpi longer than broad (fig. 157).
+
+            g. Male with pair of adanal shields, and two posterior
+                abdominal protrusions capped by chitinized points;
+                festoons present or absent. Several species, among them
+                H. AEGYPTICUM (fig. 140) from the old world. HYALOMMA
+                Koch
+
+            gg. Male without adanal shields but small ventral plaques
+                are occasionally present close to the festoons. Many
+                species, a few from the United States (fig. 157).
+                AMBLYOMMA Koch
+
+
+              h. Coxa I with but one spine; metatarsi (except I) with
+                  two thickened spurs at tips. _A. maculatum_
+
+              hh. Coxa I with two spines; metatarsi without stout spurs
+                  at tips, only slender hairs.
+
+                i. Projections of coxa I blunt and short. Large species
+                    on the gopher tortoise in Florida. _A. tuberculatum_
+
+                ii. Projections of coxa I longer, and at least one of
+                    them sharp pointed; second segment of palpus twice
+                    as long as the third; coxa IV of the male with a
+                    long spine.
+
+                  j. Porose areas nearly circular; shield of both sexes
+                      pale yellowish, with some silvery streaks and
+                      marks, and some reddish spots; shield of female as
+                      broad as long. A. CAJENNENSE (= MIXTUM).
+
+                  jj. Porose areas elongate, shield brown, in the female
+                      with an apical silvery mark, in the male with two
+                      small and two or four other silvery spots; shield
+                      of the female longer than broad (fig 158 e). A.
+                      AMERICANUM.
+
+[Illustration: 153. Rhipicentor bicornis, ventral aspect, male. After
+Nuttall and Warburton.]
+
+    cc. Hypostome small, without teeth, venter without furrows; body
+        often with coriaceous shields, posterior margin of the body
+        never crenulate (i.e. without festoons); no eyes. GAMASOIDEA.
+
+      d. Parasitic on vertebrates; mandibles fitted for piercing; body
+          sometimes constricted. DERMANYSSIDAE.
+
+        e. Anal plate present. DERMANYSSINAE.
+
+          f. Body short; legs stout, hind pair reaching much beyond the
+              tip of the body. On bats. _Pteroptus_ Dufour.
+
+          ff. Body long; hind legs not reaching beyond the tip of the
+              body.
+
+            g. Peritreme on the dorsum, very short; body distinctly
+                  constricted. _Ptilonyssus_ Berl.
+
+            gg. Peritreme on the venter, longer; body not distinctly
+                  constricted.
+
+                h. Mandibles in both sexes chelate. Parasitic on bats,
+                    mice and birds (fig. 150, h). LIPONYSSUS Kol.
+
+                  The species L. (= LEIOGNATHUS) SYLVIARUM frequents the
+                      nests of warblers. An instance is on record of
+                      these mites attacking man, causing a pruritis.
+
+                hh. Mandibles in the male chelate (fig. 158 j), in the
+                    female long, styliform. Parasitic on birds.
+                    DERMANYSSUS Dug. Two species of importance may be
+                    noted, _D. hirundinus_ and D. GALLINAE. The latter
+                    (fig. 51) is a serious pest of poultry, sometimes
+                    attacking man, causing itching and soreness.
+
+        ee. Anal plate absent. In lungs and air passages of some
+            mammals. HALARACHNINAE.
+
+      dd. Free or attached to insects, rarely on vertebrates.
+
+        e. First pair of legs inserted within the same body opening as
+            the oral tube; genital apertures surrounded by the sternum.
+            On insects. UROPODIDAE.
+
+[Illustration: 154. Rhicephalus sanguineus, male. After Nuttall and
+Warburton.]
+
+        ee. First pair of legs inserted at one side of the mouth
+            opening; male genital aperture usually on the anterior
+            margin of the sternal plate. GAMASIDAE.
+
+          This family contains a number of genera, some of which are
+              found upon mammals, though the majority affect only other
+              arthropods. One species, LAELAPS STABULARIS, frequents the
+              bedding in stables, and in one instance at least, has
+              occasioned irritation and itching, in man.
+
+  bb. No distinct spiracle in the stigmal plate on each side of the
+      body.
+
+    c. Body usually coriaceous, with few hairs, with a specialized seta
+        arising from a pore near each posterior corner of the
+        cephalothorax; no eyes; mouth parts and palpi very small;
+        ventral openings of the abdomen large; tarsi without sucker. Not
+        parasitic. ORIBATOIDEA.
+
+    cc. Body softer; without such specialized seta.
+
+      d. Aquatic species. HYDRACHNOIDEA.
+
+      dd. Not aquatic.
+
+        e. Palpi small, three segmented, adhering for some distance to
+            the lip; ventral suckers at genital opening or near anal
+            opening usually present; no eyes; tarsi often end in
+            suckers; beneath the skin on the venter are seen rod-like
+            epimera that support the legs; body often entire. Adults
+            frequently parasitic. SARCOPTOIDEA.
+
+          f. With tracheae; no ventral suckers; legs ending in claws;
+              body divided into cephalothorax and abdomen; the female
+              with a clavate hair between legs I and II. Usually not
+              parasitic on birds and mammals. TARSONEMIDAE
+
+            g. Hind legs of female ending in claw and sucker as in the
+                other pairs. PEDICULOIDINAE
+
+              To this sub-family belongs the genus PEDICULOIDES
+
+              P. ventricosus is described on page 69.
+
+[Illustration: 155. Margaropus winthemi, male. After Nuttall and
+Warburton.]
+
+[Illustration: 156. Margaropus winthemi, capitulum and scutum.
+After Nuttall and Warburton.]
+
+            gg. Hind legs of the female end in long hairs. TARSONEMINAE
+
+              TARSONEMUS INTECTUS Karpelles, normally found upon grain,
+                  is said to attack man in Hungary and Russia. Other
+                  species of the genus affect various plants (c.f. fig.
+                  150, g).
+
+          ff. Without tracheae; no such clavate hair.
+
+            g. Genital suckers usually present; integument usually
+                without fine parallel lines.
+
+              h. Legs short, without clavate hair on tarsi I and II. On
+                  insects. CANESTRINIDAE.
+
+              hh. Legs longer, with a clavate hair on tarsi I and II.
+                  Not normally parasitic except on bees. TYROGLYPHIDAE
+
+                i. Dorsal integument more or less granulate; claws very
+                    weak, almost invisible; some hairs of the body
+                    plainly feathered; ventral apertures large.
+                    GLYCIPHAGUS Her.
+
+                  This genus occurs in the United States. In Europe the
+                      mites have been found feeding on all sorts of
+                      substances. They are known as sugar mites and
+                      cause the disease known as grocer's itch. G.
+                      DOMESTICUS and G. PRUNORUM are old world species
+                      (fig. 150, d).
+
+                ii. Dorsal integument not granulate; claws distinct; no
+                    prominent feathered hairs; ventral aperture small.
+
+                  j. Mandibles not chelate; elongate, and toothed below;
+                      body without long hairs; palpi enlarged at tip and
+                      provided with two divergent bristles. Species feed
+                      on decaying substances. _Histiostoma_ Kram.
+
+                  jj. Mandibles chelate; palpi not enlarged at the tip,
+                      nor with two bristles.
+
+                    k. No clavate hair on the base of tarsi I and II; no
+                        suture between cephalothorax and abdomen. Live
+                        on bees or in their nests. _Trichotarsus_ Can.
+
+                    kk. A clavate or thickened hair at the base of tarsi
+                        I and II.
+
+                      l. The bristle on the penultimate segment of the
+                          legs arises from near the middle; no suture
+                          between the cephalothorax and abdomen. The
+                          species, some of which occur in the United
+                          States, feed on dried fruit, etc.
+                          _Carpoglyphus_ Robin.
+
+                      ll. The bristle on the penultimate segment of the
+                          legs arise from near the tip; a suture between
+                          cephalothorax and abdomen.
+
+                        m. Cephalothorax with four distinct and long
+                            bristles in a transverse row; tarsi I and II
+                            about twice as long as the preceding segment
+                            (fig. 150 f). TYROGLYPHUS Latr.
+
+                          n. Some bristles on tarsi I and II near
+                              middle, distinctly spine-like; the sense
+                              hair about its length from the base of the
+                              segment. Several species in the United
+                              States belong to this group.
+
+                          nn. No spine-like bristles near the middle of
+                              the tarsi; sense hair not its length from
+                              the base of the segment.
+
+                            o. Of the terminal abdominal bristles, only
+                                two are about as long as the abdomen;
+                                leg I of the male greatly thickened and
+                                with a spine at apex of the femur below.
+                                T. FARINAE.
+
+                            oo. Of the terminal abdominal bristles at
+                                least six or more are very long, nearly
+                                as long as the body.
+
+                              p. Bristles of the body distinctly plumose
+                                  or pectinate; tarsi very long. T.
+                                  LONGIOR.
+
+                              pp. Bristles of the body not pectinate.
+
+                                q. In mills, stored foods, grains, etc.
+                                    Third and fourth joints of hind legs
+                                    scarcely twice as long as broad;
+                                    abdominal bristles not unusually
+                                    long; legs I and II of the male not
+                                    unusually stout. T. AMERICANUS.
+
+                                qq. With other characters and habits.
+                                    _T. lintneri_ (fig. 150 f) the
+                                    mushroom mite, and several other
+                                    species.
+
+                        mm. Cephalothorax with but two long distinct
+                            bristles (besides the frontal pair), but
+                            sometimes a very minute intermediate pair;
+                            tarsi I and II unusually short and not twice
+                            as long as the preceding segment.
+
+                          n. Tarsi with some stout spines. RHIZOGLYPHUS
+                              Clap.
+
+                            The species of this genus are vegetable
+                                feeders. Several occur in the United
+                                States. R. PARASITICUS and R.
+                                SPINITARSUS have been recorded from the
+                                old world, attacking human beings who
+                                handle affected plants.
+
+                          nn. Tarsi with only fine hairs. MONIEZIELLA
+                              Berl.
+
+                            The species of this genus, as far as known,
+                                are predaceous or feed on recently
+                                killed animal matter. Several species
+                                occur in the United States. M. (=
+                                HISTIOGASTER) ENTOMOPHAGA (fig. 152)
+                                from the old world has been recorded as
+                                injurious to man.
+
+            gg. Genital suckers absent; integument with fine parallel
+                lines. Parasitic on birds and mammals.
+
+              h. Possessing a specially developed apparatus for clinging
+                  to hairs of mammals. LISTROPHORIDAE.
+
+              hh. Without such apparatus.
+
+                i. Living on the plumage of birds. ANALGESIDAE.
+
+                ii. In the living tissues of birds and mammals.
+
+                  j. Vulva longitudinal. In the skin and cellular
+                      tissues of birds. CYTOLEICHIDAE.
+
+                    This family contains two species, both occurring in
+                        the United States on the common fowl.
+                        _Laminosioptes cysticola_ occurs on the skin and
+                        also bores into the subcutaneous tissue where it
+                        gives rise to a calcareous cyst. _Cytoleichus
+                        nudus_ is most commonly found in the air
+                        passages and air cells.
+
+                  jj. Vulva transverse. In the skin of mammals and
+                      birds. SARCOPTIDAE
+
+                    k. Anal opening on the dorsum.
+
+                      l. Third pair of legs in the male without apical
+                          suckers. On cats and rabbits. NOTOEDRES
+                          Rail.
+
+                        The itch mite of the cat, N. CATI (fig. 61) has
+                            been recorded on man.
+
+                      ll. Third leg in the male with suckers. On bats
+                          _Prosopodectes_ Can.
+
+                    kk. Anal opening below.
+
+                      l. Pedicel of the suckers jointed; mandibles
+                          styliform and serrate near the tip. PSOROPTES
+                          Gerv. P. COMMUNIS OVIS is the cause of sheep
+                          scab.
+
+                      ll. Pedicel of the suckers not jointed; mandibles
+                          chelate.
+
+                        m. No suckers on the legs of the females;
+                            parasitic on birds, including chickens. _C.
+                            mutans_ is itch mite of chickens.
+                            _Cnemidocoptes_ Furst.
+
+                        mm. Suckers at least on legs I and II; parasitic
+                            on mammals.
+
+                          n. Legs very short; in the male the hind pairs
+                              equal in size; body usually short.
+                              SARCOPTES Latr.
+
+                            S. SCABIEI is the itch mite of man (fig.
+                                56).
+
+[Illustration: 157. Amblyomma, female. After Nuttall and Warburton.]
+
+                          nn. Legs more slender; in the male the third
+                              pair is much larger than the fourth; body
+                              more elongate.
+
+                            o. Female with suckers on the fourth pair of
+                                legs. Species do not burrow in the skin,
+                                but produce a scab similar to sheep
+                                scab. They occur in the ox, horse, sheep
+                                and goat. CHORIOPTES Gerv. C. SYMBIOTES
+                                BOVIS of the ox has been recorded a few
+                                times on man.
+
+                            oo. Female without suckers to the fourth
+                                legs.
+
+                              p. Hind part of the male abdomen with two
+                                  lobes. On a few wild animals.
+                                  _Caparinia_ Can.
+
+                              pp. Hind part of the male abdomen without
+                                  lobes. Live in ears of dogs and cats.
+                                  _Otodectes_ Canestr.
+
+                                _O. cynotis_ Hering (fig. 150 e) has
+                                    been taken in the United States.
+
+        ee. Palpi usually of four or five segments, free; rarely with
+            ventral suckers near genital or anal openings; eyes often
+            present; tarsi never end in suckers; body usually divided
+            into cephalothorax and abdomen; rod-like epimera rarely
+            visible; adults rarely parasitic.
+
+          f. Last segment of the palpi never forms a thumb to the
+              preceding segment; palpi simple, or rarely formed to hold
+              prey; body with but few hairs. EUPODOIDEA.
+
+            g. Palpi often geniculate, or else fitted for grasping prey;
+                mandibles large and snout like; cephalothorax with four
+                long bristles above, two in front, two behind; last
+                segment of leg I longer than the preceding segment,
+                often twice as long. BDELLIDAE.
+
+            gg. Palpi never geniculate (fig. 158a), nor fitted for
+                grasping prey: beak small; cephalothorax with bristles
+                in different arrangement; last segment of leg I shorter
+                or but little longer than the preceding joint; eyes when
+                present near posterior border. EUPODIDAE
+
+              Moniez has described a species from Belgium (TYDEUS
+                  MOLESTUS) which attacks man. It is rose colored;
+                  eyeless; its legs are scarcely as long as its body,
+                  the hind femur is not thickened; the mandibles are
+                  small and the anal opening is on the venter. The
+                  female attains a length of about 0.3 mm.
+
+          ff. Last segment of the palpus forms a thumb to the preceding,
+              which ends in a claw (with few exceptions); body often
+              with many hairs (fig. 158 k). TROMBIDOIDEA.
+
+            g. Legs I and II with processes bearing spines; skin with
+                several shields; coxae contiguous. CAECULIDAE.
+
+            gg. Legs I and II without such processes; few if any
+                shields.
+
+              h. Palpi much thickened on the base, moving laterally,
+                  last joint often with two pectinate bristles; no eyes;
+                  legs I ending in several long hairs; adult sometimes
+                  parasitic. CHEYLETIDAE
+
+                CHEYLETUS ERUDITUS, which frequents old books, has once
+                    been found in pus discharged from the ear of man.
+
+              hh. Palpi less thickened, moving vertically; eyes usually
+                  present; leg I not ending in long hairs.
+
+                i. Coxae contiguous, radiate; legs slender, bristly; body
+                    with few hairs; no dorsal groove; tarsi not swollen.
+                    ERYTHRAEIDAE.
+
+                ii. Coxae more or less in two groups; legs less bristly.
+
+[Illustration: 158. (_a_) Tydeus, beak and leg from below; (_b_)
+Cheyletus pyriformis, beak and palpus; (_c_) beak and claw of
+Pediculoides; (_d_) leg of Sarcoptes; (_e_) scutum of female of
+Amblyomma americana; (_f_) leg I and tip of mandible of Histiostoma
+americana; (_g_) Histiogaster malus, mandible and venter; (_h_)
+Aleurobius farinae, palpus and leg I of male; (_i_) Otodectes cynotis,
+tip of abdomen of male, (_j_) beak and anal plate of Dermanyssus
+gallinae female; (_k_) palpus of Allothrombium. (_a_) to (_j_) after
+Banks.]
+
+                  j. Body with fewer, longer hairs; often spinning
+                      threads; no dorsal groove; tarsi never swollen;
+                      mandibles styliform (for piercing). TETRANYCHIDAE
+
+                    The genus TETRANYCHUS may be distinguished from the
+                        other genera occurring in the United States by
+                        the following characters: No scale-like
+                        projections on the front of the cephalothorax;
+                        legs I as long or longer than the body; palp
+                        ends in a distinct thumb; the body is about 1.5
+                        times as long as broad. T. MOLESTISSIMUS Weyenb.
+                        from South America, and T. TELARIUS from Europe
+                        and America ordinarily infesting plants, are
+                        said also to molest man.
+
+                  jj. Body with many fine hairs or short spines; not
+                      spinning threads; often with dorsal groove; tarsi
+                      often swollen.
+
+                    k. Mandibles styliform for piercing. RHYCHOLOPHIDAE.
+
+                    kk. Mandibles chelate, for biting. TROMBIDIDAE
+
+                      The genus TROMBIDIUM has recently been subdivided
+                          by Berlese into a number of smaller ones, of
+                          which some five or six occur in the United
+                          States. The mature mite is not parasitic but
+                          the larvae which are very numerous in certain
+                          localities will cause intense itching,
+                          soreness, and even more serious complications.
+                          They burrow beneath the skin and produce
+                          inflamed spots. They have received the popular
+                          name of "RED BUG." The names LEPTUS AMERICANUS
+                          and L. IRRITANS have been applied to them,
+                          although they are now known to be immature
+                          stages. (Fig. 44.)
+
+
+HEXAPODA (Insecta)
+
+The Thysanura (springtails and bristletails), the Neuropteroids
+(may-flies, stone-flies, dragon-flies, caddis-flies, etc.), Mallophaga
+(bird lice), Physopoda (thrips), Orthoptera (grasshoppers, crickets,
+roaches), are of no special interest from our viewpoint. The remaining
+orders are briefly characterized below.
+
+
+SIPHUNCULATA (page 275)
+
+Mouth parts suctorial; beak fleshy, not jointed; insect wingless;
+parasitic upon mammals. Metamorphosis incomplete. Lice.
+
+
+HEMIPTERA (page 275)
+
+Mouth parts suctorial; beak or the sheath of the beak jointed; in the
+mature state usually with four wings. In external appearance the
+immature insect resembles the adult except that the immature form (i.e.
+nymph) never has wings, the successive instars during the process of
+growth, therefore, are quite similar; and the metamorphosis is thus
+incomplete. To this order belong the true bugs, the plant lice, leaf
+hoppers, frog hoppers, cicadas, etc.
+
+
+LEPIDOPTERA
+
+The adult insect has the body covered with scales and (with the rare
+exception of the females of a few species) with four wings also covered
+with scales. Proboscis, when present, coiled, not segmented, adapted for
+sucking. Metamorphosis complete, i.e. the young which hatches from the
+egg is quite unlike the adult, and after undergoing several molts
+transforms into a quiescent pupa which is frequently enclosed in a
+cocoon from which the adult later emerges. The larvae are known as
+caterpillars. Butterflies and moths.
+
+
+DIPTERA (page 285)
+
+The adult insect is provided with two, usually transparent, wings, the
+second pair of wings of other insects being replaced by a pair of
+halteres or balancers. In a few rare species the wings, or halteres, or
+both, are wanting. The mouth parts, which are not segmented, are adapted
+for sucking. The tarsi are five-segmented. Metamorphosis complete. The
+larvae, which are never provided with jointed legs, are variously known
+as maggots, or grubs, or wrigglers. Flies, midges, mosquitoes.
+
+
+SIPHONAPTERA (page 316)
+
+Mouth parts adapted for sucking; body naked or with bristles and spines;
+prothorax well developed; body compressed; tarsi with five segments;
+wings absent. Metamorphosis complete. The larva is a wormlike creature.
+Fleas.
+
+
+COLEOPTERA
+
+Adult with four wings (rarely wanting), the first pair horny or
+leathery, veinless, forming wing covers which meet in a line along the
+middle of the back. Mouth parts of both immature stages and adults
+adapted for biting and chewing. Metamorphosis complete. The larvae of
+many species are known as grubs. Beetles.
+
+
+HYMENOPTERA
+
+Adult insect with four, usually transparent, wings, wanting in some
+species. Mouth parts adapted for biting and sucking; palpi small; tarsi
+four or five-segmented. Metamorphosis complete. Parasitic four-winged
+flies, ants, bees, and wasps.
+
+
+SIPHUNCULATA AND HEMIPTERA
+
+a. Legs with claws fitted for clinging to hairs; wings wanting;
+    spiracles of the abdomen on the dorsal surface. (= ANOPLURA =
+    PARASITICA) SIPHUNCULATA.
+
+  b. Legs not modified into clinging hooks; tibia and tarsus very long
+      and slender; tibia without thumb-like process; antennae
+      five-segmented. HAEMATOMYZIDAE Endr.
+
+    _Haematomyzus elephantis_ on the elephant.
+
+  bb. Legs modified into clinging hooks; tibia and tarsus usually short
+      and stout; tibia with a thumb-like process; head not anteriorly
+      prolonged, tube-like.
+
+    c. Body depressed; a pair of stigmata on the mesothorax, and
+        abdominal segments three to eight; antennae three to
+        five-segmented.
+
+      d. Eyes large, projecting, distinctly pigmented; pharynx short and
+          broad; fulturae (inner skeleton of head) very strong and broad,
+          with broad arms; proboscis short, scarcely attaining the
+          thorax. PEDICULIDAE
+
+        e. Antennae three-segmented. A few species occurring upon old
+            world monkeys. _Pedicinis_ Gerv.
+
+        ee. Antennae five-segmented.
+
+          f. All legs stout; thumb-like process of the tibia very long
+              and slender, beset with strong spines, fore legs stouter
+              than the others; abdomen elongate, segments without
+              lateral processes; the divided telson with a conical
+              process posteriorly upon the ventral side. PEDICULUS L.
+
+            g. Upon man.
+
+              h. Each abdominal segment dorsally with from one to three
+                  more or less regular transverse rows of small setae;
+                  antenna about as long as the width of the head. Head
+                  louse (fig. 65). P. HUMANUS.
+
+              hh. "No transverse rows of abdominal setae; antenna longer
+                  than the width of the head; species larger." Piaget.
+                  Body louse of man. P. CORPORIS.
+
+            gg. Upon apes and other mammals. _P. pusitatus_ (?).
+
+          ff. Fore legs delicate, with very long and slender claws;
+              other legs very stout with short and stout claws;
+              thumb-like process of the tibia short and stout; abdomen
+              very short and broad; segment one to five closely crowded,
+              thus the stigmata of segments three to five apparently
+              lying in one segment; segments five to eight with lateral
+              processes; telson without lateral conical appendages (fig.
+              69). Crab louse of man. PHTHIRUS PUBIS.
+
+      dd. Eyes indistinct or wanting; pharynx long and slender, fulturae
+          very slender and closely applied to the pharynx; proboscis
+          very long. Several genera found upon various mammals.
+          HAEMATOPINIDAE.
+
+    cc. Body swollen; meso- and metathorax, and abdominal segments two
+        to eight each with a pair of stigmata; eyes wanting; antennae
+        four or five-segmented; body covered with stout spines. Three
+        genera found upon marine mammals. ECHINOPHTHIRIIDAE
+
+aa. Legs fitted for walking or jumping; spiracles of abdomen usually
+    ventral; beak segmented.
+
+  b. Apex of head usually directed anteriorly; beak arising from its
+      apex; sides of the face remote from the front coxae; first pair of
+      wings when present thickened at base, with thinner margins.
+      HETEROPTERA
+
+[Illustration: 159. Taxonomic details of Hemiptera-Heteroptera. (_a_)
+Dorsal aspect; (_b_) seta from bedbug; (_c_) wing of Heteropteron; (_d_)
+leg; (_e_) wing of Sinea.]
+
+    c. Front tarsi of one segment, spade-form (palaeformes); beak short,
+        at most two-segmented; intermediate legs long, slender;
+        posterior pair adapted for swimming. CORIXIDAE
+
+    cc. Front tarsi rarely one-segmented, never spade-form; beak free,
+        at least three-segmented.
+
+      d. Pulvilli wanting.
+
+        e. Hemelytra usually with a distinct clavus (fig. 159), clavus
+            always ends behind the apex of the scutellum, forming the
+            commissure. (Species having the wings much reduced or
+            wanting should be sought for in both sections.)
+
+          f. Antennae very short; meso- and metasternum composite; eyes
+              always present.
+
+            g. Ocelli present; beak four-segmented. OCHTERIDAE and
+                NERTHRIDAE.
+
+            gg. Ocelli wanting; antennae more or less hidden in a groove.
+
+              h. Anterior coxae inserted at or near anterior margin of
+                  the prosternum; front legs raptorial; beak
+                  three-segmented BELOSTOMIDAE (with swimming legs),
+                  NEPIDAE, NAUCORIDAE.
+
+                i. Metasternum without a median longitudinal keel;
+                    antennae always four-segmented.
+
+                  j. Beak short, robust, conical; the hairy fleck on the
+                      corium elongate, large, lying in the middle
+                      between the inner angle of the membrane and the
+                      outer vein parallel to the membrane margin;
+                      membrane margin S-shaped.
+
+                    k. The thick fore femur with a relatively deep
+                        longitudinal furrow to receive the tibia.
+                        Several American species (fig. 19f.). BELOSTOMA
+                        (= Lethocerus Mayer)
+
+                    kk. The less thickened fore femur without such a
+                        furrow. B. GRISEUS. BENACUS Stal.
+
+                  jj. Beak slender, cylindrical; the hairy spot on the
+                      corium rounded lying next to the inner angle of
+                      the membrane.
+
+                    k. Membrane large, furrow of the embolium broadened.
+                        _Z. aurantiacum_, _fluminea_, etc. _Zaitha_
+
+                    kk. Membrane very short; furrow of embolium not
+                        broadened. Western genus. _Pedinocoris_
+
+              ii. Metasternum with a long median longitudinal keel.
+                  Southwestern forms. _Abedus ovatus_ and _Deniostoma
+                  dilatato_
+
+            hh. Anterior coxae inserted at the posterior margin of the
+                prosternum; legs natatorial. Back swimmers (fig. 19 b.).
+                NOTONECTIDAE
+
+              i. Apices of the hemelytra entire; the three pairs of legs
+                  similar in shape; beak three-segmented; abdomen not
+                  keeled or hairy. _Plea_ Leach
+
+              ii. Apices of hemelytra notched; legs dissimilar; beak
+                  four-segmented; abdomen keeled and hairy.
+
+                j. Hemelytra usually much longer than the abdomen;
+                    fourth segment of the antenna longer than the third
+                    segment; hind tarsi with claws. _Bueno_ Kirk.
+
+                jj. Hemelytra but little longer than the abdomen; fourth
+                    segment of the antenna shorter than the third
+                    segment; hind tarsi without claws (fig. 19b).
+                    NOTONECTA L.
+
+          ff. Antennae longer than the head; or if shorter, then the eyes
+              and ocelli absent.
+
+            g. Eyes, ocelli, and scutellum wanting; beak
+                three-segmented; head short; hemelytra always short;
+                membrane wanting. Insects parasitic on bats. POLYCTENIDAE
+
+            gg. Eyes present.
+
+              h. First two antennal segments very short, last two long,
+                  pilose, third thickened at the base; ocelli present,
+                  veins of the hemelytra forming cells. DIPSOCORIDAE (=
+                  CERATOCOMBIDAE) including SCHIZOPTERIDAE.
+
+              hh. Third segment of the antenna not thickened at the
+                  base, second as long or longer than the third, rarely
+                  shorter.
+
+                i. Posterior coxae hinged (cardinate), if rarely
+                    rotating, the cuneus is severed, the membrane is one
+                    or two-celled, and the meso- and metasternum are
+                    composite.
+
+                  j. Ocelli absent, clypeus dilated toward the apex;
+                      hemelytra always short, membrane wanting. Species
+                      parasitic. Bed bugs, etc. CIMICIDAE
+
+                    k. Beak short, reaching to about the anterior coxae;
+                        scutellum acuminate at the apex; lateral margin
+                        of the elytra but little reflexed, apical margin
+                        more or less rounded; intermediate and posterior
+                        coxae very remote.
+
+                      l. Body covered with short hairs, only the sides
+                          of the pronotum and the hemelytra fringed with
+                          longer hairs; antennae with the third and
+                          fourth segments very much more slender than
+                          the first and second; pronotum with the
+                          anterior margin very _deeply sinuate_. CIMEX
+                          L.
+
+                        m. Sides of the pronotum widely dilated, broader
+                            than the breadth of one eye, and densely
+                            fringed with backward curved hairs; apical
+                            margin of the hemelytra nearly straight,
+                            rounded toward the interior or exterior
+                            angles.
+
+                          n. Body covered with very short hairs; second
+                              segment of the antenna shorter than the
+                              third; sides of the pronotum feebly
+                              reflexed, fringed with shorter hairs than
+                              the breadth of one eye; hemelytra with the
+                              commissural (inner) margin rounded and
+                              shorter than the scutellum, apical margin
+                              rounded towards the interior angle. The
+                              common bed bug (fig. 19h). C. LECTULARIUS
+                              Linn
+
+                          nn. Body covered with longer hairs; second and
+                              third segments of the antenna of equal
+                              length; side of the pronotum narrowly, but
+                              distinctly, reflexed, fringed with longer
+                              hairs than the breadth of one eye;
+                              hemelytra with the commissural margin
+                              straight and longer than the scutellum,
+                              apical margin rounded towards the exterior
+                              angle. Species found on bats in various
+                              parts of the United States. _C.
+                              pillosellus_ Hov.
+
+                        mm. Sides of the pronotum neither dilated, nor
+                            reflexed, fringed with less dense and nearly
+                            straight hairs; hemelytra with the apical
+                            margin distinctly rounded. Parasitic on man,
+                            birds and bats. Occurs in the old world,
+                            Brazil and the West Indies. C. HEMIPTERUS
+                            Fabr. (= rotundatus)
+
+                      ll. Body clothed with rather longer silky hairs;
+                          third and fourth segments of the antenna
+                          somewhat more slender than the first and
+                          second; anterior margin of the pronotum _very
+                          slightly sinuate_ or nearly straight in the
+                          middle, produced at the lateral angles. This
+                          is the species which in American collections
+                          is known as _C. hirundinis_, the latter being
+                          an old world form. It is found in swallows
+                          nests. O. VICARIUS. OECIACUS Stal
+
+                    kk. Beak long, reaching to the posterior coxae;
+                        scutellum rounded at the apex; lateral margins
+                        of the elytra strongly reflexed, apical margin
+                        slightly sinuate toward the middle; intermediate
+                        and posterior coxae sub-contiguous. This species
+                        infests poultry in southwest United States and
+                        in Mexico. H. INODORUS. HAEMATOSIPHON Champ.
+
+[Illustration: 160. Pselliopsis (Milyas) cinctus (x2). After C. V.
+Riley.]
+
+                  jj. Ocelli present, if rarely absent in the female,
+                      then the tarsus has two segments; or if with three
+                      tarsal segments, the wing membrane with one or two
+                      cells.
+
+                    k. Beak four-segmented, or with two-segmented tarsi.
+                        ISOMETOPIDAE, MICROPHYSIDAE, and some
+                        CAPSIDAE.
+
+                    kk. Beak three-segmented.
+
+                      l. Hemelytra with embolium; head horizontal, more
+                          or less conical; membrane with one to four
+                          veins, rarely wanting. ANTHOCORIDAE
+
+                        Several species of this family affecting man
+                            have been noted, ANTHOCORIS KINGI and
+                            CONGOLENSE, from Africa and LYCTOCORIS
+                            CAMPESTRIS from various parts of the world.
+                            LYCTOCORIS FITCHII Reuter (fig. 19 j), later
+                            considered by Reuter as a variety of L.
+                            CAMPESTRIS, occurs in the United States.
+
+                      ll. Hemelytra without embolium. Superfamily
+                          ACANTHIOIDEA (= SALDAE Fieber and LEPTOPODAE
+                          Fieber)
+
+                ii. Posterior coxae rotating.
+
+                  j. Claws preapical; aquatic forms. GERRIDAE and
+                      VELIADAE
+
+                  jj. Claws apical.
+
+                    k. Prosternum without stridulatory sulcus (notch for
+                        beak).
+
+                      l. Tarsus with three segments; membrane with two
+                          or three longitudinal cells from which veins
+                          radiate; rarely with free longitudinal veins
+                          (Arachnocoris) or veins nearly obsolete
+                          (Arbela); clavus and corium coriaceous; ocelli
+                          rarely absent. NABIDAE
+
+                        REDUVIOLUS (= CORISCUS) SUBCOLEOPTRATUS (fig. 19
+                            g), a species belonging to this family,
+                            occurring in the United States, has been
+                            accused of biting man. This insect is flat,
+                            of a jet black color, bordered with yellow
+                            on the sides of the abdomen, and with
+                            yellowish legs. It is predaceous, feeding on
+                            other insects.
+
+                      ll. With other combinations of characters.
+                          HYDROMETRIDAE, HENICOCEPHALIDAE,
+                          NAEOGEIDAE, MESOVELIADAE, JOPPEICIDAE
+
+                    kk. Prosternum with stridulatory sulcus (notch for
+                        beak); with three segments, short, strong.
+
+                      l. Antennae filiform or sometimes more slender
+                          apically, geniculate; wing membrane with two
+                          or three large basal cells; scutellum small or
+                          moderate/ REDUVIIDAE
+
+                        For a key to the genera and species see next
+                            page.
+
+                      ll. Last antennal segment clavate or fusiform; win
+                          membrane with the veins often forked and
+                          anastomosing; scutellum large; tarsi each with
+                          two segments; fore legs strong. (= PHYMATIDAE)
+                          MACROCEPHALIDAE
+
+        ee. Clavus noticeably narrowed towards the apex, never extending
+            beyond the scutellum, the two not meeting to form a
+            commissure; head horizontal, much prolonged between the
+            antennae, on each side with an antennal tubercle, sometimes
+            acute; ocelli absent; meso- and metasternum simple; tarsi
+            each with two segments; body flattened (fig. 19c). ARADIDAE,
+            including DYSODIIDAE.
+
+      dd. Pulvilli present (absent in one Australian family
+          THAUMATOCORIDAE in which case there is a membranous
+          appendage at the tip of the tibia). CAPSIDAE (=
+          MIRIDAE),[G] _Eotrechus_ (in family GERRIDAE),
+          NAEOGAIDAE, TINGITIDAE, PIESMIDAE, MYODOCHIDAE,
+          CORIZIDAE, COREIDAE, ALYDIDAE, PENTATOMIDAE,
+          SCUTELLERIDAE, etc.
+
+  bb. Apex of head directed ventrally, beak arising from the hinder part
+      of the lower side of the head; sides of face contiguous to the
+      front coxae; first pair of wings, when present, of uniform
+      thickness. Cicadas, scale insects, plant lice (Aphids),
+      spittle-insects, leaf hoppers, etc. HOMOPTERA
+
+
+REDUVIIDAE OF THE UNITED STATES
+
+(Adapted from a key given by Fracker).
+
+a. Ocelli none; wings and hemelytra always present in the adults; no
+    discoidal areole in the corium near the apex of the clavus.
+    _Orthometrops decorata_, _Oncerotrachelus acuminatus_, etc.,
+    Pennsylvania and south. _Sarcinae_
+
+aa. Ocelli present in the winged individuals; anterior coxae not as long
+    as the femora.
+
+  b. Hemelytra without a quadrangular or discoidal areole in the corium
+      near the apex of the clavus.
+
+    c. Ocelli not farther cephalad than the caudal margins of the eyes;
+        segment two of the antenna single.
+
+      d. Thorax usually constricted caudad of the middle; anterior coxae
+          externally flat or concave. PIRATINAE
+
+        e. Middle tibiae without spongy fossa, head long, no lateral
+            tubercle on neck. _S. stria_, Carolina, Ill., Cal.
+            _Sirthenia_ Spinola
+
+        ee. Middle tibiae with spongy fossa; fore tibiae convex above;
+            neck with a small tubercle on each side.
+
+          f. Apical portion of anterior tibiae angularly dilated beneath,
+              the spongy fossa being preceded by a small prominence.
+              MELANOLESTES Stal
+
+            g. Black, with piceous legs and antennae. N. E. States (fig.
+                19a) M. PICIPES
+
+            gg. Sides, and sometimes the whole dorsal surface of the
+                abdomen red. Ill., and southward. M. ABDOMINALIS
+
+          ff. Tibiae not dilated as in "f"; spongy fossa elongate;
+              metapleural sulci close to the margin. R. BIGUTTATUS (fig.
+              22). South RASAHUS A. and S.
+
+      dd. Thorax constricted in the middle or cephalad of the middle;
+          anterior tarsi each three-segmented.
+
+        e. Apex of the scutellum narrow, without spines or with a single
+            spine REDUVIINAE
+
+          f. Antennae inserted in the lateral or dorso-lateral margins of
+              the head; antenniferous tubercles slightly projecting from
+              the sides of the head; head produced strongly cephalad;
+              ocelli at least as far apart as the eyes.
+
+            g. Antennae inserted very near the apex of the head; segments
+                one and three of the beak short, segment two nearly four
+                times as long as segment one. R. PROLIXUS. W. I.
+                RHODNIUS Stal
+
+            gg. Antennae inserted remote from the vertex of the head.
+
+              h. Body slightly hairy; pronotum distinctly constricted;
+                  angles distinct; anterior lobe four-tuberculate, with
+                  the middle tubercles large and conical. _M.
+                  phyllosoma_, large species from the southwest.
+                  _Meccus_ Stal
+
+              hh. Body smooth, margin of the pronotum sinuous, scarcely
+                  constricted; anterior lobe lined with little
+                  tubercles. CONORHINUS Lap.
+
+                i. Surface of the pronotum and prosternum more or less
+                    granular.
+
+                  j. Eyes small, head black; body very narrow, a fifth
+                      as wide as long; beak reaches the middle of the
+                      prosternum. California. C. PROTRACTUS
+
+                  jj. Eyes large, head fuscous; body at least a fourth
+                      as wide as long. Southern species. _C.
+                      rubrofasciatus_
+
+                ii. Pronotum and prosternum destitute of granules.
+
+                  j. Border of abdomen entirely black except for a
+                      narrow yellowish spot at the apex of one segment.
+                      Texas. _C. gerstaeckeri_
+
+                  jj. Border of abdomen otherwise marked.
+
+                    k. Beak slender, joints one and two slightly pilose,
+                        two more than twice as long as one; tubercles at
+                        the apical angles of the pronotum slightly
+                        acute, conical. Md. to Ill. and south. The
+                        masked bed bug hunter (fig. 71). C. SANGUISUGUS
+
+                    kk. Beak entirely pilose, joint two a third longer
+                        than joint one; joint one much longer than
+                        three; tubercles at the apical angles of
+                        pronotum slightly elevated, obtuse. Ga., Ill.,
+                        Tex., Cal. _C. variegatus_
+
+          ff. Antenna inserted on top of the head between margins, close
+              to the eyes; antenniferous tubercles not projecting from
+              the side of the head.
+
+            g. Anterior lobe of the pronotum with a bispinous or
+                bituberculate disc; femora unarmed. _S. arizonica_, _S.
+                bicolor_. Southwestern species. _Spiniger_ Burm.
+
+            gg. Disc of pronotum unarmed; apex of scutellum produced
+                into a spine; ocelli close to the eyes; eyes large and
+                close together. REDUVIUS Lamarck
+
+              h. Color piceous. Widely distributed in the United States.
+                  (Fig. 20). R. PERSONATUS
+
+              hh. More or less testaceous in color. Southwestern states.
+                  R. SENILIS
+
+        ee. Apex of scutellum broad, with two or three spines.
+            ECTRICHODIINAE
+
+          f. First segment of the antenna about as long as the head. _E.
+              cruciata_ Pa. and south; _E. cinctiventris_, Tex. and Mex.
+              _Ectrichodia_ L. et S.
+
+          ff. First segment of the antennae short. _P. aeneo-nitens_.
+              South. _Pothea_ A. et S.
+
+    cc. Ocelli cephalad of the hind margins of the eyes; first segment
+        of the antennae stout, second segment divided into many smaller
+        segments. South and west. _Homalocoris maculicollis_, and
+        _Hammatocerus purcis_. HAMMATOCERINAE
+
+  bb. Hemelytra with a quadrangular or discoidal areole in the corium
+      near the apex of the clavus (fig. 159e).
+
+    c. Anal areole of the membrane not extending as far proximad as the
+        costal areole; basal segment of the antenna thickened, porrect;
+        the other segments slender, folding back beneath the head and
+        the first segment STENOPODINAE
+
+      d. Head armed with a ramous or furcate spine below each side,
+          caudad of the eyes.
+
+        e. First segment of the antenna thickened, apex produced in a
+            spine beyond the insertion of the second segment. Species
+            from Va., Ill. and south. _Pnirontis_ Stal.
+
+        ee. First segment of the antenna not produced beyond the
+            insertion of the second segment. _Pygolampis_, N. E. states
+            and south; _Gnathobleda_, S. W. and Mex.
+
+      dd. Head unarmed below or armed with a simple spine; rarely with a
+          subfurcate spine at the side of the base. Carolina, Missouri
+          and south. _Stenopoda_, _Schumannia_, _Diaditus_, _Narvesus_,
+          _Oncocephalus_
+
+    cc. Anal areole of membrane extending farther proximad than the
+        costal areole.
+
+      d. Ocelli farther apart than the eyes. _A. crassipes_, widely
+          distributed in the United States; other species occur in the
+          southwest. _Apiomerus_ Hahn.
+
+      dd. Ocelli not so far apart as the eyes. ZELINAE
+
+        e. Sides of mesosternum without a tubercle or fold in front.
+
+          f. Fore femur as long as or longer than the hind femur; first
+              segment of the beak much shorter than the second. _Z.
+              audax_, in the north eastern states; other species south
+              and west. _Zelus_ Fabr.
+
+          ff. Fore femur shorter than the hind femur, rarely of equal
+              length, in this case the first segment of the beak as long
+              or longer than the second.
+
+            g. First segment of the beak shorter than the second; fore
+                femur a little shorter than the hind femur; the first
+                segment of the beak distinctly longer than the head
+                before the eyes. _P. cinctus_ a widely distributed
+                species (fig. 160). _P. punctipes_, _P. spinicollis_,
+                Cal., Mex. (= _Milyas_) _Pselliopus_ Berg.
+
+            gg. First segment of the beak as long or longer than the
+                second.
+
+              h. Pronotum armed with spines on the disc.
+
+                i. Juga distinctly prominent at the apex and often acute
+                    or subacute; fore femur distinctly thickened;
+                    hemelytra usually not reaching the apex of the
+                    abdomen. _Fitchia aptera_, N. Y., south and west;
+                    _F. spinosula_, South; _Rocconata annulicornis_,
+                    Texas, etc.
+
+                ii. Juga when prominent, obtuse at apex; eyes full width
+                    of the head; fore femur not thickened; pronotum with
+                    four spines on posterior lobe. _R. taurus_, Pa.,
+                    south and west. _Repipta_ Stal.
+
+              hh. Pronotum unarmed on the disc.
+
+                i. Spines on each apical angle of the penultimate
+                    abdominal segment. _A. cinereus_, Pa., and south.
+                    _Atrachelus_ A. et S.
+
+                ii. Apical angle of the penultimate abdominal segment
+                    unarmed. _Fitchia_ (in part); _Castolus ferox_,
+                    Arizona.
+
+        ee. Sides of the mesosternum with a tubercle or fold in front at
+            the hind angles of the prosternum; first segment of the beak
+            longer than the part of the head cephalad of the eyes.
+
+          f. Fore femur thickened, densely granulated; hind femur
+              unarmed.
+
+[Illustration: 161. Taxonomic details of Diptera. (_a_) Ventral aspect
+of abdomen of Cynomyia; (_b_) antenna of Tabanus; (_c_) ventral aspect
+of abdomen of Chortophila; (_d_) ventral aspect of abdomen of Stomoxys;
+(_e_) claw of Aedes (Culex) sylvestris, male; (_f_) claw of Hippoboscid;
+(_g_) foot of dipterous insect showing empodium developed pulvilliform;
+(_h_) hind tarsal segment of Simulium vittatum, female; (_i_) foot of
+dipterous insect showing bristle-like empodium.]
+
+            g. Fore tibiae each with three long spines on the ventral
+                side. _S. diadema_ (fig. 159e), a widely distributed
+                species; and several southwestern species. _Sinea_ A. et
+                S.
+
+            gg. Fore tibiae unarmed. _A. multispinosa_, widely
+                distributed; _A. tabida_, Cal. _Acholla_ Stal.
+
+          ff. Fore femur unarmed, rarely a little thickened, a little
+              granulated.
+
+            g. Pronotum produced caudad over the scutellum, with a high
+                mesal tuberculate ridge (fig. 19e). A. CRISTATUS. N. Y.
+                to Cal. and south. ARILUS Hahn.
+
+            gg. Caudal lobe of the pronotum six sided, neither elevated
+                nor produced caudad. _H. americanus_, Southwest; also
+                several W. I. and Mexican genera. HARPACTOR Lap.
+
+
+DIPTERA (Mosquitoes, Midges, Flies)
+
+a. Integument leathery, abdominal segments indistinct; wings often
+    wanting; parasitic forms. PUPIPARA
+
+  b. Head folding back on the dorsum of the thorax; wingless flies
+      parasitic on bats. Genus _Nycteribia_. NYCTERIBIIDAE
+
+  bb. Head not folding back upon the dorsum of the thorax; flies either
+      winged or wingless; parasitic on birds and on bats and other
+      mammals.
+
+    c. Antennae reduced, wings when present, with distinct parallel veins
+        and outer crossveins; claws simple; palpi leaf-like, projecting
+        in front of the head. Flies chiefly found on bats. Several
+        genera occur in North America. STREBLIDAE
+
+[Illustration: 162. Hippobosca equina, x4. After Osborn.]
+
+    cc. Antennae more elongate, segments more or less distinctly
+        separated; head sunk into an emargination of the thorax; wings
+        when present with the veins crowded toward the anterior margin;
+        palpi not leaf-like. HIPPOBOSCIDAE
+
+      d. Wings absent or reduced and not adapted for flight.
+
+        e. Wings and halteres (balancers) absent. _M. ovinus_, the sheep
+            tick. _Melophagus_ Latr.
+
+        ee. Wing reduced (or cast off), halteres present.
+
+          f. Claw bidentate; ocelli present. On deer after the wings are
+              cast off. _L. depressa_. _Lipoptena_ Nitsch
+
+          ff. Claw tridentate (fig. 161 f). On _Macropis_. _B.
+              femorata._ _Brachypteromyia_ Will.
+
+      dd. Wings present and adapted for flight.
+
+        e. Claws bidentate.
+
+          f. Ocelli present; head flat; wings frequently cast off. On
+              birds before casting of the wing. _Lipoptena_ Nitsch.
+
+          ff. Ocelli absent; head round; wings present. The horse tick
+              H. EQUINA may attack man (fig. 162). HIPPOBOSCA L.
+
+        ee. Claws tridentate (fig. 161 f.).
+
+          f. Anal cell closed at apical margin by the anal crossvein.
+
+            g. Ocelli absent. _Stilbometopa_ Coq.
+
+            gg. Ocelli present.
+
+              h. R_{4+5} does not form an angle at the crossvein. On
+                  birds. There is a record of one species of this genus
+                  attacking man. ORNITHOMYIA Latr.
+
+              hh. R_{4+5} makes an angle at the crossvein. _O.
+                  confluens_. _Ornithoica_ Rdi.
+
+          ff. Anal cell not closed by an anal crossvein. _Lynchia_,
+              _Pseudolfersia_, and _Olfersia_ are chiefly bird
+              parasites. The first mentioned genus is said to be the
+              intermediate host of _Haemoproteus columbae_.
+
+aa. Abdominal segments chitinous; not parasitic in the adult stage.
+
+  b. Antennae with six or more segments and empodium not developed
+      pulvilliform; palpi often with four segments.
+
+    c. Ocelli present. BLEPHAROCERIDAE, RHYPHIDAE, BIBIONIDAE,
+        MYCETOPHILIDAE, besides some isolated genera of other families.
+
+    cc. Ocelli absent.
+
+      d. Dorsum of the thorax with a V-shaped suture; wings usually with
+          numerous veins; legs often very long and slender. Crane flies.
+          TIPULIDAE
+
+      dd. Dorsum of the thorax without a V-shaped suture.
+
+        e. Not more than four longitudinal veins ending in the wing
+            margin; wing usually hairy: antennae slender; coxae not
+            long; tibiae: without spurs, legs long and slender. Small,
+            delicate flies often called Gall gnats. CECIDOMYIIDAE.
+
+        ee. More than four longitudinal veins ending in the wing margin.
+
+          f. The costal vein is not produced beyond the tip of the wing;
+              radius with not more than three branches.
+
+            g. Antennae short, composed of ten or eleven closely united
+                segments; legs stout; body stout; abdomen oval; anterior
+                veins stout, posterior ones weak (fig. 163 b); eyes of
+                the male contiguous over the antennae. Black flies,
+                buffalo flies, turkey gnats. Many North American
+                species, several of them notorious for their blood
+                sucking propensities. SIMULIIDAE
+
+              h. Second joint of the hind tarsus with basal scale-like
+                  process and dorsal excision (fig. 161 h); radial
+                  sector not forked; no small cell at the base of the
+                  wing. _S. forbesi_, _jenningsi_, _johannseni_,
+                  _meridionale_, _piscicidium_, VENUSTUM, VITTATUM, etc.
+                  Widely distributed species (= EUSIMULIUM) SIMULIUM
+                  Latr.
+
+              hh. No basal scale-like process on the second joint of the
+                  hind tarsus; radial sector usually forked (fig. 163
+                  b).
+
+                i. Face broad, small basal cell of the wing present. _P.
+                    fulvum_, HIRTIPES, _mutatum_, PECUARUM, _pleurale_.
+                    PROSIMULIUM Roub.
+
+                ii. Face linear; small basal cell of the wing absent.
+                    One species, _P. furcatum_, from California.
+                    _Parasimulium_ Malloch
+
+            gg. Flies of a different structure.
+
+              h. Antennae composed of apparently two segments and a
+                  terminal arista formed of a number of closely united
+                  segments. Rare flies with aquatic larvae.
+                  ORPHNEPHILIDAE
+
+              hh. Antennae of six to fifteen segments, those of the male
+                  usually plumose; legs frequently slender and wings
+                  narrow. CHIRONOMIDAE
+
+                i. Media forked (except in the European genus
+                    _Brachypogon_); thorax without longitudinal fissure
+                    and not produced over the head (except in four
+                    exotic genera); antennae usually fourteen-jointed in
+                    both sexes; fore tibia with a simple comb of setulae,
+                    hind tibia with two unequal combs, middle tibia
+                    without comb. CERATOPOGONINAE
+
+                  j. Thorax produced cap-like over the head, wing narrow
+                      and very long. _Jenkinsia_, _Macroptilum_ and
+                      _Calyptopogon_, eastern hemisphere;
+                      _Paryphoconus_, Brazil.
+
+                  jj. Thorax not produced over the head.
+
+                    k. Eyes pubescent, empodium well developed, or if
+                        short then R_{2+3} distinct and crossvein-like
+                        or the branches of R coalescent; r-m crossvein
+                        present; fore femora not thickened; wing either
+                        with appressed hairs or with microscopic erect
+                        setulae. _Dasyhelea_ Kieff.
+
+                    kk. Eyes bare, or otherwise differing from the
+                        foregoing.
+
+                      l. Empodium well developed, nearly as long as the
+                          claws and with long hairs at the base; femora
+                          and fifth tarsal segments unarmed, i.e.
+                          without spines or stout setae; fourth tarsal
+                          segment cylindrical.
+
+                        m. Wing with erect and microscopic setulae.
+                            Widely distributed. (= Atrichopogon)
+                            _Ceratopogon_ Meig.
+
+                        mm. Wing with long and depressed hairs. Widely
+                            distributed. _Forcipomyia_
+
+                          n. Hind metatarsus shorter or not longer than
+                              the following (i.e. the second tarsal)
+                              segment. Subgenus _Prohelea_ Kieff
+
+                          nn. Hind metatarsus longer than the following
+                              segment. Subgenus _Forcipomyia_ Meig.
+
+                      ll. Empodium short, scarcely reaching the middle
+                          of the claws, or vestigial.
+
+                        m. R-m crossvein wanting.
+
+                          n. Palpi four segmented; inferior fork of the
+                              media obliterated at the base. Australia.
+                              _Leptoconops_ Skuse
+
+                          nn. Palpi three-segmented.
+
+                            o. Legs spinulose, tarsal claws of the
+                                female with a basal tooth or strong
+                                bristle, those of the male unequal, the
+                                anterior with a long sinuous tooth, the
+                                posterior with a short arcuate tooth.
+                                Italy. MYCTEROTYPUS Noe
+
+                            oo. Legs unarmed; no crossvein between the
+                                branches of the radius (fig. 163e). New
+                                Mexico. TERSESTHES Townsend
+
+                        mm. R-m crossvein present.
+
+                          n. Fore femora very much swollen, armed with
+                              spines below, fore tibia arcuate and
+                              applied closely to the inferior margin of
+                              the femur.
+
+                            o. R_{2+3} present, therefore cell R_1 and
+                                R_2 both present; wing usually fasciate.
+                                United States _Heteromyia_ Say.
+
+                            oo. R_{2+3} not distinct from R_{4+5}, hence
+                                cell R_3 obliterated. South America
+                                _Pachyleptus_ Arrib. (Walker)
+
+                          nn. Fore femur not distinctly swollen.
+
+                            o. R_{2+3} present therefore cells R_1 and
+                                R_3 both present, or if not, then the
+                                branches of the radius more or less
+                                coalescent, obliterating the cells.
+
+                              p. At least the tip of the wing with erect
+                                  setulae; tip of R_{4+5} scarcely
+                                  attaining the middle of the wing,
+                                  empodium rather indistinct, not
+                                  reaching the middle of the claws, the
+                                  claws not toothed, equal, with long
+                                  basal bristle; legs without stout
+                                  setae. Widely distributed. CULICOIDES
+                                  Latr.
+
+                                HAEMATOMYIDIUM and OECACTA are probable
+                                    synonyms of this.
+
+                              pp. Wings bare, if rarely with hair, then
+                                  the radius reaches beyond two-thirds
+                                  the length of the wing, or the femur
+                                  or fifth tarsal segment with stout
+                                  black spines.
+
+                                q. Media unbranched. Europe.
+                                    _Brachypogon_ Kieff
+
+                                qq. Media branched.
+
+                                  r. Hind femur much swollen and spined.
+                                      America and Europe. _Serromyia_
+                                      Meg.
+
+                                  rr. Hind femur not distinctly swollen.
+
+                                    s. Cell R_1 not longer than high;
+                                        fork of the media distad of the
+                                        crossvein; wing with microscopic
+                                        setulae. _Stilobezzia_ Kieff
+
+                                    ss. Cell R_1 elongate.
+
+                                      t. Femora unarmed. Widely
+                                          distributed. (= Sphaeromias
+                                          Kieff. 1913 not Curtis?).
+                                          JOHANNSENIELLA Will.
+
+                                      tt. Femora, at least in part, with
+                                          strong black spines. Widely
+                                          distributed. _Palpomyia_
+                                          Megerle
+
+                            oo. R_{2+3} coalescent with R_{4+5} hence
+                                cell R_3 is obliterated.
+
+                              p. In the female the lower branch of the
+                                  media with an elbow near its base
+                                  projecting proximad, the petiole of
+                                  the media coalescent with the basal
+                                  section of the radius, wing long and
+                                  narrow, radial sector ending near the
+                                  tip of the wing; venation of the male
+                                  as in _Bezzia_; front concave. United
+                                  States. _Stenoxenus_ Coq.
+
+                              pp. Venation otherwise, front not concave.
+
+                                q. Subcosta and R_1 more or less
+                                    coalescent with the costa; wing
+                                    pointed at the apex, much longer
+                                    than the body; antennae fourteen
+                                    segmented, not plumose. India.
+                                    _Haasiella_ Kieff.
+
+                                qq. Subcosta and radius distinct from
+                                    the costa.
+
+                                  r. Abdomen petiolate. _Dibezzia_
+                                      Kieff.
+
+                                  rr. Abdomen not petiolate.
+
+                                    s. Head semi-globose; hind tarsi
+                                        unusually elongate in the
+                                        female; antennae of the male not
+                                        plumose. Europe. _Macropeza_
+                                        Meigen.
+
+                                    ss. Head not globose, more or less
+                                        flattened in front; antennae of
+                                        the male plumose. Widely
+                                        distributed. _Bezzia_ Kieff.
+
+                                      t. Fore femora, at least, armed
+                                          with stout spines below.
+                                          Subgenus _Bezzia_ Kieff.
+
+                                      tt. Femora unarmed. Subgenus
+                                          _Probezzia_ Kieff.
+
+                ii. Media of the wing simple, and otherwise not as in
+                    "i". To this group belong numerous Chironomid
+                    genera, none of which are known to be noxious to
+                    man.
+
+          ff. The costal vein apparently is continued around the hind
+              margin of the wing; radius with at least four branches.
+
+            g. Wing ovate pointed, with numerous veins; crossveins, if
+                evident, before the basal third of the wing; veins very
+                hairy; very small moth-like flies. PSYCHODIDAE
+
+              h. With elongate biting proboscis; the petiole of the
+                  anterior forked cell of the wing (R_2) arises at or
+                  beyond the middle of the wing (fig. 163d). PHLEBOTOMUS
+                  Rdi.
+
+[Illustration: 163. Wings of Diptera. (_a_) Anopheles; (_b_)
+Prosimulium; (_c_) Johannseniella; (_d_) Phlebotomus (After Doerr and
+Russ); (_e_) Tersesthes (after Townsend); (_f_) Tabanus; (_g_)
+Symphoromyia; (_h_) Aphiochaeta; (_i_) Eristalis; (_j_) Gastrophilus;
+(_k_) Fannia; (_l_) Musca.]
+
+              hh. With shorter proboscis; the petiole of the anterior
+                  forked cell arises near the base of the wing.
+                  _Psychoda_, _Pericoma_, etc.
+
+            gg. The r-m crossvein placed at or beyond the center of the
+                wing; wings not folded roof-like over the abdomen.
+
+              h. Proboscis short, not adapted for piercing; wings bare
+                  (DIXIDAE); or wings scaled (CULICIDAE, Subf.
+                  CORETHRINAE).
+
+              hh. Proboscis elongate, adapted for piercing; wings
+                  scaled, fringed on the hind margin; antennae of the
+                  male bushy plumose. Mosquitoes. CULICIDAE (exclusive of
+                  CORETHRINAE)
+
+                i. Metanotum without setae.
+
+                  j. Proboscis strongly decurved; body with broad,
+                      appressed, metalescent scales; cell R_2 less than
+                      half as long as its petiole; claws of female
+                      simple, some of the claws of the male toothed.
+                      Several large southern species believed to feed
+                      only on nectar of flowers. _Megarhinus_ R. D.
+
+                  jj. Proboscis straight or nearly so, or otherwise
+                      different.
+
+                    k. Scutellum evenly rounded, not lobed; claws simple
+                        in both sexes. ANOPHELES Meig.
+
+                      l. Abdomen with clusters of broad outstanding
+                          scales along the sides; outstanding scales on
+                          the veins of the wing rather narrow,
+                          lanceolate; upper side of the thorax and
+                          scutellum bearing many appressed lanceolate
+                          scales. Florida and southward (CELLIA).
+
+                        m. Hind feet from the middle of the second
+                            segment largely or wholly snow white.
+
+                          n. With a black band at the base of the last
+                              segment of each hind foot. A.
+                              ALBIMANUS*[H] and TARSIMACULATA*
+
+                          nn. Without such a band A. ARGYRITARSIS*
+
+                        mm. Hind feet black, mottled with whitish and
+                            with bands of the same color at the sutures
+                            of the segments. W. I. A. MACULIPES
+
+                      ll. Abdomen without such a cluster of scales;
+                          outstanding scales of the wing veins rather
+                          narrow, lanceolate; tarsi wholly black.
+
+                        m. Deep black, thorax obscurely lined with
+                            violaceous, especially posteriorly; head,
+                            abdomen and legs black; no markings on the
+                            pleura; abdomen without trace of lighter
+                            bindings; wing scales outstanding, uniform,
+                            not forming spots, though little thicker at
+                            the usual points indicating the spottings.
+                            Florida. A. ATROPUS
+
+                        mm. Otherwise marked when the wings are
+                            unspotted.
+
+                          n. Wings unspotted.
+
+                            o. Petiole of the first forked cell (R_2)
+                                more than a third the length of the
+                                cell. Mississippi valley. A. WALKERI
+
+                            oo. Petiole of the first forked cell a third
+                                the length of the cell. Md. A. BARBERI
+
+                          nn. Wings spotted.
+
+                            o. Front margin of the wings with a patch of
+                                whitish and yellow scales at a point
+                                about two-thirds or three-fourths of the
+                                way from base to apex of wing.
+
+                              p. Veins of the wing with many broad
+                                  obovate outstanding scales; thorax
+                                  with a black dot near the middle of
+                                  each side. W. I. A. GRABHAMI*
+
+                              pp. The outstanding scales of the wings
+                                  rather narrow, lanceolate.
+
+                                q. Scales of the last vein of the wings
+                                    white, those at each end black;
+                                    R_{4+5} black scaled, the extreme
+                                    apex white scaled. Widely
+                                    distributed north and south (fig.
+                                    131). A. PUNCTIPENNIS
+
+                                  A dark variety from Pennsylvania has
+                                      been named A. PERPLEXENS.
+
+                                qq. Scales of the last vein of the wing
+                                    white, those at its apex black;
+                                    R_{4+5} white scaled and with two
+                                    patches of black scales. South and
+                                    the tropics. A. FRANCISCANUS and
+                                    PSEUDOPUNCTIPENNIS*
+
+                            oo. Front margin of the wings wholly black
+                                scaled.
+
+                              p. Last (anal) vein of the wings white
+                                  scaled with three patches of black
+                                  scales (fig. 132). New Jersey to
+                                  Texas. A. CRUCIANS*
+
+                              pp. Last vein of the wings wholly black
+                                  scaled.
+
+                                q. Widely distributed north and south
+                                    (fig. 130), (= MACULIPENNIS). A.
+                                    QUADRIMACULATUS*
+
+                                qq. Distributed from Rocky Mountains
+                                    westward. A. OCCIDENTALIS
+
+                    kk. Scutellum distinctly trilobed.
+
+                      l. Cell R_2 less than half as long as its petiole;
+                          thorax with metallic blue scales; median lobe
+                          of the scutellum not tuberculate; few small
+                          species which are not common. URANOTAENIA
+                          Arrib.
+
+                      ll. Cell R_2 nearly or quite as long as its
+                          petiole, or otherwise distinct.
+
+                        m. Femora with erect outstanding scales; occiput
+                            broad and exposed. Large species. P.
+                            CILIATA. P. HOWARDI PSOROPHORA R. D.
+
+                        mm. Femora without erect scales.
+
+                          n. Clypeus bearing several scales or hairs,
+                              scutellum with broad scales only; back of
+                              head with broad scales; scales along the
+                              sides of the mesonotum narrow; some or the
+                              claws toothed; thorax marked with a pair
+                              of silvery scaled curved stripes; legs
+                              black with white bands at the bases of
+                              some of the segments (fig. 134). Yellow
+                              Fever mosquito. AEDES (= STEGOMYIA)
+                              CALOPUS.
+
+                          nn. With another combination of characters.
+                              Numerous species of mosquitoes belonging
+                              to several closely related genera, widely
+                              distributed over the country. (_Culex_,
+                              _Aedes_, _Ochlerotatus_, etc.). CULEX in
+                              the wide sense.
+
+                ii. Metanotum with setae. _Wyeomyia_ (found in the United
+                    States); and related tropic genera.
+
+  bb. Antennae composed of three segments with a differentiated style or
+      bristle; third segment sometimes complex or annulate, in which
+      case the empodium is usually developed like the pulvilli, i.e.,
+      pad-like (fig. 161 g).
+
+    c. Empodium developed pad-like (pulvilliform) i.e., three nearly
+        equal membranous appendages on the underside of the claw (fig.
+        161g).
+
+      d. Squamae, head, and eyes large; occiput flattened or concave;
+          third segment of the antennae with four to eight annuli or
+          segments, proboscis adapted for piercing; body with fine
+          hairs, never with bristles; middle tibia with two spurs; wing
+          venation as figured (fig. 163f); marginal vein encompasses the
+          entire wing. Horse flies, greenheads, deer flies, gad flies
+          TABANIDAE[I]
+
+        e. Hind tibia with spurs at tip; ocelli usually present
+            (PANGONINAE)
+
+          f. Third joint of the antennae with seven or eight segments;
+              proboscis usually prolonged.
+
+            g. Each section the third antennal segment branched. Central
+                American species, _P. festae_. _Pityocera_ G. T.
+
+            gg. Sections of the third antennal segment not branched.
+
+              h. Upper corner of the eyes in the female terminating in
+                  an acute angle; wings of both sexes dark anteriorly.
+                  _G. chrysocoma_, a species from the eastern states.
+                  _Goniops_ Ald.
+
+              hh. Upper corner of the eye in the female not so
+                  terminating; wings nearly uniform in color, or
+                  hyaline.
+
+                i. Proboscis scarcely extending beyond the palpi; front
+                    of the female wide; much wider below than above. S.
+                    W. States. _Apatolestes_ Will.
+
+                ii. Proboscis extending beyond the palpi.
+
+                  j. Wing with cell M_3 closed. Tropic America. (=
+                      _Diclisa_) _Scione_ Wlk.
+
+                  jj. Cell M_3 open; ocelli present or absent. Two or
+                      three eastern species; many south and west
+                      PANGONIA Rdi.
+
+          ff. Third segment of the antenna with five divisions; ocelli
+              present.
+
+            g. First and second segments of the antenna short, the
+                second only half as long as the first, three western
+                species. SILVIUS Rdi.
+
+            gg. First and second segments of the antenna long, the
+                second distinctly over half as long as the first. Deer
+                flies. Many species, widely distributed. CHRYSOPS Meig.
+
+        ee. Hind tibia without spurs; ocelli absent.
+
+          f. Third segment of antenna with four divisions, no tooth or
+              angulation; wings marked with rings and circles of darker
+              coloring; front of the female very wide. Widely
+              distributed. _H. americana_, _H. punctulata_. HAEMATOPOTA
+              Meig.
+
+          ff. Third segment of the antenna with five divisions (fig.
+              161b).
+
+            g. Third segment of the antenna not furnished with a tooth
+                or distinct angular projection.
+
+              h. Body covered with metallic scales; front of female of
+                  normal width; front and middle tibiae greatly dilated.
+                  _L. lepidota_. _Lepidoselaga_ Macq.
+
+              hh. Body without metallic scales; antennae not very long,
+                  the third segment not cylindrical, not situated on a
+                  projecting tubercle; front of the female narrow.
+                  South. _D. ferrugatus._ (= _Diabasis_) _Diachlorus_ O.
+                  S.
+
+            gg. Third segment of the antenna furnished with a tooth or a
+                distinct angular projection.
+
+              h. Hind tibiae ciliate with long hairs. S. W. and tropics.
+                  _Snowiella_ and _Stibasoma_.
+
+              hh. Hind tibiae not ciliate.
+
+                i. Species of slender build, usually with a banded
+                    thorax and abdomen; third segment of the antenna
+                    slender, the basal prominence long; wings mostly
+                    with brownish markings. Tropic America.
+                    _Dichelacera_ Macq.
+
+                ii. Species of a stouter build; third segment of the
+                    antenna stout, its basal process short (fig. 161b).
+                    Many species, widely distributed TABANUS L.
+
+      dd. With another group of characters.
+
+        e. Squamae small, antennae variable, thinly pilose or nearly
+            bare species, without distinct bristles; wing veins not
+            crowded anteriorly, R_4 and R_5 both present, basal cells
+            large; middle tibiae at least with spurs. LEPTIDAE
+
+          f. Flagellum of the antenna more or less elongated, composed
+              of numerous more or less distinct divisions. XYLOPHAGINAE
+              and ARTHROCERATINAE.
+
+          ff. Antennae short, third segment simple, with arista or style;
+              face small, proboscis short LEPTINAE
+
+            g. Front tibiae each with one or two spurs, or if absent,
+                then no discal cell. _Triptotricha_, _Pheneus_,
+                _Dialysis_, _Hilarimorpha_.
+
+            gg. Front tibiae without terminal spurs, discal cell
+                present.
+
+              h. Hind tibiae each with a single spur.
+
+                i. Anal cell open (fig. 163g); third antennal segment
+                    kidney-shaped with dorsal or subdorsal arista; first
+                    antennal segment elongate and thickened. About a
+                    dozen species have been described from the United
+                    States, of which at least one (S. PACHYCERAS) is
+                    known to be a vicious blood sucker. SYMPHOROMYIA
+                    Frauenf.
+
+                ii. Anal cell closed; third antennal segment not
+                    kidney-shaped. _Chrysopila_, _Ptiolina_, _Spania_.
+
+              hh. Hind tibiae each with two spurs.
+
+                i. Third segment kidney-shaped, the arista subdorsal;
+                    anal cell closed. _Atherix_ Meig.
+
+                ii. Third segment of the antenna short and with terminal
+                    arista; anal cell open _Leptis_ Fabr. Two European
+                    species of this genus have been accused of blood
+                    sucking habits, but the record seems to have been
+                    based upon error in observation.
+
+        ee. With another combination of characters. STRATIOMYIIDAE,
+            CYRTIDAE, etc.
+
+    cc. Empodium bristlelike or absent.
+
+      d. Antennae apparently two segmented, with three-segmented arista,
+          wings (rarely wanting) with several stout veins anteriorly,
+          the weaker ones running obliquely across the wing (fig. 163h);
+          small, quick running, bristly, humpbacked flies. Several
+          genera; APHIOCHAETA, PHORA, TRINEURA, etc. PHORIDAE
+
+      dd. Flies with other characters.
+
+        e. No frontal lunule above the base of the antennae; both R_4
+            and R_5 often present; third segment of the antenna often
+            with a terminal bristle. ASILIDAE, MYDAIDAE,
+            APIOCERIDAE, THEREVIDAE, SCENOPINIDAE, BOMBYLIIDAE,
+            EMPIDIDAE, DOLICHOPODIDAE, LONCHOPTERIDAE.
+
+        ee. A frontal lunule above the base of the antennae; third
+            segment of the antenna always simple, i.e., not ringed,
+            usually with a dorsal arista; R_4 and R_5 coalesced into a
+            simple vein.
+
+          f. A spurious vein or fold between the radius and the media,
+              rarely absent; the cell R_{4+5} closed at the apex by vein
+              M_1; few or no bristles on the body, none on the head;
+              flies frequently with yellow markings. ERISTALIS (fig.
+              163i), HELOPHILUS, and many other genera. SYRPHIDAE
+
+          ff. No spurious vein present.
+
+            g. Body without bristles; proboscis elongate and slender,
+                often folding; front of both male and female broad.
+                CONOPIDAE
+
+            gg. Bristles almost always present on head, thorax, abdomen
+                and legs.
+
+              h. Arista terminal; hind metatarsus enlarged, sometimes
+                  ornamented, hind tarsus more or less flattened beneath.
+                  PLATYPEZIDAE
+
+              hh. Flies having a different combination of characters.
+
+                i. Head large, eyes occupying nearly the entire head;
+                    cell R_{4+5} narrowed in the margin; small flies.
+                    PIPUNCULIDAE
+
+                ii. Head and eyes not unusually large.
+
+                  j. Squamae (tegulae, or calyptrae, or alulae)
+                      not large, often quite small, the lower one
+                      lacking, or at most barely projecting from below
+                      the upper one (antisquama); front of both male and
+                      female broad, the eyes therefore widely separated;
+                      posthumeral and intraalar macrochaeta not
+                      simultaneously present; thorax usually without a
+                      complete transverse suture; postalar callus
+                      usually absent; the connectiva adjoining the
+                      ventral sclerites always visible; hypopleural
+                      macrochaetae absent; last section of R_{4+5}
+                      and M_{1+2} with but few exceptions nearly
+                      parallel; subcostal vein often wanting or
+                      vestigial or closely approximated to R_1; the
+                      latter often short, basal cells small, the
+                      posterior ones often indistinct or wanting;
+                      vibrissae present or absent. ACALYPTRATE
+                      MUSCOIDEA
+
+                    k. Subcosta present, distinctly separated from R_1
+                        at the tip; R_1 usually ends distad of the
+                        middle of the wing; the small basal cells of the
+                        wing distinct.
+
+                      l. A bristle (vibrissa) on each side of the face
+                          near the margin of the mouth. CORDYLURIDAE,
+                          SEPSIDAE, PHYCODROMIDAE, HETERONEURIDAE,
+                          HELOMYZIDAE.
+
+                      ll. No vibrissae present.
+
+                        m. Head nearly spherical, cheeks broad and
+                            retreating; proboscis short; the cell R_5
+                            closed or narrowed in the margin; legs very
+                            long; tarsi shorter than the tibiae. CALOBATA
+                            and other genera. MICROPEZIDAE
+
+                        mm. Flies with another combination of
+                            characters. RHOPALOMERIDAE, TRYPETIDAE,
+                            ORTALIDAE, SCIOMYZIDAE.
+
+                    kk. Subcosta absent or vestigial, or if present,
+                        then apparently ending in the costa at the point
+                        where R_1 joins it; R_1 usually ends in the
+                        costa at or before the middle of the wing.
+
+                      l. Arista long plumose, or pectinate above; oral
+                          vibrissae present; anal cell complete; costa
+                          broken at the apex of R_1. DROSOPHILA,
+                          PHORTICA, and other genera. DROSOPHILIDAE
+
+                      ll. With another combination of characters.
+
+                        m. The cell M and first M_2 not separated by a
+                            crossvein; anal cell absent; front bare or
+                            only bristly above; usually light colored
+                            flies. HIPPELATES, OSCINUS, and other
+                            genera. (See also m m m.) OSCINIDAE
+
+                        mm. Cell M and cell first M_2 often separated by
+                            a crossvein; anal cell present, complete,
+                            though frequently small; scutellum without
+                            spines or protuberances; oral vibrissae
+                            present; arista bare or short plumose; front
+                            bristly at vertex only; small dark flies.
+                            PIOPHILA (fig. 99), SEPSIS and other genera.
+                            SEPSIDAE
+
+                        mmm. The GEOMYZIDAE, AGROMYZIDAE,
+                            PSILIDAE, TRYPETIDAE, RHOPALOMERIDAE,
+                            BORBORIDAE and DIOPSIDAE differ in
+                            various particulars from either the
+                            OSCINIDAE and the SEPSIDAE noted above.
+
+                  jj. Squamae well developed, usually large, the lower
+                      one frequently projecting from below the upper
+                      one; both posthumeral and intraalar macrochaetae
+                      present; thorax with a complete transverse suture;
+                      postalar callus present and separated by a
+                      distinct suture from the dorsum of the thorax;
+                      front of the female broad, of the male frequently
+                      narrow, the eyes then nearly or quite contiguous;
+                      the connectiva adjoining the ventral sclerites
+                      either visible or not; hypopleural macrochaetae
+                      present or absent; subcosta always distinct in its
+                      whole course, R_1 never short. CALYPTRATE
+                      MUSCOIDEA[J]
+
+                    k. Oral opening small, mouth parts usually much
+                        reduced or vestigial. This family is undoubtedly
+                        of polyphyletic origin but for convenience it is
+                        here considered as a single family. OESTRIDAE.
+
+                      l. The costal vein ends at the tip of R_{4+5},
+                          M_{1+2} straight, not reaching the wing
+                          margin, hence cell R_5 wide open (fig. 163j);
+                          squamae small; arista bare; ovipositor of the
+                          female elongate. Larvae in the alimentary canal
+                          of horses, etc. GASTROPHILUS
+
+                        m. Posterior crossvein (m-cu) wanting; wings
+                            smoky or with clouds. Europe. G. PECORUM
+
+                        mm. Posterior crossvein (m-cu) present, at least
+                            in part.
+
+                          n. Wing hyaline with smoky median cross band,
+                              and two or three spots; posterior
+                              trochanters with hook in the male and a
+                              prominence in the female. World wide
+                              distribution. G. EQUI.
+
+                          nn. Wings without spots.
+
+                            o. Posterior crossvein (m-cu) distad of the
+                                anterior crossvein (r-m); legs,
+                                particularly the femora, blackish brown.
+                                Europe and North America. G.
+                                HAEMORRHOIDALIS
+
+                            oo. Posterior crossvein opposite or proximad
+                                of the anterior crossvein. Europe and
+                                North America. G. NASALIS
+
+                      ll. The costal vein ends at the tip of M_{1+2},
+                          M_{1+2} with a bend, the cell R_5 hence much
+                          narrowed in the margin, or closed.
+
+                        m. Proboscis geniculate, inserted in a deep
+                            slit; female without extricate ovipositor;
+                            arista either bare or plumose; squamae large;
+                            facial grooves approximated below.
+
+                          n. Arista bare, short. Larvae in rodents.
+                              Tropic America. _B. princeps_. _Bogeria_
+                              Austen
+
+                          nn. Arista pectinate above.
+
+                            o. Tarsi broadened and flattened, hairy,
+                                anal lobe of the wing large. Larvae in
+                                rodents. A number of American species.
+                                _Cuterebra_.
+
+                            oo. Tarsi slender, not hairy; anal lobe of
+                                the wing moderate. Larvae in man and
+                                other mammals. Tropic America. D.
+                                CYANIVENTRIS. DERMATOBIA Br.
+
+                        mm. Mouth parts very small, vestigial; arista
+                            bare.
+
+                          n. Facial grooves approximated below, leaving
+                              a narrow median depression or groove.
+
+                            o. Cell R_5 closed and petiolate, body
+                                nearly bare. Larvae in the nasal cavities
+                                of the smaller Ungulates. The sheep bot
+                                fly. O. OVIS. Widely distributed OESTRUS
+                                L.
+
+                            oo. Cell R_5 narrowly open, body hairy.
+                                Larvae parasitic on deer. Europe and
+                                America. _Cephenomyia_ Latr.
+
+                          nn. Facial grooves far apart, enclosing
+                              between them a broad shield-shaped
+                              surface; squamae large; female with
+                              elongate ovipositor. Larvae hypodermatic on
+                              Ungulates HYPODERMA Clark
+
+                            o. Palpi wanting; tibiae thickened in the
+                                middle.
+
+                              p. Hair at apex of the abdomen yellow;
+                                  legs including femora yellowish brown.
+                                  H. DIANA
+
+                              pp. Hair at the apex of the abdomen
+                                  reddish yellow. Europe and America.
+
+                                q. Tibiae and tarsi yellow; femora black.
+                                    H. LINEATA
+
+                                qq. Legs black with black hair; tips of
+                                    hind tibia and tarsi yellowish
+                                    brown. H. BOVIS
+
+                            oo. Palpi small, globular; tibiae
+                                cylindrical, straight. On reindeer. _O.
+                                tarandi_ _Oedemagena_ Latr.
+
+                    kk. Oral opening of the usual size; mouth parts not
+                        vestigial.
+
+                      l. Hypopleurals wanting; if three sternopleurals
+                          are present the arrangement is 1:2;
+                          conjunctiva (fig. 161c) of the venter usually
+                          present; if the terminal section of M_{1+2} is
+                          bent it has neither fold nor appendage
+                          (ANTHOMYIIDAE of Girschner).
+
+                        m. Sternopleurals wanting; M_{1+2} straight
+                            toward the apex, costa ends at or slightly
+                            beyond the tip of R_{4+5}; mouth parts
+                            vestigial. GASTROPHILINAE. See OESTRIDAE
+
+                        mm. Sternopleurals present, if rarely absent
+                            then differing in other characters.
+
+                          n. Caudal margin of the fifth ventral
+                              abdominal sclerite of the male deeply
+                              notched on the median line usually to
+                              beyond the middle; abdomen often
+                              cylindrical or linear; abdomen often with
+                              four to eight spots; eyes of the male
+                              usually widely separated; sternopleurals
+                              three, arranged in an equilateral
+                              triangle; subapical seta of the hind tibia
+                              placed very low; M_{1+2} straight; anal
+                              vein abbreviated; wings not rilled.
+                              _Caenosia_, _Caricea_, _Dexiopsis_,
+                              _Hoplogaster_, _Schoenomyia_, etc.
+                              (COENOSINAE)[K]. ANTHOMYIIDAE in part
+
+                          nn. Caudal margin of the fifth ventral
+                              abdominal sclerite of the male incurved,
+                              rarely deeply cleft, rarely entire, in a
+                              few genera deeply two or three notched;
+                              M_{1+2} straight or curved; abdomen
+                              usually short or elongate oval;
+                              sternopleurals, if three are present,
+                              arranged in the order 1:2 in a right
+                              triangle. (MUSCINAE-ANTHOMYIINAE of
+                              Girschner)
+
+                            o. M_{1+2} straight, hence cell R_5 not
+                                narrowed in the margin. ANTHOMYIIDAE in
+                                part
+
+                              p. Underside of the scutellum more or less
+                                  sparsely covered with fine hairs; anal
+                                  vein nearly always reaches the hind
+                                  margin of the wing; extensor surface
+                                  of the hind tibiae with a number of
+                                  stout setae; squamae often small and
+                                  equal. ANTHOMYIA, _Chortophila_,
+                                  _Eustalomyia_, _Hammomyia_,
+                                  _Hylemyia_, _Prosalpia_, _Pegomyia_,
+                                  etc. HYLEMYINAE-PEGOMYINAE
+
+                              pp. Underside of the scutellum bare; anal
+                                  vein does not reach the wing margin.
+
+                                q. First anal vein short, second anal
+                                    suddenly flexed upwards; hind tibiae
+                                    each with one or two strong setae on
+                                    the extensor surface. FANNIA (=
+                                    HOMALOMYIA), _Coelomyia_,
+                                    _Choristoma_, _Euryomma_, _Azelia_,
+                                    etc. FANNINAE-AZELINAE
+
+                                qq. Anal veins parallel or divergent.
+
+                                  r. Setae on the exterior surface of the
+                                      hind tibiae wanting (except in
+                                      _Limnaricia_ and _Coenosites_),
+                                      lower squama not broadened to the
+                                      margin of the scutellum.
+                                      _Leucomelina_, _Limnophora_,
+                                      _Limnospila_, _Lispa_, _Mydaea_,
+                                      _Spilogaster_, etc.
+                                      MYDAEINAE-LIMNOPHORINAE
+
+                                  rr. One (rarely more) seta on the
+                                      extensor surface of the hind
+                                      tibia; squamae usually large and
+                                      unequal. HYDROTAEA, _Aricia_,
+                                      _Drymeia_, _Ophyra_, _Phaonia_ (=
+                                      _Hyetodesia_), _Pogonomyia_,
+                                      _Trichophthicus_, etc. ARICINAE
+
+                            oo. M_{1+2} curved or bent, hence the cell
+                                R_5 more or less narrowed in the margin.
+                                (MUSCINAE). MUSCIDAE in part. See
+                                page 303 for generic synopsis.
+
+                      ll. Hypopleurals present; when three
+                          sternopleurals are present the arrangement is
+                          2:1 or 1:1:1. (TACHINIDAE of Girschner)
+
+                        m. Conjunctiva of the ventral sclerites of the
+                            abdomen present, frequently well developed,
+                            surrounding the sclerites.
+
+                          n. Mouth parts vestigial. OESTRIDAE. See page
+                              297 for generic synopsis.
+
+                          nn. Mouth parts well developed.
+
+                            o. M_{1+2} straight, hence cell R_5 wide
+                                open in the margin; costa ending at the
+                                tip of R_5; three sternopleurals
+                                present; antennal arista plumose.
+                                _Syllegoptera_. Europe.
+                                (SYLLEGOPTERINAE). DEXIIDAE in part
+
+                            oo. M_{1+2} bent, hence cell R_5 narrowed in
+                                the margin; sternopleurals rarely
+                                wanting, usually 1:1 or 0:1; facial
+                                plate strongly produced below vibrissal
+                                angle like the bridge of the nose;
+                                antennal arista bare. Parasitic on
+                                Hemiptera and Coleoptera. _Allophora_,
+                                _Cistogaster_, _Clytia_, _Phasia_, etc.
+                                (PHASIINAE) TACHINIDAE in part.
+
+                        mm. Conjunctiva of the ventral sclerites
+                            invisible (fig. 161a).
+
+                          n. Second ventral sclerite of the abdomen
+                              lying with its edges either upon or in
+                              contact with the ventral edges of the
+                              corresponding dorsal sclerite.
+
+                            o. Outermost posthumeral almost always lower
+                                (more ventrad) in position than the
+                                presutural macrochaeta; fifth ventral
+                                abdominal sclerite of the male cleft
+                                beyond the middle, often strongly
+                                developed; body color very frequently
+                                metallic green or blue, or yellow;
+                                arista plumose. (CALLIPHORINAE)
+                                MUSCIDAE in part.
+
+                              See page 303 for generic synopsis.
+
+                            oo. Outermost posthumeral macrochaeta on
+                                level or higher (more dorsad) than the
+                                presutural macrochaeta; arista bare,
+                                pubescent, or plumose only on the basal
+                                two-thirds; body coloring usually
+                                grayish (fig. 106). SARCOPHAGIDAE
+
+                              p. Fifth ventral sclerite of the male
+                                  either wanting or with the caudal
+                                  margin straight; presutural intraalar
+                                  rarely present. (SARCOPHAGINAE)
+
+                                q. Fifth ventral abdominal sclerite of
+                                    the male much reduced, the remaining
+                                    segments with straight posterior
+                                    margin, overlapping scale-like; in
+                                    the female only segment one and two
+                                    scale-like, the others wholly or in
+                                    part covered; sternopleurals usually
+                                    three or more. SARCOPHAGA and
+                                    related genera.
+
+                                qq. Fifth ventral sclerite of the male
+                                    plainly visible; sternopleurals
+                                    usually two. SARCOPHILA,
+                                    WOHLFAHRTIA, _Brachycoma_,
+                                    _Hilarella_, _Miltogramma_,
+                                    _Metopia_, _Macronychia_, _Nyctia_,
+                                    _Paramacronychia_, _Pachyphthalmus_,
+                                    etc.
+
+                              pp. Fifth ventral abdominal sclerite of
+                                  the male cleft to beyond the middle;
+                                  ventral sclerites usually visible,
+                                  shield-like. _Rhinophora_, _Phyto_,
+                                  _Melanophora_ RHINOPHORINAE
+
+[Illustration: 164. Glossina palpalis. (x4.) After Austen.]
+
+                          nn. Second ventral abdominal sclerite as well
+                              as the others more or less covered,
+                              sometimes wholly, by the edges of the
+                              dorsal sclerite.
+
+                            o. The presutural intraalar wanting; ventral
+                                sclerites two to five nearly or quite
+                                covered by the edges of the
+                                corresponding dorsal sclerites; base of
+                                the antennae usually at or below the
+                                middle of the eye; arista usually
+                                plumose; legs usually elongate;
+                                abdominal segments with marginal and
+                                often discal macrochaetae. DEXIIDAE
+
+                            oo. Presutural intraalar present, if absent,
+                                then the ventral sclerites broadly
+                                exposed or the fifth ventral sclerite
+                                vestigial; base of the antennae usually
+                                above the middle of the eye; arista
+                                bare; at least two posthumerals and
+                                three posterior intraalars present.
+                                Parasitic on caterpillars, etc.
+                                TACHINIDAE
+
+
+SYNOPSIS OF THE PRINCIPAL GENERA OF THE MUSCIDAE OF THE WORLD
+
+a. Proboscis long, directed forward, adapted for piercing, or oral
+    margin much produced, snout-like.
+
+  b. Oral margin produced snout-like; vibrissa placed high above the
+      oral margin; antennal arista either pectinate or more or less
+      plumose.
+
+    c. Antennal arista short or long-plumose; neither sex with distinct
+        orbital bristles.
+
+      d. No facial carina between the antennae. RHYNCHOMYIINAE
+
+        e. Arista short-plumose. _R. speciosa._ Europe. _Rhynchomyia_ R.
+            D.
+
+        ee. Arista long-plumose. _I. phasina_. Europe and Egypt.
+            _Idiopsis_. B. B.
+
+      dd. With flattened carina, the bases of the antennae separated; no
+          abdominal macrochaetae. COSMININAE _C. fuscipennis_. South
+          Africa. _Cosmina_
+
+    cc. Antennal arista pectinate; bases of the antennae separated by a
+        flattened carina. RHINIINAE R. D.
+
+      d. Cell R_5 open, or closed at the margin.
+
+        e. Third segment of the antenna twice as long as the second;
+            claws of both sexes short; cell R_5 open. _I. lunata._
+            Eastern Hemisphere. _Idia_ Meigen
+
+        ee. Third segment of the antenna three times as long as the
+            second; cell R_5 open or closed; claws of the male long and
+            slender, of the female shorter than the last tarsal joint.
+            _I. mandarina_, China. _Idiella_ B. B.
+
+      dd. Cell R_5 petiolate. _Rhinia_; and _Beccarimyia_ Rdi.
+
+  bb. Proboscis long, directed forward, adapted for piercing. STOMOXINAE
+
+    c. Arista flat, pectinate above with plumose rays; sternopleurals
+        1:2; bases of the veins R_1 and R_{4+5} without setae; base of
+        the media bowed down; apical cell opens before the apex of the
+        wing. African species. GLOSSINA Wied.
+
+      d. Species measuring over twelve mm. in length. _G. longipennis_
+          and FUSCA.
+
+      dd. Species less than twelve mm. in length.
+
+        e. All segments of the hind tarsi black.
+
+          f. The fourth and fifth segments of the fore tarsi black;
+              antennae black (fig. 164). G. PALPALIS R. D.
+
+          ff. Otherwise marked. _G. bocagei_, _tachinoides_,
+              _pallicera._
+
+        ee. First three segments of the hind tarsi are yellow, the
+            fourth and fifth segments are black.
+
+          f. Fourth and fifth segments of the first and second pair of
+              tarsi are black.
+
+            g. The yellow bands of the abdominal segments occupy a third
+                of the segment (fig. 165). G. MORSITANS Westw.
+
+            gg. The yellow band on each segment of the abdomen occupies
+                a sixth of the segment. G. LONGIPALPIS Wied.
+
+          ff. Tarsi of the first and second pairs of legs wholly yellow.
+              _G. pallidipes_ Austen
+
+    cc. Rays of the arista not plumose; only one or two sternopleurals;
+        base of the media not strongly bowed down; apical cell opens at
+        or very near the apex of the wing.
+
+      d. Vein R_{4+5} without setae at the base; palpi about as long as
+          the proboscis.
+
+        e. Arista pectinate (i.e. rays on one side only), the rays often
+            undulate; two yellow sternopleurals often difficult to
+            detect; vein M_{1+2} only slightly bent, the apical cell
+            hence wide open. The horn fly, H. IRRITANS (= _Lyperosia
+            serrata_) and related species. Widely distributed (figs.
+            167, 168). HAEMATOBIA R. D. not B. B.
+
+[Illustration: 165. Glossina morsitans. (x4.) After Austen.]
+
+        ee. Arista also with rays below; vein M_{1+2} more strongly
+            bent, the apical cell hence less widely open.
+
+          f. Palpi strongly spatulate at the tips, lower rays of the
+              arista about six in number, B. SANGUINOLENTUS. South Asia.
+              BDELLOLARYNX Austen
+
+          ff. Palpi feebly spatulate; apical cell of the wing narrowly
+              open slightly before the tip; sternopleurals black,
+              anterior bristle sometimes absent. H. ATRIPALPIS. Europe.
+              HAEMATOBOSCA Bezzi
+
+      dd. Vein R_{4+5} with setae at the base.[L]
+
+        e. Veins R_1 and R_{4+5} with setae at the base; two equally
+            prominent sternopleural macrochaetae; arista with rays both
+            above and below; palpi as long as the proboscis; apical cell
+            of the wing wide open. L. TIBIALIS. (_Haematobia_ B. B. not
+            R. D.). LYPEROSIOPS Town.
+
+        ee. Only vein R_{4+5} with basal setae; anterior sternopleural
+            macrochaeta wanting; arista pectinate.
+
+          f. Palpi as long as the proboscis, the latter stout, with
+              fleshy terminal labellae; apical cell narrowly open;
+              sternopleural macrochaetae black. S. MACULOSA from Africa
+              and related species from Asia. STYGEROMYIA Austen
+
+          ff. Palpi much shorter than the proboscis, the latter pointed
+              at the apex, without fleshy labellae; apical cell of the
+              wing wide open. S. CALCITRANS, the stable fly and related
+              species. Widely distributed in both hemispheres (fig.
+              110). STOMOXYS Geof.
+
+aa. Proboscis neither slender nor elongate, the labellae fleshy and not
+    adapted for piercing.
+
+  b. Hypopleurae without a vertical row of macrochaetae. MUSCINAE
+
+    c. Arista bare; distal portion of M_{1+2} broadly curved at the end;
+        hypopleurae with a sparse cluster of fine hairs. _S.
+        braziliana_, Southern States and southward. _Synthesiomyia_ B.
+        B.
+
+    cc. Arista pectinate or plumose.
+
+      d. Arista pectinate. _H. vittigera_, with the posterior half of
+          the abdomen metallic blue. Mexico. _Hemichlora_ V. d. W.
+
+      dd. Arista plumose.
+
+        e. Middle tibia with one or more prominent setae on the inner
+            (flexor) surface beyond the middle, or inner surface very
+            hairy.
+
+          f. R_1 ends distad of the m-cu crossvein; M_{1+2} with a broad
+              curve near its apical end. (= _Neomesembrina_ Schnabl. =
+              _Metamesembrina_ Town). _M. meridiana._ Europe.
+              _Mesembrina_ Meigen
+
+          ff. R_1 ends proximad of the m-cu crossvein.
+
+            g. Eyes pilose, sometimes sparsely in the female.
+
+              h. Female with two or three stout orbital setae; the hind
+                  metatarsus of the male thickened below at the base and
+                  penicillate. _D. pratorum._ Europe. _Dasyphora_ R.
+                  D.[M]
+
+              hh. Neither sex with orbital setae.
+
+                i. Abdomen without macrochaetae; arista plumose. _C.
+                    asiatica._ Eastern Hemisphere. _Cryptolucilia_ B. B.
+
+                ii. Abdomen with strong macrochaetae; arista very
+                    short-plumose, nearly bare. _B. tachinina._ Brazil.
+                    _Reinwardtia_ B. B.
+
+            gg. Eyes bare.
+
+              h. Body densely pilose; thoracic macrochaetae wanting;
+                  middle tibiae much elongate and bent; last section of
+                  M_{1+2} with a gentle curve. H. (_Mesembrina_)
+                  _mystacea, et al._, Europe and _H. solitaria_, N.
+                  America. _Hypodermodes_ Town.
+
+              hh. Body not densely pilose.
+
+                i. Dorsocentrals six; last section of M_{1+2} with a
+                    gentle curve.
+
+                  j. Inner dorsocentrals ("acrostichals") wanting;
+                      sternopleurals arranged 1:3. _P. cyanicolor_,
+                      _cadaverina_, etc. Europe and America _Pyrellia_
+                      R. D.
+
+                  jj. Inner dorsocentrals ("acrostichals") present;
+                      sternopleurals arranged 1:2. E. _latreillii._
+                      North America. _Eumesembrina_ Town.
+
+                ii. Dorsocentrals five; inner dorsocentrals present;
+                    last section of M_{1+2} with a rounded angle;
+                    sternopleurals arranged 1:2. _P. cornicina_ Europe
+                    and America. (_Pseudopyrellia_ Girsch.) _Orthellia_
+                    R. D.
+
+        ee. Middle tibia without a prominent bristle on the inner
+            surface beyond the middle.
+
+[Illustration: 166. Pycnosoma marginale. (x4.) After Graham-Smith.]
+
+          f. Squamula thoracalis broadened mesad and caudad as far as
+              the scutellum.
+
+            g. Sternopleural macrochaetae arranged in an equilateral
+                triangle; front of both sexes broad; genae bare;
+                dorsocentrals six, small; wing not rilled. (To
+                COENOSINAE). _Atherigona_ Rdi.
+
+            gg. Sternopleural macrochaetae when three are present,
+                arranged in a right triangle.
+
+              h. Last section of M_{1+2} with a more or less rounded
+                  angle (fig. 163l).
+
+                i. Eyes of the male pilose or pubescent, of the female
+                    nearly bare; m-cu crossvein usually at or proximad
+                    of the mid-distance between the r-m crossvein and
+                    the bend of M_{1+2}. P. (= _Placomyia_ R. D.)
+                    _vitripennis_. _Plaxemyia_ R. D.
+
+                ii. Eyes bare; the m-cu crossvein always nearer to the
+                    bend of M_{1+2} than to the r-m crossvein.
+
+                  j. Apex of the proboscis when extended reveals a
+                      circlet of stout chitinous teeth. P. INSIGNIS
+                      Austen, of India, bites both man and animals. (=
+                      _Pristirhynchomyia_.) PHILAEMATOMYIA Austen
+
+                  jj. Apex of the proboscis without black teeth.
+
+                    k. Eyes of male separated by a distance equal to a
+                        fourth the width of the head. House or typhoid
+                        fly. M. DOMESTICA L. Widely distributed. MUSCA
+                        L.
+
+                    kk. Eyes of the male contiguous. E. CORVINA. Europe.
+                        EUMUSCA Town
+
+              hh. Last section of M_{1+2} with a gentle curve (fig.
+                  102).
+
+                i. Eyes pilose.
+
+                  j. Claws in the male somewhat elongated; no orbitals
+                      in either sex; antennae separated at the base by a
+                      flat carina; abdomen marked with red or yellow.
+                      _G. maculata._ Europe and America. _Graphomyia_ R.
+                      D.
+
+                  jj. Claws short and equal in the two sexes; two or
+                      three stout orbital macrochaetae in the
+                      female; R_1 scarcely produced beyond the r-m
+                      crossvein; eyes contiguous in the male. _P.
+                      obsoleta._ Brazil. _Phasiophana_ Br.
+
+                ii. Eyes bare; fronto-orbital macrochaetae in a double
+                    row, antennae contiguous at the base.
+
+                  j. One or more pairs of well developed anterior inner
+                      dorsocentral (acrostichal) macrochaetae; seta on
+                      extensor surface of hind tibia. M. ASSIMILIS,
+                      STABULANS, etc. Europe and America. MUSCINA R. D.
+
+                  jj. Anterior inner dorsocentrals and the setae; on the
+                      extensor surface of the hind tibia wanting. _M.
+                      micans_, etc. Europe and North America. _Morellia_
+                      R. D.
+
+          ff. Squamula thoracalis not broadened mesad and caudad, not
+              reaching the margin of the scutellum; macrochaetae on
+              extensor surface of the hind tibia wanting.
+
+            g. Eyes pubescent. _M. meditabunda._ Europe and America.
+                _Myiospila_ Rdi.
+
+            gg. Eyes bare; R_1 ends before the middle of the wing. A
+                number of species from the tropics of both hemispheres.
+                _Clinopera_ V. d. W.
+
+  bb. Hypopleurae with a vertical row of macrochaetae.
+
+    c. Eyes pubescent.
+
+      d. R_1 ends about opposite the r-m crossvein; basal section of
+          R_{4+5} bristly nearly to the crossvein; _S. enigmatica_.
+          Africa. _Somalia_ Hough
+
+      dd. R_1 ends distad of the r-m crossvein.
+
+        e. Eastern hemisphere. Australasia. _N. ochracea_,
+            _dasypthalma_. _Neocalliphora_ Br.
+
+        ee. Western Hemisphere. _T. muscinum._ Mexico. _Tyreomma_ V. d.
+            W.
+
+    cc. Eyes bare.
+
+      d. The vibrissal angle situated at a noticeable distance above the
+          level of the margin of the mouth.
+
+        e. Sternopleural macrochaetae arranged in the order 1:1.
+
+          f. Genae with microchaetae.
+
+            g. Body grayish, with depressed yellow woolly hair among the
+                macrochaetae; wings folded longitudinally over the body
+                when at rest. Cluster flies. _P. rudis_ and related
+                species, widely distributed. _Pollenia_ R. D.[N]
+
+            gg. Body metallic blue or green. Eastern Hemisphere.
+
+              h. Vibrissal angle placed very high above the oral margin;
+                  a carina between the antennae; outer posthumeral
+                  wanting; anterior intraalar present. _T. viridaurea_.
+                  Java. _Thelychaeta_ Br.
+
+[Illustration: 167. Horn fly. (_a_) egg; (_b_) larva; (_c_) puparium;
+(_d_) adult. (x4). Bureau of Entomology]
+
+              hh. Vibrissal angle moderately high above the oral margin;
+                  carina small or wanting; no post humeral macrochaeta;
+                  lower squamae hairy above. (= _Paracompsomyia_ Hough)
+                  (fig. 166). _Pycnosoma_ Br.
+
+          ff. Genae bare. _S. terminata_. Eastern Hemisphere.
+              _Strongyloneura_ Bigot
+
+        ee. Sternopleurals arranged 2:1.
+
+          f. Body metallic green or blue, with gray stripes; genae hairy
+              to the lower margin; post humerals often wanting; lower
+              squamae bare above. (= _Compsomyia_ Rdi.). CHRYSOMYIA R. D.
+
+            g. With one or two orbitals; height of bucca less than half
+                the height of the eye. South and east U. S. (fig. 107).
+                C. MARCELLARIA
+
+            gg. No orbitals; height of bucca about a third less than
+                height of eye. West U. S. _C. wheeleri_ Hough
+
+          ff. Body black or sordidly metallic greenish gray, usually
+              yellow pollinose or variegate; genae at most hairy above.
+              _N. stygia_. Eastern Hemisphere. _Neopollenia_ Br.
+
+      dd. Vibrissal angle situated nearly on a level of the oral margin.
+
+        e. Species wholly blackish, bluish, or greenish metallic in
+            color.
+
+          f. First section of R_{4+5} with at most three or four small
+              bristles at the immediate base.
+
+            g. The bend of M_{1+2} a gentle curve; costal spine present;
+                cell R_5 closed, ending before the apex of the wing. _S.
+                cuprina._ Java. _Synamphoneura_ Bigot
+
+            gg. Bend of M_{1+2} angular; or the insect differs in other
+                characters; dorsal surface of the squamula thoracalis
+                hairy (except in _Melinda_); arista plumose only on the
+                basal two-thirds (except usually in _Calliphora_ and
+                _Eucalliphora_).
+
+[Illustration: 168. Head of horn-fly (Lyperosia irritans); (_a_) female;
+(_b_) male; (_c_) lateral aspect of female. Bureau of Entomology]
+
+              h. Arista plumose only on the basal two-thirds.
+
+                i. Base of the antennae ventrad of the middle of the
+                    eye; eyes of the male nearly contiguous; genae
+                    hairy; second abdominal segment with median marginal
+                    macrochaetae; two, rarely three, postsutural
+                    intraalar macrochaetae.
+
+                  j. Squamula thoracalis dorsally with long black hairs;
+                      male hypopygium two-segmented, large, projecting;
+                      claws and pulvilli of the male elongate; three
+                      strong sternopleural macrochaetae; genae at
+                      least half the width of the eye; buccae (cheeks)
+                      half the height of the eyes; oviviparous. _O.
+                      sepulcralis._ Europe. _Onesia_ R. D.
+
+                  jj. Dorsal surface of the squamula thoracalis bare;
+                      male hypopygium small, scarcely projecting below;
+                      claws and pulvilli not elongate; two stout
+                      sternopleural macrochaetae, sometimes with a
+                      delicate one below the anterior; genae nearly
+                      linear in the male; buccae about a third of the eye
+                      height; oviparous. _M. caerulea_. Europe.
+                      _Melinda_. R. D.
+
+[Illustration: 169. Lateral and dorsal aspects of the thorax, and
+frontal aspect of the head of a muscoidean fly, with designations of the
+parts commonly used in taxonomic work.]
+
+                ii. Base of the antennae dorsad of the middle of the eye;
+                    eyes of both sexes distinctly separated; dorsal
+                    surface of the squamula thoracalis with black hairs;
+                    two postsutural intraalar macrochaetae.
+
+                  j. Hypopygium of the male large, with a pair of
+                      slightly curved forceps whose ends are concealed
+                      in a longitudinal slit in the fifth ventral
+                      sclerite; third posterior inner dorso-central
+                      (acrostichal) macrochaetae absent; anterior
+                      intraalar rarely present; abdomen usually not
+                      pollinose; the second segment without median
+                      marginal macrochaetae; face yellow. _C.
+                      mortuorum_, _cadaverina_, and related species.
+                      Both hemispheres. _Cynomyia_ R. D.[O]
+
+[Illustration: 170. Sepsis violacea; puparium and adult. (See page 297.)
+After Howard.]
+
+                  jj. Three pairs of posterior inner dorsocentrals
+                      (acrostichals) present; second abdominal segment
+                      with a row of marginal macrochaetae; genae
+                      hairy, at least above.
+
+                    k. Hypopygium of the male with a projecting style.
+                        _S. stylifera_. Europe. _Steringomyia_ Pok.
+
+
+                    kk. Hypopygium of the male without style. _A.
+                        stelviana_ B. B. _Acrophaga_ B. B.
+
+              hh. Arista usually plumose nearly to the tip; posterior
+                  dorsocentrals and inner dorsocentrals (acrostichals)
+                  well developed; dorsal surface of the squamula
+                  thoracalis hairy; abdomen metallic and usually
+                  pollinose; genae hairy.
+
+                i. With one pair of ocellar macrochaetae. C. VOMITORIA,
+                    ERYTHROCEPHALA, VIRIDESCENS, and related species.
+                    Both hemispheres. CALLIPHORA R. D.
+
+                ii. With two strong pairs of ocellar macrochaetae. _E.
+                    latifrons._ Pacific slope of the U. S.
+                    _Eucalliphora_ Town.
+
+          ff. First section of R_{4+5} bristly near or quite half way to
+              the small crossvein; dorsal surface of the squamula
+              thoracalis is bare; the hypopygium of the male is
+              inconspicuous.
+
+            g. Genae bare; posterior inner and outer dorsocentrals
+                distinct and well developed. _L. caesar_, _sericata_,
+                _sylvarum_, and related species. Widely distributed in
+                both hemispheres (fig. 103). LUCILIA R. D.
+
+            gg. Genae with microchaetae, at least down to the
+                level of the base of the arista.
+
+              h. Mesonotum flattened behind the transverse suture.
+
+                i. Posterior dorsocentrals inconstant and unequally
+                    developed; one pair of posterior inner
+                    dorsocentrals. _P. terraenovae._ North America.
+                    _Protophormia_ Town.
+
+                ii. Posterior dorsocentrals well developed, the inner
+                    dorsocentrals (acrostichals) unequally developed.
+                    _P. azurea_, _chrysorrhoea_, etc. Europe and America.
+                    _Protocalliphora_ Hough
+
+              hh. Mesonotum not flattened behind the transverse suture;
+                  posterior inner and outer dorsocentrals inconstant and
+                  unequally developed. _P. regina._ Europe and America.
+                  _Phormia_ R. D.
+
+        ee. Species more or less rufous or yellow in color.
+
+          f. Anterior dorsocentrals wanting; first section of the
+              R_{4+5} at most only bristly at the base, bend near apex
+              of M_{1+2} rectangular, R_1 ends over the crossvein;
+              fronto-orbital macrochaeta absent; eyes of the male
+              contiguous. _C. semiviridis._ Mexico. _Chloroprocta_
+              V. d. W
+
+          ff. With another combination of characters.
+
+            g. Body robust, of large size, abdomen elongate, not round;
+                genae with several ranges of microchaetae;
+                vibrissal ridges strongly convergent; abdomen with well
+                developed macrochaetae; costal spine usually absent;
+                eyes of the male widely separated.
+
+[Illustration: 171. Stigmata of the larvae of Muscoidea. Third instar.
+(_a_) Cynomyia cadaverina; (_b_) Phormia regina; (_c_) Chrysomyia
+macellaria; (_d_) Musca domestica; (_e_) Sarcophaga sp.; (_f_) Oestris
+ovis; (_g_) Gastrophilus equi; (_h_) Sarcophaga sp.; (_i_) Pegomyia
+vicina; (_j_) Protocalliphora azurea; (_k_) Hypoderma lineata; (_l_)
+Muscina stabulans. Magnification for f, g, and k, x25; all others, x50.]
+
+              h. Peristome broad, pteropleural macrochaetae
+                  distinct; one or two sternopleurals; in the female a
+                  single orbital macrochaeta; last abdominal segment
+                  without discal macrochaetae; hypopygial processes
+                  of the male with a long stylet; second abdominal
+                  segment of the female sometimes much elongate. A.
+                  LUTEOLA (fig. 86). Africa. The sub-genus
+                  _Choeromyia_ Roub. is included here. AUCHMEROMYIA B.
+                  B.
+
+              hh. Peristome narrow; no pteropleurals, two
+                  sternopleurals; two orbitals in the female; second
+                  segment not elongate; the fourth with two well
+                  developed discal macrochaetae. B. DEPRESSA. Africa.
+                  BENGALIA R. D
+
+            gg. With another combination of characters.
+
+              h. Costal spine present; body in part black; antennae
+                  noticeably shorter than the epistome, inserted above
+                  the middle of the eye and separated from each other by
+                  a carina; abdominal segments with marginal
+                  macrochaetae; sternopleurals 2:1 or 1:1.
+                  _Paratricyclea_ Villen.
+
+              hh. Costal spine not distinct, or if present, insect
+                  otherwise different.
+
+                i. Genae with several ranges of microchaetae;
+                    vibrissal ridges strongly converging; peristome
+                    broad; arista moderately plumose; sternopleurals
+                    usually 1:1; color entirely testaceous. C.
+                    ANTHROPOPHAGA (fig. 87) and GRUNBERGI. Africa.
+                    CORDYLOBIA Grunb.
+
+                ii. Genae bare or with but one range of setae;
+                    vibrissal ridges less converging; peristome narrow;
+                    arista long plumose.
+
+                  j. Genae with a single row of microchaetae.
+
+                    k. Sternopleurals 2:1; color entirely testaceous.
+                        _Ochromyia_ Macq.[P]
+
+                    kk. Sternopleurals 1:1. _P. varia_ Hough. Africa.
+                        _Parochromyia_ Hough
+
+                  jj. Genae bare.
+
+                    k. Basal section of R_{4+5} bristly only at the
+                        immediate base, distally M_{1+2} with a broad
+                        curve; distal portion of the abdomen metallic;
+                        sternopleurals usually 1:1, rarely 2:1. _M.
+                        aeneiventris_ Wd. Tropic America.
+                        _Mesembrinella._ G. T.
+
+                    kk. R_{4+5} bristly at least nearly half way to the
+                        small crossvein; sternopleurals 1:1.
+
+                      l. Macrochaetae of the abdomen marginal;
+                          neither sex with orbitals; no carina between
+                          the base of the antennae; three pairs of
+                          presutural inner dorsocentrals. Eastern
+                          hemisphere. _T. ferruginea._ _Tricyclea V. d.
+                          W_. (= _Zonochroa_ B. B. according to
+                          Villeneuve 1914).
+
+                       ll. Abdomen without macrochaetae; wing
+                          usually with a marginal streak and gray
+                          markings. Brazil. Hemilucilia B. B.
+
+[Illustration: 172. Left hand stigmata of the larvae of muscoidea. Third
+instar. (_a_) Lucilia caesar; (_b_) Calliphora vomitoria; (_c_) Stomoxys
+calcitrans; (_d_) Orthellia cornicina; (_e_) Pyrellia cadavarina;
+(_f_) Haematobia irritans; (_g_) Mesembrina mystacea; (_h_) Mesembrina
+meridiana; (_i_) Myospila meditabunda; (_j_) Mydaea urbana; (_k_)
+Polietes albolineata; (_l_) Polietes lardaria; (_m_) Morellia hortorum;
+(_n_) Hydrotaea dentipes; (_o_) Hebecnema umbratica; (_p_) H. vespertina;
+(_q_) Limnophora septemnotata; (_r_) Muscina stabulans. (_a_ and _b_)
+after MacGregor; (_d_) after Banks; all others after Portchinsky.
+Magnification varies. The relative distance to the median line is
+indicated in each figure.]
+
+
+SIPHONAPTERA. Fleas
+
+Adapted from a table published by Oudemans.
+
+a. Elongated fleas, with jointed (articulated) head, with combs
+    (ctenidia) on head and thorax; with long, oval, free-jointed
+    flagellum of the antenna (fig. 92d). Suborder FRACTICIPATA
+
+  b. With ctenidia in front of the antennae and on the genae (cheeks);
+      maxillae with acute apices; labial palpi five-segmented,
+      symmetrical; eyes poorly developed or wanting. On rodents.
+      HYSTRICHOPSYLLIDAE
+
+    c. Abdominal segments without ctenidia.
+
+      d. Post-tibial spines in pairs and not in a very close set row;
+          head with ctenidia. _Ctenophthalmus_ Kol.
+
+      dd. Post-tibial spines mostly single and in a close set row.
+          _Ctenopsyllus_ and _Leptopsyllus_. The last genus has recently
+          been erected for _L. musculi_, a widely distributed species
+          occurring on rats and mice.
+
+    cc. Abdominal segments with one or more ctenidia; post-tibial spines
+        in numerous, short, close-set transverse rows on posterior
+        border with about four spines in each row. _H. americana._
+        _Hystrichopsylla_ Taschenb.
+
+  bb. With only two pairs of subfrontal ctenidia; labial palpi
+      five-segmented, symmetrical; eyes vestigial or wanting. On bats.
+      (= ISCHNOPSYLLIDAE). NYCTERIDIPSYLLIDAE
+
+    With more or less blunt maxilla; all tibiae with notch; a single
+        antepygidial bristle; metepimeron without ctenidium. _N.
+        crosbyi_ from Missouri was found on bats. Rothschild suggests
+        that this is probably the same as _N. insignis_. (=
+        _Ischnopsyllus_ = _Ceratopsyllus_), _Nycteridiphilus_
+
+aa. Head not jointed, i.e. the segments coalescent, traces of the
+    segmentation still being visible in the presence of the vertex
+    tubercle, the falx (sickle-shaped process), and a suture. Suborder
+    INTEGRICIPITA
+
+  b. Flagellum of the antennae long and oval.
+
+    c. Usually elongate fleas, with a free-segmented flagellum of the
+        antenna; thorax not shorter than the head, longer than the first
+        tergite.
+
+      d. Genae of the head and the pronotum with ctenidia. NEOPSYLLIDAE
+
+        e. Labial palpi four or five-segmented; symmetrical; hind coxae
+            with patch of spines inside; row of six spatulate spines on
+            each side in front of the antennae. _C. ornate_ found on a
+            California mole. _Corypsylla_
+
+        ee. Labial palpi two-segmented, transparent, membranous. On
+            hares. _Spilopsyllus_ Baker
+
+      dd. No ctenidium on the head.
+
+        e. Pronotum with ctenidium. DOLICHOPSYLLIDAE
+
+          f. Labial palpi five-segmented, symmetrical.
+
+            g. Antepygidial bristles one to three; eyes present.
+
+              h. Inner side of hind coxae distally with a comb of minute
+                  teeth; falx present. On rodents and carnivores.
+                  _Odontopsyllus_ Baker
+
+              hh. Inner side of hind coxae without comb or teeth. Many
+                  North American species on rodents. CERATOPHYLLUS
+                  Curtis
+
+            gg. Antepygidial bristles five on each side; eyes absent;
+                suture white. _D. stylosus_ on rodents. _Dolichopsyllus_
+                Baker
+
+          ff. Labial palpi four or five-segmented; asymmetrical
+              (membranous behind), apex acute. _Hoplopsyllus anomalus_
+              found on Spermophiles in Colorado. HOPLOPSYLLIDAE
+
+        ee. Pronotum without ctenidium. _Anomiopsyllus californicus_ and
+            _nudatus_ on rodents. ANOMIOPSYLLIDAE
+
+    cc. Very short fleas; flagellum of the antenna with pseudo-segments
+        coalescent; thorax much shorter than the head and than the first
+        tergite. HECTOPSYLLIDAE
+
+      Flagellum of the antenna with six coalescent pseudo-segments;
+          maxilla blunt. The chigger on man (fig. 93). D. PENETRANS. (=
+          RHYNCHOPRION = SARCOPSYLLA) DERMATOPHILUS Guerin
+
+  bb. Flagellum short, round, free portion of the first segment shaped
+      like a mandolin.
+
+    c. Thorax not shorter than the head, longer than the first tergite;
+        flagellum either with free segments or in part with the segments
+        coalescent.
+
+      d. Head and pronotum with ctenidium; labial palpi asymmetrical.
+          ARCHAEOPSYLLIDAE
+
+        With four subfrontal, four genal, and one angular ctenidia.
+            Widely distributed. CTENOCEPHALUS Kol.
+
+        e. Head rounded in front (fig. 92a). Dog flea. C. CANIS
+
+        ee. Head long and flat (fig. 92b). Cat flea. C. FELIS
+
+      dd. Neither head nor pronotum with ctenidium. Labial palpi
+          asymmetrical, membranous behind. PULICIDAE
+
+        e. Mesosternite narrow, without internal rod-like thickening
+            from the insertion of the coxae upwards. Human flea, etc.
+            PULEX L.
+
+        ee. Mesosternite broad with a rod-like internal thickening from
+            the insertion of the coxae upwards (fig. 89). X.
+            (LOEMOPSYLLA) CHEOPIS, plague or rat flea. XENOPSYLLA
+
+    cc. Thorax much shorter than the head and than the first tergite.
+        ECHIDNOPHAGIDAE. E. GALLINACEA, the hen flea also attacks man
+        (fig. 96). (= ARGOPSYLLA = XESTOPSYLLA) ECHIDNOPHAGA Olliff.
+
+
+FOOTNOTES:
+
+[E] Adapted from Banks, Nuttall, Warburton, Stiles, _et al._
+
+[F] Dr. C. W. Stiles considers the species which is responsible for
+spotted fever distinct from the _venustus_ of Banks, separating it as
+follows:
+
+Goblet cells about 75 in the male or 105 in the female. Texas. _D.
+venustus._
+
+Goblet cells 157 in the male, or 120 in the female; stigmal plate shaped
+as shown in the figure (figs. 150 a, b). Montana, etc. D. ANDERSONI.
+
+[G] Professor C. R. Crosby who has been working upon certain capsids
+states that he and his assistant have been bitten by LYGUS PRATENSIS,
+the tarnished plant bug, by CHLAMYDATUS ASSOCIATUS and by ORTHOTYLUS
+FLAVOSPARSUS, though without serious results.
+
+[H] Species marked with an * are known to transmit malaria. Species
+found only in tropical North America and not known to carry malaria have
+been omitted from this table, but all found in the United States are
+included.
+
+[I] This table to the North American genera of the Tabanidae is adapted
+from one given by Miss Ricardo.
+
+[J] The classification of the Muscoidea as set forth by Schiner and
+other earlier writers has long been followed, although it is not
+satisfactory, being admittedly more or less artificial. Within the last
+two or three decades several schemes have been advanced, that of Brauer
+and Bergenstamm and of Girschner, with the modifications of Schnabl and
+Dziedzicki having obtained most favor in Europe. Townsend, in 1908,
+proposed a system which differs from Girschner's in some respects, but
+unfortunately it has not yet been published in sufficient detail to
+permit us to adopt it. From considerations of expediency we use here the
+arrangement given in Aldrich's Catalogue of North American Diptera,
+though we have drawn very freely upon Girschner's most excellent paper
+for taxonomic characters to separate the various groups.
+
+It may sometimes be found that a species does not agree in all the
+characters with the synopsis; in this case it must be placed in the
+group with which it has the most characters in common.
+
+[K] There are several genera of flies of the family _Cordyluridae_; (i.e.
+_Acalyptratae_) which might be placed with the _Anthomyiidae_ (i.e.
+_Calyptratae_), owing to the relatively large size of their squamae. As
+there is no single character which will satisfactorily separate all
+doubtful genera of these two groups we must arbitrarily fix the limits.
+In general those forms on the border line having a costal spine, or
+lower squama larger than the upper, or the lower surface of the
+scutellum more or less pubescent, or the eyes of the male nearly or
+quite contiguous, or the eyes hairy, or the frontal setae decussate in
+the female; or any combination of these characters may at once be placed
+with the _Anthomyiidae_. Those forms which lack these characteristics and
+have at least six abdominal segments (the first and second segments
+usually being more or less coalescent) are placed with the Acalyptrates.
+There are other acalyptrates with squamae of moderate size which have
+either no vibrissae, or have the subcosta either wholly lacking or
+coalescent in large part with R_1 or have spotted wings; they, therefore
+will not be confused with the calyptrates.
+
+[L] _Pachymyia_ Macq. is closely related to _Stomoxys_. It differs in
+having the arista rayed both above and below. _P. vexans_, Brazil.
+
+[M] The genus _Eudasyphora_ Town. has recently been erected to contain
+_D. lasiophthalma_.
+
+[N] _Nitellia_, usually included in this genus has the apical cell
+petiolate. _Apollenia_ Bezzi, has recently been separated from
+_Pollenia_ to contain the species _P. nudiuscula_. Both genera belong to
+the Eastern hemisphere.
+
+[O] The following three genera are not sufficiently well defined to
+place in this synopsis. In color and structural characters they are
+closely related to _Cynomyia_ from which they may be distinguished as
+follows. _Catapicephala_ Macq., represented by the species _C.
+splendens_ from Java, has the setae on the facial ridges rising to the
+base of the antennae and has median marginal macrochaetae on the
+abdominal segments two to four: _Blepharicnema_ Macq., represented by
+_B. splendens_ from Venezuela has bare genae, oral setae not
+ascending; tibiae villose; claws short in both sexes; _Sarconesia_
+Bigot with the species _S. chlorogaster_ from Chile, setose genae;
+legs slender, not villose; claws of the male elongate.
+
+[P] _Plinthomyia_ Rdi. and _Hemigymnochaeta_ Corti are related to
+_Ochromyia_, though too briefly described to place in the key.
+
+
+
+
+APPENDIX
+
+HYDROCYANIC ACID GAS AGAINST HOUSEHOLD INSECTS
+
+
+The following directions for fumigating with hydrocyanic acid
+gas are taken from Professor Herrick's circular published by the
+Cornell Reading Course:
+
+Hydrocyanic acid gas has been used successfully against household
+insects and will probably be used more and more in the future.
+It is particularly effective against bed-bugs, and cockroaches, but
+because _it is such a deadly poison it must be used very carefully_.
+
+The gas is generated from the salt potassium cyanid, by treating
+it with sulfuric acid diluted with water. Potassium cyanid is a
+most poisonous substance and the gas emanating from it is also
+deadly to most, if not all, forms of animal life. The greatest care
+must always be exercised in fumigating houses or rooms in buildings
+that are occupied. Before fumigation a house should be vacated.
+It is not necessary to move furniture or belongings except brass or
+nickel objects, which may be somewhat tarnished, and butter, milk,
+and other larder supplies that are likely to absorb gas. If the nickel
+and brass fixtures or objects are carefully covered with blankets
+they will usually be sufficiently protected.
+
+There may be danger in fumigating one house in a solid row of
+houses if there is a crack in the walls through which the gas may find
+its way. It also follows that the fumigation of one room in a house
+may endanger the occupants of an adjoining room if the walls between
+the two rooms are not perfectly tight. It is necessary to keep
+all these points in mind and to do the work deliberately and thoughtfully.
+The writer has fumigated a large college dormitory of 253
+rooms, once a year for several years, without the slightest accident
+of any kind. In order to fumigate this building about 340 pounds
+of cyanid and the same amount of sulfuric acid were used each time.
+In addition to this, the writer has fumigated single rooms and smaller
+houses with the gas. In one instance the generating jars were too
+small; the liquid boiled over and injured the floors and the rugs.
+Such an accident should be avoided by the use of large jars and by
+placing old rugs or a quantity of newspapers beneath the jars.
+
+
+THE PROPORTIONS OF INGREDIENTS
+
+Experiments and experience have shown that the potassium
+cyanid should be ninety-eight per cent pure in order to give satisfactory
+results. The purchaser should insist on the cyanid being of
+at least that purity, and it should be procurable at not more than
+forty cents per pound. The crude form of sulfuric acid may be used.
+It is a thickish, brown liquid and should not cost more than four or
+five cents a pound. If a room is made tight, one ounce of cyanid for
+every one hundred cubic feet of space has been shown to be sufficient.
+It is combined with the acid and water in the following proportions:
+
+  Potassium cyanid                       1 ounce
+  Commercial sulfuric acid               1 fluid ounce
+  Water                                  3 fluid ounces
+
+
+A SINGLE ROOM AS AN EXAMPLE
+
+Suppose a room to be 12 by 15 by 8 feet. It will contain 12 x 15 x 8, or
+1440 cubic feet. For convenience the writer always works on the basis of
+complete hundreds; in this case he would work on the basis of 1500 cubic
+feet, and thus be sure to have enough. The foregoing room, then, would
+require 15 ounces of cyanid, 15 ounces of sulfuric acid, and 45 ounces
+of water. The room should be made as tight as possible by stopping all
+the larger openings, such as fireplaces and chimney flues, with old rags
+or blankets. Cracks about windows or in other places should be sealed
+with narrow strips of newspaper well soaked in water. Strips of
+newspaper two or three inches wide that have been thoroughly soaked in
+water may be applied quickly and effectively over the cracks around the
+window sash and elsewhere. Such strips will stick closely for several
+hours and may be easily removed at the conclusion of the work.
+
+While the room is being made tight, the ingredients should be measured
+according to the formula already given. The water should be measured and
+_poured first_ into a stone jar for holding at least two gallons. The
+jar should be placed in the middle of the room, with an old rug or
+several newspapers under it in order to protect the floor.
+
+The required amount of sulfuric acid should then be poured rather slowly
+into the water. _This process must never be reversed; that is, the acid
+must never be poured into the jar first._ The cyanid should be weighed
+and put into a paper bag beside the jar. All hats, coats, or other
+articles that will be needed before the work is over should be removed
+from the room. When everything is ready the operator should drop the bag
+of cyanid gently into the jar, holding his breath, and should walk
+quickly out of the room. The steam-like gas does not rise immediately
+under these conditions, and ample time is given for the operator to walk
+out and shut the door. If preferred, however, the paper bag may be
+suspended by a string passing through a screw eye in the ceiling and
+then through the keyhole of the door. In this case the bag may be
+lowered from the outside after the operator has left the room and closed
+the door.
+
+The writer has most often started the fumigation toward evening and left
+it going all night, opening the doors in the morning. The work can be
+done, however, at any time during the day and should extend over a
+period of five or six hours at least. It is said that better results
+will be obtained in a temperature of 70^o F., or above, than at a lower
+degree.
+
+At the close of the operation the windows and doors may be opened from
+the outside. In the course of two or three hours the gas should be
+dissipated enough to allow a person to enter the room without danger.
+The odor of the gas is like that of peach kernels and is easily
+recognized. The room should not be occupied until the odor has
+disappeared.
+
+
+FUMIGATING A LARGE HOUSE
+
+The fumigation of a large house is merely a repetition, in each room and
+hall, of the operations already described for a single room. All the
+rooms should be made tight, and the proper quantities of water and
+sulfuric acid should be measured and poured into jars placed in each
+room with the cyanid in bags besides the jars. When all is ready, the
+operator should _go to the top floor and work downward_ because the gas
+is lighter than air and tends to rise.
+
+
+PRECAUTIONS
+
+The cyanid should be broken up into small pieces not larger than small
+eggs. This can best be done on a cement or brick pavement. It would be
+advantageous to wear gloves in order to protect the hands, although the
+writer has broken many pounds of cyanid without any protection on the
+hands. Wash the hands thoroughly at frequent intervals in order to
+remove the cyanid.
+
+The operations of the work must be carried out according to directions.
+
+The work should be done by a calm, thoughtful and careful person--best
+by one who has had some experience.
+
+Conspicuous notices of what has been done should be placed on the doors,
+and the doors should be locked so that no one can stray into the rooms.
+
+The gas is lighter than air, therefore one should always begin in the
+rooms at the top of the house and work down.
+
+After fumigation is over the contents of the jar should be emptied into
+the sewer or some other safe place. The jars should be washed thoroughly
+before they are used again.
+
+_It must be remembered that cyanid is a deadly poison_; but it is very
+efficient against household insects, if carefully used, and is not
+particularly dangerous when properly handled.
+
+
+LESIONS PRODUCED BY THE BITE OF THE BLACK-FLY
+
+While this text was in press there came to hand an important paper
+presenting a phase of the subject of black fly injury so different from
+others heretofore given that we deem it expedient to reproduce here the
+author's summary. The paper was published in _The Journal of Cutaneous
+Diseases_, for November and December, 1914, under the title of "A
+Clinical, Pathological and Experimental Study of the Lesions Produced by
+the Bite of the Black Fly (_Simulium venustum_)," by Dr. John Hinchman
+Stokes, of the University of Michigan.
+
+
+RESUME AND DISCUSSION OF EXPERIMENTAL FINDINGS
+
+The principal positive result of the work has been the experimental
+reproduction of the lesion produced by the black-fly in characteristic
+histological detail by the use of preserved flies. The experimental
+lesions not only reproduced the pathological pictures, but followed a
+clinical course, which in local symptomatology especially, tallied
+closely with that of the bite. This the writer interprets as
+satisfactory evidence that the lesion is not produced by any living
+infective agent. The experiments performed do not identify the nature of
+the toxic agent. Tentatively they seem to bring out, however, the
+following characteristics.
+
+1. The product of alcoholic extraction of flies do not contain the toxic
+agent.
+
+2. The toxic agent is not inactivated by alcohol.
+
+3. The toxic agent is not destroyed by drying fixed flies.
+
+4. The toxic agent is not affected by glycerin, but is, if anything,
+more active in pastes made from the ground fly and glycerin, than in the
+ground flies as such.
+
+5. The toxic agent is rendered inactive or destroyed by hydrochloric
+acid in a concentration of 0.25%.
+
+6. The toxic agent is most abundant in the region of the anatomical
+structures connected with the biting and salivary apparatus (head and
+thorax).
+
+7. The toxic agent is not affected by a 0.5% solution of sodium
+bicarbonate.
+
+8. The toxic agent is not affected by exposure to dry heat at 100^o C.
+for two hours.
+
+9. The toxic agent is destroyed or rendered inactive in alkaline
+solution by a typical hydrolytic ferment, pancreatin.
+
+10. Incomplete experimental evidence suggests that the activity of the
+toxic agent may be heightened by a possible lytic action of the blood
+serum of a sensitive individual, and that the sensitive serum itself may
+contain the toxic agent in solution.
+
+These results, as far as they go (omitting No. 10), accord with Langer's
+except on the point of alcoholic solubility and the effect of acids. The
+actual nature of the toxic agent in the black-fly is left a matter of
+speculation.
+
+The following working theories have suggested themselves to the writer.
+First, the toxin may be, as Langer believes in the case of the bee, an
+alkaloidal base, toxic as such, and neutralized after injection by
+antibodies produced for the occasion by the body. In such a case the
+view that a partial local fixation of the toxin occurs, which prevents
+its immediate diffusion, is acceptable. Through chemotactic action,
+special cells capable of breaking up the toxin into harmless elements
+are attracted to the scene. Their function may be, on the other hand, to
+neutralize directly, not by lysis. This would explain the role of the
+eosinophiles in the black-fly lesion. If their activities be essential
+to the destruction or neutralization of the toxin, one would expect them
+to be most numerous where there was least reaction. This would be at the
+site of a bite in an immune individual. A point of special interest for
+further investigation, would be the study of such a lesion.
+
+Second, it is conceivable that the injected saliva of the fly does not
+contain an agent toxic as such. It is possible, that like many foreign
+proteins, it only becomes toxic when broken down. The completeness and
+rapidity of the breaking down depends on the number of eosinophiles
+present. In such a case immunity should again be marked by intense
+eosinophilia.
+
+[Illustration: 173. Fifth day mature lesion. Lower power drawing showing
+papillary oedema and infiltrate in the region of the puncture. After Dr.
+J. H. Stokes]
+
+Third, lytic agents in the blood serum may play the chief role in the
+liberation of the toxic agent from its non-toxic combination. An immune
+individual would then be one whose immunity was not the positive one of
+antibody formation, but the negative immunity of failure to metabolize.
+An immune lesion in such a case might be conceived as presenting no
+eosinophilia, since no toxin is liberated. If the liberation of the
+toxin is dependent upon lytic agents present in the serum rather than in
+any cellular elements, a rational explanation would be available for the
+apparent results (subject to confirmation) of the experiment with
+sensitive and immune sera. In this experiment it will be recalled that
+the sensitive serum seemed to bring out the toxicity of the ground
+flies, and the serum itself seemed even to contain some of the dissolved
+or liberated toxin. The slowness with which a lesion develops in the
+case of the black-fly bite supports the view of the initial lack of
+toxicity of the injected material. The entire absence of early
+subjective symptoms, such as pain, burning, etc., is further evidence
+for this view. It would appear as if no reaction occurred until lysis of
+an originally non-toxic substance had begun. Regarding the toxin itself
+as the chemotactic agent which attracts eosinophiles, its liberation in
+the lytic process and diffusion through the blood stream attracts the
+cells in question to the point at which it is being liberated. Arriving
+upon the scene, these cells assist in its neutralization.
+
+The last view presented is the one to which the author inclines as the
+one which most adequately explains the phenomena.
+
+A fourth view is that the initial injection of a foreign protein by the
+fly (i.e., with the first bite) sensitizes the body to that protein. Its
+subsequent injection at any point in the skin gives rise to a local
+expression of systematic sensitization. Such local sensitization
+reactions have been described by Arthus and Breton, by Hamburger and
+Pollack and by Cowie. The description of such a lesion given by the
+first named authors, in the rabbit, however, does not suggest,
+histopathologically at least, a strong resemblance to that of the
+black-fly. Such an explanation of many insect urticariae deserves further
+investigation, however, and may align them under cutaneous expressions
+of anaphylaxis to a foreign protein injected by the insect. Depending on
+the chemical nature of the protein injected, a specific chemotactic
+reaction like eosinophilia may or may not occur. Viewed in this light
+the development of immunity to insect bites assumes a place in the
+larger problem of anaphylaxis.
+
+[Illustration: 174. Experimental lesion produced from alcohol-fixed
+flies, dried and ground into a paste with glycerin. After Dr. J. H.
+Stokes]
+
+
+SUMMARY
+
+In order to bring the results of the foregoing studies together, the
+author appends the following resume of the clinical data presented in
+the first paper.
+
+The black-fly, _Simulium venustum_, inflicts a painless bite, with
+ecchymosis and haemorrhage at the site of puncture. A papulo-vesicular
+lesion upon an urticarial base slowly develops, the full course of the
+lesion occupying several days to several weeks. Marked differences in
+individual reaction occur, but the typical course involves four stages.
+These are, in chronological order, the papular stage, the vesicular or
+pseudovesicular, the mature vesico-papular or weeping papular stage and
+the stage of involution terminating in a scar. The papule develops in
+from 3 to 24 hours. The early pseudovesicle develops in 24 to 48 hours.
+The mature vesico-papular lesion develops by the third to fifth day and
+may last from a few days to three weeks. Involution is marked by
+cessation of oozing, subsidence of the papule and scar-like changes at
+the site of the lesion. The symptoms accompanying this cycle consist of
+severe localized or diffused pruritus, with some heat and burning in the
+earlier stages if the oedema is marked. The pruritus appears with the
+pseudovesicular stage and exhibits extraordinary persistence and a
+marked tendency to periodic spontaneous exacerbation. The flies tend to
+group their bites and confluence of the developing lesions in such cases
+may result in extensive oedema with the formation of oozing and
+crusted plaques. A special tendency on the part of the flies to attack
+the skin about the cheeks, eyes and the neck along the hair line and
+behind the ears, is noted. In these sites inflammation and oedema may
+be extreme.
+
+A distinctive satellite adenopathy of the cervical glands develops in
+the majority of susceptible persons within 48 hours after being bitten
+in the typical sites. This adenopathy is marked, discrete and painful,
+the glands often exquisitely tender on pressure. It subsides without
+suppuration.
+
+Immunity may be developed to all except the earliest manifestations, by
+repeated exposures. Such an immunity in natives of an infested locality
+is usually highly developed. There are also apparently seasonal
+variations in the virulence of the fly and variations in the reaction of
+the same individual to different bites.
+
+Constitutional effects were not observed but have been reported.
+
+
+
+
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+   und der Segmentierung des Hinterleibes. Wochenschr. fur Entom. i, p.
+   12-16, 30-32, 61-64, 105-112.
+
+GOELDI, E. A. 1913. Die sanitarisch-pathologische Bedeutung der Insekten
+   und verwandten Gliedertiere 8^o. Berlin. Friedlander & Sohn. (155
+   p.).
+
+GOLDBERGER, J. 1910. The straw itch. (Dermatitis Schambergi). Public
+   Health Repts., Washington, xxv, p. 779-784.
+
+GOLDBERGER, J. and ANDERSON, J. F. 1912, The transmission of typhus
+   fever, with especial reference to transmission by the head-louse
+   (_Pediculus capitis_). Public Health Repts., Washington, xxvii, p.
+   297-307.
+
+GOLDBERGER, J., WARING, C. H., and WILLETS, D. G. 1914. The treatment
+   and prevention of pellagra. Public Health Repts., Washington, xxix,
+   p. 2821-2826.
+
+GRAHAM-SMITH, G. S. 1913. Flies in relation to disease: non-bloodsucking
+   flies. 8vo. Cambridge Univ. Press. (xiv + 292 p.)
+
+GRASSI, B. 1907. Ricerche sui Flebotomi. Memorie della Societa ital.
+   della Scienze, ser. 3 a, xiv, P. 353-394, pls. i-iv.
+
+GRASSI, B. and NOE, G. 1900. Propagation of the filariae of the blood
+   exclusively by means of the puncture of peculiar mosquitoes. British
+   Med. Journ. ii, p. 1306-1307.
+
+GRIFFITH, A. 1908. Life history of house-flies. Public Health, xxi, p.
+   122-127.
+
+GRUNBERG, K. 1907. Die blutsaugenden Dipteren. 8vo. Jena, Fischer. (vi +
+   188 p.).
+
+HADWEN, S. 1913. On "tick paralysis" in sheep and man following bites of
+   _Dermacentor venustus_. Parasitology, vi, p. 283-297.
+
+HADWEN, S. and NUTTALL, G. H. F. 1913. Experimental "tick paralysis" in
+   the dog. Parasitology, vi, p. 298-301.
+
+HALL, M. C. and MUIR, J. F. 1913. A critical study of a case of myasis
+   due to _Eristalis_. Arch. Int. Med., Chicago, xi, p. 193-203.
+
+HAMILTON, J. 1893. Medico-entomology. Entom. News iv, p. 217-219.
+
+HART, C. A. 1895. On the entomology of the Illinois river and adjacent
+   waters. Bul. Ill. State Lab. Nat. Hist., iv, p. 149-273.
+
+HEADLEE, T. J. 1914. Anti-mosquito work in New Jersey. Jour. Econ. Ent.
+   vii, p. 260-268.
+
+HECKER, J. F. C. 1885. The dancing mania of the Middle Ages. Transl. by
+   B. G. Bahington. 8vo. New York, Humboldt Library. (53p.).
+
+HENDEL. 1901. Beitrag zur Kenntniss der Calliphorinen. Wiener Ent.
+   Zeitung. xx, p. 28-33.
+
+HERMS, W. B. 1911. The housefly in its relation to public health. Cal.
+   Agric. Exp. Sta. Bul. 215, p. 511-548.
+
+---- 1913. Malaria: cause and control. 8^o. New York, Macmillan Co. (xi
+   + 163 p.).
+
+HERRICK, G. W. 1903. The relation of malaria to agriculture and other
+   industries of the South. Pop. Sci. Mo. lxii, p. 521-525.
+
+---- 1913. Household insects and methods of control. Cornell Reading
+   Course, (N. Y. State College of Agric.), iii, 47 p.
+
+---- 1914. Insects injurious to the household and annoying to man. 8vo.
+   New York, Macmillan Co. (xvii + 470).
+
+HEWITT, C. G. 1910. The house-fly. A study of its structure,
+   development, bionomics, and economy. 8vo. Manchester Univ. Press.
+   (xiv + 196 p.).
+
+---- 1912. _Fannia_ (_Homalomyia_) _canicularis_ Linn. and _F. scalaris_
+   Fab. Parasitology, v. p. 161-174.
+
+HEYMONS, R. 1901. Biologische Beobachtungen an asiatischen Solifugen,
+   nebst Beitrage zur Systematik derselben. Abl. Ak. Berlin, 1901, Anh.
+   i, 1-65 p.
+
+HIGGINS, F. W. 1891. Dipterous larvae vomited by a child. Insect Life,
+   Washington. iii, p. 396-397.
+
+HINDLE, E. 1911 a. The relapsing fever of tropical Africa. A Review.
+   Parasitology, iv, p. 183-203.
+
+---- 1911 b. On the life cycle of _Spirochaeta gallinarum_. ibid., iv.
+   p. 463-477.
+
+HINDLE, E. and MERRIMAN, G. 1914. The range of flight of _Musca
+   domestica_. Journ. of Hygiene, xiv. p. 23-45.
+
+HINE, J. S. 1903. Tabanidae of Ohio. Papers Ohio Acad. Sci. No. 5, 55 p.
+
+---- 1906. Habits and life-histories of some flies of the family
+   Tabanidae. U. S. Dept. Agric. Bur. Ent. tech. bul. 12, p. 19-38.
+
+---- 1907. Second report upon the horse-flies of Louisiana. La. Stat.
+   Exp. Bul. 93, p. 1-59.
+
+HODGE, C. F. 1910. A practical point in the study of the typhoid, or
+   filth-fly. Nature Study Review, vi, p. 195-199.
+
+---- 1913. The distance house-flies, blue-bottles, and stable flies may
+   travel over water. Science, n. s. xxxviii, p. 513.
+
+HONEIJ, J. A. and PARKER, R. R. 1914. Leprosy: flies in relation to the
+   transmission of the disease. Journ. Med. Research, Boston, xxx, p.
+   127-130.
+
+HOOKER, W. A. 1908 a. Life history, habits, and methods of study of the
+   Ixodoidea. Jour. Econ. Ent. i, p. 34-51.
+
+---- 1908 b. A review of the present knowledge of the role of ticks in
+   the transmission of disease. ibid., i, p. 65-76.
+
+HOPE, F. W. 1837. On insects and their larvae occasionally found in the
+   human body. Trans. Ent. Soc., London, ii, p. 256-271.
+
+HOUGH, G. DE N. 1899 a. Synopsis of the Calliphorinae of the United
+   States. Zoological Bulletin, ii, p. 283-290.
+
+---- 1899 b. Some Muscinae of North America, Biological Bulletin i, p.
+   19-33.
+
+---- 1899 c. Some North American Genera of Calliphorinae. Entom. News,
+   x, p. 62-66.
+
+HOVARTH, G. 1912. Revision of the American Cimicidae. Ann. Mus. Nat.
+   Hungarici, x, p. 257-262.
+
+HOWARD, C. W. 1908. A list of the ticks of South Africa, with
+   descriptions and keys to all the forms known. Ann. Transvaal Mus. 1,
+   p. 73-170.
+
+HOWARD, C. W. and CLARK, P. F. 1912. Experiments on insect transmission
+   of the virus of poliomyelitis. Journ. Exper. Med. xvi, p. 805-859.
+
+HOWARD, L. O. 1899. Spider bites and kissing bugs. Pop. Sci. Mo. lv, p.
+   31-42.
+
+---- 1900. A contribution to the study of the insect fauna of human
+   excrement. Proc. Wash. Acad. Sci. ii, p. 541-604.
+
+---- 1901. Mosquitoes, how they live, how they carry disease, how they
+   are classified, how they may be destroyed. 8vo. New York, Doubleday,
+   Page & Co. (xv + 241 p.)
+
+---- 1909. Economic loss to the people of the United States, through
+   insects that carry disease. U. S. Dept. Agric. Bur. of Ent. Bul. 78,
+   p. 1-40.
+
+HOWARD, L. O., DYAR, H. G. and KNAB, F. 1913-. The mosquitoes of North
+   and Central America and the West Indies. Vol. I. A general
+   consideration of mosquitoes, their habits, and their relations to the
+   human species. 4^o. Carnegie Institution of Washington (vii + 520
+   p.).
+
+HOWARD, L. O. and MARLATT, C. L. 1902. The principal household insects
+   of the United States. U. S. Dept. Agric., Bur. Ent. Bul. 4.
+
+HUEBNER, W. 1907. Ueber das Pfeilgift der Kalahari. Arch. exper. Path.
+   und Pharm., lvii, p. 358-366.
+
+HUNTER, S. J. 1913. Pellagra and the sand-fly. Jour. econ. Ent. vi, p.
+   96-99.
+
+HUNTER, W. D. 1913. American interest in medical entomology. Jour. econ.
+   Ent. vi, p. 27-39.
+
+HUNTER, W. D. and BISHOPP, F. C. 1910. Some of the more important ticks
+   of the United States. U. S. Dept. Agric. Yearbook 1910, p. 219-230,
+   pls. xv-xvi.
+
+---- 1911. The Rocky Mountain spotted fever tick. With special reference
+   to the problem of its control in the Bitter Root Valley in Montana.
+   U. S. Dept. Agric., Bur. Ent. Bul. 105, p. 1-47.
+
+HUTCHISON, R. H. 1914. The migratory habit of housefly larvae as
+   indicating a favorable remedial measure. An account of progress. U.
+   S. Dept. Agric., Bul. 14, p. 1-11.
+
+JENNINGS, A. H. 1914. Summary of two years' study of insects in relation
+   to pellagra. Journ. of Parasitology, i, p. 10-21.
+
+JENNINGS, A. H. and KING, W. V. 1913. One of the possible factors in the
+   causation of pellagra. Journ. Amer. Med. Assoc., lx, p. 271-274.
+
+JEPSON, F. P. 1909. Notes on colouring flies for purposes of
+   identification. Rep't to the Local Gov't Board on Publ. Health, n. s.
+   16, p. 4-9.
+
+JOHANNSEN, O. A. 1903. Aquatic Nematocerous Diptera. N. Y. State Mus.
+   Bul., 68, p. 328-448, pls. 32-50.
+
+---- 1905. Aquatic Nematocerous Diptera II. (Chironomidae). ibid. 86, p.
+   76-330, pls. 16-37.
+
+---- 1908. North America Chironomidae. ibid., 124, p. 264-285.
+
+---- 1911. The typhoid fly and its allies. Maine Agric. Exp. Sta. Bul.,
+   401, p. 1-7.
+
+---- 1911. Simulium and pellagra. Insect Notes for 1910. Maine Agr.
+   Exper. Station. Bul. 187, p. 4.
+
+KELLOGG, V. L. 1915. Spider poison. Jour. of Parasitology, i, p. 107+
+
+KELLY, H. A. 1907. Walter Reed and yellow fever. 8vo. New York, McClure,
+   Phillips & Co. (xix + 310 p.).
+
+KEPHART, CORNELIA F. 1914. The poison glands of the larva of the
+   browntail moth (Euproctis chrysorrhoea Linn.). Journ. Parasit., i,
+   p.
+
+KIEFFER, J. J. 1906. Chironomidae. Genera Insectorum. Fasc. 42, p. 1-78.
+
+---- 1913. Nouv. etude sur les Chironomides de l'Indien Museum de
+   Calcutta. Records of the Indian Mus., ix, p. 119-197.
+
+KING, A. F. A. 1883. Insects and disease--mosquitoes and malaria. Pop.
+   Sci. Mo. xxiii, p. 644-658.
+
+KIRKLAND, A. H. 1907. Second annual report of the Superintendent for
+   suppressing the gypsy and browntail moths. 8vo. Boston. 170 p.
+
+KLEINE, E. 1909. Postive Infektionsversuche mit _Trypanosoma brucei_
+   durch _Glossina palpalis._ Deutsche med. Wochenschr., xxxv, p.
+   469-470.
+
+   Weitere wissenschaftliche Beobachtungen uber die Entwicklung von
+      Trypanosomen in Glossinen. ibid. p. 924-925.
+
+   Weitere Untersuchungen uber die Aetiologie der Schlafkrankheit. ibid.,
+      p. 1257-1260.
+
+   Weitere Beobachtungen uber Tsetsefliegen und Trypanosomen. ibid., p.
+      1956-1958.
+
+KLING, C. and LEVADITI, C. 1913. Etudes sur la poliomyelite aigue
+   epidemique. Ann. Inst. Pasteur, xxvii, p. 718-749, 739-855.
+
+KNAB, F. 1912. Unconsidered factors in disease-transmission by
+   blood-sucking insects. Journ. Econ. Ent., v, p. 196-200.
+
+---- 1913 a. The species of Anopheles that transmit human malaria. Amer.
+   Journ. Trop. Dis. and Preventive Med., i, p. 24-43.
+
+---- 1913 b. Anopheles and malaria. ibid., i, p. 217.
+
+---- 1913 c. The life history of _Dermatobia hominis_. ibid., i, p.
+   464-468.
+
+KNAB, F. See Howard, Dyar, and Knab.
+
+KOBERT, R. 1893. Lehrbuch der Intoxikationen. 4^o. Stuttgart, Enke. (xxii
+   + 816 p.). 2d ed. in 2 vols., 1906.
+
+---- 1901. Beitrage zur Kenntniss der Giftspinnen. 8^o. Stuttgart, Enke.
+   (viii + 191 p.).
+
+KOLBE, H. J. 1894. Der Pfeilgiftkafer der Kalahari-Wuste, _Diamphidia
+   simplex_. Stett. Ent. Zeitg., iv, p. 79-86.
+
+KRAUSE, M. 1907. Untersuchungen uber Pfeilgifte aus unseren
+   africanischen Kolonien. Verhand. deutsche Kolonien kong. 1905. p.
+   264-288.
+
+LALLIER, P. 1897. Etude sur la myase du tube digestif chez l'homme.
+   Thesis, Paris, 8^o. 120 p.
+
+LANGER, J. 1897. Ueber das Gift unserer Honigbiene. Archiv. exper. Path.
+   und Pharm., xxxviii, p. 381-396.
+
+LAVINDER, C. H. 1911. Pellagra: a precis. U. S. Publ. Health Service
+   Bul. 48, 37 p.
+
+LEIDY, J. 1847. History and anatomy of the hemipterous genus
+   _Belostoma_. Journ. Acad. Philad. (2), i, p. 57-67.
+
+LEIPER, R. T. 1907. The etiology and prophylaxis of dracontiasis.
+   British Med. Journ. 1907, p. 129-132.
+
+LEISHMAN, W. B. 1910 a. Observations on the mechanism of infection in
+   tick fever and on the hereditary transmission of _Spirochaeta duttoni_
+   in the tick. Trans. Soc. Trop. Med. Hyg., iii, p. 77-95. Abstr. in
+   Bul. Inst. Pasteur, viii, p. 312-313.
+
+---- 1910 b. On the hereditary transmission and mechanism of infection
+   in tick fever and on the hereditary transmission of _Spirochaeta
+   duttoni_ in the tick. Lancet., clxxvii, p. 11.
+
+LINNELL, R. McC. 1914. Notes on a case of death following the sting of a
+   scorpion. Lancet, 1914, p. 1608-1609.
+
+LIVINGSTONE, D. 1857. Missionary travels and researches in South Africa.
+
+LUCAS, H. 1843. (note) _Latrodectus malmignatus_ Bul. Soc. Ent., France,
+   1843, p. viii.
+
+LUDLOW, C. S. 1914. Disease bearing mosquitoes of North and Central
+   America, the West Indies and the Philippine Islands. War Dept.,
+   Office of Surgeon General. Bul. No. 4, 1-96.
+
+LUGGER, 1896. Insects injurious in 1896. Agr. Exp. Sta. Bul. 48. p. 33
+   to 270.
+
+MacCALLUM, W. C. 1898. On the haematozoan infection of birds. Journ. Exp.
+   Med. iii, p. 117.
+
+MacGREGOR, M. E. 1914. The posterior stigmata of dipterous larvae as a
+   diagnostic character. Parasitology, vii, p. 176-188.
+
+MacLOSKIE, G. 1888. The poison apparatus of the mosquito. Amer.
+   Naturalist, xxii, p. 884-888.
+
+MALLOCH, J. P. 1913. American black-flies or Buffalo gnats. U. S. Dept.
+   Agric. Bur. Ent. Tech. Bul. 26, p. 1-72.
+
+---- 1914. Notes on North American Diptera. Bul. Illinois State Lab.
+   Nat. Hist., x, p. 213-243.
+
+MANSON, P. 1911. Tropical diseases: a manual of the diseases of warm
+   climates. 8^o. London, Cassell & Co. (xx + 876 p.). 4 ed. (1907).
+   Reprinted.
+
+MARCHOUX, E. and COUVY, L. 1913. Argas et spirochaetes (1 memoire). Les
+   granules de Leishman. Ann. Inst. Pasteur, xxvii, p. 450-480. 2
+   memoire. Le virus chez l'acarien. ibid. p. 620-643.
+
+MARCHOUX, E. and SELIMBENI, A. 1903. La spirillose des poules. Ann.
+   Inst. Pasteur, xvii, p. 569-580.
+
+MARCHOUX, E. and SIMOND, P. L. 1905. Etudes sur la fievre jaune. Ann.
+   Inst. Pasteur, xx, pp. 16-40, 104-148, 161-205.
+
+MARLATT, C. L. 1902. (See Howard, L. O. and Marlatt, C. L.)
+
+---- 1907. The bed-bug (_Cimex lectularius_ L.) U. S. Dept. Agric., Bur.
+   Ent., Circ. No. 47, revised ed., 8 pp.
+
+MARTIN, G. LEBOEUF, and ROUBAUD. 1909. Rapport de la mission d'etudes de
+   la maladie du sommeil au Congo francais. 4^o. Paris, Masson & Cie.
+   (vi + 722 p., 8 pls. and map.).
+
+MAVER, MARIA B. 1911. Transmission of spotted fever by other than
+   Montana and Idaho ticks. Journ. Infec. Dis., viii, p. 322-326.
+
+McCLINTIC, T. B. 1912. Investigations of and tick eradications in Rocky
+   Mountain spotted fever. Publ. Health Repts., Washington, xxvii, p.
+   732-760.
+
+MECKEL, H. 1847. Uber schwarzes Pigment in der Milz und im Blute einer
+   Geisteskranken. Allgem. Zeitschr. f. Psychiatrie, iv, p. 198-226.
+
+MEGNI, P. 1906. Les insectes buveurs de sang. 12mo. Paris, Rudeval. (150
+   p.).
+
+MELNIKOFF, N. 1869. Ueber die Jugendzustande der _Taenia cucumerina_.
+   Arch. f. Naturg., xxxv, p. 62-70.
+
+MENSE, C. 1913. Handbuch der Tropenkrankheiten. 1 Band. 4^o. Leipzig,
+   Barth (xv + 295 p.) Entomological parts by A. Eysell, and by Doerr
+   and Russ.
+
+MINCHIN, E. A. 1912. An introduction to the study of the Protozoa, with
+   special reference to the parasitic forms. 8^o. London. Arnold (xi +
+   517 p.).
+
+MITCHELL, EVELYN G. 1907. Mosquito life. 8vo. New York, Putmans. (xxii +
+   281 p.).
+
+MITZMAIN, M. B. 1910. General observations on the bionomics of the
+   rodent and human flies. U. S. Publ. Health Service. Bul., 38, p.
+   1-34.
+
+---- 1912. The role of _Stomoxys calcitrans_ in the transmission of
+   _Trypanosoma evansi_. Philippine Journ. Sci., vii, p. 475-519, 5 pls.
+
+---- 1913 a. The biology of _Tabanus striatus_ Fabricius, the horsefly
+   of the Philippines. ibid., vii, B. p. 197-221.
+
+---- 1913 b. The mechanical transmission of surra. ibid., viii, sec. B.,
+   p. 223-229.
+
+---- 1914 a. Experimental insect transmission of anthrax. U. S. Public
+   Health Repts. xxix, p. 75-77.
+
+---- 1914 b. I. Collected studies on the insect transmission of
+   _Trypanosoma evansi_. II. Summary of experiments in the transmission
+   of anthrax by biting flies. U. S. Pub. Health Service, Hyg. Lab.
+   Bul., 94, p. 1-48.
+
+MIYAKE, H. and SCRIBA, J. 1893. Vorlaufige Mitteilung uber einen neuen
+   Parasit des Menschen. Berl. klin. Wochenschr., xxx, p. 374.
+
+MOLLERS, B. 1907. Experimentelle Studien uber die Uebertragung des
+   Ruckfallfiebers durch Zecken. Zeitschr. fur Hyg. u.
+   Infektionskrankheiten, lviii, p. 277-286.
+
+MOTE, D. C. 1914. The cheese-skipper (_Piophila casei_). Ohio Naturalist
+   xiv, p. 309-310.
+
+NEIVA, A. 1910. Beitrage zur Biologie der _Conorhinus megistus_ Burm.
+   Memorias de Institute Oswaldo Cruz., ii, p. 206-212.
+
+NEVEU-LEMAIRE, M. 1907. Un nouveau cas de parasitisme accidental d'un
+   myriapode dans le tube digestif de l'homme, C. R. Soc. der Biol.,
+   lxiii p. 305-308.
+
+---- 1908. Precis de parasitologie humaine. 8vo. Paris, Rudeval. (v +
+   712 p.).
+
+NEWSTEAD, R. 1911. The papataci flies (Phlebotomus) of the Maltese
+   Islands. Bul. of Ent. Research, ii, p. 47-78, pls. 1-3.
+
+NICOLL, W. 1911. On the part played by flies in the disposal of the eggs
+   of parasitic worms. Repts. to the Local Gov't. Board on Publ. Health
+   and Med. Subjects, n. s. No. 53, p. 13-30.
+
+NICOLLE, C. 1910, Recherches experimentales sur la typhus exanthematique
+   entreprises a l'Institut Pasteur de Tunis pendant l'annee 1909. Ann.
+   Inst. Pasteur, xxiv, p. 243-275.
+
+---- 1911. Recherches experimentales sur la typhus exanthematique
+   entreprises a l'Institut Pasteur de Tunis pendant l'annee 1910.
+   ibid., xxv, p. 1-55, 97-154.
+
+NICOLLE, C., BLAIZOT, A., and CONSEIL, E. 1912 a. Etiologie de la fievre
+   recurrente. Son mode de transmission par le pou. C. R. Acad. Sci.,
+   cliv, p. 1636-1638.
+
+---- 1912 b. Conditions de transmission de la fievre recurrente par le
+   pou. ibid., clv., p. 481-484.
+
+NICOLLE, C. and CATOUILLARD, G. 1905. Sur le venin d'un scorpion commun
+   de Tunisie (_Heterometrus maurus_). C. R. Soc. Biol. lviii: p.
+   100-102.
+
+NOE, G. 1901. Sul ciclo evolutivo della _Filaria bancrofti_ e delta
+   _Filaria immitis_. Ricerche labr. anat. comp. norm. Univ. di Roma.,
+   viii, p. 275-353.
+
+NORMAN, W. W. 1896. The effect of the poison of centipedes. Trans. Texas
+   Acad. Sci., i, p. 118-119.
+
+NUTTALL, G. H. F. 1899. On the role of insects, arachnids, and myriapods
+   as carriers in the spread of bacterial and parasitic diseases of man
+   and animals. Johns Hopkins Hosp. Repts., viii, 154 p., 3 pls.
+
+---- 1908 a. On the behavior of Spirochaetae in _Acanthia lectularia_.
+   Parasitology, i, p. 143-151.
+
+---- 1908 b. The transmission of _Trypanosoma lewisi_ by fleas and lice.
+   ibid., i, p. 296-301.
+
+---- 1908 c. The Ixodoidea or ticks, spirochaetosis in man and animals,
+   piroplasmosis. Journ. Roy. Inst. Publ. Health, xvi, p. 385-403,
+   449-464, 513-526.
+
+---- 1914. Tick paralysis in man and animals. Parasitology, vii, p.
+   95-104.
+
+NUTTALL, G. H. F. and JEPSON, F. P. 1909. The part played by _Musca
+   domestica_ and allied (non-biting) flies in the spread of infective
+   diseases. A summary of our present knowledge. Rept. to the Local
+   Gov't Board on Publ. Health and Med. Subjects, n. s. 16, p. 13-41.
+
+NUTTALL, G. H. F. and SHIPLEY, E. A. 1901-03. Studies in relation to
+   malaria. The structure and biology of Anopheles. Journ. Hyg., vols.
+   i, ii, and iii.
+
+ORTH, J. 1910. Ueber die Beziehungungen der Haarsackmilbe zu
+   Krebsbildungen in der Mamma. Berliner klin. Wochenschr., xlvii, p.
+   452-453.
+
+OSBORN, HERBERT. 1896. Insects affecting domestic animals. U. S. Dept.
+   Agric., Bur. of Ent. Bul., 5, n. s., 302 p.
+
+---- 1902. Poisonous insects. Article in Reference Handbook. Med. Sci.,
+   v, p. 158-169.
+
+OSLER, W. 1887. An address on the Haematozoa of malaria. British Med.
+   Jour. i. p. 556.
+
+OSTEN SACKEN, C. R. 1875-78, Prodrome of a Monograph of North American
+   Tabanidae. Mem. Boston Soc. Nat. Hist., ii, p. 365-397, 421-479, and
+   555-566.
+
+OUDEMANS, A. C. 1910. Neue Ansichten uber die Morphologie des
+   Flohkopfes, sowie uber die Ontogenie, Phylogenie und Systematik der
+   Flohe. Novit. Zool., xvi, p. 133-158.
+
+PATTON, W. S. 1907. Preliminary report on the development of the
+   Leishman-Donovan body in the bed-bug. Sci. Mem., Med. and Sanitary
+   Dept., Gov't of India, 28, p. 1-19.
+
+PATTON, W. S. and CRAGG, F. W. 1913. A textbook of medical entomology.
+   4^o. London, Christian Literature Society for India. (xxxiv + 764 p.)
+
+PAWLOWSKY, E. 1906. Ueber den Steck- und Saug-apparat der Pediculiden.
+   Zeitschr. wiss. Insektenbiol., ii, p. 156-162, 198-204.
+
+PAWLOWSKY, E. 1913. Scorpiotomische Mitteilungen. I. Ein Beitrag zur
+   Morphologie des Giftdrusen der Skorpione. Zeitschr. wiss. Zool., cv.,
+   p. 157-177. Taf. x-xi.
+
+PEPPER, W., SCHNAUSS, F. W., and SMITH, A. J. 1908. Transient parasitism
+   in men by a species of _Rhizoglyphus_. Univ. of Pa. Med. Bul. xxi, p.
+   274-277.
+
+PETROVSKAIA, MARIA. 1910. Sur les myases produites chez l'homme par les
+   Oestrides (Gastrophilus et Rhinoestrus). These, Fac. de medecine,
+   Paris, 79 p.
+
+PETTIT, A. and KROHN, A. 1905. Sur la structure des glandes salivaires
+   du Notonecte (_Notonecta glauca_). Arch. anat. micr. Paris, vii, p.
+   351-368, pl. 13.
+
+PHISALIX, MME. 1900. Un venin volatil. Secretion cutanee du _Iulus
+   terrestris_. C. R. Soc. Biol. Paris, 1900, p. 1033-1036.
+
+---- 1912. Effets physiologiques du venin de la Mygale de Haiti, le
+   _Phormictopus cancerides_ Pocock. Effets physiologiques du venin de
+   la Mygale de Corse (_Cteniza sauvaga_ Rossi); Bul. Mus. Paris, 1912:
+   134-138.
+
+PORTSCHINSKY, I. A. 1908. _Rhinoestrus purpureus_, a parasite of
+   horses which deposits its larvae in the eyes of man. Mss. transl. by
+   Miss S. L. Weissman, in library of Ent. Dept., Cornell University.
+
+---- 1910. Biology of _Stomoxys calcitrans_ and other coprophagous
+   flies. Monograph in Russian. Mss. summarized transl. by Miss S. L.
+   Weissman, in Library of Ent. Dept., C. U.
+
+---- 1911. _Gastrophilus intestinalis_. Mss. transl. by Miss S. L.
+   Weissman, in library of Ent. Dept., C. U.
+
+---- 1913 a. The sheep gad-fly, _Oestrus ovis_, its life, habits,
+   methods of combating it, and its relation to man. Russian. Mss.
+   summarized trans. by Miss S. L. Weissman, in library of Ent. Dept.,
+   C. U.
+
+---- 1913 b. _Muscina stabulans_. A monograph in Russian. Mss., trans.
+   by J. Millman, in library of Ent. Dept., Cornell Univ.
+
+PROWAZEK, S. 1905. Studien uber Saugetiertrypanosomen. Arb. aus dem
+   kais. Gesundheitsamte xxii, p. 351-395.
+
+PUSEY, W. A. 1911. The principles and practice of dermatology. 2 ed,
+   8vo. Appleton & Co. (1079 p.)
+
+RABINOWITSCH, L. and KEMPNER, W. 1899. Beitrag zur Kentniss der
+   Blutparasiten, speciell der Ratten trypanosomen. Zeitschr. f. Hyg.
+   xxx, p. 251-291.
+
+RANSOM, B. H. 1904. An account of the tape worms of the genus
+   _Hymenolepis_ parasitic in man. Bul. No. 18, Hyg. Lab., U. S. Pub.
+   Health and Mar.-Hosp. Serv., Wash., p. 1-138.
+
+---- 1911. The life history of a parasitic nematode, _Hebronema muscae_.
+   Science n. s. xxxiv, p. 690-692.
+
+---- 1913. The life history of _Habronema muscae_, (Carter), a parasite
+   of the horse transmitted by the house-fly. U. S. Dept. Agric. Bur.
+   Animal, Ind. Bul. 163, p. 1-36.
+
+REAUMUR, R. A. F. DE. 1738. Memoires pour servir a l'histoirie des
+   insectes. Histoire des cousins, iv, p. 573-636.
+
+REED, WALTER. 1900. The etiology of yellow fever. Philadelphia Med.
+   Jour. Oct. 27, 1900, vi, p. 790-796.
+
+REED, W. and CARROLL, J. 1901. The prevention of yellow fever. Med.
+   Record, Oct. 26, 1901, p. 441-449.
+
+REUTER, ENZIO. 1910. Acari und Geschwulstatiologie. Centralbl. Bakt.
+   Jena. Abt. 1 lvi.; Originale 339-344.
+
+REUTER, O. M. 1912. Bemerkungen uber mein neues Heteropterensystem. Ofv.
+   Finska Vetensk. Soc. Forh., liv. Afd. A. vi, p. 1-62.
+
+RIBAGA, C. 1897. Sopra un organo particolare della Cimici dei letti
+   (_Cimex lectularius_ L.). Rivista di Patologia Vegetale, v, p.
+   343-352.
+
+RICARDO, GERTRUDE. 1900. Notes on the Pangoninae. Ann. and Mag. Nat.
+   Hist. v, p. 97-121.
+
+---- 1901. Further Notes on the Pangoninae. ibid. viii, p. 286-315.
+
+---- 1904. Notes on the smaller genera of the Tabanidae. ibid. xiv, P.
+   349-373.
+
+RICKETTS, H. T. 1906-1910. Contributions to medical sciences by Howard
+   Taylor Ricketts. 1870-1910. Univ. of Chicago Press. 1911.
+
+---- 1909. A microorganism which apparently has a specific relationship
+   to Rocky Mountain spotted fever. A preliminary report. Jour. Amer.
+   Med. Assoc. iii, p. 373-380.
+
+---- Spotted fever reports 1 and 2. In the 4th Bien. Rept. State Board
+   of Health, Montana, 1909, p. 87-191.
+
+RICKETTS, H. T. and WILDER, R. M. 1910. The transmission of the typhus
+   fever of Mexico (tabardillo) by means of the louse, _Pediculus
+   vestimenti_. Journ. Am. Med. Assoc. liv. p. 1304.
+
+RILEY, C. V. and HOWARD, L. O. 1889. A contribution to the literature of
+   fatal spider-bites. Insect life, Washington, i. p. 204-211.
+
+RILEY, W. A. 1906. A case of pseudoparasitism by dipterous larvae.
+   Canadian Ent. xxxviii, p. 413.
+
+---- 1910 a. Earlier references to the relation of flies to disease.
+   Science n. s. xxxi, p. 263-4.
+
+---- 1910 b. _Dipylidium caninum_ in an American child. Science n. s.
+   xxxi, p. 349-350.
+
+---- 1911. The relation of insects to disease. Cornell Countryman ix, P.
+   51-55.
+
+---- 1912 a. Notes on the relation of insects to disease. 8vo. Ithaca,
+   N. Y. 51 p.
+
+---- 1912 b. Notes on animal parasites and parasitism. 8vo. Ithaca, N.
+   Y. 55 p.
+
+---- 1913. Some sources of laboratory material for work on the relations
+   of insects to disease. Ent. News. xxiv, p. 172-175.
+
+---- 1914. Mr. Nott's theory of insect causation of disease. Jour. of
+   Parasitology. i, p. 37-39.
+
+ROSENAU, M. J. and BRUES, C. T. 1912. Some experimental observations on
+   monkeys, concerning the transmission of poliomyelitis through the
+   agency of _Stomoxys calcitrans_. Monthly Bul. Mass. State Board of
+   Health. Vol. vii, p. 314-317.
+
+ROSS, R. 1904. Researches on Malaria. The Nobel Medical Prize Lecture
+   for 1902, Stockholm, Norstedt & Soner. 89 p. 9 pls. In "Les Prix
+   Nobel en 1902."
+
+---- 1910. The prevention of malaria. 4^o. New York. Dutton & Co. (xx +
+   669 p.).
+
+ROTHSCHILD, N. C. 1905 a. North American Ceratophyllus. Novitates
+   Zoologicae xii, p. 153-174.
+
+---- 1905 b. Some further notes on _Pulex canis_ and _P. felis_. ibid.
+   xii, p. 192-193.
+
+ROUBAUD, E. 1911. Les Choeromyies. C. R. Acad. Sci. Paris, cliii, p.
+   553.
+
+---- 1913. Recherches sur les Auchmeromyies. Bul. Sci. France et Belg.
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+
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+
+SAMBON, L. W. 1908. Report presented at the International Conference on
+   Sleeping Sickness.
+
+---- 1910. Progress report on the investigation of pellagra. Reprinted
+   from the Journ. Trop. Med. and Hyg.; London; Bale, Sons and
+   Danielsson, 12^o. 125 p.
+
+SANDERSON, E. D. 1910. Controlling the black-fly in the White Mountains.
+   Jour. Econ. Ent. iii, p. 27-29.
+
+SAUL, E. 1910. Untersuchungen uber Beziehungen der Acari zur
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+   15-18.
+
+SAUL, E. 1913. Beziehungen des Helminthen und Acari zur
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+
+SAWYER, W. A. and HERMS, W. B. 1913. Attempts to transmit poliomyelitis
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+
+SCHAUDINN, F. 1904. Generations- und Wirtwechsel bei _Trypanosoma_ und
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+
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+
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+
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+
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+   son mode de transmission, dans une epidemie algerienne. Ann. Inst.
+   Pasteur xxiv, p. 337-373.
+
+---- 1911. Typhus recurrent Algerien. Sa transmission par les poux. Sa
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+   1039-1040.
+
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+
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+
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+   M. C. Journ., xx, p. 291.
+
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+   192.
+
+SMITH, G. U. 1909. On some cases of relapsing fever in Egypt and the
+   question of carriage by domestic vermin. Resume in Ann. Inst. Pasteur
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+
+SMITH, J. B. 1904. Report upon the mosquitoes occurring within the
+   State, their habits, life history, etc. N. J. Agric. Exp. Sta. 1904,
+   p. 1-482.
+
+---- 1908. The house mosquito, a city, town, and village problem. N. J.
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+
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+   causation, and prevention of Texas or southern cattle fever. U. S.
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+
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+
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+
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+   transmission, and source of Rocky Mountain fever. U. S. Public Health
+   and Marine Hosp. Serv. Hyg. Labr. Bul. 14, 121 p.
+
+---- 1907. Diseases caused by animal parasites. Osler's Modern Medicine,
+   i, p. 525-637.
+
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+   Health Bul. No. 37. U. S. Pub. Health and Marine Hosp. Service, p.
+   1-24.
+
+---- 1910 b. The taxonomic value of the microscopic structure of the
+   stigmal plates in the tick genus _Dermacentor_. Bul. No. 62; Hyg.
+   Lab., U. S. Pub. Health and Mar. Hosp. Serc., Washington, p. 1-72. 43
+   pls.
+
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+   excreta. Public Health Repts. Washington. xxv, p. 1825-1830.
+
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+   Repts. Washington, xxviii, p. 2530-2534.
+
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+
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+   common rat-flea of Great Britain. Jour. Hygiene, xiv, p. 139-142.
+
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+   Intern. Plague Conf. held at Mukden, Apr. 1911, p. 83-87.
+
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+   Oroya fever and uta. Journ. Amer. Med. Assoc. lxi, p. 1713-1716.
+
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+
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+
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+   325 p.).
+
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+   _Glossina morsitans_ zur Schlafkrankheit. Zeitschr. f. Hyg. lxix, p.
+   553-558.
+
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+   Medical Sentinel, Portland, Oregon. Sept. 1912. (Reprint unpaged.)
+
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+   volumes. London.
+
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+   par des larves de Diptere. Arch. Parasit. iv, p. 353-361
+
+THOMPSON, D. 1913. Preliminary note on bed-bugs and leprosy. British
+   Med. Journ. 1913, p. 847.
+
+TIRABOSCHI, C. 1904. Les rats, les souris et leurs parasites cutanes
+   dans leurs rapports avec la propagation de la peste bubonique. Arch.
+   Parasit. viii, p. 161-349.
+
+TOPSENT, E. 1901. Sur un cas de myase hypodermique chez l'homme. Arch.
+   Parasit., iv. p. 607-614.
+
+TORREY, J. C. 1912. Numbers and types of bacteria carried by city flies.
+   Journ. of Inf. Dis., x, p. 166-177.
+
+TOWNSEND, C. H. T. 1908. The taxonomy of the Muscoidean flies.
+   Smithsonian Misc. Col., p. 1-138.
+
+---- 1911. Review of work by Pantel and Portchinski on reproductive and
+   early stage characters of Muscoid flies. Proc. Ent. Soc., Washington,
+   xiii, p. 151-170.
+
+---- 1912. Muscoid names. ibid., xiv, p. 45.
+
+---- 1913 a. Preliminary characterization of the vector of verruga,
+   _Phlebotomus verrucarum_ sp. nov. Insecutor Inscitiae Menstruus,
+   Washington, i, p. 107-109.
+
+---- 1913 b. The transmission of verruga by _Phlebotomus_. Journ. Amer.
+   Med. Assoc., lxi, p. 1717.
+
+---- 1914 a. The relations between lizards and _Phlebotomus verrucarum_
+   as indicating the reservoir of verruga. Science n. s., xl, p.
+   212-214.
+
+---- 1914 b. Progress of verruga work with _Phlebotomus verrucarum_ T.
+   Journ. Econ. Ent., vii. p. 357-367.
+
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+   espece de Sarcoptidae detriticole, (_Histiogaster spermaticus_). Arch.
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+
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+
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+   2d Rept. of the Supt. for Suppressing the Gypsy and Brown-tail Moths,
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+
+VAUGHAN,
+
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+   d'un myriapode, (_Chaetachlyne vesuviana_) chez l'homme. C. R. Soc.
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+
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+
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+   Calliphorinae. Bul. Soc. Ent., France, No. 8, p. 256-258.
+
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+
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+   207-218.
+
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+
+WELLMAN, F. C. 1906. Human trypanosomiasis and spirochaetosis in
+   Portuguese Southwest Africa, with suggestions for preventing their
+   spread in the Colony. Journ. Hyg., vi, p. 237-345.
+
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+
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+
+WILLISTON, S. W. 1908. Manual of the North American Diptera, New Haven,
+   p. 1-405.
+
+WILSON, G. B. and CHOWNING, W. M. 1903. Studies in _Piroplasmosis
+   hominis_. Journ. Inf. Dis., iv, p. 31-57.
+
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+   School of Medicine, Cairo, ii, p. 7-44.
+
+
+
+
+INDEX
+
+
+Abscess, 178
+
+Acanthia, 87
+
+Acariasis, 58
+
+Acarina, 23, 58, 131, 259
+
+Acarus dysenteriae, 132
+
+Accidental parasites, 131, 132, 134
+
+Aedes, 194, 293
+
+Aedes calopus, 182, 201, 205, 206, 208
+
+Aedes cantator, 101
+
+Aedes sollicitans, 101
+
+Aedes taeniorhynchus, 101
+
+Aerobic bacteria, 152
+
+Aestivo-autumnal, 186
+
+African Relapsing Fever, 230
+
+Akis spinosa, 177
+
+Alternation of Generations, 175
+
+Amblyomma, 264
+
+Amblyomma americanum, 67
+
+Amblyomma cajennense, 67
+
+American dog tick, 228
+
+Amoeboid organism, 189
+
+Anisolabis annulipes, 177
+
+Anterior poliomyelitis, 241
+
+Anopheles, 194, 291
+
+Anopheles crucians, 199
+
+Anopheles maculipennis, 182
+
+Anopheles punctipennis, 198
+
+Anopheles quadrimaculatus, 197
+
+Anopheline, 192
+
+Anthocoris, 279
+
+Anthomyiidae, 300
+
+Anthomyia, 138
+
+Anthrax, 165
+
+Antipruritic treatment, 72
+
+Ants, 42
+
+Aphiochaeta, 295
+
+Apis mellifica, 36
+
+Arachnida, 258
+
+Araneida, 6
+
+Argas, 64
+
+Argas persicus, 63, 235, 237
+
+Argasidae, 62
+
+Argopsylla, 317
+
+Argus, 259
+
+Arilus, 284
+
+Arthropods, poisonous, 6
+
+Asopia farinalis, 177
+
+Assassin-bugs, 31, 219
+
+Auchmeromyia, 117
+
+Automeris io, 47
+
+Avicularoidea, 12
+
+
+Babesia, 226
+
+Babesia bovis, 223
+
+Babesia ovis, 225
+
+Babesiosis, 221-222
+
+Bacilli, 170
+
+Bacillus icteroides, 202, 205
+
+Bacillus pestis, 166
+
+Bacillus typhosus, 153
+
+Back swimmers, 30
+
+Bdellolarynx, 304
+
+Beauperthuy, Louis Daniel, 2
+
+Bed-bug, 86, 88, 90, 173, 219-220
+
+Bed-bug, cone-nosed, 92
+
+Blister beetles, 54
+
+Belostoma, 28, 277
+
+Belostoma americana, 31
+
+Belostomatidae, 30
+
+Bengalia, 314
+
+Bird-spiders, 10
+
+Black death, 1, 166
+
+Black flies, 33, 104, 247
+
+Black heads, 80
+
+Blaps mortisaga, 134
+
+Blepharoceridae, 286
+
+Boophilus, 264
+
+Boophilus annulatus, 67, 223-225
+
+Bot-flies, 112
+
+Blue bottle flies, 140
+
+Brill's disease, 238
+
+Brown-tailed moth, 48
+
+Bruck, 34
+
+Buthus quinquestriatus, 21
+
+
+Cabbage butterfly, 56
+
+Calliphora, 136, 140, 312
+
+Calliphora erythrocephala, 141
+
+Calobata, 296
+
+Camponotinae, 43
+
+Cancer, 254
+
+Cantharidin, 54
+
+Cantharidin poison, 55
+
+Canthariasis, 134
+
+Capsidae, 280
+
+Carriers, simple, 4, 144
+
+Carriers of disease, 144
+
+Carrion's fever, 253
+
+Caterpillar rash, 45
+
+Cat flea, 172
+
+Cattle ticks, 222
+
+Causative organism, 170
+
+Cellia, 291
+
+Centipedes, 25, 257
+
+Ceratophyllus, 120, 316
+
+Ceratophyllus acutus, 123
+
+Ceratophyllus fasciatus, 122, 172, 213
+
+Ceratopogon, 108
+
+Cheese-fly, 137
+
+Cheyletus eruditus, 271
+
+Chigger, 60, 70
+
+Chigoes, 126
+
+Chilopoda, 25, 257
+
+Chiracanthium nutrix, 18
+
+Chironomidae, 107
+
+Chorioptes, 270
+
+Chrysomelid, 55
+
+Chrysomyia, 136, 308
+
+Chrysomyia macellaria, 117, 140
+
+Chrysops, 294
+
+Chylous dropsy, 179
+
+Chyluria, 178
+
+Cicadidae, 55
+
+Cimex L., 278
+
+Cimex boueti, 92
+
+Cimex columbarius, 92
+
+Cimex hemipterus, 91, 220
+
+Cimex hirundinis, 92
+
+Cimex inodorus, 92
+
+Cimex lectularius, 87, 219
+
+Citheronia regalis, 44
+
+Clinocoris, 87
+
+Coleoptera, 134, 274
+
+Comedons, 80
+
+Complete metamorphosis, 80
+
+Compressor muscle, 20
+
+Compsomyia, 117
+
+Cone-nosed bed-bug, 92
+
+Conjunctivitis, nodular, 52
+
+Conorhinus, 282
+
+Conorhinus megistus, 93, 219-220
+
+Conorhinus rubrofasciatus, 220
+
+Conorhinus sanguisugus, 32, 92
+
+Copra itch, 72
+
+Cordylobia, 118
+
+Coriscus, 280
+
+Coriscus subcoleoptratus, 32
+
+Creeping myasis, 112
+
+Crustacea, 257
+
+Cryptocystis, 176
+
+Cryptotoxic, 54-55
+
+Cteniza sauvagei, 13
+
+Ctenocephalus, 120, 172, 213, 317
+
+Culex, 194, 201, 293
+
+Culex pipiens, 35, 98
+
+Culex quinquefasciatus, 180
+
+Culex sollicitans, 200
+
+Culex territans, 101
+
+Culicidae, 33, 97
+
+Culicin, 34
+
+Culicoides, 109, 288
+
+Cyclops, 183, 257
+
+Cynomyia, 136, 311
+
+
+Dance, St. Vitus, 8
+
+Dancing mania, 8
+
+Deer-flies, 110
+
+Definitive host, 192
+
+Demodecidae, 78
+
+Demodex, 259
+
+Demodex folliculorum, 78
+
+Dermacentor, 262
+
+Dermacentor andersoni, 67, 228
+
+Dermacentor occidentalis, 227
+
+Dermacentor variabilis, 67
+
+Dermacentor venustus, 24, 228
+
+Dermanyssidae, 68
+
+Dermanyssus, 266
+
+Dermanyssus gallinae, 68
+
+Dermatitis, 72, 77, 85
+
+Dermatobia, 115, 298
+
+Dermatobia cyaniventris, 163
+
+Dermatophilus, 317
+
+Dermatophilus penetrans, 60, 126
+
+Diamphidia simplex, 55
+
+Dimorphism, 65
+
+Direct inoculators, 4
+
+Diplopoda, 25, 257
+
+Diptera, 33, 94, 274
+
+Dipterous Larvae, 135
+
+Dipylidium, 175, 221
+
+Dipylidium caninum, 4, 175-176
+
+Dog flea, 172
+
+Dracunculus, 257
+
+Dracunculus medinensis, 182
+
+Drosophila, 296
+
+Dum-dum fever, 220
+
+Dysentery, 154
+
+
+Ear-flies, 110
+
+Earwig, 177
+
+Echidnophaga, 317
+
+Echinorhynchus, 185
+
+Elephantiasis, 178-179
+
+Empoasca mali, 33
+
+Empretia, 46
+
+English Plague Commission, 171
+
+Epeira diadema, 18
+
+Epizootic, 170
+
+Eristalis, 137, 295
+
+Essential hosts, 4, 165
+
+Eumusca, 307
+
+European Relapsing Fever, 233
+
+Euproctis chrysorrhoea, 48
+
+Eusimulium, 286
+
+
+Facultative parasites, 131
+
+Fannia, 136, 138, 145, 300
+
+Federal Health Service, 169
+
+Fever, lenticular, 237
+  African Relapsing, 230, 234
+  Carrion's, 253
+  dum-dum, 154
+  European Relapsing, 233
+  pappatici, 96
+  red water, 220
+  Rocky Mt. Spotted, 226
+  three day, 96
+  Typhus, 237
+
+Filaria, 178, 221
+  immitis, 182
+
+Filariasis, 178
+
+Flannel-moth larvae, 44
+
+Fleas, 119, 166, 213
+  cat, 172
+  dog, 172
+  human, 172, 176
+  rodent, 123, 172
+  rat, 171
+
+Flesope, 125
+
+Formaldehyde, 91
+
+Fomites, 199, 204
+
+Fulgoridae, 28
+
+Fumigation, 320
+
+
+Gamasid, 68
+
+Gangrene, 129
+
+Gastrophilus, 113, 297
+
+Giant crab spiders, 13
+
+Giant water bugs, 30
+
+Gigantorhynchus, 185
+
+Glossina, 117, 297, 303
+
+Glossina morsitans, 214, 217
+  palpalis, 215, 217, 218
+
+Glyciphagus, 267
+
+Grain moth, 69
+
+Grocer's itch, 72
+
+Guinea-worm, 182
+
+
+Habronema muscae, 156, 183
+
+Haematobia, 166, 304
+  irritans, 146
+
+Haematobosca, 304
+
+Haematomyidium, 288
+
+Haematopinus spinulosus, 213
+
+Haematopota, 294
+
+Haematosiphon, 279
+
+Haemoglobinuria, 222
+
+Haemozoin, 189
+
+Harpactor, 284
+
+Harvest mites, 60
+  effect of, 59
+
+Head-louse, 173
+
+Helminthiasis, 138
+
+Helophilus, 295
+
+Hemiptera, 27, 86, 273-275
+
+Heteropodidae, 13
+
+Heuchis sanguinea, 55
+
+Hexapod larvae, 58
+
+Hexapoda, 27, 80, 258
+
+Hippelates, 297
+
+Hippobosca, 285
+
+Histiogaster, 269
+  spermaticus, 132
+
+Homalomyia, 136, 138, 300
+
+Honey bee, 36
+  poison of, 37
+
+Hornets, 43
+
+Horn-fly, 137, 304, 308
+
+Horse-fly, 110, 165
+
+House-fly, 137-139, 144, 183
+  control of, 156, 160
+
+Human flea, 124
+
+Host, definitive, 175
+  intermediate, 175
+  primary, 175
+
+Hyalomma, 264
+  aegypticum, 224-225
+
+Hydrocyanic Acid Gas, 318
+
+Hydrotaea, 300
+
+Hymenolepis diminuta, 176
+
+Hymenoptera, 36, 275
+
+Hypoderma, 113, 298
+  diana, 113
+  lineata, 113
+
+Hypopharynx, 80
+
+
+Immunity from stings, 39
+
+Incomplete metamorphosis, 80
+
+Infantile paralysis, 162, 241
+  splenic, 220
+  Direct inoculation, 164
+
+Insects, 258
+  blood-sucking, 170
+
+Intermediate host, 192, 203
+
+Intestinal infestation, 112, 133
+  myasis, 137
+
+Isosoma, 69
+
+Itch, 73-74
+  mite, 73
+  Norwegian, 77
+
+Ixodes, 260
+  ricinus, 66, 225
+  scapularis, 66
+
+Ixodidae, 64-65
+
+Ixodoidea, 62
+
+
+Janthinosoma lutzi, 116
+
+Jigger, 60
+
+Johannseniella, 110, 288
+
+Journal of Tropical Medicine and Hygiene, 36
+
+Julus terrestris, 25
+
+June bug, 185
+
+
+Kala-azar, 220
+
+Karakurte, 14
+
+Katipo, 14
+
+King, A. F. A., 3
+
+Kircher, Athanasius, 1, 8
+
+Kissing-bug, 31
+
+
+Labium, 29, 80
+
+Labrum, 28, 80
+
+Lachnosterna, 185
+
+Laelaps, 266
+
+Lagoa crispata, 45
+
+Lamblia intestinalis, 154
+
+Langer, Josef, 37
+
+Larder beetles, 135
+
+Latrodectus, 12, 14, 17
+  mactans, 15
+
+Leishmanioses, 220
+
+Lenticular fever, 237
+
+Lepidoptera, 274
+
+Lepidopterous larvae, 134
+
+Leprosy, 252
+
+Leptidae, 112
+
+Leptis, 295
+
+Leptus, 60, 273
+
+Lice, 80
+
+Linguatulina, 258
+
+Liponyssus, 265
+
+Loemopsylla, 172, 317
+
+Lone star tick, 228
+
+Louse, body, 84
+  crab, 85
+  dog, 176
+  head, 82
+  pubic, 85
+
+Lucilia, 136, 312
+
+Lycosa tarantula, 10
+
+Lycosidae, 10
+
+Lyctocoris, 279
+
+Lygus pratensis, 33
+
+Lymphangitis, 67
+
+Lymph scrotum, 178
+
+Lyperosia, 304
+
+Lyperosiops, 305
+
+
+Macloskie, 34
+
+Maggots, rat-tail, 137
+
+Magnes sive de Arte Magnetica, 8
+
+Malaria, 186
+
+Malmigniatte, 14
+
+Mandibles, 28, 80
+
+Mange, 73-75
+
+Margaropus, 237, 264
+  annulatus, 223
+
+Masked bed-bug hunter, 32
+
+Mastigoproctus giganteus, 19, 80
+
+Maxillae, 28
+
+Meal infesting species, 135
+
+Melanin granules, 189
+
+Melanolestes, 280
+  picipes, 32
+
+Mena-vodi, 14
+
+Mercurialis, 1
+
+Merozoites, 190
+
+Metamorphosis, 80
+
+Miana bug, 63
+
+Microgametoblast, 192
+
+Midges, 107
+
+Migratory ookinete, 192
+
+Millipedes, 25, 257
+
+Mites, 23, 58
+
+Monieziella, 269
+
+Mosquitoes, 33, 97, 178, 196, 250
+  treatment for bites of, 34, 36, 102
+
+Musca, 137, 307
+  domestica, 139, 145, 146, 157, 162
+
+Muscidae, 117
+
+Muscina, 137, 146, 307
+  stabulans, 140
+
+Mutualism, 57
+
+Myasis, 112, 135
+  intestinal, 135-140
+  nasal, 141
+
+Mycterotypus, 287
+
+Myiospila, 146, 307
+
+Myriapoda, 225, 132, 257
+
+
+Nagana, 165, 214
+
+Nasal infestation, 114, 133
+
+Necrobia, 135
+
+Nematode parasite, 182
+
+Nepa, 28
+
+Nephrophages sanguinarius, 132
+
+Nettling insects, 43
+  larvae, poison of, 53
+
+Neurasthenia, 89
+
+Nits, 86
+
+North African Relapsing Fever, 234
+
+Norwegian itch, 77
+
+No-see-ums, 109
+
+Notoedres, 269
+  cati, 78
+
+Notonecta, 28, 277
+
+Notonectidae, 30
+
+Nott, Dr. Josiah, 2
+
+Nuttall, 34
+
+
+Occipital headaches, 138
+
+Oecacta, 288
+
+Oeciacus, 279
+
+Oesophageal diverticula, 35
+
+Oestridae, 112, 136
+
+Oestris ovis, 113
+
+Oestrus, 298
+  oocyst, 192
+  ookinete, 192
+
+Opsicoetes personatus, 32
+
+Opthalmia, 155
+  nodosa, 52
+
+Oriental sore, 221
+
+Ornithodoros, 65, 260
+  moubata, 220, 230
+
+Orthotylus flavosparsus, 33
+
+Ornithomyia, 286
+
+Oroya, 253
+
+Oscinus, 297
+
+Otiobius, 259
+  megnini, 65
+
+Otodectes, 271
+
+
+Pangonia, 294
+
+Pappatici fever, 96
+
+Parasimulium, 286
+
+Parasite, 3, 57, 131, 134, 182
+  accidental, 3, 131, 134
+  facultative, 3, 57, 131
+  nematode, 182
+  stationary, 57
+  temporary, 57
+  true, 3
+
+Parasitism, accidental, 134
+
+Pathogenic bacteria, 152
+  organisms, 144, 164
+
+Pawlowsky, 81
+
+Pediculoides, 267
+  ventricosus, 69, 72
+
+Pediculosis, 81
+
+Pediculus, 275
+  corporis, 84, 233, 238
+  humanus, 82, 173
+
+Pellagra, 162, 246
+
+Pernicious fever, 186
+
+Pest, 166
+
+Phidippus audax, 19
+
+Philaematomyia, 306
+
+Phisalix, 13, 43
+
+Phlebotomus, 289
+  papatasii, 94
+  verrucarum, 254
+  vexator, 95
+
+Phora, 295
+
+Phormia, 136
+
+Phormictopus carcerides, 13
+
+Phthirus pubis, 85, 275
+
+Phortica, 296
+
+Pieris brassicae, 56
+
+Piophila, 297
+
+Piophila casei, 136, 137
+
+Piroplasmosis, 222
+
+Plague, 166
+  bubonic, 166, 169, 170
+  pneumonic, 167
+
+Plasmodium, 186
+
+Platymetopius acutus, 33
+
+Plica palonica, 83
+
+Pneumonic, 166
+  plague, 167, 173
+
+Poisoning by nettling larvae, 53
+
+Poison of spiders, 7
+
+Pollenia, 308
+  rudis, 146, 147
+
+Primary gland, 28
+
+Prionurus citrinus, 20
+
+Prosimulium, 286
+
+Protocalliphora, 136, 312
+
+Protozoan blood parasite, 165
+
+Pseudo-tubercular, 52
+
+Psorophora, 293
+
+Psoroptes, 270
+
+Psychodidae, 94
+
+Pulex, 120, 124, 126, 172, 317
+  cheopis, 172
+  irritans, 124
+  penetrans, 126
+  serraticeps, 120
+
+Pulvillus, 150
+
+Punkies, 109
+
+Pycnosoma, 308
+
+
+Rasahus, 280
+  thoracicus, 32
+
+Rat fleas, 120, 124, 171
+
+Rat louse, 213
+
+Red bugs, 70-72
+
+Reduviidae, 31
+
+Reduviolus, 280
+
+Reduvius, 282
+  personatus, 32
+
+Redwater fever, 222
+
+Relapsing fever, 230, 233
+
+Rhinoestrus nasalis, 115
+
+Rhipicentor, 264
+
+Rhipicephalus, 264
+
+Rhizoglyphus, 269
+
+Rhodnius, 281
+
+Rocky Mountain Spotted Fever, 226
+  spotted fever tick, 67
+
+Russian gad-fly, 115
+
+
+St. Vitus's or St. John's dance, 8
+
+Salivary syringe, 28
+
+Sand-flies, 109, 250
+
+Sanguinetti, 11
+
+Sarcophaga, 136, 142, 143
+
+Sarcophila, 302
+
+Sarcopsylla, 317
+  penetrans, 126
+
+Sarcoptes, 270
+  minor, 78
+  scabiei, 73
+
+Sarcoptidae, 72
+
+Scabies, 72, 73, 74, 75
+
+Scaurus striatus, 177
+
+Schaudinn, 34
+
+Schizont, 189, 190
+
+Scholeciasis, 134
+
+Scolopendra morsitans, 26
+
+Scorpions, 20
+  poison of, 21
+
+Screw worm fly, 140
+
+Sepsidae, 296
+
+Sepsis, 136, 297
+
+Shipley, 34
+
+Sibine, 46
+
+Silvius, 294
+
+Simple carriers, 4, 144
+
+Simuliidae, 33, 104
+
+Simulium, 247, 249, 286, 321
+  pictipes, 104
+
+Siphonaptera, 119, 274, 316
+
+Siphunculata, 80, 275
+
+Sitotroga cerealella, 69
+
+Skippers, 137
+
+Sleeping sickness, 166, 215
+
+Snipe-flies, 112
+
+Solpugida, 22
+
+Spanish fly, 54
+
+Spermatozoa, 192
+
+Spinose ear-tick, 65
+
+Spirochaeta, 35
+  berberi, 234
+  duttoni, 234
+
+Spirochaetosis, 235
+
+Sporozoite, 189
+
+Spotted fever, 67, 226
+
+Squirrel flea, 123
+
+Stable-fly, 137, 160, 163, 165
+
+Stegomyia, 182, 293
+  calopus, 206
+  fasciata, 206
+
+Stomoxys, 137, 305
+  calcitrans, 117, 146, 160, 161, 165, 242
+
+Straw-worm, 69
+
+Stygeromyia, 305
+
+Sucking stomach, 35
+
+Sulphur ointment, 77
+
+Surra, 165
+
+Symbiosis, 57
+
+Symphoromyia, 112, 295
+
+
+Tabanidae, 110
+
+Tabanus, 110, 166, 294
+  striatus, 165
+
+Taenia, 175
+
+Tapeworm, 4, 176
+
+Tarantella, 8
+
+Tarantism, 8
+
+Tarantula, 10
+
+Tarsonemidae, 69
+
+Tarsonemus, 267
+
+Tenebrionid beetles, 127
+
+Tersesthes, 110, 288
+
+Tetanus, 129
+
+Tetranychus, 273
+
+Texas fever, 220-223
+
+Three-day fever, 96
+
+Tick, 23, 226
+  bites, Treatment of, 68
+  fever, 230
+  paralysis, 67
+
+Treatment,
+  Bee stings, 36, 41
+  Bites of,
+    Bed-bugs, 90, 93
+    Blackflies, 107
+    Buffalo flies, 107
+    Bugs, 31, 33
+    Centipedes, 26, 27
+    Chiggers, 127
+    Chigoes, 127
+    Fleas, 127
+    Harvest mites, 61
+    Jiggers, 129
+    Lice, 83, 85
+    Mosquitoes, 34, 36, 102
+    Phlebotomus flies, 97
+    Sand flies, 96, 107, 109
+    Scorpions, 22, 23
+    Spiders, 19
+    Ticks, 61, 68, 72
+    Ticks, ear, 65
+  Blister beetle poison, 55
+  Brown-tail moth rash, 45
+  Cantharidin poison, 55
+  Caterpillar rash, 45
+  Ear ticks, 65
+  House fly control, 156, 160
+  Itch, 77
+  Itch, grocer's, 72
+  Lice, 85
+  Nasal myasis, 143
+  Rocky Mt. spotted fever, 228, 229
+  Rash, caterpillar, 45
+  Scabies, 77
+  Sleeping sickness control, 218
+  Spotted fever, 228, 229
+  Stings, bee, 36, 41
+  Typhus fever, prophylaxis, 239
+
+Trichodectes canis, 176
+
+Trichoma, 82
+
+Trineura, 295
+
+Trochosa singoriensis, 11
+
+Trombidium, 60, 273
+
+True insects, 80
+
+Trypanosoma, 35
+
+Trypanosoma, brucei, 165
+
+Trypanosoma cruzi, 219
+
+Trypanosoma lewisi, 213
+
+Trypanosomiases, 212
+
+Trypanosomiasis, 165, 219
+
+Tsetse flies, 117, 166, 214, 219
+
+Tsetse flies disease, 165
+
+Tuberculosis, 155
+
+Tumbu-fly, 118
+
+Tydeus, 271
+
+Typhoid, 155
+
+Typhoid fever, 154
+
+Typhus, 237
+
+Typhus fever, 237
+
+Tyroglyphus, 72, 131, 268
+
+Dr. Tyzzer, 49
+
+
+Uranotaenia, 292
+
+
+Vancoho, 14
+
+Varicose groin glands, 178
+
+Verruga peruviana, 253
+
+Vescicating insects, 54
+
+
+Wanzenspritze, 29
+
+Warble-flies, 112
+
+Wasps, 43
+
+Whip-scorpions, 19
+
+Wohlfahrtia, 143, 302
+
+Wolf-spiders, 10
+
+Wyeomyia smithii, 101, 293
+
+
+Xenopsylla, 172, 317
+
+Xenopsylla cheopis, 171, 124
+
+Xestopsylla, 317
+
+
+Yaws, 2
+
+Yellow fever, 196, 203, 205
+
+
+
+
+TRANSCRIBER'S NOTES
+
+The following discrepancies in the text are as in the original:
+
+  The inconsistent hyphenation of the following:
+    assassin-bugs/assassin bugs;
+    bedbug/bed-bug (and bedbugs);
+    beekeeper/bee-keeper (and beekeepers);
+    blackflies/black-flies;
+    blow-flies/blow flies;
+    bluebottles/blue-bottles;
+    bot-flies/bot flies;
+    bristlelike/bristle-like;
+    browntail/brown-tail;
+    coextensive/co-extensive;
+    deer-flies/deer flies;
+    dorsocentral/dorso-central;
+    ectoparasites/ecto-parasites;
+    endoparasites/endo-parasites;
+    flesh-fly/flesh fly (and flesh flies);
+    hotbed/hot-bed;
+    housefly/house-fly (and houseflies);
+    horsefly/horse-fly (and horse flies);
+    horse-manure/horse manure;
+    midsummer/mid-summer;
+    preeminently/pre-eminently;
+    sandfly/sand-fly (and sandflies);
+    screw-worm fly/screw worm fly;
+    stable-fly/stable fly;
+    subequal/sub-equal;
+    subfamily/sub-family;
+    subtropical/sub-tropical;
+    tapeworm/tape-worm (and tapeworms);
+    today/to-day;
+    tsetse-flies/tsetse flies;
+    widespread/wide-spread;
+    wormlike/worm-like.
+
+  Inconsistent spelling of the following:
+    defence/defense;
+    disc/disk;
+    hemolysis/haemolysis;
+    hemolytic/haemolytic;
+    hexapod/hexopod;
+    Levaditi/Lavaditi;
+    metalescent/metallescent;
+    Mitzmain/Mitzman;
+    Neveau-Lemaire/Neveau-Lamaire;
+    offence/offense;
+    Phthirus/Phthirius
+    Portschinsky/Portchinsky/Portchinski;
+    travelled/traveled;
+    ventra-/ventro-;
+    Villot/Villet;
+    Wohlfartia/Wohlfahrtia;
+
+toxine, insiduous, efficaceous, cyanid are spelt as in the original
+
+In the first paragraph of chapter XII, "the student might not be lead"
+is as in the original. Lead perhaps should be led
+
+In the bibliography, the entry for Vaughan without a text specified is
+as in the original
+
+
+
+
+
+End of the Project Gutenberg EBook of Handbook of Medical Entomology, by 
+William Albert Riley and Oskar Augustus Johanssen
+
+*** END OF THIS PROJECT GUTENBERG EBOOK HANDBOOK OF MEDICAL ENTOMOLOGY ***
+
+***** This file should be named 34279.txt or 34279.zip *****
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