THIL HOUS L.O.HOWARD ••••••••IIHHMHI THE HOUSE FLY— DISEASE CARRIER THE HOUSE FLY DISEASE CARRIER THE HOUSE FLY DISEASE CARRIER AN ACCOUNT OF ITS DANGEROUS ACTIVITIES AND OF THE MEANS OF DESTROYING IT BY L. O. HOWARD, PH.D. NEW YORK FREDERICK A. STOKES COMPANY PUBLISHERS Public Health Lib. Copyright, 1911, by FREDERICK A. STOKES COMPANY All rights reserved, including that of translation into foreign languages, including the Scandinavian May, 1911 Ft CONTENTS PAGE INTRODUCTION xv CHAPTER I ZOOLOGICAL POSITION, LIFE HISTORY, AND HABITS i Life History 6 The Egg ........... 18 The Larva 19 The Pupa and Puparium 23 Emergence of the Adult 25 Structure of the Adult 27 Difference in Size of Adults 32 Summary of Duration of Life Round . . 35 Number of Generations 36 Possibilities in the Way of Numbers . . 37 Number by Actual Count in Relation to Quantity of Food 39 Hibernation 41 Habits of the Adult Fly 44 Do Flies have a Color Preference? ... 47 Fly-Specks 48 Distance of Flight 51 Marking Flies for Experiment .... 56 Length of Life of the Adult 58 Time Elapsing between the Iss'ning of the Adult and the Period of Sexual Maturity 60 v M638258 vi CONTENTS CHAPTER II PAGE THE NATURAL ENEMIES OF THE TYPHOID FLY . 62 Fungous Diseases 62 Protozoan Enemies of the House Fly . . 70 Nematode Parasites of the Typhoid Fly . . 72 The Mite Enemies of Musca Domestica . . 75 Spiders as Fly Enemies 78 False Scorpions on Flies 80 The House Centipede 82 Insect Enemies of the House Fly .... 84 Predatory Enemies 84 Parasitic Enemies 88 Vertebrate House Fly Enemies 95 Fly-Catching Rats 97 CHAPTER III THE CARRIAGE OF DISEASE BY FLIES .... 100 Exact Experiments 102 Typhoid or Enteric Fever 112 Suspicions of the Carriage of Typhoid by Flies 114 Inferential Proof 116 Exact Proof 125 Chronic Carriers 128 Influence of Flies in the Carriage of Typhoid in Cities 138 Other Points .148 Cholera 150 Dysentery 155 Diarrhea in Infants 156 Tuberculosis 162 CONTENTS vii PAGE Anthrax 164 Yaws (FrambcKsia tropica) 165 Ophthalmia 167 Diphtheria 170 Small-pox 170 Plague 171 Tropical Sore 172 Parasitic Worms 173 CHAPTER IV REMEDIES AND PREVENTIVE MEASURES .... 175 Screening 177 Fly Traps and Fly Poisons 178 Formalin 185 Pyrethrum and Carbolic Acid 188 Repellents 189 Search for Breeding Places 190 The Treatment of Horse Manure .... 193 Removal of Manure and Receptacles for Its Temporary Storage 201 The Sanitary Privy . 203 A Compulsory Sanitary Privy Law . . . 210 The Capture of Adult Flies Outside of Houses 212 Special Considerations for Towns and Cities . 217 Organization 218 • Interesting the Children . . . . . . 224 Boards of Health 230 Army Camps 233 CHAPTER V OTHER FLIES FREQUENTING HOUSES . 2i~ The Cluster Fly (Pollenia rudis Fabr.) . . 236 viii CONTENTS PACK The Biting House Fly (Stomoxys calcitrant L.) 240 The Little House Fly (Fannia [Homalomyia] canicularis L.) . 246 The Stable Fly (Muscina stabnlans Fall.) . 248 The Cheese Fly (Piophila casci L.) . . . 249 The Fruit Flies (Drosophila ampclophila Loevv.) 251 The Bluebottle or Greenbottle Flies ... 252 The Blow Flies (Calliphora crythroccphala Meig., Lucilia cccsar L., Phormia terrccno- v<£ Desv.) 252 The Flesh Flies (Sarcophaga assidua Walk.) 254 The Dung Flies (Sepsis riolacea Meig., Sca- tophaga furcata Say.) 255 The Moth Flies (Psychoda minuta Banks.) . 256 The Humpback Flies 257 The Window Flies (Scenopimis fcnestralis L.) 258 BIBLIOGRAPHICAL LIST ' . .261 APPENDIX I 273 APPENDIX II 281 APPENDIX III 285 APPENDIX IV 293 APPENDIX V 3°5 ILLUSTRATIONS The house fly — Disease carrier . . . Frontispiece FIG. PACK 1. Eggs, approximately natural size; photographed on surface of manure pile (from New- stead) facing 18 2. Eggs, approximately natural size (from New- stead) facing 18 3. Eggs, greatly enlarged (from Newstead) facing 20 4. Eggs, greatly enlarged — another view (from Newstead) facing 20 5. Egg of house fly; greatly enlarged .... 19 6. Egg hatching; greatly enlarged . . facing 22 7. Full grown larva of house fly; greatly en- larged facing 22 8. Larvae in horse manure (from Newstead) facing 24 9. Larvae and puparia (from Newstead) . facing 24 10. Puparia on a bit of old rotting cloth from an ash barrel (from Newstead) . . facing 26 11. House fly puparium and pupa; greatly enlarged 24 12. Adult house fly from above; greatly en- larged facing 28 13. Adult house fly from below; greatly en- larged facing 28 14. Head of adult house fly ; greatly enlarged facing 30 15. Head of adult house fly from side; greatly en- larged facing 30 x LIST OF ILLUSTRATIONS FIG. PAGE 1 6. A diagrammatic figure of the alimentary canal of the house fly; greatly enlarged ... 29 17. The house centipede (Scutigera forceps) ; some- what enlarged (after Marlatt) . . facing 82 1 8. Colonies of bacteria on a sterilized plate, aris- ing from fly tracks facing 108 19. Details of window trap (redrawn from Parrott) 181 20. Fly trap for garbage can .... facing 214 21. Poster issued by the Florida State Board of Health ; greatly reduced .... facing 224 22. The cluster fly (Pollcnia rudis) ; greatly en- larged facing 238 23. The biting house fly (Stomo.vys calcitrant) ; greatly enlarged facing 238 24. The little house fly (Homalomyia breris) ; greatly enlarged facing 246 25. The stable fly (Muscina stabulans) ; greatly en- larged facing 246 26. The cheese fly (Piophila casei) ; enlarged facing 250 27. The fruit fly (Drosophila ampclophila) \ en- larged facing 250 28. Lucilia ccesar ; enlarged facing 254 29. Calliphora erythrocephala; enlarged . facing 254 30. Phormia tcrrcenovcc ; enlarged . . . facing 254 31. Sarcophaga assidua; enlarged . . . facing 256 32. Sepsis violacea; enlarged .... facing 256 33. Scatophaga fnrcata; enlarged . . . facing 254 34. Phora femorata; enlarged greatly .... 257 35. Scenopinns fencstralis; enlarged 258 36. Scantling for framework of single-seated privy (Redrawn from Stiles) 295 37. The framework for a single-seated privy (Re- drawn from Stiles) 297 LIST OF ILLUSTRATIONS xi "G- PAGE 38. Front view of single-seated sanitary privy (Re- drawn from Stiles) 299 39. Rear view of single-seated sanitary privy (Re- drawn from Stiles) 301 40. The Lumsden, Roberts and Stiles apparatus for the safe disposal of night-soil (Redrawn from Lumsden, Roberts and Stiles) .... 307 INTRODUCTION INTRODUCTION IT is only within the last twelve years that the dan- gerous character of the common house fly has been known; and only within the last two years have the people at large begun to wake up to this danger and to inquire concerning the means by which this fly can be kept down. The writer published some account of its life history in a bulletin on household insects published by the U. S. Department of Agriculture in 1896. Later he made some experiments with regard to remedies, and in 1900 published a rather lengthy paper on the insect fauna of human excrement with especial reference to the carriage of typhoid fever by flies. Within the last two years, however, articles relating to the so-called house fly in connection with its disease-carrying possibilities have been published literally by the thousand, and this interest, perhaps having its origin in the United States, has spread to nearly all parts of the civilized world, and yet in no one of these published articles is the .whole story told. No one can find in condensed and convenient shape the general information he desires in regard to this insect. The publishers of this book, realizing this fact, have invited the author to attempt to fill this want. This book is not intended to be a scientific mono- graph ; it is simply an attempt to tell in an understand- able way what is known about the subjects indicated in the title. xv xvi THE HOUSE FLY— DISEASE CARRIER And mention of the title brings up the point as to whether the writer was justified when he proposed the name typhoid fly for the old and well-known house fly at the meeting of the Committee of One Hundred on Public Health at the meeting of the American As- sociation for the Advancement of Science, in Baltimore, during the Christmas week in 1908. He has been crit- icized for making this suggestion by the Association of Economic Entomologists' Committee on Popular Names and also by certain medical men. The objec- tions have been that this name would indicate the be- lief on the part of the proposer and of those who should subsequently use it that the house fly is the sole car- rier of typhoid or that it is the principal carrier of ty- phoid ; in other words, that it is given too much prom- inence from the standpoint of the etiology of typhoid fever. As a matter of fact, however, the writer never claimed that it was the only carrier of typhoid or that it was the principal carrier of typhoid except under certain peculiar conditions. In fact, the suggestion seems to him to have been quite sufficiently guarded. It was as follows: "The name 'typhoid fly' is here proposed as a substitute for the name 'house fly' now in general use. People have altogether too long con- sidered the house fly as a harmless creature, or at the most simply a nuisance. While scientific researches have shown that it is a most dangerous creature from the standpoint of disease, and while popular opinion is rapidly being educated to the same point, the re- tention of the name 'house fly' is considered inadvis- INTRODUCTION xvii able as perpetuating in some degree the old ideas. Strictly speaking, .the term 'typhoid fly' is open to some objection as conveying the erroneous idea that this fly is solely responsible for the spread of typhoid, but, considering that the creature is dangerous from every point of view and that it is an important element in the spread of typhoid, it seems advisable to give it a name which is almost wholly justified and which con- veys in itself the idea of serious disease. Another repulsive name that might be given to it is 'manure fly/ but recent researches have shown that it is not confined to manure as a breeding place, although per- haps the great majority of these flies are born in horse manure. For the end in view, 'typhoid fly' is consid- ered the best name." As a matter of fact this name has been adopted very generally. The newspapers took it up with avidity, and during the summers of 1909 and especially of 1910, many good journals conducted a constant ed- itorial campaign, almost every issue during the sum- mer months containing some reading matter calling attention to the danger of the creature and the ne- cessity of fighting it. It is undoubtedly true that peo- ple will fear and fight an insect bearing the name "ty- phoid fly" when they will ignore one called the "house fly," which they have always considered a harmless insect. So to gain the practical end the retention of the name "typhoid fly" seems by all means to be ad- visable. The only substitute suggested in the two years since this term has been adopted which ap- xviii THE HOUSE FLY— DISEASE CARRIER preaches it for suggestiveness and availability is the name "filth fly," proposed by Dr. C. W. Stiles, of the U. S. Public Health and Marine-Hospital Service. But "filth fly," while a nauseating name associated as it must be with the dinner tables of unscreened houses, carries simply the noisome idea and not the dangerous idea, and the latter is one that will induce people to fight. It will not be an easy fight. The species is firmly intrenched; it multiplies with startling rapidity, and its breeding places are everywhere. Improved sanitary methods in cities and the gradual disappearance in cities of horse stables, due to the rapid increase in the number of motor vehicles, are bringing about a de- cided lessening of the myriads of flies in the cities. In small towns, however, and in the country and at army posts, and especially in concentration camps, and wherever large bodies of men are brought together for temporary purposes in construction work, there is great need of intimate practical knowledge of the ty- phoid fly and of the measures to be taken against it. The residents of cities must also have this knowledge, but they need it less than the others. Acknowledgments of assistance from others will be made in the text from time to time. The writer wishes especially, however, to thank Prof. S. A. Forbes, Dr. C. W. Stiles, and Dr. B. H. Ransom for allowing him to use their very valuable but as yet unpublished notes on several aspects of the fly question. He wishes also to thank Mr. R. B. Watrous, Secretary of the INTRODUCTION xix American Civic Association, for access to his large correspondence on the fly crusade. He is also indebted to Mr. Gilbert H. Grosvenor, editor of the National Geographic Magazine, and to Mr. Robert Newstead, for permission to use certain illustrations which will be found properly accredited in the text. The House Fly— Disease Carrier ZOOLOGICAL POSITION, LIFE HISTORY, AND HABITS ZOOLOGICAL POSITION 'VOOLOGICALLY speaking, this insect belongs to 1-* the order Diptera, or two-winged flies. In this order it is the type of a superfamily known as the Mus- coidea, of a family known as the Muscidae and of the genus Musca, the specific name given to it originally by Linnaeus being domestica; and among zoologists it is referred to as Musca domestica L. The superfamily Muscoidea, to which it belongs and of which it is the type, is a very large group contain- ing a number of families and many species which so closely resemble the house fly that to the untrained eye they cannot be distinguished. Dr. David Sharp, in the Cambridge Natural History, writing of the house fly, states that "it sometimes occurs in large numbers away from the dwellings of man," and the writer is often asked to explain why parties camping in the Northwest, on the prairies for example, many miles away from human habitations, almost immediately find their camps infested with the house fly. The an- swer to such questions, and possibly the answer to the 2 THE HOUSE FLY— DISEASE CARRIER statement made by Doctor Sharp, is that the flies found under such conditions are not house flies, but some species closely resembling Musca domcstica. In the family Tachinidae, a group composed almost entirely of species which lay their eggs upon other living in- sects, there are many species which almost precisely resemble the gray-and-black-striped house fly. In the family Dexidae, of similar habits, there are also many which closely resemble the house fly. In the family Sarcophagidae, which includes most of the so-called flesh flies, the species of which either live in carrion or excreta or in dead insects or in putrid matter, and are occasionally parasitic, as with the species which breed in the egg-masses of grasshoppers, there are also many species hardly to ,be distinguished from Musca. There is another great family, the Anthomyidae, which has many species which closely resemble the house fly and give rise to many mistakes in identity. These insects in their early stages feed upon decaying vege- table matter and also to some extent upon growing plants, and a few prey upon the eggs of grasshoppers. Then, too, in the family Muscidae itself there are many genera of similar habits and similar appearance. The writer once, as a test, selected twenty distinct species from among these insects and carefully pinned them into a tray, asking chance visitors for several weeks to pick out the true house flies from among them. No one was ever able to distinguish between the different forms by looking at them with the naked eye. The habits of the different genera of Muscidae are ZOOLOGICAL POSITION 3 rather uniform, except that with a few of them the adults bite and suck blood, while the majority, like Musca domestica, do not. The tsetse flies of Africa, belonging to the genus Glossina, bite, as also do the stable flies of the genus Stomoxys and the cattle flies of the genus Hsematobia (this genus includes the so- called horn fly of cattle). Of the other genera, Graph- omyia, Morellia, Mesembrina, Pyrellia, Pseudopyrel- lia, and Phormia all breed in excrementitious matter. The genus Myospila, formerly placed in the Muscidse but really anthomyid, is also a breeder in this material. The flies of the genus Muscina breed in decaying vege- tation and in cow dung, as also do those of the genus Pollenia. Those of the genus Cynomyia and of the genus Calliphora and of the genus Lucilia breed in dead animal matter, while Chrysomyia inacellaria — the famous screw-worm fly — breeds in living flesh. Some of these flies are occasionally found in houses, and further consideration of them will be found in Chapter V. For practical purposes they are all equally dangerous, as possible disease carriers, and to the prac- tical person there is no especial need to distinguish among them ; but fortunately the house fly is the only one that comes in abundance to houses. It is the only one which really deserves the term domestic. For the two following paragraphs, which indicate the easiest method of distinguishing the house fly from any of its allies, I am indebted to Mr. D. W. Coquil- lett, an authority on the order Diptera : "From nearly all the other kinds of flies that resem- 4 THE HOUSE FLY— DISEASE CARRIER ble it, the house fly can be distinguished by having no bristles on the sides of the thorax above the attach- ment of the last pair of legs and by having the vein that ends near the tip of the wing distinctly elbowed, a short distance before its apex. Several different kinds of Tachinidae, Dexidae and Sarcophagidre have a superficial resemblance to the house fly, and, like it, have the elbowed vein, but all of them differ from the house fly in possessing a row of bristles above the point of attachment of the last pair of legs. The only other family containing species that might be mis- taken for the house fly is the Anthomyidae, but none of these has an elbowed vein. "In the foregoing paragraph I stated that the house fly can be distinguished from nearly all of the other kinds of flies that resemble it by the two characters mentioned. We have, in this country, a species agree- ing with it even in regard to the two characters given. Indeed the resemblance is so close that only an ex- amination under a lens or microscope will reveal the principal difference existing between these two spe- cies. I refer to Musca autiujiualis DeGeer.* In the male of this form the eyes are in contact on the upper part of the head, whereas in the male of the house fly the eyes are widely separated and the black stripe be- tween them is of nearly the same width throughout its length. In the female of autvmnalis the dark stripe between the eyes is only as wide as the added breadth of the narrowest part of the two gray stripes which *The Musca corvina Fabricius, 1781. ZOOLOGICAL POSITION 5 border it, while in the female of the house fly this dark stripe almost touches the eyes. Autumnalis, like its near relative, is almost cosmopolitan, but appears to have been rarely met with in this country." Possibly a simpler way of putting it would be as follows : Musca domcstica has four black lines on the back of its thorax. All Sarcophagidae have three such black lines. Most Tachinidee have four such black lines, but the Tachinidse have the bristle of the antennae smooth, whereas in Musca domestica this bristle is feathered. From all Anthomyidae, Musca domestica is at once separated by the bent vein near the tip of the wing. Moreover, Musca domestica has no bristles on the abdomen except at the tip which separates it from all others except some Tachinids and many An- thomyids, but from these it is separated by the char- acters given above. Musca domestica is not alone in its genus. There are fifteen species of the genus Musca according to Bezzi and Stein in their Catalogue of the Palearctic Diptera. In North America there are thirteen species of Musca, according to Aldrich. Of none of these other species of Musca do the habits appear to be known. There is, however, an Indian species, Musca cntccniata, which breeds in the same fecal masses with the typhoid fly. 6 THE HOUSE FLY— DISEASE CARRIER LIFE HISTORY A long experience with the study of insects has in- dicated the somewhat remarkable fact that it is about the commonest things in general that we know the least. When Mr. C. L. Marlatt and the writer began in 1895 to work on the subject of household insects, we discovered that very few of the species found so abundantly in households were included in the museum collections. There would be a large series of a rare beetle from Brazil, but no specimens of the common house cockroach, for example ; and when we began to look into the literature of their life histories we learned that published accounts of their transformations were even more scarce than the specimens in the collections. Doctor Hewitt (1910) calls attention to the vision of Sir James Crichton Browne of the aged person show- ing the wondering child the only existing specimen of the house fly, in the British Museum. This was in- tended as a prophecy, but it would not be surprising if before the recent house fly crusade began there really was only one specimen of the house fly in the British Museum. With this condition of affairs existing in general, it is perhaps not so surprising that an exhaustive study of the conditions which produce house flies in numbers has really never been made. The life history of the insect was, down to 1873, mentioned in only a few old European works and one more modern one (Taschen- LIFE HISTORY 7 berg).* In 1873, Dr. A. S. Packard (1874), then of Salem, Mass., studied the transformations of the in- sect and gave descriptions of all the stages, showing that the growth of a generation from the egg to the adult state occupies from ten to fourteen days. In 1895, the writer traced the fly's life history, discover- ing that 120 eggs are laid by a single female at a time and that in Washington in midsummer a generation is produced in ten days. Substances in Which This Fly Passes Its Early Life It is safe to say that the typhoid fly will breed in almost any fermenting organic matter, and it is also probably safe to say that if given its preference it will lay its eggs on a pile of horse manure. The writer once estimated that under ordinary city and town con- ditions more than ninety per cent, of the flies present in houses have come from horse stables or their vi- cinity, and he is still inclined to think that this esti- mate is probably correct. But the eggs will also be laid upon the excreta of almost any animal. Cow manure drying rapidly in a dry season and forming a hardened caked surface is not a favorable nidus, yet this fly is reared from cow manure at times. Many other species of flies prefer cow manure, and a long list of *The best of these old papers is little known. It was published at Nurenberg in 1764, and is entitled "Geschichte der gemeinen Stubenfliege, Herausgeben von J. C. Keller" and covers thirty- four pages of text and four plates. The real author is said by Hagen to be Freiherr Friedrich Wilhelm von Gleichen (genannt Russworm). 8 THE HOUSE FLY— DISEASE CARRIER species reared from this substance has been published by the writer (1901). The typhoid fly is, possibly next to horse manure, attracted to human excreta, and not only visits it wher- ever possible for food, but lays its eggs upon it and lives during its larval life within it. It will not only do this in the latrines of army camps, in the open box privies of rural districts and small villages, but also upon chance droppings in the field or in the back alley- ways of cities, as has been repeatedly shown experi- mentally in Washington. It may very readily happen that the flies of any given neighborhood have come from a single source, and that the substances in which they breed differ accord- ing to locality and according to the supply of breed- ing substance. Under ordinary city conditions, un- doubtedly the most frequent nidus is in the horse manure of stables, but when the conditions in a com- munity of a radically different nature are studied the result is sometimes surprising. In the course of his investigations of conditions in small towns with espe- cial reference to the hookworm disease, Stiles has found that in cotton-mill towns, for example, the privies may be a much more important breeding place of flies than the manure piles, not only more important since flies breeding in this substance are more likely to carry disease germs, but also numerically more important; for you may have 250 uncared-for privies and perhaps only one or even no manure pile. And there are com- munities also where horses are scarce and pigs are LIFE HISTORY 9 numerous. Stiles has seen great accumulations of pig manure fairly swarming with fly larvse. With regard to ordinary kitchen refuse, such as is found in the garbage pail, it is the opinion of Prof. J. S. Hine, of the Ohio State University, who has paid much attention to the subject, that, while house flies visit garbage in numbers, they appear in most cases to be after food only, as only a few specimens of this species were reared from such material during the sea- son when he was at work. With fermenting vegetable refuse from the kitchen, he found that the very common fly which bred in it was not the typhoid fly, but Muscina stabulans, the so- called stable fly. Hundreds of these flies were reared and their larvae were exceedingly abundant in all of the samples of garbage examined. Musca domestica was also reared, as was also another species known as Phormia regina, but it seems from these observations, although they were limited to a single locality in Cen- tral Ohio, that the recently acquired general opinion to the effect that the typhoid fly breeds abundantly in vegetable refuse when it has reached the proper fer- menting stage is due many times to the mistake of considering the stable fly and its larvae as those of M. domestica. And this is an important point, since the stable fly is rather rarely found in houses and on food and therefore is not an important carrier of disease. The substances in which flies will breed were care- fully investigated in the city of Liverpool by Mr. Rob- ert Newstead, lecturer in economic entomology and 10 THE HOUSE FLY— DISEASE CARRIER parasitology in the School of Tropical Medicine of the University of Liverpool in 1907. Mr. Newstead is of the opinion that the chief breeding places of the house fly in Liverpool should be classified under the follow- ing heads: (i) Middensteads (places where dung is stored) containing horse manure only; (2) Midden- steads containing spent hops; (3) Ash pits containing fermenting materials. He found, as has been the ex- perience of observers in this country and India, that the dung heaps of stables containing horse manure only were the chief breeding places. Where horse and cow manures were mixed the flies bred less numer- ously, and in barnyards where fowls were kept and al- lowed freedom comparatively few flies were found. Only one midden containing warm spent hops was in- spected, and this was found to be as badly infested as any of the stable middens. A great deal of time was given to the inspection of ash pits, and it was found that wherever fermentation had taken place and arti- ficial heat had been thus produced such places were infested with house fly larvae and pupae, often to the same extent as in stable manure. Such ash pits as these almost invariably contained large quantities of old bedding or straw and paper, paper mixed with hu- man excrement, or old rags, manure from rabbit hutches, etc., or a mixture of all of these. About twenty-five per cent, of the ash pits examined were thus infested, and house flies were found breeding in smaller numbers in ash pits in which no heat had been engendered by fermentation. The typhoid fly was also LIFE HISTORY 11 found breeding by Mr. Newstead in certain temporary breeding places, such as collections of fermenting vege- table refuse, accumulations of manure at the wharves and in bedding in poultry pens. Mr. F. V. Theobald states that swarms of flies are reported to breed in the huge masses of dust-bin refuse in certain London sub- urbs. It does not appear to be certain, however, that these are Musca domestica. In India, according to the observations of Surgeon Major F. Smith, of the Royal Army Medical Corps, horse manure is the most abundant breeding place for the house fly around military stations. He also reared this fly from cow dung in company with Musca entaniata. DeGeer states that the larvae of this species live in dung, but only in that which is warm and moist, or, stated better, which is in a condition of perfect fermen- tation. The importance of the factor of fermentation has already been referred to in the account of Mr. Newstead's observations and is insisted upon by Dr. C. Gordon Hewitt in Part II of his important paper on the Structure, Development and Bionomics of the House Fly. He points out that Keller, writing of this fly in 1790, reared the larvae of the typhoid fly in de- caying grain, where no doubt fermentation was taking place; also in small portions of meat, slices of melon, and in old broth. Doctor Hewitt also found that horse manure is preferred to all other substances by the fe- male flies for egg-laying. He also found that the lar- vae will feed upon paper and textile fabrics, such as woolen and cotton garments and sacking which were 12 THE HOUSE FLY— DISEASE CARRIER foul with excremental products, if they were kept moist and at a suitable temperature. He also reared adult flies from decaying vegetables thrown away as kitchen refuse, and on such fruits as bananas, apricots, cherries, plums, and peaches, which were mixed when in a rot- ting condition with earth to make a more solid mass. He succeeded in rearing them in bread soaked in milk and boiled egg and kept at a temperature of 25° C, but he was unable to rear them to maturity in cheese. The preference which the typhoid fly has for horse manure as a breeding nidus has been clearly shown by a multitude of observations. One of the early ex- periences of the writer consisted in an effort to keep the stables of the U. S. Department of Agriculture at Washington in a strictly sanitary condition. The ma- nure was swept up and placed each day in a screened closet. As a result there was a notable diminution of flies in all of the buildings for hundreds of yards around for several weeks ; whereas up to the time when the experiment began they had been a nuisance through- out that portion of the city. One of the many letters received which bear upon this point may be quoted : WASHINGTON, D. C, February 10, 1908. "DR. L. O. HOWARD, Department of Agriculture, Washington, D. C. "DEAR DR. HOWARD: "For the greater part of the last two years I have oc- cupied a room on the third floor of the Faculty Club on the Campus of the University of California at Berkeley, Calif. During most of the time the number of flies in LIFE HISTORY 13 the Club House has been notably small, considering the fact that the Club maintains a dining-room and its win- dows and doors are not screened. A year ago last fall there was a sudden incursion of flies, so that they created much annoyance in all parts of the Club House ; and they were specially abundant in my room. I protected my windows by screens, and then captured the flies on sticky fly paper, securing in that way more than 2,000. The nuisance in other rooms continued several weeks longer, and then gradually abated. There was no recurrence at the corresponding season last fall. "Recalling some statements of yours with reference to the life history of the house fly, I noted that the epidemic was coincident with the grading of the University ath- letic field, about 200 yards from the Faculty Club, and that in that grading many horses were employed, probably as many as fifty. So far as I am aware there are no horses stabled on the University campus, and I do not recall having seen any horse stables at a less distance than two blocks, or, say, three times the distance of the athletic field. These various relations of time and space serve to connect the local fly epidemic in a fairly definite way with the temporary proximity of a large number of horses. "Yours very truly, "G. K. GILBERT." In an article entitled "Experiments on Transmission of Bacteria by Flies with Especial Relation to an Epi- demic of Bacillary Dysentery at the Worcester State Hospital," Dr. Samuel T. Orton (1910), after describ- ing a series of very interesting experiments indicating the spread of a species of bacillus throughout the in- stitution by the agency of flies, describes a search made to discover the breeding places of the unusual number of flies infesting the hospital. Searching first for horse 14 THE HOUSE FLY— DISEASE CARRIER manure, he found that there were only two such ac- cumulations on the hospital grounds. The one at the stable was in a large masonry pit drained below and covered so that while not fly-proof it was dark and dry. No larvae or puparia were found in the pit. The ma- nure was molding and heating rapidly. Two other piles where the manure was kept dry and in the dark showed the same condition of rapid heating and mold- ing and no larvae were found. At the farm barn the manure was dropped through four traps where a pile accumulated, and was then taken to the part of the barn where the cow manure is collected and the two were mixed together. Here a considerable number of larvae and puparia were found, but not in sufficiently great numbers to account for the swarms around the buildings. They were more abundant in the part of the pile which consisted of pure horse manure and grew noticeably less until the cow manure was reached, when they were very few. Examination of the pig pen showed piles of pig manure mixed with the straw bedding exposed to air and rain. This was badly in- fested ; one ounce of material taken from a point a few inches below the surface displayed 868 puparia. An- other prolific source was found in piles of spent hops and barley malt — brewery waste which had been hauled in as a fertilizer. The hops showed a tendency to mold rapidly, and the flies did not breed in it as abundantly as in the looser barley malt. In parts of the malt where there was plenty of moisture the maggots were ex- tremely numerous; one ounce contained 1,018 mag- LIFE HISTORY 15 gots. There had been considerable rain and the piles were damp throughout. At one place there was a layer of six or eight inches of soggy barley over the ground, which was simply crawling with larvae. After six days of continued dry weather, however, they had practically all disappeared. An interesting experiment was made. One pound of material from each of the breeding places was taken to the laboratory and kept in screen-covered glass jars for ten days, with the following result: Stable manure o adult flies issued Farm barn, horse end .... 77 Farm barn, mixed 19 Farm barn, cow end I Piggery manure pile 361 Spent hops 129 Barley malt 539 fly flies These results as recorded are very interesting and are probably in the main correct, although Doctor Or- ton states that the identification of species was by no means thorough and the determination of the house fly was made simply by observation of its size and gen- eral appearance and the characters of the mouth parts. It is possible that the stable fly (Muscina stabulans) may have formed a portion at least of the flies bred from the spent hops and the barley malt. There is a statement in Taschenberg's Praktische Insektenkunde to the effect that the female house fly lays its eggs not only upon spoiled and moist food- stuffs, decaying meat, meat broth, cut melons, dead animals, manure pits, manure heaps, but even in cus- 16 THE HOUSE FLY— DISEASE CARRIER pidors and open snuff-boxes. The entomological world has accepted the statement, with, however, some doubt as to the snuff-boxes. Prof. S. A. Forbes, however, informs the writer that August 22, 1889, ne received from an old friend, T. A. E. Holcomb, then a druggist at Kensington, 111., a box of snuff containing dipterous larvae. From these dipterous larvae Professor Forbes bred the true house fly. His recollection of the matter is very clear, and he has now in his collection a very under-sized specimen labeled Musca domcstica and bearing an old pencil label in his handwriting, "Snuff, August 26th." He afterwards called upon Mr. Holcomb in his drug store and learned that among his constant customers were some old foreigners who came so frequently t<> have their snuff-boxes filled that for convenience in serving them he was accustomed to keep an open box of snuff upon one of his show-cases, and from this box the specimens came. A very important series of observations was carried on under the direction of Professor Forbes in the sum- mers of 1908-1909 by his assistants, Mr. A. A. Girault, at Urbana, and Mr. J. J. Davis, in Chicago, for the pur- pose of ascertaining exactly what other substances aside from horse manure will serve as breeding places for house flies. The results of these observations, not previously published, have been placed at the writer's disposal by Professor Forbes. They constitute a very valuable addition to our knowledge on this subject. It was a surprise to find that nearly a thousand flies had LIFE HISTORY 17 been reared from cow dung. This dung was in a stable, and it is to be presumed that the conditions were such that the dung did not dry readily and that there was no preferred food in the immediate vicinity. Precon- ceived notions are also somewhat upset by the rearing of 267 flies from carrion found in the street. The list as a whole is of the greatest practical interest and is asfollows: Number house Date Media flies bred Sept. 1-3 Rotten water-melon and muskmelon 14^ Aug. 18 and Sept. 8-1 1 Rotten carrots and cucumbers 23 -" Sept. 7 Rotten cabbage stump i - Sept. 7 Banana peelings i^~ Aug. 30 Rotten potato peelings 12 "" Sept. 25 Cooked peas i - Oct. i Ashes mixed with vegetable wastes. i Sept. 7-14 Rotten bread or cake 8 "" Aug. 22 Kitchen slops and offal 193 ^ Sept. 10-26 Mixed sawdust and rotting vege- tables 41 / Aug. 3O-Sept. 4. . Old garbage, city dump 15 Aug. 14 and 18.. Rotten meat, slaughter houses . . 40 Aug. 3o-Sept. ii. Carrion in street 267 Sept. 7 Seepage from garbage pile i Aug. 17-20 Hogs' hair, slaughter house waste.. 9 Aug. 23-28 Sawdust sweepings, Stock Yards slaughter house no Aug. 23 Sawdust sweepings, meat market... 4 Aug. 16-28 Animal refuse, Stock Yards 39 Aug. 14 Contents of paunches of slaugh- tered cattle 168 Sept. 2- 1 1 Rotten chicken feathers 258 Aug. 16 Chicken manure, stock-car dump. ... 3 Aug. 3i-Sept. 7. .Cow-dung, stable, Urbana 997 Sept. 7-10 Cow-dung, outdoor yard 22 Sept. 6 Cow-dung, pasture i Aug. 24-Sept. 16. Human excrement 196 18 THE HOUSE FLY— DISEASE CARRIER The Egg The eggs are minute and glistening white, and they are all long ovoid in shape. In length they vary from one-sixth of an inch to a little longer. They are laid in clusters of small size and irregular shape, either on their ends or on their sides. Seen under a high power of the microscope, the polished surface appears to be cov- ered with minute hexagonal markings such as is seen in what the histologist calls pavement epithelium. Each female fly lays on the average 120 eggs, or perhaps more, at a time and may lay several times. Forbes' s assistants in Illinois found that eggs from a single fly vary from 120 to 150 in each deposit and that as many as four deposits may be made, or say, 600 eggs by a single fly (in lit.). One hundred and twenty was the number observed by the writer to be the average num- ber, but Doctor Hewitt has counted as many as 150. The duration of the egg stage, as observed in Wash- ington, was usually eight hours; that is to say, eight hours after it was laid the egg hatched. These ob- servations were made in midsummer and have not been repeated at other times of the year. Mr. Newstead in Liverpool found that the eggs hatched in periods vary- ing from eight hours to three or four days, the average time being about twelve hours. But he noted that when laid in fermenting materials the incubation period was reduced to a minimum of eight to twelve hours. In a temperature of from 75° F. to 80° F. they hatched in from eight to twelve hours; in a temperature of 60° Fig. i. — Eggs, approximately natural size; photographed on surface manure pile. (From Newstead.) ERRATUM p. 18, line 3, one-sixth should be one-twentieth the microscope, the polished surface appears to be cov- ered with minute hexagonal markings such as is seen in what the histologist calls pavement epithelium. Each female fly lays on the average 120 eggs, or perhaps more, at a time and may lay several times. Forbes' s assistants in Illinois found that eggs from a single fly vary from 120 to 150 in each deposit and that as many as four deposits may be made, or say, 600 eggs by a single fly (in lit.). One hundred and twenty was the number observed by the writer to be the average num- ber, but Doctor Hewitt has counted as many as 150. The duration of the egg stage, as observed in Wash- ington, was usually eight hours; that is to say, eight hours after it was laid the egg hatched. These ob- servations were made in midsummer and have not been repeated at other times of the year. Mr. Newstead in Liverpool found that the eggs hatched in periods vary- ing from eight hours to three or four days, the average time being about twelve hours. But he noted that when laid in fermenting materials the incubation period was reduced to a minimum of eight to twelve hours. In a temperature of from 75° F. to 80° F. they hatched in from eight to twelve hours; in a temperature of 60° Fig. i. — Eggs, approximately natural size; photographed on surface of manure pile. (From Newstead.) Fig. 2. — Eggs, approximately natural size. (From Newstead.) LIFE HISTORY 19 R, in twelve hours, but at 45° F. they did not hatch until the third day, and then only when placed in a warmer temperature for the purpose of studying them under the microscope. Doctor Hewitt has carefully observed the hatching of the eggs, and this is a process which has now be- come familiar to many Americans through the excel- lent moving-picture exhibitions given under the auspices of the American Civic Association from films prepared in England at the expense of Mr. Daniel Hatch, Jr., m Fig. 5.— Egg of house fly; greatly enlarged. (Original.) Chairman of the Fly-fighting Committee of the Asso- ciation. Doctor Hewitt's description follows : "A minute split appeared at the anterior end of the dorsal side to the outside of one of the ribs [refer- ring to two distinct curved rib-like thickenings along the dorsal side of the egg] ; this split was continued posteriorly and the larva crawled out, the walls of the chorion [the eggshell] collapsing after its emergence. The Larva We have just described how the egg hatches. The young larva as it issues from the egg is a slender 20 THE HOUSE FLY— DISEASE CARRIER creature tapering from the blunt, round, hinder end to the pointed head end. It is glistening white in color and only about two mm. in length. It is ex- tremely active and burrows at once into the substance upon which the egg from which it hatched had been laid, rapidly disappearing from sight. In the course of its growth it casts its skin twice, and therefore passes through three distinct stages of growth. In the first one the anal spiracles, or breathing holes, on the last segment, are contained in a heart-shaped aperture. After the first molt these spiracles issue in two slits, and after the second molt there are three winding slits. In the third and last stage the larva is still white, sometimes appearing yellowish. It is slender and taper- ing in front, large and truncate behind. The head has a tiny papilla on each side. There is one great hook above the mouth orifice. On each side of the pro- thorax there are spiracles which show six or seven lobes. On the ventral base of the sixth and following segments there is a transverse fusiform, swollen area provided with minute teeth. The anal area is only slightly prominent, and shows two processes close to- gether. The anal spiracles are prominent, less than their diameter apart, and each with three sinuous slits and a button at the base. In some cases two of the winding slits are apparently connected together. With- in the head, or rather the anterior part of the body, is a chitinous framework consisting of several articu- lated parts called the cephalopharyngeal skeleton, which is indicated in figure 7. Fig. 3. — Eggs, greatly enlarged. (From Newstead.) Fig. 4. — Eggs, greatly enlarged — another view. (From Newstead.) LIFE HISTORY 21 The rate of growth of the house fly larva varies ac- cording to temperature in much the same way as does the period of duration of the egg stage. In the writ- er's original observations in midsummer in Washing- ton he found that the time from the hatching to the first molt was twenty-four hours ; from the first molt to the second molt twenty-four hours; from the second molt to transformation to pupa seventy-two hours ; mak- ing the duration of larval life five days. The larvae are very active and migrate from place to place in a ma- nure pile with facility. Mr. Newstead in Liverpool ob- served that they mature in the shortest period in fer- menting materials in a temperature of between 90° and 98° F., but that they usually leave the hotter por- tions of the stable manure when it reaches a temper- ature of from 100° to 110° F. At 54° F. the larval stage was considerably prolonged, and larvae kept at that temperature had not matured at the end of eight weeks. Doctor Hewitt at Manchester, England, showed that larvae of the first stage might molt as early as twenty hours after hatching, but that from twenty-four to thirty-six hours usually elapsed before ,the first molt. Under favorable conditions of temperature larvae in this stage remained three days without molting. In molting he noted that the skin was shed from the head and posteriorly, and that not only the skin was shed, but also the cephalopharyngeal sclerites, as well as the chitinous lining of the fore portion of the alimentary tract. He observed that the second stage of the larvae 22 THE HOUSE FLY— DISEASE CARRIER might last only twenty-four hours, but at a lower tem- perature or with a deficiency of moisture the period was prolonged and might take several days. The third stage occupied as a rule between three and four days. At all times the larvae are very active. When their breeding place is disturbed they wriggle actively about in the endeavor to conceal themselves, and so rapidly do they accomplish this purpose that it is difficult to take a satisfactory moving picture of them, or indeed a photograph of any kind. When full-grown and ready to transform, the yellowish color becomes more pronounced, owing to the proliferation of fat cells in great numbers in anticipation of the resting, non-feed- ing pupal condition. The transformation to pupa may take place almost anywhere, but as a rule there is an effort on the part of the larvae to descend deeper into the manure pile or other substance in which they may be living, and sometimes, when the substance upon which they have fed is moist and the earth below it is also moist and easy of entrance, they may descend two or three inches below the surface of the ground. The only good word that can be said for this fly is the fact that its larvae destroy enormous quantities of excrementitious and waste material, greatly assisting the bacteria of putrefaction. E. Guyenot (1907) shows, first, that the liquefaction of albuminoid sub- stances is the result of a true process of digestion un- der the influence of certain germs of putrefaction; second, that fly larvae, absorbing exclusively liquid substances, easily assimilable, have the digestive tract Fig. 6. — Egg hatching; greatly enlarged. (Original.) c Fig. 7. — Full grown larva of house fly ; greatly enlarged : a, anal spiracle ; b, side view of larva ; c, cephalo-pharyngeal skeleton ; d, same ; e, anal spiracle still more enlarged. (Original.) LIFE HISTORY 23 reduced to the minimum and do not produce soluble ferments in appreciable quantity; third, that the larvae accelerate putrefaction of bodies by assisting in the increase of microbes; fourth, that the larvae nourish themselves at the expense of the products of germ chemistry — the germs can develop rapidly and spread in all directions only by the assistance of the larvae; there exists between these two agents of putrefaction a true symbiosis. These conclusions, although reached by a study of two species of the genus Lucilia, are un- doubtedly applicable to the larvae of other flies feeding in animal material. The Pupa and Puparium Before beginning its transformation to the pupa, the full-grown larva empties its alimentary canal, con- tracts from its own skin, the skin itself forming a nearly cylindrical pupal case, the posterior portion be- ing slightly larger in diameter than the anterior and both ends being equally rounded. It is then about six mm. in length and of the shape shown at figure n. At first this pupal skin remains pale yellowish, but rapidly changes to red and finally to a dark chestnut color. The insect inside loses its tracheal system, which is withdrawn by the surrounding skin and eventually remains inside of the skin or pupa shell but outside of the insect itself. The insect rapidly assumes a true pupal shape, and at the end of thirty hours, according to Doctor Hewitt, most of the parts of the future fly can be distinguished, although they are sheathed in a pro- 24 THE HOUSE FLY— DISEASE CARRIER tecting nymphal membrane. A fully formed pupa taken from the pupal sheath, or puparium as it is called, is shown in figure n. In this stage in Washington in midsummer the writer has shown the normal duration to be about five days. Mr. Newstead gives the period as from -five to Fig. ii. — House fly puparium (at left) and pupa (at right) ; greatly enlarged. (Original.) seven days in cases where there is heat produced by fermentation, but where there is no such heat the stage may last from fourteen to twenty-eight days, or even considerably longer. Doctor Hewitt states that with a constant temperature the adult flies may emerge be- tween the third and fourth day after pupation, but that the period is more usually four or five days, since the larvae when ready to pupate as a rule leave the hotter Fig. 8. — Larvae in horse manure. (From Newstead.) Fig. 9. — Larvae and puparia. (From Newstead.) LIFE HISTORY 25 portions of the substance in which they have been feed- ing and transform in the cooler portions. He sug- gests the idea that this migration outward may be a provision for the more easy emergence of the fly when the time should come. In some cases he found that the pupal stage lasted through several weeks, but he was never successful in keeping pupae through the winter. Mr. Newstead found that in stable middens the puparia occur chiefly at the sides or at the top of the wall or framework of the receptacle where the temperature is lowest. He found them in such situations often packed together in large masses numbering many hundreds. In ash pits he found the same conditions. Where the manure is in small piles, or is partly spread out, the full-grown larvae almost ready for transforma- tion are apt to migrate into the loose ground under the pile or from the edges of the pile outwards, to trans- form under nearby rubbish. This habit may have a very important practical value, since municipal regu- lations of individual stable practice in regard to the removal of manure should take into consideration that such removal at intervals longer than those required for the larva to reach full growth may result in the leaving of many puparia, except of course in cases where especial receptacles for manure are in use. Emergence of the Adult This has been well described by Doctor Hewitt as follows : "When about to emerge, the fly pushes off the an- 26 THE HOUSE FLY— DISEASE CARRIER terior end of the pupal case in dorsal and ventral por- tions by means of the inflated frontal sac, which may be seen extruded in front of the head above the bases of the antennae. The splitting of the anterior end of the pupal case is quite regular, a circular split is formed in the sixth segment and two lateral splits are formed in a line below the remains of the anterior spiracular processes of the larva. The fly levers itself up out of the barrel-like pupa [puparium] and leaves the nymphal sheath. With the help of the frontal sac, which it al- ternately inflates and deflates, it makes its way to the exterior of the heap and crawls about while its wings unfold and attain their ultimate texture, the chitinous exoskeleton hardening at the same time; when these processes are complete the perfect insect sets out on its career." The frontal sac just mentioned is the distended mem- branous portion of the front of the head. This is con- stantly distending as the fly walks rapidly about after issuing. When it is contracted at this early time, it forms a dull area, soft and fleshy-looking, and free from hairs. The fly possesses the power of distending it into a bladder-like expansion, trapezoidal in outline and almost as big as the rest of the head, pushing the antennae down out of sight. This membrane is evi- dently distended with air, and, as pointed out by Pack- ard, its connection with the tracheae and the mechanism of its movements would form a very interesting sub- ject of inquiry. Lowne, in his Anatomy of the Blow- fly, has described a similar structure with that insect, Fig. 10. — Puparia on a bit of old rotting cloth from an ash barrel. (From Newstead.) LIFE HISTORY 27 and he is obviously correct in supposing it to be a pro- vision for the pushing away of the end of the puparium when the pupa emerges from its case. This frontal sac has been noticed by many observers, and was well described as long ago as 1764 by Count von Gleichen. Structure of the Adult In the section on zoological position, a description has been given of the characters which separate the adult typhoid fly or house fly from other allied or sim- ilar flies. The excellent illustrations given here (fig- ures 12 and 13) show in more or less detail its exact structure. 'Especial attention should be called, how- ever, to the character of the mouth parts and of the feet. The whole insect is more or less bristly and well capable of carrying micro-organisms from putrescent or semi-liquid substances, but the mouth parts and the feet are especially adapted to this purpose. In addition to two claws, each of the six feet is supplied with two sticky pads of a light color. These are called pulvilli. On the walking surface these pads are closely covered with hairs which secrete a sticky fluid, and it is by their help that flies are able to walk in any position upon highly polished surfaces. The mouth parts are very complicated, but form in the main a proboscis which is not fitted for piercing but for sucking and is illustrated so well in figure 15 that detailed description will be unnecessary. This organ can be retracted and expanded to a certain extent. It is somewhat complicated in structure and consists 28 THE HOUSE FLY— DISEASE CARRIER of an upper and a lower portion, the upper portion bearing two curved bristly lobes. The lower portion or true haustellum expands at the tip into two lobes which are called the oral lobes. On their under sur- face they have transverse chitinous bars which are called false tracheae (pseudotracheae). The presence of these hard ridges under the oral lobes fit it to a certain extent for rasping solid food. The orifice to the haustellum occurs between the lobes. In feeding upon fluid or semi-fluid substances, the oral lobes are simply applied to the surface and the fluid is sucked up. When, however, they feed upon soluble solids the process is somewhat different. Doc- tor Graham-Smith has carefully watched them feeding upon crystals of brown sugar, and has done this through the Zeiss binocular microscope. He states that the oral lobes of the proboscis are very widely opened and closely applied to the sugar. Fluid (saliva) seems to be first deposited on the sugar and then strong suck- ing movements are made. Doctor Graham-Smith watched a fly sucking an apparently quite dry layer of sputum. It put out large quantities of saliva from its proboscis and seemed to suck the fluid in and out until a fairly large area of the dry layer of sputum was quite moist; then as much as possible was sucked up and the fly moved away to another spot. The same observer noticed that flies which had the opportunity of feeding either on fluid or partly dried milk often chose the drier portions, and states that under natural conditions they can often be seen sucking the dried LIFE HISTORY 29 remains near the top of a milk jug. They constantly apply their mouth parts to the surface over which they are walking, attempting to suck up some nutrition, and under certain conditions the imprints of their oral lobes can afterwards be made out under the lens. In order to understand the digestive processes of a fly and to comprehend fully just what a disease germ Fig. 16. — A diagrammatic figure of tjie alimentary canal of the house fly ; greatly enlarged. Ph., Pharynx ; Oes., Esophagus ; P. Ven., Proventriculus; Ven., Stomach; F. Int., Fore intestine; H. Int., Hind Intestine; Cr., Crop; Rect., Rectum. passes through after it is sucked up by one of these creatures, it is necessary to know something of the structure of the alimentary canal. This is simpler with the house fly than with many other flies, more so in fact than that of the blow fly, whose anatomy was so carefully worked out by the famous English micro- scopist, Lowne. It consists of a pharynx, a rather narrow esophagus, a proventriculus or chyle stomach, a crop, a ventriculus or true stomach, a fore and a hind 30 THE HOUSE FLY— DISEASE CARRIER intestine. The proventriculus is a nodular structure with muscular walls and probably acts also as a pump- ing stomach. The food, passing through the esophagus into the proventriculus, immediately goes by an almost continuous route into the crop. The tube leading into the crop leads out from the proventriculus on the under side backwards and ends in the crop itself, which is a double organ situated in the lower part of the abdomen of the fly. This crop is really a temporary storehouse for the fly's food, and in this storehouse it remains practically unchanged, as has been proved by exact experimentation. Returning from the crop, possibly pumped back by the muscular walls of the proventricu- lus, it recedes again into the true stomach or ventricu- lus, which is a somewhat expanded tubular organ run- ning fore and aft and situated above the tube leading to the crop. The stomach proper extends back through the thorax under the big muscles of the back and into the abdomen, where it ends just over the point where the crop begins to dilate. It runs into the rather nar- row fore intestine, which con volutes upon itself four or five times, and ends in the hind intestine, which in turn ends in the rectum. The intestine is called the hind intestine from the point where the Malpighian or urinary tubules enter. Naturally the structure and function of the crop and the proventriculus are matters of considerable in- terest in considering the distribution of disease germs by flies. As Graham-Smith points out, the crop is first distended with liquid food at the beginning of a meal, Fig. 14.— Head of adult house fly; greatly enlarged. (Photograph by N. A. Cobb. Copyright by National Geographic Society of Washington, D. C.) Fig. 15. — Head of adult house fly from side; greatly enlarged. (Photo- graph by N. A. Cobb. Copyright by National Geographic Society of Washington, D. C.) LIFE HISTORY 31 and, if after this the fly continues to feed, the food may pass directly into the true stomach through the chyle stomach. If the fly is disturbed before any of the food has entered the stomach, the food which has been sucked into the crop is gradually passed into the stomach. Eventually the contents of the crop get into the intestine. The proventriculus seems to act also as a valve and be capable of closing the orifice into the stomach so that the food shall all pass into the crop. \Yhen the crop is fully distended it opens so that food can pass directly into the stomach, and naturally also opens later to allow the food to pass from the crop forward and back. Careful observations made by this author indicated the rate at which food passes from the crop into the intestine, in which he showed that, using colored fluid, after three minutes the crop was full of red fluid, but none was found in the stomach or intestine. After ten minutes the fluid was just beginning to pass into the stomach. After fifteen minutes the crop was still full and the upper third of the stomach was full. After two hours in one case the crop was still full and the upper three-fourths of the intestine was full. Other observations indicated that the crop may remain full, after a single feeding, for as long as four days, thus acting as a storage reservoir against any possible scar- city of food. Some interesting observations were also made by the same author on the habits of flies after feeding on dif- ferent fluids. These observations were made in cages, 32 THE HOUSE FLY— DISEASE CARRIER and he found that after gorging themselves they usually climbed up the sides of the cage and moved from place to place, often stopping to rub one leg against another or to clean themselves by passing the legs over their heads and wings. At intervals he noticed that they sat still and regurgitated large drops of liquid from the tips of their beaks. He showed that the drops gradually enlarged until they were about equal in size to the head of the fly. Sometimes the drop was de- posited, sometimes slowly withdrawn, and this occurred several times. When disturbed, the drops were de- posited or withdrawn with great rapidity. Flies were often seen to suck up the drops deposited by other flies. It is these regurgitated drops which make the larger stains upon a window covered with fly-specks. Attention should be called to the shape of the com- pound eyes of the fly, and it will be noticed that they are so situated that a fly can see in all directions at the same time. Difference in Size of Adults There is a considerable difference in the size of the adult winged flies, but this by no means signifies that small adult flies grow into large ones. This is a wide- spread popular fallacy. The writer once in his younger days attended a meeting of the Philosophical Society of Washington to listen to a paper by the late C. V. Riley on some phases of insect life, in the course of which the house fly was incidentally mentioned. With his entomological training, he was amazed in the dis- LIFE HISTORY 33 cussion which followed to hear one of the most emi- nent of America's scientific men (an astronomer, by the way) ask Professor Riley, "It is true, of course, is it not, that the little flies one occasionally sees on the window-pane grow and become the large flies that are so numerous?" No fly, after it issues from the puparium,. grows at all ; no insects grow after the last molt ; in fact, insects can grow only by casting their skins, and none of the insects having what is called a perfect metamorphosis casts the skin after reaching the imago or winged stage. But some typhoid flies are larger than others, and the explanation is a different one from that of the growth of the winged form. The same thing is seen with other insects, and it results as a rule from the amount of larval food ; certain larvae stinted in their supply of food transform to pupae when small and nat- urally become small adults. There is a distinct con- nection with them, as with human beings, in stint and stunt, aside from the similarity of the words and their origin. With the house fly, however, some exact observa- tions have been made on this point by Griffith (1908) and Packard (1874). Griffith found that when the larvae were kept cool and the pupae warm all the flies that came out were small. In fact, he found that it was a rule that cold surroundings, even with plenty of food, produced small flies. And he further states that such small flies are incapable of reproduction. He 34 THE HOUSE FLY— DISEASE CARRIER points out that small flies are found at the end of sum- mer when it has become cooler, and also in the early spring, the latter having hatched late the previous au- tumn. The question of the hibernation of flies will be considered in a later paragraph, but in this connection it should be stated that Doctor Griffith secured repro- duction in the late autumn and winter, but that all of the resulting flies were of small size, though their lar- vae were kept at a warm temperature. The flies from only one of these batches were of normal size, while those in one set were "extremely small, quite pigmies ; and these died from no Apparent cause, probably from marasmus, after a month." He further states that from the same batch of eggs he has reared large, me- dium and small flies. Packard ( 1874) found that those larvae which were reared in too dry manure were nearly one-half smaller than those taken from the ma- nure heap. No direct warmth and the absence of mois- ture seemed to cause them to become dwarfed. The error of deduction made by the famous astron- omer was by no means an error of observation, as ap- pears from what precedes, but there are found in houses other flies of entirely different species from the house fly, as will be shown in another chapter. Some of these are considerably smaller, and one of them, the little fly often seen on window-panes (Homalomvui canicularis), is very much smaller. In fact, as though to perpetuate the error, the Germans call this last spe- cies "die kleine Stubenfliege" — the little room fly or house fly. LIFE HISTORY 35 Summary of Duration of Life Round In summarizing the duration of the life round, we find that the writer's Washington observations made the total life round approximately ten days, as indi- cated in an earlier paragraph. These were midsummer observations made in August, 1895, on the Depart- ment of Agriculture grounds in the city of Washing- ton, but in a warmer climate they may be hastened even beyond this minimum. Thus, in India Surgeon Major F. Smith, of the Royal Army Medical Corps, found at Benares that from a collection of one day's fresh droppings of three horses the adult Musca domes- tica was obtained on the eighth day after the laying of the eggs, thus shortening the period considerably. Moreover, Doctor Hewitt's minimum rate of growth was : egg, eight hours ; first-stage larva, twenty hours ; second-stage larva, twenty- four hours; third-stage larva, three days; pupa, three days — a total of eight days and four hours, surely a much shorter period than often happens in England, although the occa- sionally high summer temperature combined with the moist climate of that country may occasionally bring about this shortening. Mr. Newstead's observations in Liverpool, on the other hand, show a minimum period of from ten to fourteen days and a maximum of from four to five weeks or longer. Dr. A. Griffith, Medical Officer of Hove, England (a seaport on the English Channel), experimented with house flies during 1904-7. He gives as the minimum 36 THE HOUSE FLY— DISEASE CARRIER time in any of his sets of rearings, which he tabulates in Public Health, May, 1908, four and one-half to six days from egg to pupa, and three and one-half days from pupa to adult fly, a minimum for the life round of eight days. He found great variations in this period, according to the prevailing temperature. Number of Generations Taking the minimum duration of a generation in Washington so far as observed (and this must not be taken as the scientific minimum, since it depends upon observations taken only during midsummer of a single year), or we will say perhaps a midsummer average under Washington conditions, and accepting Doctor Hewitt's observations as to the time elapsing between the issuing of the adult flies and their sexual maturity as being, perhaps under American conditions, ten days, we see that there is time for the development of seven generations between April I5th and September loth. Flies, it is true, continue to emerge from manure piles and other breeding places much later than September loth, and in fact during the season of 1910 active lar- vse were found as late as the 3Oth of November, while on the occasional warm days of that period adult flies were still active and laid eggs. The generations of springtime and of autumn, however, are of much slower development than those of midsummer, so that it is probably safe to say that there are seldom more than nine generations a year under outdoor conditions in places comparable in climate to Washington. LIFE HISTORY 37 Farther south, however, where the summer is longer, and particularly where the climate is moist, there may be more generations than this. In India, for example, where Surgeon Major Smith made his observations showing a minimum rate of eight days to a generation and where the warm spell is very long, an extraordi- nary abundance of flies in the autumn, with proper conditions of moisture, is a certainty. No wonder that the punkah was invented in India! In the same way, as one goes north the number of generations per year is naturally smaller and the autumnal abundance of flies becomes greatly lessened in consequence. Forbes's assistants in Illinois found the life round in midsummer to vary from nine to fourteen days. Possibilities in the Way of Numbers This number of generations has a direct bearing upon the number of flies, not only at different periods during the summer, but also in the early autumn, since there is, barring accidents, a constant and definite and enormous increase. Of course some summers are warmer than others and some are moister than others, and upon these two factors, taken in connection with that of available places for breeding, the number of flies must depend. Take, for example, the possibilities in Washington, and let us estimate — on the basis of the survival of all eggs and all individual flies — upon plenty of places for the insect to develop and for the larvae to feed, upon an average of ten days to a generation in midsummer 38 THE HOUSE FLY— DISEASE CARRIER (this period increasing in the autumn and being greater also in the springtime), and also upon a period of ten days after emerging of the adult flies before sexual maturity is gained (this point of the duration of the existence of the adult fly before the attainment of sex- ual maturity has been the weak element in other cal- culations that have been made of house fly abundance) — let us start, then, on April I5th with a single over- wintering fly which on that day lays 1 20 eggs, and we will have the following table: April 1 5th, the over-wintering female fly lays 120 eggs. May ist, 120 adults issue, of which 60 are females. May loth, 60 females lay 120 eggs each. May 28th, 7,200 adults issue, of which 3,600 are females. June 8th, 3,600 females lay 120 eggs each. June 2oth, 432,000 adults issue, of which 216,000 are females. June 30th, 216,000 females lay 120 eggs each. July loth, 25,920,000 adults issue, of which 12,960,000 are females. July I9th, 12,960,000 females lay 120 eggs each. July 29th, 1,555,200,000 adults issue, of which 777,600,000 are females. August 8th, 777,600,000 females lay 120 eggs each. August 1 8th, 93,312,000,000 adults issue, of which 46,- 656,000,000 are females. August 28th, 46,656,000,000 females lay 120 eggs each. September loth, 5,598,720,000,000 adults issue, of which one-half are females. Such figures as these stagger the imagination. They are apt to make one feel hopeless at the thought of at- tempting to exterminate or to hold in check a creature LIFE HISTORY 39 with such possibilities of multiplication ; but it must be remembered that in the supposed instance upon which we have figured, all of the eggs hatched and all of the progeny have survived, whereas in nature a fly has many chances of death, not only between the egg and the adult, but as an adult before the period of sexual maturity has been reached. And it is upon this period which must elapse between the issuing of a fly and the time when it shall lay eggs that one of the several ex- cellent plans for the warfare against this species has been based. It must be remembered, on the other hand, that in the table we have assumed that each female has laid only 120 eggs, that is one batch, while in reality she may lay four such batches. The task of estimating the possibilities on the larger basis is left to some reader who likes to multiply. Does not a con- templation of these possibilities, even with all the pos- sible accidents of nature to limit them, indicate in the strongest possible way, even if the carriage of disease by these pernicious creatures were not considered, the necessity of an effort on the part of people to assist nature in limiting a nuisance to humanity? Number by Actual Count in Relation to Quantity of Food On August 9th in Washington a quarter of a pound of rather well-infested horse manure was taken from a manure pile, and in it were counted 160 larvae and 146 puparia. This would make about 1,200 house flies to the pound of manure. This, however, cannot be taken 40 THE HOUSE FLY— DISEASE CARRIER as an average, since no larvae are found in perhaps the greater part of ordinary horse manure piles. Neither, however, does it show the limit of what can be found, since on the same date about 200 puparia were found in less than one cubic inch of manure taken from a spot two inches below the surface of the pile where the lar- vae had congregated in very great numbers. This, as stated, was in August and the height of the fly season had not yet been reached. Major N. Faichnie, of the Royal Medical Corps, in the Journal of the Royal Med- ical Corps for November, 1909, gives the result of cer- tain experiments with flies, indicating that in India he reared 4,000 flies from one-sixth of a cubic foot of trench ground. He also states that he reared 500 flies from one dropping of human excreta. Further counts have been made by Dr. W. B. Herms, of the University of California ( 1910) . Doctor Herms took four samples from different parts of an average horse manure pile in Berkeley, Cal. (not near a livery stable). The four samples weighed fifteen pounds in all and contained by actual count 10,282 larvae, nearly all of which were nearly or quite full grown. The weight of the entire manure pile was estimated at 1,000 pounds, and, at the rate counted, estimating that possibly one-third of the pile was uninfested, the pile contained 455,000 and more larvae. Is it any wonder that flies swarm near the average stable? LIFE HISTORY 41 Hibernation The typhoid fly apparently suddenly disappears with the first sharp frost. It will reappear later on the warmest days. With a great reduction of the tem- perature of their breeding places, many larvae are killed, and eggs as well. Whether the pupae in their tight puparia are destroyed by a certain degree of cold does not seem to be known. The adult flies undoubtedly linger in warmed houses throughout the winter, but that enough of them remain in active condition in such locations to perpetuate the species and to start the rap- idly multiplying generations of the following summer seems doubtful. The adult flies undoubtedly remain dormant even in warmed dwellings, and it is altogether likely that some of them remain dormant throughout the winter months in sheltered but cold situations. Many adult insects pass the winter in this way, and observations have been made which indicate that this is the case with the house fly, although as a matter of fact sufficient attention has not been paid in the obser- vations on record of the exact specific identity of the flies in question. As has been pointed out before, there are so many species of flies which so exactly resemble the typhoid fly to the macroscopic eye that any one may be pardoned for stating that house flies have been seen tucked away carefully in cracks, when a micro- scopic examination would have shown that some other species was concerned. The best observations on this general subject which 42 THE HOUSE FLY— DISEASE CARRIER have been published are those made by Mr. F. P. Jep- son, research student in medical entomology, Cam- bridge University, England. According to Mr. Jepson (1909), when the frosts come and the cold weather begins in earnest, unprotected flies are probably killed. Those which have found the shelter of some place like a kitchen or a restaurant or a bake house, where the arti- ficial temperature is sufficient unto their needs, continue to live actively; and will even breed when conditions are favorable. He states that some flies possibly exist in dormant condition in such protected localities as be- hind pictures and loose wallpaper. He found sluggish specimens behind books on a bookshelf in December and January and observed them for some time, find- ing them in the same positions and still living a month later. His observations ceased at the end of January, but he saw no reason why they should not live on until spring and then begin to breed. In the course of his experiments he found that the flies occurring at the close of the year are much more hardy than those oc- curring in summer. This fact was experimentally proved, as will be shown later. He further states that one of his friends found flies, presumably typhoid flies, to issue in large numbers from the empty frame of an old window which was removed during the winter. Jepson experimented with the early stages, and, knowing the idea that possibly the puparia hibernate, he attempted to carry 200 pupae through the winter, but without success. The most interesting part of his experimental work, LIFE HISTORY 43 however, was with 200 flies captured in February fly- ing about in the sculleries and kitchens of one of the colleges at Cambridge. They were quite as active as in the summer. The kitchens are underground, and the fires are kept up continuously. The temperature varied from 65° F. in the mornings to 80° F. in the evenings, and the flies, although somewhat sluggish in the morning, became active when the fires were poked up. The 200 flies under experimentation were transferred to a greenhouse, which was kept in a sim- ilar temperature to the kitchens where they were cap- tured, and were kept in closed vessels with a supply of moist bread beginning to ferment. It is worthy of note, by the way, that he found that on several occa- sions the flies would not lay their eggs upon bread which had not begun to ferment. After the flies had been confined twenty-four hours they laid their eggs, and on the following day all of the eggs hatched. As the bread became moldy the larvae avoided it, and were transferred to other enclosures and fed upon stale bread slightly moistened. They fed until full grown, then crawled away from the moisture and transformed to pupae under pieces of newspaper. At a temperature ranging between 65° F. and 75° F. in February, the entire duration of the life round occupied three weeks. It thus appears that under artificial heat conditions the typhoid fly, given food for its larvae, will continue to breed almost as rapidly as during the summer time. Mr. Jepson's observations on the length of life of the adult flies in the winter time further .support the 44 THE HOUSE FLY— DISEASE CARRIER idea that the species constantly hibernates in this con- dition. Upon the emergence of the adults which he reared in confinement in February, they were trans- ferred to a large net cage and were kept alive success- fully for eleven and one-half weeks. The original flies caught in the kitchens in February were kept in cap- tivity for ten weeks. How long they had lived before capture, of course, was unknown, but presumably since the previous autumn. The question of the length of life of the adult fly under all conditions will be con- sidered in a later paragraph. HABITS OF THE ADULT FLY On issuing from its pupal sheath, the first impulse of the adult fly is to feed. After its rest in the pupal condition, during which time it has taken no food and has subsisted by the physiological consumption of the fat cells stored up during the last larval period, it has naturally become hungry, and it flies immediately to the first point offering sustenance. The sense of smell of the typhoid fly must be very keen, although its selec- tion of attractive odors undoubtedly differs from our own. It is very catholic in its choice of food — the milk jug and the freshly baked custard pie are apparently equally in favor with the slop bucket, the garbage pan, and all sorts of unmentionable filth. It knows the odor of cooking, and it flies unerringly towards the nearest kitchen, although here the temperature of the kitchen stove may attract it almost as much as the possibility of something good to eat. As has been shown in our HABITS OF THE ADULT FLY 45 brief discussion of the mouth parts of the adult fly, its food must be liquid, and when it alights upon a solid a plentiful flow of a salivary liquid enables it to make some slight impression and to gain sustenance. Thus it drinks as well as eats, and liquids apparently contain- ing little that will help it to exist are sought by it, but it especially prefers semi-liquid mixtures. Every one who reads this book knows how in the old days, and even now in some places, the typhoid fly swarmed or swarms in a certain class of public restaurants and in poorly cared-for eating places. The story of the man who entered a dimly lighted railway restaurant and asked for "a piece of that huckleberry pie" and was in- formed that it was not huckleberry but custard, is lit- erally true. Dr. Theobald Smith phrased it very hap- pily in a paper written a few years ago in the following words : "When we go into a public restaurant in mid- summer, we are compelled to fight for our food with the myriads of house flies which we find there alert, persistent and invincible." Doctor Smith has been very fortunate in the choice of the word "persistent." The typhoid fly does not seem to have any common sense. At one time he is alert, to use Doctor Smith's word, and it is impossible to catch him, but his persistence even in the face of imminent danger is one of his char- acteristics which is most impressive. When one lies drowsily in bed of a summer morning with but one fly in the room, "persistence" is the only word to apply to its annoying return again and again and again to the face of the sleeper in spite of repeated slaps. Here 46 THE HOUSE FLY— DISEASE CARRIER it is the perspiration which attracts the fly. It is hungry and thirsty and wants food and drink. The typhoid fly is a diurnal species. It rests during the night. It is not especially fond of the bright sun- shine, and if one stays in direct sunlight he is not often troubled by it. But it revels on the shaded porch and in the lighted house away from the sun's direct rays. It flies into the dimly lighted stable in search of places to lay its eggs, but in absolute darkness and even in darkness which is not absolute it rests immovable. Its resting position seems to be a matter of indifference to it ; it can sleep equally well on the ceiling or on the side wall. It does seem to have some preference for anything hanging perpendicularly, such as an old-fash- ioned rod supporting a candelabrum or a central gas fixture or a window-curtain string, and this observed preference has been taken advantage of by the inventors of certain fly traps which consist of a suspended strip of sticky paper. Reverting once more to the feeding of the adult fly, a correspondent whose name the writer has unfortu- nately forgotten described an instance where he had left a blood-stain on a slide at which a house fly sub- sequently sucked. On examining it afterwards under the microscope, the fly, he found, had taken up all of the red blood corpuscles and had left all of the white. Flies are great feeders. Where food is abundant they will suck at it almost continuously or at very brief intervals. As indicated elsewhere, the alimentary canal is comparatively simple, the digestive processes seem HABITS OF THE ADULT FLY 47 of the simplest and the food passes through the body with the greatest facility. Do Flies Have a Color Preference? Galli-Valerio (1910) states that the French agri- cultural journals have published a statement that Fe, having observed that flies do not rest upon walls cov- ered with blue paper, blue-washed the walls of his milk stables and that the flies then disappeared, and asks the question whether a similar method could be used to keep flies out of houses. He himself conducted ex- periments with a box having glass walls, 35 X 35 X 35 cm. in size, and pasted on the walls bits of paper all the same size but of different colors, and afterwards introduced a certain number of house flies. For sev- eral days, after turning the cage in different positions so as to avoid error from other causes, he counted the flies which were standing on the different colors. The results were as follows : Clear green 18 Dark green 5 Rose 17 Red 4 Clear yellow 14 Orange 3 Azure 13 Clear brown 3 Clear red 10 Pale rose 3 Dark gray 9 Very clear green 2 White 9 Blue I Dark red 8 Pale violet I Black 7 Dark brown i Pale gray 5 Lemon yellow I Dark yellow 5 The observer noted that eighty-seven flies stood on the clear light colors, and fifty-two on the dark. Blue 48 THE HOUSE FLY— DISEASE CARRIER was surely one of the colors least visited, but on the contrary azure was one of those most frequented. He thinks that possibly after all it was only a chance, but is of the opinion that Fe's observation should be the basis of an experiment on a large scale with the same ultramarine blue which he employed. It seems doubt- ful, however, that a cold, hungry fly will be kept from a warm, odoriferous kitchen by the bluest of blue col- ors. Fly-specks Since, on account possibly of the simplicity of the digestive processes just referred to, pathogenic bacteria and other micro-organisms pass unchanged through the alimentary canal of the typhoid fly, the question of fly-specks becomes one of great importance. Every casual observer knows that they are laid with great frequency, and that when flies are abundant their specks are to be found everywhere. Curiously enough, few exact observations have been made upon the fre- quency with which the fly deposits its excreta. Major N. Faichnie, previously referred to, working in India, found that when a fly is put in a clean paper box it passes its excrement fifty times in twenty-four hours; that is to say, about once every half hour; but he neglects to state whether there was food in the box. Presumably there was some food, and also presumably there was not much of a semi-liquid character. Cobb (1910) gives a table of the intervals between defecation of a well-fed fly, together with notes on the spores in the excreta. One naturally infers, from the title of the HABITS OF THE ADULT FLY 49 article, that the fly in question was a house fly, but upon consulting- an important paper by the same author (1906), entitled "Fungous Maladies of the Sugar Cane," the same table is found printed on page 64 and the fly in question is said to be a Sarcophagid, and therefore not Musca domestica. In his opening paragraph in the 1910 article, Doctor Cobb explains, "In some of these paragraphs, however, the statements are inferences fully justified by experiments with very similar species," and this table is evidently one of these inferential statements. It is not safe to state that be- cause, as shown in the table, a well-fed Sarcophagid fly will defecate on the average once every four and one-half minutes, from half past nine until half past eleven, a true Musca will do the same. It is by no means impossible that it will do so, but unfortunately we have not the proof. Still with this explanation it will be interesting to state that in the interval between 9: 35 and 11:26 the fly observed by Doctor Cobb (it had been fed at 9 : 23) made twenty-three fly-specks at intervals varying from one to fifteen minutes, an av- erage of about four and one-half minutes ; and in ten of these twenty-three specks Doctor Cobb found spores. Herein lies one very great danger from flies. Certain authors believe that the danger from disease germs that pass through the fly's body in this way is greater than from those that are supposed to be carried from foul substances on its feet. With the abundance of flies in the late summer, the number of fly-specks becomes almost unlimited. Doc- 50 THE HOUSE FLY— DISEASE CARRIER tor Cobb states that he possesses actual counts made by the use of a little counter of his own invention, but that he does not publish these records for fear that he will be accused of sensationalism. He says that win- dow-panes with from 1,000 to 10,000 fly-specks per square foot are not at all uncommon, and that from ten to fifty per square foot is a common number in what are considered well-kept homes. And this is only in places where the dirt can be readily seen. He states that on neutral-tinted objects which are not cleaned so frequently fly-specks occur in millions. "On wallpaper, chandeliers, outside veranda posts, on cornices, ceil- ings, and window blinds, the numbers are almost past computation." He further shows that examination of the excreta of flies captured in the open shows that they contain a great variety of spores in living con- dition. He finds that the digestion of the fly consists simply in the absorption of those substances readily soluble in its weak digestive fluids and the evacuation of all others; therefore the fly is an enormous feeder. Doctor Cobb states that in a single meal it frequently swallows nearly half of its own weight of food. This accounts for the frequency of the fly-specks, and, con- sidering the number of flies, for the enormous num- ber of specks. Doctor Graham-Smith, elsewhere quoted, made a few studies of the number of deposits left by flies. He found that the rate at which the deposits are produced depends upon temperature and the form of food, flies being most lively in hot weather or when placed in a HABITS OF THE ADULT FLY 51 warm incubator. He fed three lots of flies on syrup, milk, and sputum, respectively, for several days, and noted that those fed on syrup produced an average of four and seven-tenths deposits per fly per day, those on milk eight and three-tenths and those fed on sputum twenty-seven. In the latter case he states that the feces were much more abundant and liquid than usual, and that in fact the flies seemed to suffer from diarrhea. In another series of experiments ten flies were given a single feed of milk and then transferred to fresh cages. They deposited either by regurgitation or as excrement forty-one spots in the first hour, sixteen in the second and third, twenty-four in the fourth, twenty- four in the fifth, and fifty-nine in the prolonged inter- val between the sixth and twenty-second hour. With another series of eleven flies, milk was always present in the cage so that the flies could feed as often as they wished, and here thirty-two spots were made in the first hour, forty in the second and third, ten in the fourth, eighteen in the fifth, and 134 in the sixth to the twenty-second hour; making a total of 164 spots from the ten flies that had had but one feeding and 224 from the eleven flies which had the milk contin- uously in their cage. Distance of Flight Prof. S. P. Langley, the late Secretary of the Smith- sonian Institution, was, as every one knows, greatly interested in the problem of aeronautics, and his ex- periments with flying machines heavier than air prac- 52 THE HOUSE FLY— DISEASE CARRIER tically made him the first successful investigator in this direction, since the Wright brothers acknowledge that they owe very much to Langley's scientific papers on this subject. From his interest in this direction, Pro- fessor Langley devoted certain grants from the so- called Hodgkins fund* to the study of the mechanism of flight of various birds and insects. Some of the results of these studies have already been published in the Smithsonian Miscellaneous Collections. During the past ten years a series of these investigations have been carried on under Prof. Robert von Lendenfeld of the University of Prague, and from a report received from Professor von Lendenfeld by the present Secretary of the Smithsonian Institution, Doctor Walcott, which the writer has been permitted to see, it appears that, after a study of the organs of flight in the Lepidoptera, Hymenoptera, and Diptera by Messrs. Hauptmann, Groschl, Ritter, and Professor von Lendenfeld, the latter became convinced that of all the forms of insects, and indeed of all flying animals, the Diptera would furnish the best models for flying machines. He thinks that a model built according to this pattern should be made and experimented with. Certain studies by Mr. Ritter on the blow fly, which are at the time of this writing in the hands of the Smithsonian Institution for publication, indicate that this insect and its flight would form the best basis for a model. This is an interesting and important statement, since *A bequest to the Smithsonian Institution for the investigation of the properties of the upper air. HABITS OF THE ADULT FLY 53 it has been made after a long series of comparative studies, and its truth will readily be admitted by any one who has paid much attention to the flight of Dip- tera. Cobb, in his paper on the Fungous Maladies of the Sugar Cane, records a number of observations on the flight of flies in connection with the distribution by the flies of the spores of a fungous disease of sugar cane. He states that he never succeeded in tiring his flies very perceptibly if they had a free space to move around in. When confined in a room they were kept on the wing for hours without showing much fatigue. By dissection he showed that with certain of the Sar- cophagid flies the thoracic or wing muscles constituted twenty-six and two-tenths per cent, of the weight of the fly, and that the mass of the great thoracic muscles is proportional to the apparent power of flight among dif- ferent flies. He records also a remarkable example of the power of flight of one of the larger flies. On a voyage across the Mediterranean from Algiers to Mar- seilles, he observed a Dipterous insect keeping pace with the steamer "so accurately that it almost seemed as if it were joined to the boat by some invisible rigid connection. The boat left Algiers at noon and as long as there was any light left by which to observe, the insect kept its place steadily. This was in midsummer. The insect never made any attempt to come aboard. The boat was not particularly fast, her speed being about thirteen knots." Every one who has driven a fast team of horses over a road through pine timber must have noticed the ex- 54 THE HOUSE FLY— DISEASE CARRIER traordinary flight of the gadflies of the family Taban- idae, which for hours will circle about the horses, fly- ing with ease much more rapidly than the speed of the vehicle, alighting only occasionally. It is not intended to convey by these instances the impression that it is known that the house fly is at all extraordinary as a flier among the Diptera — in fact, when the truth is fully known it may be shown to be comparatively a weak flier among its relatives; but it darts here and there through the air with great speed, and if it were obliged to fly great distances the writer has little doubt of its ability to do so. The practical question involved in the distance of flight, however, is the one of protection of food sup- plies at a distance from fly breeding places which can- not be controlled. Will the proper care of the stables and houses in a given city square relieve the houses in this square from the fly pest to a measurable degree, provided stables and houses one square or two squares away remain uncared for? The situation must be much as it is with mosquitoes, although the house fly is a much stronger flier than any mosquito. The house fly will seldom travel very much farther than it has to fly for food and a proper nidus for its eggs, but as a matter of fact it is very difficult to prove this. Fur- ther experimental work should be carried on in this di- rection. J. S. Hine (in lit.) states that in the summer of 1910 he made an effort to determine the distance that flies travel. At a barn where he was carrying on some work HABITS OF THE ADULT FLY 55 he captured some 350 flies and marked each one's wing or thorax with a small spot of gold enamel. Flies so marked were repeatedly observed about dwellings from twenty to forty rods from the barn up to the third day, but in a dwelling house a half mile away none of the marked specimens was detected. This, however, was a very unsatisfactory experiment, because it does not in the least show that if the dwellings twenty to forty rods from the barn had not existed flies would not have been found in the dwelling half a mile away. As Hine himself states, "It appears most likely that the dis- tance flies may travel to reach dwellings is controlled by circumstances. Almost any reasonable distance may be covered by a fly under compulsion to reach food or shelter. Where these are close at hand the insect is not compelled to go far, and consequently does not do so." Hewitt is of the opinion that normally house flies do not fly great distances, and compares them to do- mestic pigeons which hover about a house in the im- mediate neighborhood. He states that they are able to fly, however, for a considerable distance and can be carried by the wind. At one time when he was vis- iting the Channel Islands he found the house fly from one and one-half to two miles from any house or any likely breeding place that he was able to find. He mentions some exact experiments made by Dr. M. B. Arnold at the Monsall Fever Hospital, Manchester, where 300 flies were captured alive and marked with a spot of white enamel on the back of the thorax. They 56 THE HOUSE FLY— DISEASE CARRIER were liberated in fine weather, and out of the 300 five were recovered in fly traps at distances of from thirty to 190 yards from the place of liberation, and all within five days. He further states that he had found them at an altitude of eighty feet above the ground, and calls attention to the fact that such a height would fa- cilitate their carriage by the wind. An experiment made under the direction of Prof. S. A. Forbes, of which he has sent me a written ac- count, indicates that house flies may spread naturally for at least a quarter of a mile, going, in one significant instance, from the tuberculosis hospital to the general hospital of Cook County, Illinois. House flies trapped at one point were sprayed with a chemical solution and liberated. Then flies caught on fly paper elsewhere were sprayed with another solution, the result being that those which had previously been sprayed were turned dark blue in color by the second solution. Marking Flies for Experiment Professor Hine found that it was a very difficult matter to mark flies so that they might be recognized from others, since they are very sensitive to anything unusual, and any foreign substance on their bodies or wings causes them to act abnormally. They contin- ually try to remove the foreign substance and seem to tire themselves out. He found that many specimens marked with the greatest care would hardly fly after they were marked, so that it was easy in many cases to approach them and pick them up with the fingers. He HABITS OF THE ADULT FLY 57 is of the opinion, therefore, that marked flies are likely to be abnormal and are not fit for purposes of exact experimentation. He found that it was impossible to clip off the wing extremity and not inconvenience the flight. On this subject of marking, Mr. J. P. Jepson, of Cambridge, England, conducted some interesting ex- periments during July and August, 1908, under the di- rection of Professor Nuttall. He first tried ordinary household flour, but the flies soon rid themselves of it. This substance was used on account of the observation that flies seen in mills often seem quite white in color. Rice starch powder was next tried, with no success. They were finally marked with ordinary colored black- board chalks which were finely ground up in a mortar and dusted on the flies until they were completely cov- ered. They tried to clean themselves, beginning with the eyes, but never succeeded in removing the chalk from the upper portion of the thorax or from the base of the wings. Further experiments were tried with aniline dyes either made in the form of a powder with rice starch or mixed with alcohol in the form of a spray. Then again shellac was mixed with the alcohol in order to make the color sticky. In his summary he found that the use of various aniline dyes did not prove satisfactory; with fuchsine the mortality was very large. He found that dusting with rice starch powder and then spraying with shellac and alcohol give an excellent color, but decided that the flies must be allowed to clean their eyes before spraying and that 58 THE HOUSE FLY— DISEASE CARRIER the spray must be thinly applied. The best result reached by this method was ten days. The reverse, namely, spraying with alcohol and shellac and then dusting with rice powder, was satisfactory where the shellac was not applied too thickly. Colored chalks gave very satisfactory results, yellow and brick red being the best ; the yellow lasting for nine days and the brick red for twenty days. Length of Life of the Adult It seems that in midsummer the adult flies do not live long, and it is extremely difficult to keep them for any length of time in an enclosure, which, of course, is the only true way of ascertaining exact age. At this time of the year, flies die rapidly in confinement. In June, 1898, the writer was unable to keep alive flies collected at large and placed under a gauze enclosure three feet cube for more than three days, but of course this experiment meant nothing, since the age of the flies collected was not known. Mr. Hine is convinced that flies do not live a great many days in warm sum- mer weather. Marked flies in his experiments in Au- gust were not to be found after the third day, and in his experiments with individuals, in confinement with all necessary food, he was unable to keep them alive for more than twelve days. He mentions an instance where on a farm at Ira, Ohio, a pile of infested manure at the barn was hauled up and spread in a field a quarter of a mile away on August I5th; the occupants of the house stated that there was a notable reduction in the HABITS OF THE ADULT FLY 59 number of flies by August 2Oth. Major N. Faichnie, referred to above, in experimenting with flies in India in the summer, found that they lived eleven days only. Mr. Jepson, in his notes on the breeding of the com- mon house fly during the winter months, incidentally mentions the fact that during the summer of the pre- vious year (1908) in no case was he able to keep flies alive for more than three weeks, and then only with a few individuals; whereas, as previously stated, flies reared during the winter were kept alive for eleven and one-half weeks, and flies caught in kitchens in Febru- ary were kept alive for ten weeks and had presumably been living since the previous autumn. If we take Jepson's statement of three weeks as be- ing the probable limit of the life of the adult fly in midsummer, and if we conclude, as we must, that the average life at that period is much shorter than this, it becomes evident from what will be stated in the fol- lowing paragraph that after the female fly has laid her eggs in summer she has not much longer to live. The plain inference from this will naturally be that the hi- bernating flies in the winter time are probably for the most part females which have not laid their eggs. Un- fortunately for the conclusions just stated, Doctor Hewitt records the fact that he has kept flies in cap- tivity in the summer time for seven weeks, while Grif- fith (1908) was able to keep a male sixteen weeks. Ficker (1903), in an account of experiments carried on between June and October, states that he kept flies alive in confinement for four weeks, feeding them on 60 THE HOUSE FLY— DISEASE CARRIER sugar, bread, water, or milk. Unfortunately he does not give the exact dates of this particular observation, and it may have been on an October generation, which would have hibernated. Time Elapsing Betiveen the Issuing of the Adult and the Period of Sexual Maturity The practical value of the determination of this period is very great. If an adult female fly can be destroyed before she lays her eggs, we will have killed not only the actual fly, but 120 to 600 potential flies due in a very short time, and if this female fly can be caught in the early spring the table on an earlier page will indicate that instead of performing a very simple act we have apparently saved the world from almost a calamity. From this can be seen the value of fly traps. Of course the destruction of breeding places is very important, but traps for adult flies are by no means to be despised when we have this idea in view ; and the use of fly traps in the early part of the season becomes obviously all-important. The destruction of hibernating flies is equally of value ; but these subjects will be considered in the chapter on remedies. So far as the writer knows, the only observers who have paid any attention to this very important point of the period elapsing before sexual maturity are Hewitt (1910) and Griffith (1908). Hewitt states that he found flies become sexually mature in ten to fourteen days after emergence from the pupal state, and that four days after copulation they begin to de- HABITS OF THE ADULT FLY 61 posit their eggs; that is to say, from the fourteenth day from the time of their emergence. The experi- mental data upon which this statement is based are not given in the paper in question, and the writer there- fore wrote to him for a transcript of his record, from which it appears that the flies under observation emerged between August 2ist and August 28, 1907. They were given fresh horse manure daily, and accu- rate thermometrical readings were recorded for each of the following days. Not until September 4th was copulation observed, and on September Qth larvae were found in the manure. Doctor Griffith, in his observations at Hove, found that the female flies oviposited ten days after issuing from the puparia, and that they could lay new batches of eggs at intervals of from ten to fourteen days until four batches have been laid. It seems to the writer that this period between issu- ance and sexual maturity must surely be shorter, and perhaps much shorter, under midsummer conditions and in the freedom of the open air, than that indicated by Hewitt and by Griffith. Breeding-cage observations are never quite conclusive. So great is the practical importance of this point, as already shown and as will be elaborated later, that the most careful experimental work should be under- taken under all sorts of circumstances and in very many different localities. II THE NATURAL ENEMIES OF THE TYPHOID FLY AS with every other living creature, nature makes its own effort to limit the abundance of the fly under consideration, and the extraordinary facility for multiplication which the fly possesses is in turn the re- sult of the instinctive effort of the organism to main- tain its status in spite of the numerous enemies which confront it. The natural enemies of the house fly be- gin with the acme of the vertebrate series (man him- self) and end with the lower forms of plant life, and we will begin our consideration of these agencies with the latter forms. FUNGOUS DISEASES In the autumn it is a matter of common observation that many flies in houses and on the windows become sluggish and frequently die in such positions. The sluggishness may be accounted for in a measure by the advent of cold weather, and as a matter of fact cold weather frequently drives indoors other species of flies of a more sluggish nature than the house fly. In this way the so-called cluster fly (Pollenia rudis), a rather sluggish species, which will be referred to in another chapter, is frequently found in houses in the autumn. 62 NATURAL ENEMIES 63 But the principal cause of the sluggishness on the part of the house fly in the autumn is the attack of fungous diseases. Sometimes they are found to be dead without any evidence of the cause of death. Later they are seen to be surrounded by a white fungus growth. There is a group of fungi belonging to the En- tomophthorese, many of which are parasitic upon in- sects. There are several genera in this group, but the only one which need be considered at present is the genus Empusa. The fungi of this group have been studied by Dr. Roland Thaxter of Harvard University, and it is from his writings that the following state- ments have been drawn. The infection of insects by these fungi results from contact with a spore which, adhering to the insect, en- ters its body by means of a fungous thread known as a hypha. The exact method of the entrance of the hypha is not known, but it must be through the thin- ner membrane connecting the body segments and the leg joints, or through the breathing pores. It has been suggested that the spores may be eaten, but Thaxter thinks that this is not the usual means of introduction, since experiments that he has made contradict it, and he finds that as a rule the digestive tract during life does not seem to be penetrated by the fungus. After one of these hyphae has entered the body of the insect it develops with some rapidity at the expense of the softer tissues. It multiplies, not by branching or by continuing to grow, but by the formation of short, thick fragments of various sizes and shapes that are 64 THE HOUSE FLY— DISEASE CARRIER continually reproduced by budding or division until the insect is more or less completely filled with them. These fragments are called hyphal bodies. They con- tain a highly concentrated, fatty protoplasm and are capable of subsequent and often very extended develop- ment. When the mass of these bodies has been completed and the death of the insect attacked has occurred, the fungus may proceed at once to the completion of its development under proper conditions of temperature and moisture, but if these conditions are absent a rest- ing stage ensues in which the contents of each hyphal body becomes Surrounded by a single wall which in- creases in thickness as the resting stage continues. The fungus may remain dormant in this condition for i considerable period. Doctor Thaxter has observed the hyphal bodies germinating after several weeks, and thinks that they probably retain their vitality for a much longer period, and may perhaps hibernate under certain circumstances. When a moist atmosphere and a sufficiently high temperature come they germinate with great rapidity. With the common house fly fungus (Empusa musca) a slight change in the amount of atmospheric moisture is sufficient to bring about germination. This, accord- ing to Thaxter, is very noticeable on the seashore, where slight changes of the wind from the water or from the shore bring about a very rapid and noticeable effect upon the flies thus parasitized when watched in the ordinary atmosphere of the house. With other NATURAL ENEMIES 65 species of Emptisa attacking other insects, a much greater degree of moisture is necessary, and certain forms occur only in very moist situations. In germinating, each hyphal body or resting spore sends out one or more hyphse, which grow with great rapidity, but the manner of this germination, together with the subsequent development of the resulting hy- phae, varies considerably with different species and un- der different conditions. In the simplest case a single hypha thus produced may grow directly to the outer air and then produce a single conidium or set of con- idia. In other cases a single hypha may branch indefi- nitely, each final branch bearing a conidium or conidia. This usually happens where the conditions of growth have been very favorable, and the complex may be found side by side with the more simple form. The conidium or spore is formed by budding from one of these hyphse, which in this case is called a con- idiophore. This bud increases in size and becomes separated from the conidiophore by a cross-partition. Within the mother cell thus formed is developed a single spore. When this cell increases in size by the absorption of water, the wall of the mother cell be- comes separated from that of the conidium and some- times to such an extent that the conidium is seen float- ing free in the large spherical mother cell. Finally by a rupture the conidium is discharged violently into the air, often for a considerable distance. With Empusa muscce, the conidia are bell-shaped or nearly spherical, with a broad base and a measurably pointed apex, 66 THE HOUSE FLY— DISEASE CARRIER They contain usually a large oil globule and are sur- rounded after discharge by a mass of protoplasm. If the conidium when discharged has come in con- tact with a suitable host insect, it adheres to it and sends out a hypha of germination which enters its body as just described. Secondary conidia are formed as a provision for further dissemination in case the primary spore has fallen on a substance unsuited to its proper development. With Empusa musca the secondary con- idia are like the primary, or more commonly they are sub-ovoid, small, round at the apex, and formed by direct budding from the primary form. These also are discharged, but are apparently better suited to resist unfavorable conditions than the primary ones, and probably retain their power cf germination much longer. There is also another morphological character of these fungi — the formation of simple hyphae which pro- ject out beyond the conidiophores. When they reach in the direction of the material upon which the de- stroyed insect stands they attach the body to it, and are then called rhizoids. When they stick out in any other direction, however, they seem to be functionless and are called cystidia or paraphyses. The hyphae of attachment or rhizoids may be simple or variously branched, and their germination may be variously modified into an extended sucker. They do not seem to enter into soft substances, and their adhesion is ap- parently due to the presence of a viscous secretion. They are produced with great rapidity, appearing often NATURAL ENEMIES 67 before the host is dead, and increase greatly in number with the appearance of the conidiophores. This will suffice perhaps for a general account of the development of these curious parasitic fungi. Empusa muscce Cohn., one of the most abundant of them, at- tacks the house fly, and also certain other large flies, such as the blow flies and many flower flies. It was first described by DeGeer in 1782, and has since been carefully studied by many observers. It is almost as universal as the house fly itself, and is the only Em- pusa known south of the Equator. As a rule, accord- ing to Thaxter, the species is found about houses, usu- ally within them, and occurs in great abundance from late June until late in the autumn. It seems altogether likely that the majority of the deaths of flies in the late autumn are caused by this species. In England, ac- cording to Hewitt, it is found from about the begin- ning of July to the end of October, usually indoors. In Washington the epidemic ceases in December. It is not yet known how this fungus lasts over from one year to another. Mycologists have never grown it in artificial cultures, and there is evidently much yet to be learned about many important points in its life history. Much experimental work has been done with the fungus diseases of other injurious insects, particu- larly with those of forms injuring cultivated crops, but no striking large-scale results of value have been obtained. It is possible that something practical can be gained from a close and prolonged study of this disease of the house fly, and it is interesting to note 68 THE HOUSE FLY— DISEASE CARRIER that the city of London local government board on public health and medical subjects is now aiding Dr. Julius Bernstein in a detailed investigation of the life history of Empusa musca and in an attempt to cultivate it in artificial media, with the object, if possible, of em- ploying these cultures to destroy flies on a large scale. Two other species of Empusa are recorded by Thax- ter as developing in the typhoid fly. These are E. sphcerosperma (Fres.) Thaxter and E. amcricana Thaxter. E. spharosperma is peculiar for the great diversity of its hosts, since it destroys insects of all or- ders except that to which the grasshoppers belong. It is a very common form and often produces very con- siderable epidemics among insects. It is recorded as destroying the clover weevil in great numbers on one occasion near Geneva. N. Y., by Dr. J. C. Arthur, and in 1909 produced an extraordinary epidemic in the same insect in the vicinity of Washington, D. C. As it happens, an allied insect, probably accidentally imported from Europe, is causing great damage at the present time in the alfalfa fields in Northeastern Idaho. Prof. F. M. Webster of the Bureau of Entomology at Washington immediately conceived the idea of attempt- ing to introduce this fungus from Washington into Idaho, in the hope that it would attack the alfalfa weevil. Owing to the dry climate out there, however, the experiment failed; the conidia would not develop, and it would seem very difficult if not impossible to produce, artificially, moisture conditions which will en- able alfalfa growers to handle this disease practically. NATURAL ENEMIES 69 The only record of the attack of this species on Musca domestica is by Brefeld. Empusa americana seems confined to large flies, like the house fly, the blow flies and the like. Doctor Thaxter states that it is frequently met with from June to October on the borders of woods near brooks or in shrubbery about houses. The fly is generally found fixed to the under, or rarely the upper, sides of leaves or bare twigs a few feet above the ground. It occurs in New England and North Carolina. The rhizoids or attaching hyphse, in- stead of growing out in the form of numerous scat- tered threads, are developed in an even layer around the insect's body, forming with the conidiophores a con- tinuous mat-like covering, which often becomes dark rust colored on exposure to the weather. These are, so far as known, the only true botanical enemies of the house fly. Of course, breeding as it does in fermenting organic matter and in the dirtiest and filthiest locations, and frequenting such situations as it does in search of food, it carries upon its body, and within its alimentary canal for the brief period which it takes for its food to pass through, any num- ber of spores of fungi and of bacteria, but it is prob- able that nearly all of these are carried accidentally by the fly and do it no harm. Many species of many genera of fungi and bacteria have been cultivated upon sterilized plates upon which flies caught haphazard have been allowed to walk and which they have been allowed to speck, but as just stated these are probably innoxious to the fly itself. From the observations of 70 THE HOUSE FLY— DISEASE CARRIER Mr. H. T. Giissow, Dominion Botanist of Canada, quoted by Hewitt, the fungi reared in this way have numbered seven species, while the bacteria have num- bered eleven species. PROTOZOAN ENEMIES OF THE HOUSE FLY Certain microscopic protozoa of the group Flagel- lata have been found in the alimentary canals of vari- ous insects, and one species known as Herpetomonas muscce domestic^ has been found in the intestine of the house fly. The genus to which it belongs is said by Calkins to be the most primitive and least changed from the free-living forms of the flagellated intestinal parasites. It is a general parasite of flies of very wide distribution. It was carefully studied by Prowazek in 1904 and by Captain W. S. Patton of the Indian Med- ical Service in 1908 and 1909. Patton found that in Madras, India, about one hun- dred per cent, of the flies caught in the bazaar meat shops are infected with this parasite, and he made an exhaustive study of its life history which continued for more than a year. He found that it exists in three stages which he calls the preflagellate, the flagellate and the postflagellate. The first stage is usually found in the midgut, the parasites lying in masses within the peritracheal membrane. They are round or slightly oval bodies of very minute size, which multiply by simple longitudinal division or by multiple segmenta- tion so that a large number is formed in a short time. The flagellate stage is characterized by the projection NATURAL ENEMIES 71 of a single stout filament. In this stage it elongates and divides later by simple longitudinal division. In the postflagellate stage the organism shortens in length and eventually loses its filament. Whether the presence of these intestinal parasites affects the vitality of the fly is not mentioned, nor is it understood whether they can be transmitted to any other animal. Since the typhoid fly does not bite, it seems likely that such a transfer does not take place. It is inter- esting to note, however, that a parasitic flagellate of the same genus, namely, Herpetomonas donovani, is the causative organism of the tropical disease known as kala azar, characterized by an enlargement of the spleen, by irregularly recurrent fevers, anaemia and emaciation, usually resulting in death, and that Cap- tain Patton has discovered that the same parasite un- dergoes a transformation in the intestine of a bedbug (Cimex rotundatus) in India, confirming a suggestion made with reasons by L. Rogers, who had previously discovered the flagellated stage of the parasite. When the blood of a kala azar patient is sucked into the ali- mentary canal of the bedbug the parasites are liberated by the digestive process and begin to develop from the second to the fifth day. There is no evidence that the bedbugs are infected except from human beings, and there is no scientific proof that human victims ac- quire the disease from the bugs. Another flagellate genus, Crithidia, is found in the intestinal tract of certain flies, and one of them has 72 THE HOUSE FLY— DISEASE CARRIER also been given the specific name Mnsca domestic^ by H. Werner. NEMATODE PARASITES OF THE TYPHOID FLY The nematodes, or thread-worms, have long been subjects of observation. They are greatly elongated, thread-like organisms, frequently of considerable size ; for the most part laying eggs, but in rare cases bearing living young. The younger stages or larvae of most of them have a different habitat from that of the adult worm. Some of them develop in damp, muddy earth, migrating finally to lead a parasitic life within some animal ; some are parasitic in plants. The old time super- stition that a horse-hair when left in water for a suffi- cient length of time becomes a living worm arises from observations upon some of the largest nematodes. Very many insects are parasitized by the worms of this group. H. J. Carter, in Bombay, in November, 1859, while examining the head of a common house fly, noticed that two nematode worms came out of it. Later, in July, 1860, he discovered that on the average about every third fly in Bombay contained from two to twenty or more of these worms, which were chiefly to be found in the proboscis, though occasionally oc- curring among the soft tissues of the head and hinder part of the abdomen. He described them as bisexual, mature, and nearly all of the same size. He placed them in the genus Filaria, and described them as Filaria muscc? in the Annals and Magazine of Natural History, Vol. VII, pages 30-31. NATURAL ENEMIES 73 Other observers have studied this parasitic worm, which is now placed in the genus Habronema. Hewitt, in England, after dissecting many hundreds of flies, found only two specimens of this parasite. He feels certain that the one found in England is the same as the one found by Carter in India. The same species occurs in the United States and has received some attention from Dr. B. H. Ransom, of the Bureau of Animal Industry of the U. S. De- partment of Agriculture at Washington. Doctor Ran- som has very kindly given the writer the following note, hitherto unpublished, which is sufficiently interest- ing to print in full : "Referring to Habronema musca, this parasite seems to be very common in the house fly. Out of thirty- four flies examined between June loth and July nth, most of them caught in the laboratory of the Zoological Di- vision, the remainder bred from horse manure obtained at the Experiment Station of the Bureau of Animal Industry, Bethesda, Md., nine were infested. The number and distribution of the parasites in these nine flies were as follows : 1. Five in the proboscis. 2. Six in the head and proboscis, one in the thorax. 3. One in the head. 4. Two in the head. 5. Five in the head. 6. Two in the head. 7. One in the head. 8. One in the abdomen. 9. Two in the thorax. 74 THE HOUSE FLY— DISEASE CARRIER "Twenty-six dipterous larvae (species not deter- mined) from horse manure which were examined for the presence of nematodes were all free from infection with H. muse a. Thirteen larvae of Musca dorncstica and several pupae were examined with negative results. These were bred from house flies confined in a dish with horse manure which had previously been boiled to destroy any fly larvae or nematodes which might have been present. That some of the flies were infested with Habronema was determined by examining a num- ber after oviposition had occurred. An undersized male which developed in the culture just referred to, the only adult that was obtained in this culture, was examined with negative results. "That infection with Habronema musce is acquired during some stage prior to the imago was proved by the discovery of the parasites in a fly caught just as it was emerging from the pupa (No. 9, referred to above). Beyond this fact the observations made by me (made incidentally in the course of another in- vestigation) have proved little as to the life history of the parasite. On several occasions I have placed the worms taken from flies in water and in horse manure, but in no case was it observed that any further develop- ment occurred. The worms invariably died within a few days. It would seem, however, that the larval stage of the parasite which is found in the fly must in some way escape from its host, reach sexual maturity either as a free living form or in another host, and produce young which find their way into other flies NATURAL ENEMIES 75 during an early stage in the development of the insects. It is improbable that the worms develop to maturity in the fly, since they have been found only in the larval stage in that host. It might be noted in this connec- tion that Carter erred in identifying certain structures as reproductive organs." Other nematodes have been found in the typhoid fly, but it is not as yet determined that they are surely distinct from the one just mentioned. THE MITE ENEMIES OF MUSCA DOMESTICA Many flies of different species are often noticed to have small red mites attached to their bodies. This has been found to be the case with small flies as well as with large ones — even mosquitoes have enemies of this kind. Some of these mites probably exert a dele- terious effect upon their host and are true parasites, but with others the flies simply act as aeroplanes to carry the mites from one place to another. (A free ride seems to be the only object for which they have at- tached themselves to the fly.) Attention was called to these mites in the first place by DeGeer in 1735. Linnaeus wrote of one of them in 1758, and other writers have made mention of them and have described several species. Mr. Nathan Banks, an authority upon this group of creatures (Arachnids), has given the writer the following information : "Latreille based a new genus and species on mites from the house fly, and he called it Atomus parasiticum. This is the young of one of the harvest mites of the 76 THE HOUSE FLY— DISEASE CARRIER family Trombidiidae, but the adult has not been reared and is still unrecognized in Europe. Riley found these harvest mites on house flies in Missouri, in some years so abundantly, he says, that scarcely a fly could be caught that was not infested with some of them cling- ing tenaciously at the base of the wings. Later he suc- ceeded in rearing the adult, and described it as Trom- bidium muscarum. In recent years Oudemans has de- scribed TrombidiuiJi inusca from larval mites found on house flies in Holland. "All these forms are minute, six-legged, red mites, which cling to the body of the fly and with their thread- like mandibles suck up the juices of the host. They are nearly related to the so-called 'red-bugs,' or 'chig- gers,' of the Southern United States. When ready to transform, they leave the fly and cast their skins, the mature mite being a free-living, hairy, scarlet creature about one and five-tenths mm. long. The adults are usually found in the spring and early summer, while the larvae are usually found in the autumn on house flies and other insects. Mites of the genus Pigmeophorus, of the family Tarsonemidae, have also been taken on house flies. They cling to the abdomen of the fly, but it is not cer- tain whether they feed on the insect or use it simply as a means of transportation. The hypopus, or mi- gratorial nymphal stage of several species of Tyro- glyphus, has been found on house flies. This hypopus attaches itself by means of suckers to the body of any insect that may be convenient. The mites do not feed NATURAL ENEMIES 77 on the fly, but when the fly reaches a place similar to that inhabited by the mites the latter drop off, cast their skins, and start new colonies. DeGeer observed large numbers of these tiny mites on the back and neck of the house fly. Linnaeus named one of them Acarns miiscarum. Berlese has reared from stable flies what he considers as this Acarus miiscaruni of Linnaeus, and finds that the adult belongs to the genus Histiostoma. The hypopi most commonly found on the house fly are those of the common household cheese- ham- and flour- mites. All through the summer months, and in warm houses during the winter months, these creatures breed with astonishing rapidity and fecundity. The females bring forth their young alive, and these in turn reach full growth and reproduce until a cheese, once infested by a few, swarms with the crawling multitude which causes its solid mass to crumble and become mixed with excremental pellets and cast-off skins. During the summer months the mites are soft-bodied and have comparatively feeble powers of locomotion, and, as they become numerous enough to devour the whole of a cheese with no other food at hand, it was for a long time a puzzle to know what became of them and to understand how a cheese could become in- fested without coming in contact with another infested cheese or without being placed in an infested room. It has been learned, however, that when necessity requires it and when the insects happen to be in the proper stage of growth, they have the power not only of almost in- definitely prolonging existence but of undergoing a 78 THE HOUSE FLY— DISEASE CARRIER complete change of form, acquiring hard, brown, pro- tective coverings into which all of the legs can be drawn in repose. In this hard shell, or hypopus state, it may remain for many months without food. In the majority of cases, however, where a given cheese is completely destroyed, all of the young and old mites perish, and only those of middle age, which are ready to take on the hypopus condition, survive. These fortunate survivors, possessing their souls in patience, retire into their shells and fast and wait, and, as everything comes to him who waits, some lucky day a house fly comes that way and the little mite clings to it and is carried away to some spot where another cheese or food in some other form is at hand. SPIDERS AS FLY ENEMIES In spite of the well-remembered poem beginning "'Will you walk into my parlor?' said the spider to the fly," it is a curious psychological fact that the writer had practically completed the writing of this chapter on the natural enemies of the house fly before he dis- covered that he had forgotten to say anything about spiders. That was not because he is getting old and forgetful, but because in the rooms which he has had the good fortune habitually to frequent during later years he has rarely seen a spider. Although, if given the opportunity, they would kill an unlimited number of flies, they are not permitted to build their webs and increase in localities where the flies are the greatest nuisances; that is to say, in houses, shops, and hos- NATURAL ENEMIES 79 pitals. It will not be necessary, therefore, to give, spiders any extended consideration here. Mr. Nathan Banks, the well-known writer on these interesting crea- tures, has jotted down for the writer the following brief notes on the subject : "The most common spider in houses is Theridium tepidariorum Koch. It occurs throughout the civilized world. It builds an irregular web in the upper corners of rooms, and if the housewife is not too tidy, one may often see flies in its webs. Steatoda borealis and Teutana triangulosa are related spiders, occurring in this coun- try and in Europe; their webs are commonly under or behind furniture, in darker places than those of the Theridium. They do not catch as many flies, but their webs are safer from the housekeeper's broom. "Agalena ncevia, a common field spider, is frequently found in houses, especially outhouses, outside kitchens, etc. ; sometimes they live in these double screens ; they need some crack or hole in which to retire; the web spreading fan-like from this hole, which they line with silk. "Salticus scenicus is a common jumping spider about houses, usually on the outer side of houses, but often seen on windows, where one may watch with much in- terest their method of stalking and suddenly leaping on unsuspecting flies. "In cellars, packing boxes, and other dark places, other spiders occur; Tegenaria derhami and Amauro- bius ferox being common in the United States and in Europe. 80 THE HOUSE FLY— DISEASE CARRIER "Several of the orb-weaving spiders are often found on porches, where their snares will intercept many flies. Epcira scricata nearly always occurs near or on buildings." FALSE SCORPIONS ON FLIES ^ There is a group of Arachnids, known as the false scorpions or pseudoscorpions, which are much smaller and simpler in structure than the true scorpions. They have no poison gland and no spine at the end of the body. They bear much the same relation to the true scorpions that the mites do to the true spiders. They live beneath the bark of trees, in moss, between the leaves of old books, etc. They run sidewise and backwards, and live on mites and small insects. Two or three species of the false scorpions are sometimes found clinging by their claw-like pedipalps to the legs of the house fly and other kinds of flies. It is not known why they attach themselves to these insects, but it is hardly probable that they feed on them, and it seems altogether likely that they simply attach themselves in the same way as does the hypopus of the Tyroglyphid mite, in order to be carried to some better feeding ground. Much has been written upon this subject, and many different views are held about this attach- ment, but there is no sound evidence on the one side or on the other. The suggestion has been made that the false scorpion seizes the legs of the flies without realizing their size, and that they remain attached until the fly dies and then they feed upon the body. Doctor NATURAL ENEMIES 81 Hewitt has reviewed the habits of one of the species known as Chernes nodosus Schrank, which, he states, is more abundant in England in some years than in others. He quotes Godfrey (1909): "The ordinary habitat of Chernes nodosus, as Mr. Wallace Kew has pointed out to me, appears to be among refuse, that is, accumulations of decaying vegetation, manure heaps, frames and hotbeds in gardens. He refers to its occur- rence in a manure heap in the open air at Lille, and draws my attention to its abundance in a melon frame near Hastings in 1898, where it was found by Mr. W. R. Butterfield." Doctor Hewitt very justly calls attention to the fact that it is not difficult to under- stand the frequent occurrence of this false scorpion on the legs of flies, in view of the facts just quoted from Mr. Godfrey, since flies frequent such rubbish heaps for the purpose of laying eggs, or he suggests that when they have recently emerged from puparia in such places and are crawling about while their wings are drying their legs are readily to be seized by the Chernes. In closing his account of this species he writes, "It is obvious that the association [between the Chernes and the fly] will result in the distribution of the pseudoscorpionid, but whether this is merely incidental and the real meaning lies in a parasitic or predaceous intention on the part of the Arachnid, as some of the observations appear to indicate, further experiments alone will show." 82 THE HOUSE FLY— DISEASE CARRIER THE HOUSE CENTIPEDE There is a small, rather fragile-looking centipede, known scientifically as Scutigcra forceps Raf., which for many years has been a constant inhabitant of houses in the Southern United States, and which seems to have been gradually extending its northward range. It is now occasionally found in houses as far north as Albany. N. Y., and perhaps even farther. It seems to be peculiarly a domestic animal ; that is to say, it has accommodated itself perfectly to the con- ditions existing in human habitations. Its form and its sudden movements have made it an object of fear, especially to women and children. It is fond of damp localities, and is especially abundant in bathrooms, in basements, in cellars, and in ground-floor kitchens and pantries, where there is more or less dampness and warmth. It has been called the skein centipede, since when crushed its long legs look like a mass of threads. This creature, as has been shown by Marlatt (1896), seems to be a normal inhabitant of the southern tier of the United States, spreading north into Pennsyl- vania as early as 1849 and reaching New York and Massachusetts twenty or twenty-five years later. It is now common throughout New York and the New England States and extends westward beyond the Mississippi. The character of its mouth parts indicates that it is predatory and carnivorous in its habits; the jaws are strong, and its food consists principally of other in- Fig. 17.— The house centipede (Scutigera forceps) ; somewhat enlarged. (After Marlatt.) NATURAL ENEMIES 83 sects living in houses, such as house flies, small cock- roaches, and clothes moths. Years ago the writer ob- served its method of catching both Croton bugs and house flies upon the wall of the kitchen of a house in which he lived in Georgetown, D. C. It feeds and is especially active at night, being seen in the daytime usually only when disturbed. On this occasion, with the late Dr. James Fletcher, the writer went to the pantry in the evening and saw a good-sized specimen of the Scutigera on the wall eating something. The light was turned as low as was consistent with fairly clear observation. The object held in its front legs was seen to be a small Croton bug. It was eaten with astonishing rapidity, but in the act of eating this speci- men a house fly was observed by the centipede, close to it, resting upon the wall. It instantly jumped, ap- parently with all of its legs at once, and covered the fly, which was thus confined as if it had been in a hen coop. When the Croton bug was devoured, the pair of legs opposite the fly seized it and passed it to the pair of legs immediately in front, and in succession it was passed up to the front legs, by which it was held while being devoured. So it is obvious that its great number of legs are of use, not only in walking, but in the capture of its prey. The same operation was repeated several times. The popular belief is that this little creature is very poisonous, and indeed it belongs to the poisonous group of centipedes. Very few cases are recorded, however, of its having bitten a human being, and it is question- 84 THE HOUSE FLY— DISEASE CARRIER able whether it would attack any animal or insect larger than itself. Marlatt states that if pressed with the bare foot or hand, or if caught between sheets in beds, it will unquestionably bite in self-defense. He also shows that the few such cases on record indicate that severe swelling and pain may result from the poisonous injection. Prompt application of ammonia, however, will alleviate the symptoms. No one knows much about the life history of this creature. Full-grown specimens are found in houses all through the year; half-grown individuals are some- times found in the summer; the youngest ones known differ from the older ones chiefly in having fewer legs. It is interesting to note that a careful look at the hind segments of the young will show the long posterior legs folded up within and ready to be extended after the next molt. Under present conditions of house fly abundance, it might be as well not to disturb this Scutigera when it is found in houses, but with the conditions which will shortly be brought about, we hope, it will be easy to destroy the centipedes with pyrethrum powder, even if they do not, as is likely, die of starvation. INSECT ENEMIES OF THE HOUSE FLY Predatory enemies. — It seems rather strange that, with the very numerous predaceous insects which de- rive their sustenance from soft-bodied and more or less helpless species, there should not be more which gain their livelihood from the larvae of the typhoid fly. It NATURAL ENEMIES 85 is true that the larvae of certain Carabaeid beetles, and especially those of the genera Harpalus, Platynus and Agonoderus, are sometimes found frequenting manure and feeding upon young fly larvae, and that certain rove beetles and their larvae, of the family Staphylinidae, are also found in the same situations, engaged in the same task. And Packard (1874) records the rinding of a beetle pupa in the puparium of the house fly. But one would think that a pile of horse manure swarming with fly larvae would attract hordes of predatory beetles and of pirate bugs and the like. Is it that house fly maggots are distasteful to these Voracious creatures? Or is their perception of odors keen and are the am- moniacal odors of the manure pile repugnant? It is difficult to say. The typhoid fly belongs plainly to a most persistent type, and it feeds freely and abundantly in close proximity to many insects which we would naturally suppose to be its enemies. But we must not forget the ants. It is true that many ants are nuisances, and in the case of the destruc- tion of the typhoid fly by ants we have simply one nui- sance multiplying at the expense of another, but Forel and Wheeler admit that as a group ants are beneficial and that many species deserve our protection. Capt. P. L. Jones of the U. S. Army Medical Corps (quoted by Garrison, U. S. Naval Med. Bull., Oct., 1910, p. 551) made certain experiments in the Philippines to determine whether the scarcity of flies in those islands was due to some epidemic disease. In the course of the experiments it was found impossible to raise flies 86 THE HOUSE FLY— DISEASE CARRIER unless the eggs and larvae (in manure) were protected from ants, as the latter invariably carried off both eggs and larvae and even pupae. In the work against the cotton boll weevil carried on in the Southern United States by the experts of the Bureau of Entomology of the U. S. Department of Agriculture, it was found that the "fire ant" of the Southern cotton fields (Solenopsis gemminata, var. diabola) is an important enemy of the weevil, and strong efforts were made to multiply the ants. It was soon found that they were strongly attracted to horse manure and undoubtedly destroyed all its other insect inhabitants. Mr. W. D. Pierce of the Bureau informs the writer that the little black ant Monomorium mini- mum also frequents horse manure heaps in Texas, and he also says that several species of the ant genus Phei- dole have this habit. Moreover, that famous pest in Louisiana and parts of California, known as the "Argentine ant" (Iri- domyrmex humulis) nests readily dn horse manure, and its active, pugnacious and predatory habits undoubtedly induce it to prey upon the maggots found there. Mr. Pierce' s ant suggestion was of sufficient interest to follow up, and therefore the writer has corresponded with Prof. Wilmon Newell, of College Station, Texas ; Prof. J. B. Garrett of the State University of Louisiana at Baton Rouge; and Mr. T. C. Barber, in charge of the Audubon Park laboratory of the U. S. Bureau of Entomology at New Orleans — all of them men who have had intimate acquaintance with the Argentine ant, NATURAL ENEMIES 87 and who have made special studies of its habits. The reply from each was the same in its general tone. Professor Newell never found the Argentine ant nesting in pure horse manure, but has found them in manure that contained a large amount of straw or hay. A certain public dumping ground carrying much ma- nure was heavily infested with the ants, but house flies bred from it in such enormous numbers that the health officer was called in. The observer found colonies of ants on the ground and also an abundance of fly larvae. His experience has been that house flies are not notice- ably reduced in places where the Argentine ant swarms. Professor Garrett writes that the mess hall in which about 300 of the students take their meals is in a lo- cality where the ants are very abundant, and yet the house flies are apparently as numerous as ever. He thinks that the ants do destroy quite a number of lar- vae in manure, but that they do not use them as an article of food to a sufficient extent to cause an appre- ciable decrease. Mr. Barber is of the same opinion. Mr. F. C. Pratt, an agent of the Bureau of Entomol- ogy, located at Sabinal, Texas, made an especial study of fly larvae at Dallas on one occasion. He found that the fire ant, on one occasion when he was experiment- ing with cow manure in order to raise parasites of the horn fly, took complete possession of his rearing cages and their contents. In his opinion, they feed upon all fly larvae. Aside from ants, there are other predatory insect ene- mies of flies not yet mentioned. Wasps catch house 88 THE HOUSE FLY— DISEASE CARRIER flies, sometimes in considerable numbers. It is not an uncommon sight to see any one of several different species of wasps flying about houses, capturing flies both on the wall and on .the wing. The robber flies of the family Asilidae also catch house flies, on porches sometimes. On the whole, however, the predatory in- sect enemies of the house fly are negligible, so far as the beneficial result of their work is concerned. Parasitic Enemies To a certain extent the same may be said of the para- sitic enemies of this species, but these are perhaps more numerous than the predatory insect enemies, and sev- eral of them are accustomed to frequent excreta in the search of larvae in which to deposit their eggs. This is especially true of cow dung, and many minute hy- menopterous parasites may be found frequenting drop- pings in the pasture in order to lay their eggs in some one of the many species of maggots which are to be found there in a very short time. These very minute, active, four-winged parasites be- long either to the subfamily Figitinse of the gall-fly family Cynipidse or to the superfamily of true parasites known as Chalcidoidea. In the gall-fly family, Cynipida?, most of the species of which produce galls upon living plants and very numerously upon the oak, there is one subfamily of minute forms, the Figitinse, parasitic upon other insects and for the most part upon dipterous maggots. Those frequenting cow dung will lay their eggs in apparently NATURAL ENEMIES 89 almost any one of the many species of dipterous larvae found there, and have been reared from the larvae of the horn fly, from several species of true dung-flies (family Scatophagidae), and from others. Two spe- cies, however, are reared from the maggots of the ty- phoid fly. These are Figites anthotnyiarum, reared from the house fly in Germany by Reinhard, and Figites scutellaris, also a European species. If careful rearing experiments were carried out continuously in this country with house fly larvae, it is probable that other species of this group would be reared. Prof. T. D. A. Cockerell, for example, caught one of them — Eucoila impatiens Say — on horse dung at Las Cruces, N. Mex., in 1894, and suspected its parasitism on house fly larvae (Insect Life, VII, 209). Many similar ob- servations can doubtless be made very easily. The Chalcidoid parasites of Musca domestica are more numerous. In the family Pteromalidae there is a genus, Spalangia, which seems practically confined to dipterous larvae. One species, Spalangia niger, was found by the German author Bouche to lay its eggs in the pupae of the house fly and to issue in April and May. The larvae of the Spalangia are spindle-formed and white, almost translucent, and are to be found in the autumn in the puparia of the house fly, where they destroy the true pupae. Several species belonging to this same genus are to be found in the United States, and one of them at least has similar habits. Mr. H. L. Sanford, of the Bureau of Entomology at Washington, in opening a series of 90 THE HOUSE FLY— DISEASE CARRIER puparia of Musca domestica in January, 1911, in order to ascertain what proportion of the pupae were living, was surprised when a fully formed and active adult black Spalangia crawled immediately from the opening made by his dissecting needle. This will be described by Girault as Spalangia musccc. A certain proportion of the house fly puparia are affected by this parasite in precisely the same way as are the puparia in Europe by Spalangia nigcr as described by Bouche. Mr. San- ford's observation shows that the adults may be fully formed and ready to emerge at a very early date. Another European Pteromalid parasite, namely, Ste- nomalus mnscarum, is recorded as being a parasite of the house fly pupa. Much attention has been given to the Chalcidoid parasites of the typhoid fly by A. A. Girault and G. E. Sanders, of the University of Illinois. In their first paper (Psyche, December, 1909, pp. 119-132) they described an interesting form under the name Nasonia brcvicornis from a series of 640 specimens, nearly all reared from puparia of various flies in the Office of the State Entomologist of Illinois at Urbana during 1908. They came from various decomposing materials, from which several species of flies were reared, but a num- ber undoubtedly came from Musca domestica. It is a minute, dark, metallic, brassy-green fly with clear wings and rather stolid and serious temperament. Girault and Sanders state that it heeds external influ- ences very slightly, and quietly and persistently gives its whole attention to reproduction. They found that NATURAL ENEMIES 91 both sexes crawled rapidly. The female is able to fly ; but the favorite mode of locomotion appears to be crawling. The wings of the male appear to be non- functional. Actual experimentation with fifty maggots and ten puparia of the house fly showed that the para- sites laid their eggs in the puparia and, developed rap- idly. The maggots and puparia were placed in a breed- ing jar on September pth, and on September 26th six males and ten females of the parasites issued from the puparia. On September I2th, eight female parasites were confined separately in small gelatine capsules, each with a healthy puparium of the house fly. The parasites appeared to lay their eggs in several cases, but none issued afterwards and about half of the flies came out. Most careful observations were made by the authors on the egg-laying process of this parasite. The female was observed to walk carefully over a two-days' old puparium, examining the entire surface. After a point was selected, the ovipositor was inserted with some dif- ficulty, the operation requiring one minute and a half. The hole was then enlarged, and the ovipositor was again pushed in for its entire length and remained for forty-five seconds, during which time apparently an egg was deposited. After the ovipositor was with- drawn the parasite examined the puncture with its antennse and mandibles. The parasite apparently attacks only the puparium, and that only after it has been formed for about twenty- four hours, and a number of them issue from the same 92 THE HOUSE FLY— DISEASE CARRIER puparium. Observations were carried on through suc- ceeding months and the duration of the life cycle was carefully studied (Psyche, February, 1910). The life cycle is longer in the spring and shorter in summer, the average life cycle being twenty-two and one- half days with usual temperature. They found that one female was able to parasitize twenty-two puparia and another one seventeen. The authors suspect that the phenomenon of polyembryony, that is to say, the development of a number of adult individuals from a single egg, takes place with this species. Counts of several thousand reared specimens of the parasite in- dicated that fifty-eight and nineteen-hundredths per cent, of them were female and forty-one and eighty-one- hundredths per cent, were males. They found that the adult parasites issue from the host puparium through from one to three circular holes of various positions, several issuing from each hole. As to the abundance of the parasite, the authors indicate that during Sep- tember and October, 1908, they reared 8,000 or more specimens, and these were reared quite accidentally, that is to say, without conscious effort on their part to in- crease the number. The local abundance of the para- site was indicated by the fact that in a portion of a given experiment the percentage of parasitism was as high as ninety per cent. This percentage of mortality on the part of the house fly, however, was by no means general, and the parasite had apparently concentrated its attack on certain spots. The authors made an un- successful attempt to propagate the species artificially NATURAL ENEMIES 93 by scattering 1,000 specimens of mixed sexes over a garbage heap on September 23d. This, however, was too late in the season, and weekly collections of fly puparia thereafter gave no result. The authors found that this parasite hibernates as a full-grown larva in the puparia of the flies, trans- forming to pupa early in the spring and emerging shortly afterwards. As examples of intensive and care- ful study of a given species, the papers on this form by the authors mentioned are excellent. The same authors have made a careful study of an- other house fly parasite of this group, known as Pachy- crepoideus dubius. This species was reared in com- pany with the preceding species, and the experiments of the writers indicated that it is a true primary para- site of the house fly. They were unable to make any observations on the biology of the species, except to notice that the adults in three cases emerged from the fly puparium through a single hole with jagged edges. Still another parasite of this group, studied by Gir- ault and Sanders, and described in Psyche for August, 1910, is Muscidifurax raptor. This is another small, clear-winged species, black in color, which was reared in some numbers from puparia of the typhoid fly at Urbana and Champaign, Illinois. It also breeds in the puparia of other flies, is solitary in its habits, and more sensitive than the Nasonia which the experiment- ers have described so fully. They state that the bio- logical history of the species can be learned with ease in the laboratory, as the females are not at all averse 94 THE HOUSE FLY— DISEASE CARRIER to ovipositing in confinement ; they are, however, seem- ingly not as prolific or as generally parasitic as Nasonia. The writers did not obtain certain data concerning the entire seasonal history of this parasite, but they think that it confines itself principally to the puparium stage of the house fly, hibernating in the puparium as a larva and pupating itself and emerging early in the spring as an adult four-winged parasite. The first specimens found by them emerged the first week in September, and from that time on until frost it was comparatively abundant. It was reared from puparia collected on September 23d and again from some col- lected on October 2ist, emerging from these Novem- ber 6th. Hibernation probably commenced about Oc- tober 2 1 St. Examination of the house fly pupae, after the para- sites have emerged, indicates that the larva of the para- site feeds externally on the pupa of the fly, sucking its juices. The attachment is to any portion of the body of the pupa. Opening a puparium from which the adult parasite had emerged revealed the blackened and shrunken remains of the fly pupa lying in its natural position along the floor of the pupal shell. The meconium, or excrement passed by the para- site larva when about to change to pupa, is distinctive — dark in color and round-angled, looking like a small, solid, black, round bit, resembling somewhat a coarse grain of powder but not as irregular or angular. It differs from the meconium of the other parasites of the house fly studied by the authors mentioned. The adult NATURAL ENEMIES 95 parasite issues through a single rounded hole cut in the pupal skin of the fly. The two sexes issue almost simultaneously, the males a little before the females. Each female appears to lay thirty to forty eggs. Out of 288 specimens reared, eighty-five were males and 203 females, and the average duration of the life cycle was nineteen days and seventeen hours. Girault will continue his intensive study of fly para- sites and will undoubtedly learn many new and im- portant facts. Additional species have already been reared by him and await systematic study. VERTEBRATE HOUSE FLY ENEMIES The common garden toad, the great collector of in- sects, will catch a house fly whenever it is able to do so. It is, in fact, a pleasing occupation to feed house flies to a good-sized toad, in order to ascertain his capacity. But these animals are not inhabitants of houses. Some of the lizards that run about houses in tropical regions feed upon flies, and the occupancy of houses by these creatures is not objected to by natives, for this as well as for other reasons. Birds are not effective as house fly enemies. Of the wild birds, comparatively few feed upon them at all, although there are many insectivorous species which would do so if they were allowed to nest in houses. As a matter of fact, however, in all the records of the Bu- reau of Biological Survey of the U. S. Department of Agriculture, which represent the examination of the contents of the stomachs of many thousands of birds, 96 THE HOUSE FLY— DISEASE CARRIER there are only two records of the finding of house flies, and one of these is somewhat doubtful. One of their records shows the finding of thirty-three larvae in the stomach of a horned lark, but it is quite possible that these larvae were not those of Musca do- mestica. The other record shows the finding of a single adult house fly in the stomach of a white-eyed vireo. The writer has watched the house wren feeding its young hour after hour, and has noticed that the in- sects brought to the nest were for the most part small caterpillars, although there were plenty of flies on the porch where the nest was built. The great group of insectivorous birds known as the fly-catchers as a matter of fact do not prefer the flies. As the writer has been told by Prof. F. E. L. Beal, an authority on the subject, they feed by preference upon winged hymenopterous insects, which constitute the bulk of their food. W. D. Doan in Bulletin 3 of the West Virginia Ex- periment Station records finding house flies in the stomachs of the cedar bird, the wood pewee, and the palm warbler. Domestic poultry, however, when given the oppor- tunity, will feed with some avidity upon house fly lar- vae. Hens given the run of a barnyard destroy very many larvae in scraping about the edge of the manure pile, and more than one letter has been received from persons who, admitting flocks of poultry to the barn- yard for the first time, have discovered an appreciable reduction in the number of adult flies visiting the house. NATURAL ENEMIES 97 Fly-Catching Rats A number of mammalia in captivity have been seen to capture flies, but as a rule they seem to do this very much as the idle house dog will snap at the fly circling about his head. A most interesting observation, how- ever, has been made by Prof. B. W. Evermann, of the Bureau of Fisheries in Washington. At a meeting of the Biological Society of Washington, held January 7th, he gave an account of a visit in early July of 1910, at Kokomo, Indiana. He stopped at a hotel and was sitting on the piazza on the evening of his arrival. Back of him was a window which opened into a storeroom for provisions, etc. Inside the window was a lace cur- tain which hung closely, and uniformly covered the entire window. Happening to look at the window quite by accident, Professor Evermann saw a brown rat run back and forth on the window-sill inside. It seems that a large number of flies had accumulated between the curtain and the window, probably attracted by the light from outside, and the rat was engaged in catching these flies. In Professor Evermann's words, "It was very expert. It would move back and forth the full length of the window-sill, catching such flies as it could reach. It would frequently stand upon its hind legs to its full length with its fore paws and body resting against the glass and move backward and forward across the win- dow. It ordinarily caught the flies with its paws, by raking the fly with one paw over against the other or 98 THE HOUSE FLY— DISEASE CARRIER bringing the two paws together on a fly and then feed- ing it into its mouth." The observer watched it for some little time and must have seen it catch more than one hundred flies. Next morning the same performance was repeated, and a large number of flies were captured. Moreover, a second rat appeared during the time the observer was watching the first one, and its methods were the same. Inquiry from the clerk at the hotel indicated that the people of the hotel had noticed the rats engaged in this occupation and had refrained from disturbing them. Mr. W. L. McAtee, recently, in looking over an old file of The Rod and the Gun found the following item in the number of September 25, 1875. It is quite be- lievable in view of Doctor Evermann's personal ob- servations : "Mr. C. B. Odell, at his hotel on Front Street, is the happy owner of a fly exterminator, which, for thor- ough work, is unsurpassed by anything we have ever seen. In one of the windows facing Front Street, where samples of his wares are occasionally shown, a rat began several weeks since to make sly visits, and secured a good meal as often as he came by catching the many flies which are on the panes of glass. He grew very expert at it, and though at first quite shy, soon became emboldened when he found he was not disturbed in his foraging expeditions, and would pur- sue his business not in the least intimidated by spec- tators, who were only separated from him by a pane of glass. He obtained entrance to this window by NATURAL ENEMIES 99 gnawing a hole through the wooden base, coming from below. For weeks he has pursued his fly-hunting busi- ness undisturbed. "On Sunday one of the waiters discovered him in the act of introducing a friend or member of his family to his foraging ground. The newcomer was very shy, and only put his head through, while the old habitue tried to coax him in the window. He would catch a fly, gravely hand it to his friend, who would as gravely eat it, and look for more. By degrees he lost a little of his fear, walked out, and soon became an expert in the new business. Either one or both may be seen al- most any day by any one who may be patient enough to wait for their appearance a short time. It is certainly a very novel sight, and well worth a few minutes' time to see. — Neivburgh Telegraph." Mr. Nat. C. Dearborn, of the Biological Survey of the U. S. Department of Agriculture, states that he has frequently seen evidence of the destruction of adult flies by mice on window-sills, the work having been done at night. Ill THE CARRIAGE OF DISEASE BY FLIES IT would probably be impossible to trace the first sug- gestion of the carriage of disease by flies. They have been conspicuously connected with accounts of epidemics of one kind or another for hundreds of years, and before discussing some of the specific diseases which they are thought to carry some attention may be given to some of these early suggestions. . It should be pointed out before taking up this subject, however, that the house fly is simply a carrier of disease germs, and that it differs in its relation to disease from the malarial mosquitoes, which are the necessary secondary hosts of the causative organisms of malaria, in that only in mosquitoes of the genus Anopheles can the germs complete their life round and develop sexual forms. In this they differ also from the yellow fever mos- quito (Aedcs calopus), since, although the causative organism of yellow fever has not yet been discovered, close analogy shows that it must be a protozoan de- pendent for its full development upon a lodgment in the stomach of the mosquito in question. It differs in the same way from the bedbug, which has more re- cently been seen to be probably the necessary secondary host of the causative organism of kala azar. The house fly simply carries the germs of disease, either on its 100 CARRIAGE OF DISEASE 101 legs or in its alimentary canal, just as these germs could be carried in any other way — by water, by shell-fish, by unwashed and uncooked vegetables grown in land dressed with night-soil, on dust particles, or by personal contact. Most of the wrriters who have collected data on this subject refer to 'the statement by Sydenham, who is said to have lived between 1624 and 1689, to the effect that if house flies are abundant in the summer the autumn will be unhealthy, and very many people hold that view; but Sydenham was by no means the first to believe that the house fly is insanitary. There are many references to this insect in the Hebrew Scrip- tures, and the sanitary regulations of the camps of the children of Israel in their march through the wilder- ness refer to flies in terms which indicate that the au- thors of the regulations were almost as well posted on the subject of the danger of flies as the Japanese sur- geons in the recent Japanese-Russian War. I have often wondered whether the twenty-fourth verse of the eighth chapter of Exodus, "and there came a griev- ous swarm of flies into the house of- Pharaoh, and into his servants' houses, and into all the land of Egypt: the land was corrupted by reason of the swarm of flies," did not mean that the flies corrupted the land, and whether there is not something very significant in the statement that among the plagues that followed were the murrain of cattle and the death of all the first- born of Egypt. Several of the great surgeons of the seventeenth and 102 THE HOUSE FLY— DISEASE CARRIER eighteenth centuries have referred to this possibility, and our own Leidy, in 1871, said that he believed that house flies were responsible for the spread of hospital gangrene during the Civil War. In that same year (1871) Lord Avebury (then Sir John Lubbock), in an article in the London Lancet, mentioned the fact that flies alight on decomposing matter and carry se- cretions with them. He uses this significant sentence: "Far from looking upon them as dipterous angels danc- ing attendance on Hygeia, regard them rather in the light of winged sponges spreading hither and thither to carry out the foul behests of Contagion." EXACT EXPERIMENTS There was, for a long time, no experimental proof of such carriage. There have been outbreaks of disease and single cases of disease where the carriage of the causative organism by house flies seemed to be the best explanation. Actual experimental proof satisfactory to the laboratory worker, however, has been of recent ac- quirement, and it will be well before entering upon the subject of specific diseases to mention some of this work. One of the latest and one of the most careful series of laboratory observations has been made by Doctor Graham-Smith (1910). His experiments covered a wide range and seem to have been carried out with the utmost pains. The most satisfactory method of con- veying his results is to give his conclusions in his own words : "Infection experiments show that non-spore-bearing CARRIAGE OF DISEASE 103 pathogenic bacteria do not usually survive more than a few hours (five to eighteen) on the legs and wings. Nevertheless, flies allowed to walk over sterile agar plates may cause infection for several days. This seems to be due to the fact that they frequently attempt to suck the surface, and in so doing infect it with fluid regurgitated from the crop. Within the crop non- spore-bearing bacteria frequently survive for several days, and they usually survive even longer in the intestine. No evidence of multiplication in either of these situations has been obtained. The feces deposited by such flies often contain the organisms in consider- able numbers for at least two days, and are frequently infective for much longer periods. Anthrax spores survived for many days on the exterior and in the ali- mentary canal. ''Experiments with B. prodigiosus show that flies may infect sugar forty-eight hours after feeding on infected material, and that clean flies may infect them- selves by feeding on the recent deposits of infected flies. In the few experiments which were tried, milk and meat were not infected. Flies fed on anthrax spores did, however, infect the syrup which was given to them as food. "In the experiments which have been described, very gross infection was produced in most cases by emul- sions of pure cultures. It is improbable, however, that under natural conditions flies would often have the op- portunity of feeding on materials which contain path- ogenic organisms practically in pure culture. The ef- 104 THE HOUSE FLY— DISEASE CARRIER fects of contaminating with non-pathogenic and putre- factive bacteria have as yet not been studied, and the effects of season, temperature, atmospheric conditions, different diets, irregular and scanty feeding, and other disturbing factors have not received sufficient attention. "Consequently it would be premature to conclude that the experiments and observations described in this paper do more than indicate that, under exceptionally favorable conditions, certain bacteria can be recovered from the contents of the alimentary canal and fecal deposits of infected flies for several days after infec- tion; and that these flies are capable of infecting cer- tain materials on which they feed for several days. The experiments with tubercular sputum and anthracic blood alone afford evidence as to the duration of life in the contents of the alimentary canal of pathogenic bacteria taken up under natural conditions. 'That flies sometimes do become grossly infected under natural conditions is shown by the fact that in a few instances pathogenic bacteria have been isolated from naturally infected flies. Simmons (1892) iso- lated cholera vibrios from flies which were captured in a post-mortem room in which the bodies of persons dead of cholera were lying. Tsuzuki (1904) was able to cultivate the same organism from flies captured in a cholera house, and Tizzoni and Cattani (1886) ob- tained cultures from flies caught in cholera wards. Hamilton (n. 1903) and Picker (1902) isolated B. typhosus from flies caught in houses in which persons were lying ill of typhoid fever, and Faichnie (1909) CARRIAGE OF DISEASE 105 obtained B. typhosus from a number of flies caught in various places where typhoid fever prevailed. He further showed that B. typhosus or B. paratyphosus (A) could be cultivated for several days from the in- testines of perfect insects which emerged from larvae fed on feces containing these organisms. "Several observers [Celli (1888), Hay ward (1904), Lord (1904) and Buchanan (1907)] have shown that the feces of flies which have fed on tubercular sputa contain virulent tubercle bacilli. Buchanan (1907) demonstrated that flies which had walked over nat- urally infected anthracic meat were capable of infect- ing agar plates. Yersin (1894) in Hong-Kong ob- served many dead flies lying about in his laboratory where he made autopsies on plague animals. He dem- onstrated by inoculation into animals that a dead fly contained virulent plague bacilli. "Finally the experiments of Macrae (1894) at the Gaja jail show that exposed milk may become infected by the agency of flies. "Even these observations only prove that cultures of pathogenic organisms may occasionally be obtained from naturally infected flies, and they do not afford conclusive evidence that such flies are a frequent source of disease in man by infecting food materials. Though many of the observations cited by JSTuttall and Jepson seem to indicate that flies have frequently acted as car- riers of disease, it has only once (Macrae) been dem- onstrated that food has actually been grossly contam- inated by them." 106 THE HOUSE FLY— DISEASE CARRIER Early laboratory experimental work in the labora- tory was carried on in this country by Dr. Jocelyn Man- ning (1902) of Eau Claire; Wis., who succeeded in making pure cultures from infected flies of the fol- lowing bacteria : Bacillus pyocyaneus, Staphyllococcus pyogencs aureus, Bacillus typhi abdoininalis and B. coli communis. The care with which Doctor Graham-Smith sum- marizes the results of his experiments and the similar observations of previous workers, in order to preserve an exactly judicial and thoroughly scientific frame of mind, is worthy of all praise, but the accumulation of evidence which has been gathered and which will be displayed in our consideration of the different diseases is so overwhelming, both from the standpoint of exact observation and of sound inference, that surely every possible effort to do away with Musca domcstica is am- ply justified on the disease-bearing ground. Other laboratory observations have been made by trained bacteriologists and mycologists in the direction of the carriage of micro-organisms by flies. One inter- esting series, to which the writer has referred else- where, was published by W. N. Esten and C. J. Mason (1908). The following table and the two subsequent paragraphs are quoted from their bulletin: CARRIAGE OF DISEASE 107 I ill :~ > oS .1, .«- 111 OJ.Q' 3 v* ooooooooooo ss'g QO o* ooi o* eo oS hs c be C UX) be c be c bo.5 ' • s°~< >. S V C o - --«-a^8?Sf* " ^ 3«tSS»ls ^ c s; °^ T-H »— < {* O OJ O* 0* 3* tn >, >, bo bfl 60 108 THE HOUSE FLY— DISEASE CARRIER "From the above table the bacterial population of 414 flies is pretty well represented. The domestic fly is passing from a disgusting nuisance and troublesome pest to a reputation of being a dangerous enemy to hu- man health. A species of mosquito has been demon- strated to be the cause of the spread of malaria. An- other kind of mosquito is the cause of yellow fever, and now the house fly is considered an agency in the distribution of typhoid fever, summer complaint, chol- era infantum, etc. "The numbers of bacteria on a single fly may range all the way from 550 to 6,600,000. Early in the fly sea- son 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 average for the 414 flies was about 1,250,000 bacteria on each. It hardly seems possible for so small a bit of life to carry so large a number of organisms. The method of the experiment was to catch the flies from the several sources by means of a sterile fly net, introduce them into a sterile bottle, and pour into the bottle a known quan- tity of sterilized water, then shake the bottle to wash the bacteria from their bodies, to stimulate the number of organisms that would come from a fly falling into a lot of milk. "In experiments 'd,' 'e/ and T the bacteria were analyzed into four groups. The objectionable class, coli-cero genes type, was two and one-half times as abundant as the favorable acid type. If these flies Fig. 18. — Colonies of bacteria on a sterilized plate, arising from fly tracks. (From photograph by William Lyman Underwood.) CARRIAGE OF DISEASE 109 stayed in the pig-pen vicinity, there would be less ob- jection to the flies and the kinds of organisms they carry, but the fly is a migratory insect and it visits everything 'under the sun.' It is almost impossible to keep it out of our kitchens, dining-rooms, cow stables, and milk rooms. The only remedy for this rather serious condition of things is, remove the pig-pen as far as possible from the dairy and dwelling house. Ex- treme care should be taken in keeping flies out of the cow stables, milk rooms and dwellings. Flies walking over our food are the cause of one of the worst con- taminations that could occur from the standpoint of cleanliness and the danger of distributing disease germs." A great deal of work of this general nature in re- gard to the carriage of micro-organisms by flies with- out specific reference as to the character of the organ- isms has been done and the results have been published here and there. The illustration shown at Fig. 18 is an early one made from a photograph taken by Wil- liam Lyman Underwood of a gelatin plate over which a fly, captured by chance in a room, was allowed to walk. On each spot which the fly's feet touched there grew a colony of bacteria. Cobb ( 1906) studied the spores of a sugar cane fun- gus left by the feet of a fly which had been feeding upon the fungus on the sides of a glass vessel. The spores from five of the tracks on the glass were cal- culated and the number per track was found to be 860,000. A second calculation gave 700,000 per foot- 110 THE HOUSE FLY— DISEASE CARRIER print. Germination experiments showed that spores carried about in this way, if deposited in suitable loca- tions, will germinate, and therefore the fungus may sometimes be spread in this way. Other work of this kind, but devoted to specific dis- ease germs, will be mentioned under the different dis- eases in the following pages. But in order perhaps to remove at once the impression which may be left by the cautious words of Doctor Graham-Smith, we may read the conclusions of Professor Nuttall and Mr. Jepson, of Cambridge University, England (1909), both in- vestigators of the highest type, after their critical exam- ination of the accounts of experiments made in this direction : "Although there were some who at a very early date looked upon the common house fly with suspicion, it is only of recent years that 'flies' have come to be regarded as a serious factor in the spread of infective diseases. "The evidence we have sifted and ordered in these pages is obviously very unequal in value, the most im- portant relating to cholera and typhoid fever — in both cases the evidence incriminating house flies, of which Musca domestica may be regarded as the type, appears to be quite conclusive, and these agents will have to henceforth receive the serious attention they demand at the hands of sanitary authorities. From a practical point of view, it scarcely appears necessary to charge the house fly with more misdoings, bacteriological tests having shown that they are capable of taking up a number of different pathogenic germs and of transport- CARRIAGE OF DISEASE 111 ing them from one place to another. We regard it as certain that they convey cholera and typhoid fever, and we look forward with confidence to the complete demonstration that they convey the causative agents of infantile diarrhea and of dysentery, always remem- bering that there are other vehicles, water, milk, etc., by which these diseases may be communicated. "It should be remembered that a fly may cause rela- tively gross infection of any food upon which it alights after having fed upon infective substances, be they typhoid, cholera, or diarrhea stools. Not only is its exterior contaminated, but its intestine is charged with infective material in concentrated form which may be discharged undigested upon fresh food which it seeks. Consequently, the excrement voided by a single fly may contain a greater quantity of the infective agents than, for instance, a sample of infected water. In potential possibilities the droppings of one fly may, in certain circumstances, weigh in the balance as against buckets of water or of milk !" Surely no more authoritative or complete statement than this could be made by scientific men. The whole literature of the subject of the transfer of disease by insects and like creatures was first compre- hensively studied and collected by Dr. George H. F. Nuttall and published in 1900 in an admirable and ex- tended paper in the Johns Hopkins Hospital Reports, entitled "On the Role of Insects, Arachnids and Myria- pods, as Carriers in the Spread of Bacterial and Para- sitic Diseases of Man and Animals. A Critical and 2 THE HOUSE FLY— DISEASE CARRIER Historical Study." This paper has been of the greatest use to physicians and to naturalists, and few general articles on this subject have been written in the last ten years without the freest use of the data collected by Doctor Nuttall. In many cases writers have gone to original sources, but it is safe to say that for the most part they have learned of these original sources through Doctor Nuttall's bibliography. The writer, among others, in the numerous papers he has published on this general subject during the years since 1900, has had constant occasion to refer to this paper, and gladly ex- presses his obligations to its author. More recently ( 1909), Doctor Nuttall (now of Cam- bridge University, England) in collaboration with Mr. Jepson, of Cambridge, has published a series of ab- stracts of literature and a bibliography relating solely to the carriage of disease by the house fly and allied non-biting flies, which has been freely used in this book and will be later referred to simply by references to Nuttall and Jepson. TYPHOID OR ENTERIC FEVER Typhoid fever is a disease which has been differen- tiated from other fevers and especially from typhus within the last eighty years. It is a disease of civiliza- tion, or rather, as Doctor Sedgwick has beautifully expressed it, "a disease of defective civilization." It depends upon defective sanitation, and surely, as Sedg- wick says, defective sanitation means defective civiliza- tion. CARRIAGE OF DISEASE The true cause of the disease was not known until 1880, when it was discovered by Eberth, and it was not long before it was isolated and studied in pure cul- ture. Technically this organism is known as Bacillus typhosus. It is isolated from persons who are sick with typhoid fever or who have been sick from it, and only from such persons. The disease which it causes is an intestinal disease, and through the multiplication of the bacilli in the body, and with a poisonous substance which it produces, conditions are caused which give rise to the characteristic symptoms of the disease. Ulcerations of the intestines and enlargements of the spleen and mesenteric glands follow, and the bacilli frequently invade other portions of the body, such as the kidney, the liver, spinal column, the lungs, and they have even been found in the brain. They are given off from the body in the excrement and in the urine. The characteristic symptoms of the fever are an increasing temperature which fluctuates rather regu- larly, and rose rash over the abdomen, diarrhea or constipation, distention of the intestines, emaciation, and sometimes intestinal hemorrhages and delirium. The average period is four or five weeks, and this is followed by a long period of convalescence. Re- lapses are frequent and are dangerous and may cause death. Fatal cases before a relapse usually terminate during the fourth or fifth week. Typhoid is thus a parasitic disease, and its onset depends upon the introduction into the system of the typhoid bacillus. Its presence in the human body is 114 THE HOUSE FLY— DISEASE CARRIER brought about by eating or drinking something carry- ing the bacilli. Water, milk, oysters, raw vegetables may and do carry them. They may be carried to food in other ways : by contact ; by dust ; and by certain household insects, such as cockroaches, household ants, and undoubtedly frequently by the typhoid fly, the most numerous of all household insects, and the one which breeds in substances which may be normally swarming with typhoid bacilli. Suspicions of the Carriage of Typhoid by Flies Probably the first American to point out the prob- able transference of typhoid germs from box privies to food supplies by the agency of flies was Dr. George M. Kober, of Washington, D. C. In "Report on the Prevalence of Typhoid Fever in the District of Colum- bia," published in 1895, under the caption of "Chan- nels of Invasion and Mode of Dissemination," Doctor Kober wrote: "The agency of flies and other insects in carrying the germs from box privies and other receptacles for typhoid stools to the food supply cannot be ignored." On the following page he gave an account of certain cases on the Ivy City and Bladensburg Road, in the course of which he used the following words, "There is abundant evidence of unlawful surface pollution, * * * and as the germs find a suitable soil in such surroundings, it is possible that the flies which abound wherever surface pollution exists may carry the germs into the houses and contaminate the food. * * * CARRIAGE OF DISEASE 115 There was nothing in common in the milk supply of the different houses, and as there was no well liable to contamination from the first source, it is not im- probable that the infection was conveyed in the man- ner indicated." Writing of nine cases occurring in a certain locality in Washington, he says, "There was nothing in com- mon in the milk supply, and the fact that the cases oc- curred at considerable intervals indicates with more or less certainty that the first case was a focus of in- fection; but how the germs were carried, unless by flies, or through the air, is a matter impossible to de- termine." Later, in writing of methods for the dis- posal of human excreta, he says, "These boxes, even if there are no wells, are still a source of danger in so far as they favor the transmission of germs by means of infected flies." In his conclusion, he writes, "A large percentage of the cases occurred in houses supplied with box privies which, apart from being an important cause of soil pollution, are believed to be otherwise instrumental in the dissemination of germs, chiefly through the agency of flies." The attention of all interested was riveted to the question of the agency of flies by the results of the investigations carried on during the Spanish-American War in 1898. In his first circular of directions to army surgeons, the Surgeon-General of the Army, Dr. George M. Sternberg, gave explicit directions regard- ing sinks, which, if followed carefully, would have pre- vented the spread of typhoid by flies, and he definitely 116 THE HOUSE FLY— DISEASE CARRIER stated that no doubt typhoid fever and camp diarrhea are frequently communicated to soldiers in camp through the agency of flies which swarm about fecal matter and directly convey infectious material attached to their feet or contained in their excreta to the food which is exposed while being prepared at the common kitchen or while being served in the mess tent. These directions from the Surgeon-General, however, were ignored, with the result that the world got its first large-scale and convincing demonstration of the car- riage of typhoid by flies, although the laboratory method was not used in this demonstration. Inferential Proof 7//A.V. put ihv fHMbMidMcdl to youncH. »»utrK flics should not tx. dtMniytd. «>f. at kj«t. an effort be (nmi (..illuiina food prepared few you to cat. F//Vj an- disease carriers Live and breed in all kinds of filth I iifcct food and drink by germ-laden feet female fly can lay 150 eggs Should be kept out of dwellings STATE BOARD o/ HEALTH £*.'"«£ Fig. 21. — Poster issued by the Florida State Board of Health ; greatly reduced. PREVENTIVE MEASURES 225 considering this delay, it is a delight to see the com- parative rapidity with which the anti-house-fly idea is spreading. Possibly had this latter crusade been be- gun first it would not have moved so rapidly ; possibly the education which people have had in regard to mos- quitoes makes them more ready to accept the ideas that are being put forward by the anti-fly movers. But in the case of mosquitoes, in more than one com- munity it was found absolutely impossible to do any- thing with the adults, and education was begun with the children in the schools. Probably the first of this work was carried on by Prof. C. F. Hodge in Worces- ter, Mass., in 1901 or 1902, and he was very successful in interesting the school children in the search for mos- quito breeding places. The most serious and productive effort, however, was made at San Antonio, Texas, a year or two later, at the initiative of Dr. J. S. Lankford. The school board approved the idea of endeavoring to educate all of the school children of the city in prophylaxis, and to make sanitarians out of all of them. The best medical lit- erature on the subject was procured and furnished to the teachers. A circular letter was sent to them out- lining the proposed course, and offering a cash prize for the best model lesson on the subject. Teachers became greatly interested; a crude aquarium with eggs and wrigglers was kept in every schoolroom where the pupils could watch them develop, and large mag- nifying glasses were furnished in order that they might study to better advantage. The children were en- 226 THE HOUSE FLY— DISEASE CARRIER couraged to make drawings on the blackboard of mos- quitoes in all stages of development. Lessons were given ; compositions were written on the subject ; com- petitive examinations were held, and groups of boys and girls were sent out with the teachers on searching expeditions for the breeding places. Rivalry sprang up between the 10,000 public school children in the city in finding and reporting to the health office the greatest number of breeding places found and destroyed. Records were kept on the black- boards in the schools of the progress of the competi- tion, and great enthusiasm was stirred up. In addition to these measures a course of stereopticon lectures was arranged, grouping the pupils in audiences of about 1,000, from the high school down, and in Doctor Lank- ford's wrords, "It was an inspiring sight to watch these audiences of 1,000 children, thoughtful, still as death, and staring with wide-open eyes at the wonders re- vealed by the microscope. It seemed to me that in bringing this great question of preventive medicine be- fore public school children we had hit upon a power for good that could scarcely be over-estimated." As a result there was a decided diminution in the numbers of mosquitoes in San Antonio. There was some oppo- sition among the people, but the movement on the whole was very popular, and the mortality of the city from malarial trouble was reduced seventy-five per cent, the first year after the work was begun, and in the second year it was entirely eliminated from San An- tonio! PREVENTIVE MEASURES 227 It follows that in "organizing community work, not only against mosquitoes but against flies as well, the school children must be counted upon as a most im- portant factor. Almost all children are born naturalists, and interest in such things comes to them more readily than anything else outside of the necessities of life. They are quick-witted, wonderfully quick-sighted, and as finders out of breeding places they cannot be ap- proached except by adults with the most especial train- ing. The specific question of interesting school children in the house-fly campaign was brought up at the De- cember meeting of the American Civic Association. It was introduced by the writer and had also been previously considered by the Fly Committee of the as- sociation, of which, as previously stated, Mr. Hatch is the chairman. The association plans to offer prizes for school children in certain selected cities, prizes ag- gregating for the ordinary town say from thirty to fifty dollars. These are to be competed for by chil- dren of the public schools, and in two classes: first, young children between the ages of nine and eleven; and, second, children from twelve to fifteen; so that the younger children will not come into competi- tion with the older and presumably better prepared ones. It will be necessary in order to do this, in some cases, to do a little work with school boards, so that they may be willing to admit into the schools the literature which will be the basis of the essays. Health boards 228 THE HOUSE FLY— DISEASE CARRIER and medical societies, however, will naturally be will- ing to co-operate. The association hopes that there will be public-spirited citizens in the various towns who will themselves institute competitions of this sort. Referring to this matter, in a paper read later at the meeting. Doctor Woods Hutchinson said, "I be- lieve that we could utilize an enormous amount of good enthusiasm and good human activity going to waste under the name of 'mischief/ and if we could take the enthusiasm of a boy and his delight of get- ting into mischief and put him to work on the fly problem, I believe we could do a great deal towards putting any community into a practical process of cleansing." An important point which we have not yet men- tioned is that it will be important to have one or more well-posted physicians on the advisory board of any fly-fighting organization, in order that the tendency of enthusiastic people to make extreme statements which are unscientific and not perfectly justified by facts may be held within bounds by others posted as to scientific methods and as to the exact truth of the sanitary aspects of the crusade. The advisory com- mittee, and especially its medical members, will find themselves much embarrassed by the difficulty of re- fraining from over-statements. The fly situation is an extremely bad one in all truth, but if it is exaggerated in order to attract and inten- sify universal popular interest, the very exaggeration PREVENTIVE MEASURES 229 will have the contrary effect upon the minds of con- servative people, and upon medical men who stand for absolute exactness of statement. Moreover, there are in every large community scientific men trained in laboratory methods, who believe that exact truth can be obtained only by laboratory methods and who hold the verdict of "not proven" against certain things which on the strongest circumstantial evidence have been claimed against the fly. It is best to carry this con- servative class with you if you can, and this can be done by a certain moderation in statement and by the avoidance of methods which may be termed ultra-yel- low-journalistic. And there is the quandary: how to frighten the ig- norant and slothful and educate them on the fly ques- tion without creating a distaste for your methods and a consequent lack of helpful interest on the part of some who could be of the most valuable assistance. The writer, although he was trained to scientific methods and has followed them for many years, is inclined to think that over-statement to bring about a great san- itary reform may be justified so long as this over- statement is based upon sound circumstantial evidence. He is thoroughly optimistic as to the progress, in the immediate future, of the campaign of education against the typhoid fly, and he is certain in his own mind that, take the country by and large, and includ- ing all classes of citizens, whether living in cities, towns, villages, or on farms, there is no single way in which the mortality rate of the country can be so rapidly de- 230 THE HOUSE FLY— DISEASE CARRIER creased, and, per contra, the health of the people so easily bettered, as by the reduction of the numbers of the house fly to a negligible quantity. BOARDS OF HEALTH The health officers, both State and local, of the coun- try have their associations and organizations of one kind or another. Probably all of them are members of the Public Health Association of the United States. All are thus, or should be, acquainted with the work of all the rest, since there is a constant interchange of ideas at the meetings and a constant interchange of publications in the intervals between the meetings. But it is well for citizens' associations, civic leagues, wom- en's clubs who take up sanitary matters, and public- spirited citizens generally, to know what an effective health officer or board of health should do, in order that they may intelligently criticise the administration of such matters by their own local officials in case, when, as it sometimes happens, these are lax; or, on the other hand, back up efficient officials where village trustees or town councils or city boards of aldermen are not disposed to grant the funds necessary to carry out proper sanitary regulations. This is our excuse for quoting at length the sanitary regulations of the District of Columbia in so far as they relate to the fly problem. The regulations are sound and the citizens of the District have no cause in this respect to criticise the health officer, but the appropriating body in this case (and it happens to be PREVENTIVE MEASURES 231 the Congress of the United States) has not down to the present time appropriated sufficient funds to carry these regulations into full effect. Good regulations require an efficient force of inspectors, and efficient in- spectors must be paid. Dr. William C. Woodward, the health officer of the District, has called the writer's attention to the fact that it really requires, from the practical standpoint, two inspectors to do one inspec- tor's work, since a solitary inspector, coming into court with a charge of violation of the regulations against a given citizen, is invariably confronted with such a mass of testimony against his charge that he is sworn out of court. He must take some one along with him to prove it. The orders in question may be briefly con- densed as follows; their full text will be found in Ap- pendix III : All stalls in which animals are kept shall have the surface of the ground covered with a water-tight floor. Every person occupying a building where domestic animals are kept shall maintain, in connection there- with, a bin or pit for the reception of manure, and pending the removal from the premises of the manure from the animal or animals shall place such manure in said bin or pit. This bin shall be so constructed as to exclude rain water, and shall in all other respects be water-tight, except as it may be connected with the public sewer. It shall be provided with a suitable cover and constructed so as to prevent the ingress and egress of flies. No person owning a stable shall keep any manure or permit any manure to be kept in or upon 232 THE HOUSE FLY— DISEASE CARRIER any portion of the premises other than the bin or pit described, nor shall he allow any such bin or pit to be overfilled or needlessly uncovered. Horse manure may be kept tightly rammed into well-covered barrels for the purpose of removal in such barrels. Every person keeping manure in any of the more densely populated parts of the District shall cause all such manure to be removed from the premises at least twice every week between June ist and October 3ist, and at least once every week between November ist and May 3ist of the following year. No person shall remove or transport any manure over any public highway in any of the more densely populated parts of the District except in a tight vehicle, which, if not inclosed, must be effectu- ally covered with canvas, so as to prevent the manure from being dropped. No person shall deposit manure removed from the bins or pits within any of the more densely populated parts of the District without a per- mit from the health officer. Any person violating any of these provisions shall, upon conviction thereof, be punished by a fine of not more than forty dollars for each offense. In addition to this excellent ordinance, others have been issued from the health department of the District of Columbia which provide against the contamination of exposed food by flies and by dust. The ordinances are excellently worded so as to cover all possible cases. They provide for the registration of all stores, markets, cafes, lunch rooms, or of any other place where food or beverage is manufactured or prepared for sale, PREVENTIVE MEASURES 233 stored for sale, offered for sale, or sold, in order to facilitate inspection, and still more recent ordinances provide for the registration of stables. An excellent campaign was begun during the summer of 1908 against insanitary lunch rooms and restaurants. A number of cases were prosecuted, but conviction was found to be difficult for the reasons already mentioned. All boards of health should follow, and doubtless are following, the very interesting experiment which the Louisiana Board is now making, of sending out a "Health Train" and visiting one town after another, conducting health demonstrations and lectures and showing moving pictures which appeal directly to the intelligence of every one. Three hundred and fifty towns in Louisiana have already been visited in this way, and education on the house fly has been a very important part of the work. The first train was sent out from New Orleans November 5, 1910, and con- sisted of two especially equipped cars. An illustrated article on the subject was published in the Quarterly Bulletin of the Louisiana State Board of Health, i, No. 4, November 15, 1910. ARMY CAMPS The severe lessons of the past in regard to fly-borne typhoid in army camps have borne fruit, and there is reason to believe that among the more civilized nations in the future there will be no recurrence of the frightful experiences of the summer of 1898 and of those in South Africa. It is with the greatest pleasure that the THE HOUSE FLY— DISEASE CARRIER writer learns, just as this book is going to the press, of the regulations in force at San Antonio, Texas, in the large encampment of troops there present. The camp sanitary regulations appear to be of the most perfect kind and to be admirably enforced. An account of the methods used will doubtless soon be published by the Medical Corps of the Army, and the writer re- frains from anticipating such publication, since the ob- servations on which he bases this statement of the per- fection of the arrangements have been made by persons not connected with the service. He may state however that the Medical Corps deserves the greatest praise for the introduction of novel and very perfect arrangements for the disposal of all camp waste. OTHER FLIES FREQUENTING HOUSES IN a series of experiments carried on during the sum- mer of 1900, flies were collected in the kitchens and dining-rooms of many houses in many different parts of the country. These collections were made in the States of Massachusetts, New York, Pennsylvania, District of Columbia, Virginia, Florida, Georgia, Lou- isiana, Nebraska, and California. In all, 23,087 flies were thus collected. On critical examination in Wash- ington by Mr. Coquillett, 22,808, that is to say, ninety- eight and eight-tenths per cent, of the whole number captured, were Musca domestica. The remainder, con- sisting of one and two-tenths per cent, of the whole, comprised various species, none of them of any espe- cial significance. These and a few others will be con- sidered in more or less detail in the following para- graphs. Of course there are other flies than these occasionally found in houses, and some quite commonly so. Mos- quitoes are flies, that is to say, they belong to the or- der Diptera, but they form no part of the present book : they are treated in other volumes. Aside from those especially mentioned here, other flies of the same group are occasionally found, not attracted to a house, but trying to escape from it. Occasionally, however, some 235 236 THE HOUSE FLY— DISEASE CARRIER of the biting flies known as gad flies or horse flies, of the family Tabanidse, enter houses seeking blood. They bite painfully, but for the most part prefer to stay out of doors, although they frequent shady situations as a rule. They are common in pine woods, and the in- habitants of summer houses built in such locations are occasionally bothered by them to some extent. Trav- elers in Alaska, where some of these gad flies abound during the short and damp summer, have stated that they sometimes become almost a scourge in the cabins. The species which we are about to mention more fully, however, are the commonest of the flies found in houses, although their numbers are so insignificant as to be almost disregarded when compared with Alnsca dorncstica. THE CLUSTER FLY (Pollcnia rudis Fabr.) There is a rather sluggish fly, a little larger than the house fly, which is frequently found in houses, espe- cially in the spring and fall. It has a dark-colored, smooth abdomen and a sprinkling of yellowish hair. It is very sluggish, in the fall especially, and at such times it may be picked up readily. It is subject to the attacks of a fungous disease which causes it to die upon window panes, where it is often seen surrounded with a white efflorescence. (Fig. 22.) The cluster fly is a European species, and the date of its introduction into the United States is not known. It could easily have been brought over upon slow sail- THE CLUSTER FLY 237 ing vessels, especially in the cooler season of the year, since it apparently hibernates in the adult condition and seeks the shelter of cracks and crevices. It is men- tioned by Loew in 1864 as one of the flies common to Europe and America. Attention was first particularly called to it and to its house habits by Dr. W. H. Ball, of the Smithsonian Institution. In an article published in the Proceedings of the U. S. National Museum for 1882 (Vol. V, pp. 635-636) Doctor Dall related that far several years he had heard of a fly which was a great nuisance in country houses near Geneva, N. Y. He secured specimens of the fly, which were turned over to professor Riley for identification. One of his relatives in Geneva wrote him that it was probably thirty years since the fly had first appeared in that neighborhood. They were at once a terror to good housekeepers and a constant surprise, since they were found in beds, in pillow slips, under table covers, behind pictures, in wardrobes, and in all sorts of places. In clean, dark bedchambers seldom used, they would form in large clusters about the ceilings. They seemed oily, and if crushed left a great grease spot on the floor. The correspondent stated that about the first of April they came out of the grass and flew up to the sunny side of houses, which they entered. They remained in evidence until some time in May, and then disappeared and were not seen again until September, when they came and remained all winter. They were stated to be very sluggish — to crawl rather than to fly away when disturbed. They were said to be often found in incred- 238 THE HOUSE FLY— DISEASE CARRIER ible numbers under buildings, between the earth and the floor. Dr. J. A. Lintner, in his Ninth Report of the State Entomologist of New York (Albany, 1893), gave a number of instances of like occurrences of this fly in houses, both in spring and in winter, in various parts of New York State. A good description was given by a correspondent of the Washington Bureau of Entomol- ogy, living in Lasalle County, Illinois. The corre- spondent stated that the cluster fly had been a pest, in her household for fifteen years. She wrote, "They seem to prefer to occupy the rooms on the north side of the house and those that are used but little. They gather in large bunches in the corners and along the edge of the ceiling of the room. They cannot be driven out as other flies, but must be killed outright to get rid of them, and when you mash them the odor is like that of honey. We have tried nearly everything that we heard of that was recommended to us, with no ef- fect. It seems impossible to get rid of them or to keep them out of the house, for they crawl in through the smallest places in the windows." Other correspondents have reported the odor of the crushed bodies as being very disagreeable. Incredible as it must seem, practically nothing is known about the early stages of this abundant and trou- blesome fly. European writers either admit that they know nothing about it or give rather vague statements. Robineau Desvoidy, speaking of the genus Pollenia as a whole, states that their eggs are laid in decomposing Fig. 22.— The cluster fly (Pollcnia rudis) ; greatly enlarged. (Original.) Fig. 23.— The biting house fly (Stomoxys calcitrant) ; larva and pupa at right; head at left and anal spiracle of larva below; greatly enlarged. (Author's illustration.) THE CLUSTER FLY 239 animal and vegetable matter. Macquart, also speaking of the genus and not especially of this species, states that the larvae develop in the manure pile and cow droppings. The only definite recorded observation which seems to have been made upon the actual breed- ing habits of this species, in fact, is the rearing of a single specimen from cow dung. This single specimen was reared in the Insectary of the Bureau of Entomol- ogy December 23, 1899. The writer has, however, received a letter from Prof. J. S. Hine, of the Ohio State University, in which he states that during the summer of 1910 he reared numbers of cluster flies, to- gether with other dipterous insects from accidental cow droppings in the pasture.* In the absence of further exact observations, it is fair to suppose that the cluster fly breeds in decompos- ing animal matter of some kind or other, and it is alto- gether likely that measures taken against the breeding places of the true Musca domestica will also be meas- urably effective against this species. There is as yet, however, the possibility that it may breed in rich soil or decomposing vegetable substances. It is difficult to keep out of the house by screening, but it may be killed by a light kerosene spray or by the free use of a fresh pyrethrum powder. Marlatt (Insect Life, Vol. IV, 1891) records an ex- traordinary mortality among these flies which he no- ticed on the grounds of the Department of Agriculture in the autumn of that year. He found often as many as eight or ten flies fastened by a fungous growth to *D. Keilin (C. R. Soc. de Biologic, Vol. 67, p. 201) states that the larvae of Pollenia are parasitic in certain earth-worms. 240 THE HOUSE FLY— DISEASE CARRIER the under side of leaves near the buildings. Specimens of these fungus-infested flies were sent to Doctor Thax- ter of Harvard University, and the organism that killed them was found to be, not Empusa musca, as was thought, but Empusa amcricana. THE BITING HOUSE FLY (Stomoxys calcitrant L.) This insect is rather closely related to the house fly and greatly resembles it in appearance, in fact it is dif- ficult to distinguish one from the other except by the closest observation. Raillet has stated that the Sto- moxys holds its head up while the house fly holds its head down, but there are other ways of telling them apart, as can be seen by comparing the illustrations of the two species. The Stomoxys is of the same gray color with dark lines, but its mouth parts are quite dif- ferent; in fact a good way to distinguish between the two flies is to allow them to walk over your hand ; if it bites, Stomoxys; if it does not it is probably the house fly. It is this other species about which we are writing that gave rise to the old saying that flies begin to bite before a rain, since the biting house fly is not normally a house fly at all, but loves the out-of-doors. It has not yet and probably never will become as truly a domestic species as Musca domestica. It is not attracted to the garbage pail and the kitchen and din- ing-room for food, but finds plenty of food on cattle and horses and other domestic and also wild animals. Under certain circumstances, however, it may become a very common resident of houses. (Fig. 23.) THE BITING HOUSE FLY Dr. John B. Smith, at a meeting of the Entomolog- ical Society of Washington, once stated that these flies were very abundant at his house; that he had not been able to observe any increase in numbers in rainy weather, but on the contrary he had found them gradually becoming more abundant until at that time (November ist) they had almost replaced the common house fly, which was being rapidly killed off by the fungous disease mentioned in a previous chapter. Hewitt states that in England it is often found in houses, and he himself has found it in large numbers in the windows of a country house in March and April. He states that it is popularly known in England as the "storm fly" from its habit of seeking the shelter of houses during wet weather. Newstead states that in England (and the same con- ditions hold for this country) farm yards and stables are the favorite haunts of this fly, but that it occurs also in the fields and parks and open woods, especially where cattle are grazing. He has seen it resting on the shop fronts of the main streets of both Liverpool and Chester, and states that it is fond of resting on surfaces fully exposed to the sun and that painted sur- faces are also attractive to it. The greatest number he ever saw congregated together was on the sunny side of a red-painted iron tank at the old Chateau de Goumont, Waterloo, Belgium. At night, he states, they retire to some sheltered spot, and numbers may be found at rest on the beams and rafters in open sheds THE HOUSE FLY— DISEASE CARRIER at farm yards, where they remain until the morning sun tempts them out. Both males and females suck blood. According to Osborn, while this fly inflicts a deep bite it does not gorge itself at a single animal, but may fly from one to another in securing a meal. From this fact he thinks the idea that this fly is apt to be a transmitter of glan- ders from diseased to healthy horses, and anthrax among cattle, receives important support. The punc- ture under ordinary circumstances does not seem to be poisonous to men, and aside from the pain given it is less dangerous than a mosquito bite. Newstead no- ticed a female drive its proboscis into the thorax of a dead companion and apparently suck up the juices of its body. The same writer permitted one to suck blood from his hand and observed it carefully during the process. The insect sat high on its legs, the whole of the proboscis was straightened and held vertically, and the lower third was driven into the flesh. During the process, which lasted fifteen minutes, the proboscis was constantly but somewhat slowly moved up and down, and also with an occasional semi-rotary movement, like the action of a quarryman's hand drill. There was no subsequent irritation or soreness of any kind. The fly died twelve hours after feeding. During other ob- servations Newstead found that the flies lived for sev- eral days in captivity, and that the females died either immediately or shortly after laying their eggs. The biting house fly has almost as wide a geographic distribution as the true house fly. It was probably orig- THE BITING HOUSE FLY 243 inally an European species and has spread by the help of commerce to many parts of the world. It occurs all over North America and is also to be found in Cen- tral and South America. It is also found in Australia, China, India, and the Canary Islands. The writer has reared the biting house fly from cow manure and from horse manure. I judge from the fact that it is attracted to human excreta that it may become a carrier of intestinal disease. It has been reared from sheep's dung and from warm decaying vegetable refuse, especially from piles of fermenting lawn grass. Lucien Iches, in the Bulletin de la Societe Nationale d'Acclimatation de France, March, 1909, published a very interesting article on Stomoxys calcitrans and Ar- gentine cattle, giving the results of a brief investigation made by him in 1908 in the province of Santa Fe, Ar- gentina. The biting flies swarmed on a large estate in almost incredible numbers. The cattle were driven nearly crazy by them. Certain valuable Durham bulls which were observed were covered with the flies. They had lost their hair in large spots and the skin was cracking. Monsieur Iches naturally sought at once for the prin- cipal breeding places of the flies, and found them to be in the stacks of debris from the threshing of wheat and flax. Larvae and puparia were found by the millions in the lower portions of these piles of straw, where some fermentation had already begun. The sensible measure which he recommended was to have this de- THE HOUSE FLY— DISEASE CARRIER bris burned within forty-eight hours after the com- pletion of the threshing, the ashes being used for fer- tilizing purposes. It turned out that there was an old provincial law in the province of Santa Fe ordering the burning of the debris after threshing, but it had not been carried out during recent years, and therefore the Stomoxys multiplied until this veritable plague en- sued. In 1888 this Stomoxys made its appearance in extraordinary numbers near Salem, Oregon, and it is altogether likely that there was some similar reason for its extraordinary abundance that year. At that time, however, its true breeding places were not known and the cause of the outbreak was not found. There are undoubtedly many substances in which the biting house fly breeds, and it evidently requires about the same conditions as does the true house fly. The larvae and puparia of this species have been figured by the writer, but the full life history has been carefully studied by Newstead. He found that the eggs are laid in an irregular heap and that the average num- ber deposited is about sixty. The egg is much like that of the house fly, and is one millirrieter long. It hatches in from two to three days in an average temperature of 72° F. in the day and 65° F. in the night. The larva need not be described, since it is similar to that of the house fly. Newstead found that in this stage they lived from fourteen to twenty-one days, but that the absence of excessive moisture and the admission of a little light materially retarded development, which then extended over a period of thirty-one to seventy- THE BITING HOUSE FLY 245 eight days. In the puparium the insect remained from nine to thirteen days. The development of the species is therefore slower than that of the true house fly. It is Newstead's opinion that the winter is passed chiefly in the pupal condition. Packard (1874) describes the pupa of this species. The extraordinary effects of numbers of the bites of this fly, indicated in the account of the epidemic of 1908 in Argentina, cannot be exaggerated. Cattle and horses suffer severely from these bites when the in- sects are numerous. Mr. T. J. Bold, in the Entomolo- gists' Monthly Magazine for 1865, p. 143, gives an account of the condition of these animals at Long Benton in September of that year. Fourteen cows were under treatment by a veterinary surgeon at one time. The animals were generally bitten on the out- side of the legs, on the shoulders, and, rarely, on the neck. In severe cases the joints were so much swollen that the animals could not bend their legs to lie down, and the swelling from the inflammation was so great that the outer skin cracked and the hair fell off. It is stated that the flies appeared to prefer the knees and upper portion of the foot of the cow, frequently crawl- ing from them to the hands of the veterinary, but their bites had no bad effect on him. It would seem from this as though animals are more susceptible than man. This biting fly has often been thought to be a dis- ease carrier and especially of blood parasites of do- mestic animals. The evidence for and against has been carefully considered by Austen (1909, p. 153), who 246 THE HOUSE FLY— DISEASE CARRIER summarizes his conclusions in the following words : "It may be regarded as proved that Stomoxys calcitrant L., as also S. nigra, Macq., and probably other species of the genus, can convey trypanosomes directly from an infected to a healthy animal, when the bites follow one another immediately. On the other hand, the evi- dence tends to show that when the interval between the bites is longer (the maximum period within which a bite is infectious has not yet been determined), al- though active trypanosomes may be present in the in- testine of the fly, its life is innocuous. There is no indication that trypanosomes ingested by 5". calcitrant pass through a developmental cycle, and they appar- ently disappear within twenty-four hours. With re- gard to diseases other than trypanosomiases, there are some grounds for thinking that S. calcitrans, like other biting flies, may occasionally disseminate the bacillus of anthrax, and, in Europe, it would appear that the fly is the intermediate host of a species of Filaria para- sitic in cattle. THE LITTLE HOUSE FLY (Fannia [Homalomyia] canicularis L.) In discussing the size of the adult house fly in Chap- ter I, we mentioned this little fly which is found rather commonly upon window-panes in houses, and stated that it was the source of the prevalent error to the effect that house flies grow after they become winged and that these little flies are the young of the larger flies. They belong, however, not only to an entirely Fig. 24. — The little house fly (Homalomyia brevis} ; antennae and larva at right; greatly enlarged. (Author's illustration.) Fig. 25. — The stable fly (Muscina stabulans) ; larva at right; greatly enlarged. Anatomical details b, c, d, e, g, h, i, still more enlarged. (Author's illustration.) THE LITTLE HOUSE FLY 247 distinct species but to a different family, these little ones being members of the family Anthomyidae. There are several of these species of Homalomyia, including not only canicularis, but H. brevis Rond. and H. scalaris Fab., but canicularis is the one found most abundantly in houses. The name "little house fly" has not been definitely applied to it in this country, but it is a translation of the German popular name, "Kleine Stubenfliege." The larvae of this species live in de- caying vegetable material and have also been found living in dead insects of different kinds. They have even been found in the nests of the common bumble- bee. They will breed also in excreta of animals and in human excreta, and therefore would be quite as dangerous as the true house fly were they as numerous. They make their appearance early in the summer and persist until autumn. The allied species, H. brevis, is not so common in houses as the one just mentioned, but it is an abundant breeder in human excrement. Both species are rapid breeders, and a generation is produced every two weeks, in the vicinity of Wash- ington, in summer. The full development has not been traced, but the larvae are quite different from the larvae of the house fly. That of brevis is shown in Fig. 24. It and its relatives are all furnished with a double row of spiny processes on either side, giving them a very characteristic appearance. Their larvae have occa- sionally been found in freshly passed human dejecta and are surely on occasion voided by persons who have 248 THE HOUSE FLY— DISEASE CARRIER probably swallowed them with uncooked vegetable food. THE STABLE FLY (Muscina stabulans Fall.) This is one of the flies which very much resemble the house fly, and is frequently mistaken for it. It be- longs to the same family and is of the same general color. It is not so abundant in houses as some of the others we have mentioned. In 1900, out of the 23,087 flies collected in dining-rooms and kitchens in different parts of the country, thirty-seven belonged to this spe- cies. It is common throughout Europe, everywhere in the United States, and extends south to Argentina. In England it is said to be found in and near houses. Hewitt has found it occurring in early summer before the house fly has appeared in great numbers. It is somewhat larger than the true house fly, and is well shown in the accompanying figure, which also shows some of the structural details of both the adult and the larva. The adult may be at once distinguished from the house fly by the gradual curve of the vein reaching the tip of the wing, instead of the abrupt angle in the same vein in the house fly. The larvae of the stable fly live upon decaying sub- stances, fungi, etc., but it is recorded in Europe as feeding upon caterpillars and larval bees. Schiner states that it breeds in cow dung, and it has also been found in dead animals. In this country it feeds upon the dead chrysalids of insects, and has been reared from dying squash plants. The fly has also been reared from THE CHEESE FLY masses of the larvae and pupae of the imported elm leaf beetle; also from a decaying squash. Aldrich in Idaho has reared it from rotting radishes. In Wash- ington it has been reared from human excreta. The complete round of a generation is said to occupy from five to six weeks. (Fig. 25.) This fly is one of the dangerous occasional inhab- itants of houses, not only because it may breed in hu- man excreta, but because it is greatly attracted to this substance when it chances to be deposited in the open. There seems to be no especial reason why it should be called the stable fly, since the preferred food habits of its larvae should make it more abundant away from stables, and its scientific name stabulans was given to it by Fallen before its real habits were known. It is interesting to note, by the way, that the larva of the fly has been found to have passed through the human stomach, to which it had probably gained en- trance through the eating of spoiled vegetables. THE CHEESE FLY (Piophila casei L.) The little, shining-black flies of the genus Piophila breed in cheese, ham, chipped beef, and other fatty or spoiled and decaying animal matter. The eggs hatch into small, white, cylindrical maggots which feed upon the cheese or meat and rapidly reach full growth, at which time they are one-half of an inch in length. The maggot is commonly called the cheese skipper or the ham skipper from its wonderful leaping powers, which it possesses in common with certain other fly larvae, all 250 THE HOUSE FLY— DISEASE CARRIER of which lack legs. The leap is made by bringing the two ends of the body together and suddenly releasing them, like a spring. In this way it will sometimes jump three or four inches. The species is cosmopolitan at present, and it was doubtless originally imported from Europe into the United States in old cheeses. Careful observations have been made on the life his tory of this fly by several writers. In 1892 Miss Mary E. Murtfeldt studied the life history of the summer generation in a western packing establishment. She found that the eggs were laid in rather close clusters of from five to fifteen, and were also deposited singly. About thirty seem to have been laid by a single female. The egg is white, slender, oblong, slightly curved, one millimeter in length, and with a diameter about one- fourth of its length. It hatches in about thirty-six hours, and the larva completes its growth in from seven to eight days, reaching a length of seven to nine milli- meters. Where food is sufficient the larva does not move about, and groups of them will sometimes com- plete their growth in the same crevice in which the mother fly deposited her eggs. When full grown, how- ever, the larva moves away to some dry spot, contracts in length, assumes a yellowish color, and gradually forms into a golden-brown puparium four or five milli- meters in length. The adult fly issues in ten days. Thus three weeks may complete the entire life cycle, in August, in St. Louis. In Europe, Kessler found that the average summer duration of this insect is four to five weeks, and states Fig. 26. — The cheese fly (Piophila casei) : a, larva ; b, puparium ; c, pupa; d, adult male; e, adult female ; all enlarged. (Author's illustration.) Fig. 27.— The fruit fly (Drosophila ampelophila) ; a, adult male; b, antennae ; c, fore tibia ; d, e, puparium ; f, larva ; g, anal segment of larva; enlarged. (Author's illustration.) THE FRUIT FLIES 251 that the larva over-winters in the puparium. Other writers say that the insect passes the winter as an adult fly. (Fig. 26.) In this country this fly does not play so important a part as a cheese insect as it does as an enemy to smoked meat. It seems certain that the mother fly prefers the older and richer cheeses in which to de- posit her eggs. Her taste is excellent, and, while it is a fair thing to say that skippery cheese is usually the best, it will hardly do to support the conclusion that it is good because it is skippery, although this con- clusion is current among a certain class of cheese eaters. The cheese fly, under ordinary circumstances, is not a dangerous species, but it is well to remember that not only has it been reared from dead bodies, but that it is also attracted to excreta of all kinds. THE FRUIT FLIES (Drosophila ampelophila Loew) The minute flies of the family Drosophilidse, com- monly known as fruit flies or pomace flies, are attracted to decaying vegetation, especially to fruit, and are fre- quently found in houses in the autumn about dishes containing pears, peaches, and grapes. They are at- tracted to fruit both for food and for places to lay their eggs, since their larvae live in decaying vegetable matter. The commonest of the fruit flies in the United States is Drosophila ampelophila. It occurs .also in the West Indies and South Europe. It does considerable dam- age to canned fruits and pickles, breeds in decaying 252 THE HOUSE FLY— DISEASE CARRIER apples and the refuse of cider mills and fermenting vats of grape pomace. It is a rather rapid breeder, and a generation may develop in twenty days, more or less. It is attracted especially to preserves and canned goods, and frequently damages raspberry vinegar. It is often very difficult to prevent the fly from entering fruit jars. There are about thirty species of Drosophila in North America, and the majority of them breed in the juices of decaying and fermenting fruit. Aside from the one just mentioned, D. amocna, D. funebris, D. graminum, and D. transversa are occasionally found in houses. Another species, D. cellaris, occurs in cel- lars in fermenting liquids, such as wine, cider, vinegar, and beer; also in decaying potatoes. Another species damages flour paste ; and still another mustard pickles. One species, D. flaveola, does not need decaying vege- tation for its larval food, since its larvae mine the leaves of cabbages and radishes. The fruit flies may be dangerous inhabitants of houses, since they are nearly all attracted to excreta, and some of them breed in human excrement. The larva and puparium, as well as the adult fly of D. ampclophila, are shown in Fig. 27. THE BLUEBOTTLE OR GREENBOTTLE FLIES THE BLOW FLIES (Calliphora erythrocephala Meig., Lucilia ccesar L., Phormia terranovce Desv.) Several species of bluebottle or greenbottle flies oc- casionally gain entrance to houses, and all are danger- THE BLOW FLIES 253 ous species and liable to carry intestinal diseases. Their larvae as a rule feed in excreta or in decaying flesh, but a bluebottle fly in a milk jug is no more dangerous than a house fly in the same situation. Lucilia ceesar L. (Fig. 28) is a common and wide- spread form, abundant in both Europe and North America, and is one of several species of the shining green or bluish flies commonly found about dead ani- mals and different kinds of excreta. It is not ordinarily found in houses, but may be driven in at the approach of a heavy storm, just as is the case with the biting house fly. On May 17, 1899, for example, a heavy storm occurred about four P.M., and the next morning twenty-eight specimens of this species were found to have come into one of the rooms of my office. In Europe L. ccesar is known as the "greenbottle fly," and is almost exclusively a carrion feeder. Calliphora erythrocephala Meig. (Fig. 29) is an- other widespread species common to Europe and North America. It is a large bluebottle fly of rather dull color with black spines on the thorax. It is the com- mon blow fly of Europe and is the species treated by Lowne in his classic work on the anatomy of the blow fly. Its larvae are indistinguishable from those of the greenbottle fly. The eggs are laid on meat and dead animals and even upon dead insects. The species is unusual from the enormous number of eggs laid by a single female. The Russian author, Porchinsky, re- cords from 450 to 600 eggs from a single female. Hewitt records the duration of a single generation as 254 THE HOUSE FLY— DISEASE CARRIER from twenty-two to twenty-three days. This blow fly is a characteristically out-of-door fly, but under cer- tain circumstances may be found in houses in some numbers. In October, 1899, f°r example, a gentleman living in the suburbs of Washington found thousands of these flies in his cellar. No cows or horses were kept near the house, and there had been no dead ani- mals about so far as he knew. It is probable, however, that these flies had come from some dead animal, and had sought the cellar for hibernating purposes, al- though the weather was still warm. Phormia terr&novcc Desv. (Fig. 30.) The bluebot- tle fly just mentioned is a rather- large species. The Phormia, however, is a medium-sized or rather small bluebottle. It was originally described from New- foundland, but is widespread in the United States. It is occasionally found in houses, and I have more than once seen them upon window panes. It is abundantly attracted to human excreta, and has been taken under many varying conditions about Washington : enormous numbers were found on one occasion in the sinks of a deserted militia camp at Leesburg, Virginia. THE FLESH FLIES (Sarcophaga assidna Walk.) We include under this heading the flies of the genus Sarcophaga, on account of the significance of the sci- entific name, although many Sarcophagids are not true flesh eaters. Several of them very closely resemble the house fly, and some of them are sometimes found in houses. The common widespread flesh fly of Europe Fig. 28. — Lucilia casar ; enlarged. (Author's illustration.) Fig. 29. — Calliphora erythrocephala enlarged. (Author's illustration.) Fig. 30. — Phonnia terrccnovce; en- larged. (Author's illustration.) Fig- 33- — Scatophaga furcata; en- larged. (Author's illustration.) THE DUNG FLIES 255 and Australia, a very general scavenger, is known as Sarcophaga carnaria L., and in countries which it in- habits is once in a while found in houses. It does not seem to occur in the United States, although a species which much resembles it, S. sarracenice Riley, is abun- dant throughout the country. It looks like a very large and active house fly, and is occasionally found in houses. It is commonly reared from the remains of dead insects, but is also attracted to and breeds in ex- creta. (Fig. 31.) A smaller species, 5*. assidua Walk., much resembles the house fly and is of about the same size. - It is con- fined to the United States and is occasionally found in houses. It, like the preceding species, breeds in dead insect remains, but is attracted to and breeds in ex- creta and is therefore dangerous. THE DUNG FLIES ' (Sepsis violacea Meig., Scatophaga furcata Say) There is a little black fly known as Sepsis violacea Meig., which is shown in Fig. 32 and which is not at all uncommon in houses, being found as a rule upon the window panes. It belongs to the same family as the cheese fly, but does not attack stored foods or any- thing to be found in the pantry. It breeds almost ex- clusively in excreta and has been reared in swarms from an old human deposit collected on the Potomac flats near the city of Washington. It is very small in size, glistening black in color, and of slender shape. There is a whole family of small, brownish flies 256 THE HOUSE FLY— DISEASE CARRIER known as the Scatophagidae, which, as the scientific name indicates, are attracted to and breed in the dung of different animals, and also to some extent in decay- ing vegetable material. They are, as a rule, rather light-colored, bristly flies. The species shown at Fig. 33 is known as Scatophaga furcata Say. It is a North American species of rather wide distribution, which in its early stages lives in all sorts of excreta and is once in a great while found in houses. It does not hibernate as an adult fly, but in its puparia in dung. THE MOTH FLIES (Psychoda minuta Banks) There are certain very minute flies belonging to a family known as the Psychodidae, which are very pe- culiar from the fact that they resemble little moths, their broad wings being covered with hairs, making them look like moths. They are very weak fliers, and are frequently found upon windows and on the under surfaces of leaves. They are so small and fragile that they are difficult to capture and preserve. What they do in houses no one knows, unless possibly they enter them for protection. The larvae of some species breed in excreta; others in decaying vegetation, and still others in water, sewage-polluted water being preferred. Psychoda minuta Banks has been reared from cow dung at Washington. None of the North American species has the blood-sucking habit, although a genus (Phlcebotomus) which occurs in Southern Europe and in other parts of the world bites human beings and has been accused of disease-carrying probabilities. Fig. 31. — Sarcophaga assidua; larva at right, puparium at left; enlarged. (Author's illustration.) Fig. 32. — Sepsis violacea; puparium at left; enlarged antennae at upper right; enlarged. (Author's illustration.) THE HUMPBACK FLIES 257 THE HUMPBACK FLIES The humpback flies of the family Phoridse need not be mentioned here especially, except for the fact that one of the species, Hypocera (Phora) femorata, occurs occasionally in houses, and possibly others of the family Fig. 34. — Phora femorata; greatly enlarged. (Original.) may also be found from time to time in domiciles. In the collection of flies made in houses in 1900 there were thirty-three specimens of P. femorata out of the 23,087 flies captured. The larval habits of this par- 258 THE HOUSE FLY— DISEASE CARRIER ticular species are not known, but its relatives feed in the earlier stages on decaying vegetable matter, dead insects, snails, etc. The species in question possibly- fed upon decaying vegetation in the neighborhood of the houses in which it was collected. THE WINDOW FLIES (Scenopinus fenestralis L.) Comstock has applied the term window flies to the little flies of the family Scenopinid?e. The term, how- ever, does not apply to all of them ; but the best-known Fig. 35.— Scenopinus fenestralis; a, adult; b, pupa; c, larva; d, eggs ; enlarged. (Original.) species, namely, Scenopimts fenestralis, is not uncom- monly found upon windows both in this country and in Europe. These flies are usually black and rather smooth, S. fenestralis being about one quarter of an THE WINDOW FLIES 259 inch long. It has a humpbacked appearance, and the abdomen is flattened. Osten Sacken (1886) has given a good review of the European literature on the habits of this fly, and has shown that it has been reared from decaying tree fungi, from horse hair in a mattress, from a swallow's nest, from the cocoon of a large moth, from carpets, from a branch of a tree, from pine boards, from the pupa of a large moth, and from a root of aconite. The different European authors making these obser- vations from time to time have thought variously that the window fly was carnivorous or vegetarian, in ac- cordance with the substances from which they reared it. Osten Sacken, however, concludes rather positively that it is carnivorous, that the larva does not frequent fungi, rotten wood, swallows' nests, etc., for the sake of vegetable material or animal remains, but for the sake of the pupae and perhaps also of the larvae which it finds there. He deduces from this that when it oc- curs in carpets and horse hair, it is not because it feeds on them, but because it hunts there for the larvae and pupae of the moths or other insects that live in them. Similarly in this country divers observations have been made, and the records of the Bureau of Entomol- ogy at Washington show that it has been reared from strawberry plants, from the egg-pods of grasshoppers, from the hair of a Navajo blanket, from a sack of rye infested with the grain beetle, from under carpets, among stored oats and stored corn, from a basket con- taining small rolls of cotton and woolen goods, and 260 THE HOUSE FLY— DISEASE CARRIER from the seeds of sugar beets stored in a mill; also from larva? found with other larva? on the roots of roses, as well as from under the bark of a post-oak pole. Ex- act observations have been made here showing that the larva is undoubtedly carnivorous : it has been fed upon the larvae of stored grain insects, and when found in woolen goods and under carpets it is undoubtedly in search of clothes moths upon which to feed. The larva is long, white, and snake-like in shape, with a dark head. It apparently has many segments to the body, since each of the abdominal segments is di- vided by a strong constriction. In feed stores the flies are nearly always to be found around the windows, and the probability is very strong that they feed upon such small soft-bodied creatures as flour mites and beetle larvae. Nothing definite has been ascertained concerning the duration of the different stages, but from larvae taken in January adults issued in April, and from larvae re- ceived April 1 8th adults issued on the Qth of June; with larvae received August 6th, one changed to pupa on August 25th, another on August 29th, the flies issu- ing September loth and I2th respectively. It is a pleasure to state that at least one of the flies found in houses is probably beneficial rather than in- jurious, and that this species is Scenopinus fenestralis. BIBLIOGRAPHICAL LIST AINSWORTH, R. B. (1909). The house fly as a disease carrier. 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Etudes sur 1'oasis de Biskra. Paris. (Cited by different authors.) BIBLIOGRAPHICAL LIST SIMMONDS, M. (1892). Fliegen und cholera-ubertra- gung. Deutsche Med. Wochenschr., 931. SIMPSON, R. J. S. (1910). Medical history of the South African war. Journ. Roy. Army Med. Corps, XV, 3, 257 and 260-1. SKINNER, H. (1909). The relation of house flies to the spread of disease. New Orleans Med. and Surg. Journ., LXI, 12, 950-959. (Good bibliography added.) SMITH, F. (1903, et seq.). Municipal sewerage. Journ. Trop. Med., VI, 285-291, 304-308, 33O-334, 353-355, 381-383- SMITH, F. (1907). House flies and their ways at Be- nares. Journ. Roy. Army Med. Corps, IX, 150-155. SMITH. T. (1908). The house fly as an agent in the dis- semination of infectious diseases. Am. Journ. of Public Hygiene, XVIII, 3, 312-317. SriLLMAN and HAUSHALTER (1887). Dissemination du bacilli de la tuberculose par la mouche. Compt. Rend., CV, 352-353- STILES/ C. W. (1910). The sanitary privy: its purpose and construction. Public Health Bulletin No. 37, U. S. Pub. Health and Marine-Hospital Service, pp. 24, figs. 12. SYKES, G. F. (1910). The distribution of flies in Provi- dence, R. I. Ann. Kept. Supt. Health, Providence, for 1909, 7-15. TASCHENBERG, E. L. (1879). Praktische Insekten- Kunde. Bremen. 5 vols. (House fly IV, 102-107.) THAXTER, R. (1888). The Entomophthorese of the U. S. Mem. Bost. Soc. Nat. Hist., IV, I, 133-201, 21 plates. TIZZONI, G., and CATTANI, J. (1886). Untersuchungen itber cholera. Centralbl. f. d. Med. Wissensch. Ber- lin. 769-77L TOOTH, H. H., and CAVERLY, J. E. G. (1901). In A Civ- ilian War Hospital, London, John Murray. 272 THE HOUSE FLY— DISEASE CARRIER TSUZUKI, J. (1904). Bericht iiber meine epidemiologi- schen Beobachtungen Forschungen Wahrend der Choleraepidemie in Nordchina in Jahre 1902. Arch. f. Scliiffs-u. Tropcn-Hyg., VIII, 71-81. UFFELMANN, J. (1892). Beitrage zur Biologic des chol- erabacillus. Berlin Klin. IVochcnschr., 1213-1214. VEEDER, M. A. (1898). The spread of typhoid and dys- enteric diseases by flies. Public Health, XXIV, 260- 262. VEEDER, M. A. (1898). Flies as spreaders of disease in camps. N. Y. Med. Rec., 429-430. WELANDER (1896). Gonorrhoeal ophthalmia carried by flies. Wicn. Klin. IVochcnschr., No. 52. WERNER, H. (1908). Uber eine eingeisselige Flaggel- laten form im Darm der Stubenfliege. Arch. f. Protistenk., XIIT, 19-22, 2 pis. WHIPPLE, G. C. (1908). Typhoid fever, its causation, transmission and prevention, pp. 397, Wiley and Sons, N. Y., Chapman and Hall, London. WILSON, E. (1868). Diseases of the skin (Philadelphia), p. 466. WOODHOUSE, T. P. (1910). Notes on the causation and prevention of enteric fever in India. Journ. Roy. Army Med. Corps, X, 616. YERSIN (1894). La Peste bubonique a Honkong. Ann. Inst. Pasteur, 662-667. APPENDIX I FLIES FREQUENTING HUMAN DEJECTA AND THOSE FOUND IN KITCHENS IN summing up the results of the work carried on by the writer, the number of species of insects found breeding in or frequenting human excrement was very large. There were many coprophagous beetles — forty- four species in all — and many Hymenopterous para- sites, all of the latter having probably lived in the lar- val condition in the larvae of Diptera or Coleoptera breeding in excrement. Neither the beetles nor the Hymenoptera, however, have any importance from the disease-transfer standpoint. The Diptera alone were the insects of significance in this connection. Of Dip- tera there were studied in all seventy-seven species, of which thirty-six were found to breed in human feces, while the remaining forty-one were captured upon such excrement. The following list indicates the exact spe- cies arranged under their proper families. The paren- thetical remarks after each species should be estimated in the following order, from "scarce" to "extremely abundant" : scarce, rather scarce, not abundant, mod- erately abundant, abundant, very abundant, extremely abundant. 273 274 THE HOUSE FLY— DISEASE CARRIER REARED (USUALLY ALSO CAPTURED) FAMILY CHIRONOMID^: I. Ceratopogon sp. (scarce). FAMILY BIBIONID^E 2.. Scatopse pulicaria Loew (moderately abundant). FAMILY EMPIDID^: 3. Tachydromia sp. (rather scarce). FAMILY DOLICHOPODID.E 4. Diaphorus leucostomus Loew (scarce). 5. Diaphorus sodalis Loew (not abundant). FAMILY SARCOPHAGIOE 6. Lucilia caesar L. (abundantly captured; one reared), 7. Sarcophaga sarraceniae Riley (abundant). 8. ' Sarcophaga assidua Walker (abundant). 9. Sarcophaga trivialis V. d. W. (abundant). 10. Helicobia quadrisetosa Coq. (very abundant). FAMILY MUSCID^: 11. Musca domestica L. (abundant). 12. Morellia micans Macq. (abundant). 13. Muscina stabulans Fall, (abundant). 14. Myospila meditabunda Fabr. (abundant). FAMILY ANTHOMYHXE 15. Homalomyia brevis Rondani (very abundant). 16. Homalomyia canicularis L. (moderately abundant) 17. Homalomyia scalaris Fabr. (scarce). 18. Hydrotaea dentipes Meig. (moderately abundant). 19. Limnophora arcuata Stein (moderately abundant). 20. Ophyra leucostoma Wied. (abundant). 21. Phorbia cinerella Fall, (abundant). 22. Phorbia fusciceps Zett. (moderately abundant). APPENDIX I 275 FAMILY ORTALID^: 23. Euxesta notata Wied. (moderately abundant). FAMILY LONCH^ID^E 24. Lonchsea polita Say (moderately abundant). FAMILY SEPSID.E 25. Sepsis violacea Meig. (extremely abundant). 26. Nemopoda minuta Wied. (very abundant). FAMILY DROSOPHILID^: 27. Drosophila ampelophila Loew (moderately abundant). FAMILY OSCINID^E 28. Oscinis trigramma Loew (rather scarce). FAMILY AGROMYZID^E 29. Ceratomyza dorsalis Loew (rather scarce). 30. Desmometopa latipes Meig. (rather scarce). FAMILY EPHYDRID^E 31. Scatella stagnalis Fall, (scarce). FAMILY BORBORID^E 32. Limosina albipennis Rond. (very abundant). 33. Limosina fontinalis Fall, (very abundant). 34. Sphaerocera pusilla Meig. (abundant). 35. Sphserocera subsultans Fabr. (very abundant). FAMILY SCATOPHAGID^: 36. Scatophaga furcata Say (very abundant). CAPTURED (NOT REARED) FAMILY CHIRONOMHXE 1. Chironomus halteralis Coq. (scarce). FAMILY TIPULID^: 2. Limnobia sciophila O. S. (scarce). 276 THE HOUSE FLY— DISEASE CARRIER FAMILY EMPIDHXE 3. Rhamphomyia manca Coq. (not abundant). FAMILY DOLICHOPODID^: 4. Neurigonia tenuis Loew (scarce). FAMILY SARCOPHAGID^: 5. Chrysomyia macellaria Fabr. (rather abundant). 6. Calliphora erythrocephla Meig. (rather abundant) 7. Sarcophaga lambens VVied. (rather scarce). 8. Sarcophaga plinthopyga Wied. (rather scarce). 9. Cynomyia cadaverina Desv. (rather scarce). 10. Phormia terraenovae Desv. (very abundant). FAMILY MUSCHXE 11. Muscina caesia Meig. (scarce). 12. Muscina tripunctata V. d. W. (scarce). 13. Stomoxys calcitrans L. (rather abundant). 14. Pseudopyrellia cornicina Fabr. (abundant). 15. Pyrellia ochricornis Wied. (rather scarce). FAMILY ANTHOMYIID^E 16. Hylemyia juvenalis Stein (rather scarce). 17. Hydrotaea metatarsata Stein (rather scarce). 18. Coenosia pallipes Stein (rather scarce). 19. Mydaea palposa Walker (rather scarce). FAMILY ORTALID.C 20. Rivellia pallida Loew (rather scarce). FAMILY SEPSID^E 21. Piophila casei L. (rather scarce). FAMILY DROSOPHILID^ 22. Drosophila funebris Meig. (scarce). 23. Drosophila busckii Coq. (scarce). APPENDIX I 277 FAMILY OSCINIDJE 24. Hippelates flavipes Loew (rather scarce). 25. Oscinis carbonaria Loew (moderately abundant). 26. Oscinis coxendix Fitch (scarce). 27. Oscinis pallipes Loew (rather scarce). 28. Elachiptera costata Loew (moderately abundant). FAMILY EPHYDRID^: 29. Discocerina parva Loew (rather scarce). 30. Hydrellia formosa Loew (rather scarce). FAMILY BORBORID^E 31. Borborus equinus Fall, (very abundant, undoubtedly breeds here also). 32. Borborus geniculatns Macq. (moderately abundant). 33. Limosina crassimana Hal. (abundant). FAMILY SYRPHID^ 34. Syritta pipiens L. (scarce). FAMILY PHORHLE 35. Phora femorata Meig. (scarce). FAMILY SCATOPHAGID^E 36. Scatophaga stercoraria L. (moderately abundant). 37. Fucellia fucorum Fall, (rather scarce). FAMILY MICROPEZID^E 38. Calobata fasciata Fabr. (rather scarce). 39. Calobata antennipes Say (moderately abundant). FAMILY HELOMYZHLE 40. Leria pectinata Loew (scarce). 41. Tephrochlamys rufiventris Meig. (scarce). It should be stated here that this list, containing as it does only a record of actual observations, should by no means be considered as indicating definitely the habits of the species or their relative abundance under 278 THE HOUSE FLY— DISEASE CARRIER other conditions. Thus some of the species here indi- cated as scarce in connection with excrement may be very common under other conditions, which would indicate that their occurrence upon excrement was more or less accidental. Moreover, certain of the species which have been captured on excrement, but not reared from it, are nevertheless undoubtedly excrement breed- ers, as will be proved by future observations. Thus we have in several cases certain species which have been reared while congeneric species have simply been cap- tured, as, for example, Nos. 7 and 8 of the captured species are congeneric with 7, 8 and 9 of the reared series; n and 12 of the captured series are congeneric with 13 of the reared series; 17 of the captured series is congeneric with 18 of the reared series; 22 and 23 of the captured series are congeneric with 27 of the reared series; 25, 26 and 27 of the captured series are congeneric with 28 of the reared series ; 33 of the cap- tured series is congeneric with 32 and 33 of the reared series, and is undoubtedly an excrement breeder, and the same may be said of 36 of the captured series which is congeneric with 36 of the reared. From these data it will be noticed that the most abundant species reared were Helicobia quadrisetosa, Sepsis violacea, Nemopoda minuta, Limosina albipen- nis, Limosina fontinalis, Spharoccra subsnltans, and Scatophaga furcata, while the most abundant forms captured on excrement were Phorbia terranovcu and Borborus equinus. It will also be noticed that among the reared forms there are ten others which are simply APPENDIX I . 279 entered as "abundant," and among the captured two others. With these facts in mind we are prepared to examine the results of the kitchen and dining-room captures. The results so far stated have a distinct entomolog- ical interest as regards the exact food habits of a large number of species, many of the observations being novel contributions to previous knowledge of these forms; but the practical bearing of the work is only brought out when we consider which of these forms are likely from their habits actually to convey disease germs from the excrement in which they have bred, or which they have frequented, to substances upon which people feed. Therefore collections of the Dipterous insects occurring in kitchens and pantries were made, with the assistance of correspondents and observers in different parts of the country, all through the summer of 1899 and also in the summer and autumn of 1900. Such collections were made in the States of Massachu- setts, New York, Pennsylvania, District of Columbia, Virginia, Florida, Georgia, Louisiana, Nebraska, and California. Nearly all of the flies thus captured were caught upon sheets of the ordinary sticky fly paper, which, while ruining them as cabinet specimens, did not disfigure them beyond the point of specific recog- nition. The others were captured in the ordinary man- ner. In all there were examined 23,087 flies, which had been caught in rooms in which food supplies were or- dinarily exposed ; and they may safely be said to have 280 THP HOUSE FLY— DISEASE CARRIER been attracted by the presence of these food supplies. Of these 23,087 flies, 22,808 were Mitsca domestica, i. e., ninety-eight and eight-tenths per cent, of the whole number captured. The remainder, consisting of one and two-tenths per cent, of the whole, comprised vari- ous species, the most significant ones being Hornalomyia canicularis (the species ordinarily called the "little house fly") of which eighty-one specimens were cap- tured; the stable fly (Muscina stabulans), thirty-seven specimens; Phora femorata, thirty-three; Liicilia cccsar, eighteen; Drosophila ampelophfta, fifteen; Sarcophaga trivialis, ten ; Calliphora crythroccphala, seven. Mnsca domestica is, therefore, the species of great significance. Homalomyia canicularis is important. Muscina stabu- lans is of somewhat lesser importance. Drosophila anipclophila is an important form, and had more of the captures been made in the autumn its numbers would probably have been greater, since beyond doubt it is an abundant species in houses after fruit has begun to make its appearance (say, in August and September and on until winter time) in pantries and on dining- room sideboards. The Calliphora and the Lucilia are of slight importance, not only on account of their rar- ity in houses, but because they are not true excrement insects. Other forms were taken, but either their household occurrence was probably accidental, or from their habits they have no significance in the disease- transfer function. — Extracted from : A Contribution to the Study of the Insect Fauna of Human Excrement. By L. O. Howard (p. 547). APPENDIX II ON SOME FLIES REARED FROM Cow MANURE* IN the summer of 1889, while engaged in an investi- gation of the habits and life history of the horn fly of cattle (Hcematobia serrata), the writer at various times brought to Washington, from different points in Virginia, large quantities of cow manure collected in the field, and eventually succeeded in working out the complete life history of the horn fly, as displayed in Insect Life, Vol. II, No. 4, October, 1889. In this article the statement is made, in concluding, that the observations were greatly hindered and rendered dif- ficult by the fact that fresh cow dung is the nidus for a number of species of Diptera, some about the same size and general appearance as the horn fly, and that no less than twenty distinct species of flies had been reared from horse and cow dung, mainly the latter, and six species of parasitic insects as well. The plan finally adopted of securing the isolation of the horn flies was to remove the eggs from the surface of the dung and place them with dung which was absolutely fresh and collected practically as it fell from the cow. A report upon trie other species was promised, but was never published, although Professor Riley, in his re- *Reprinted from an article with this title, by L. O. Howard, published in the Canadian Entomologist, Vol. 33 (1901), pp. 42-44. 281 282 THE HOUSE FLY— DISEASE CARRIER port for 1890, listed eight parasites, only two of which were specifically determined. The writer's recent investigations of the insect fauna of human excrement (Proc. Wash. Acad. of Sciences, Vol. II, pp. 541-604. Dec. 28, 1900) aroused his in- terest in the general subject of coprophagous insects, and the flies reared in 1889-90, from cow dung, were looked up and have been named by Mr. D. W. Coquil- lett. The list is so interesting that it should be re- corded. It will be noticed that several of the species are identical with those found breeding in human ex- crement. These are: Sarcophaga inccrta, Helicobia quadrisetosa, Musca domestica, Morellia micans, My- ospila meditabunda, Ophyra leucostoma, Sepsis viola- cea, Splicer ocera subsultans and Limosina albipouiis. The rearing of Ceratopogon spccularis from cow dung is of especial interest, since, down to the record in the Washington Academy paper just referred to, no in- sects of this genus had been found to be coprophagous. Some of the other records are interesting for the same reason. The list follows: FAMILY CECIDOMYIIXE Diplosis, sp. Issued Dec. 26, 1889; and Jan. 18, 1890; 4 specimens. FAMILY MYCETOPHILIOE Sciara, sp. Issued March 26 and 29, 1890; 2 specimens. FAMILY CHIRONOMID^: Camptocladius bvssinus, Schrank. Issued Jan. 2, 1890. Issued Dec. 31, 1889; and March 25, 1890; 9 speci- mens. APPENDIX II 283 Camptocladius minimus, Meigen. Issued Dec. 23, 26, 27. 30 and 31, 1889; Jan. 13, 18, and March 25, 1890; 12 specimens. Ceratopogon specularis, Coq. Issued August 28, 1889. Issued Dec. 30, 1889; 6 specimens. Psychoda minuta, Banks. Issued Dec. 26, 30 and 31, 1889; and Jan. u, 1890; 4 specimens. FAMILY RHYPHID^E Rhy films punctatus, Fabr. Issued Sept. 2, 3, and 4, 1889. Issued Jan. 13, 16, 18, 20, 22, 24 and 29, Feb. i, March 26 and 29, and April 5 and 9, 1890; 64 speci- mens. FAMILY SARCOPHAGID^: Sarcophaga incerta, Walker. Issued Aug. 31, 1889. Is- sued Aug. 30, 1889; 7 specimens. Sarcophaga, sp. Issued April 23, 1890; i specimen. Helicobia quadrisetosa, Coq. Issued Aug. 6 and 30, 1889 ; 2 specimens. Pollenia rudis, Fabr. Issued Dec. 23, 1889; i specimen. FAMILY MUSCID^: Musca domestica, Linne. Issued Aug. 30 and Sept. 2 and 4, 1889 ; 20 specimens. Morellia micans, Macq. Issued Aug. 30, 1899. Issued Dec. 23, 26. 27, 28, 30 and 31, 1889; Jan. 2, 6, 8, 9, 10, n, 13, 14, 16, 17, 18, 20, 25 and 27, Feb. i, March 25, April 5 and 9, 1890; 125 specimens. Myospila meditabunda, Fabr. Issued Aug. 26, 28, 29, 30, Dec. 23, 1889; Jan. 9, March 25, 26, April 2, 9, 14, 15, 1890. Issued April 5, 1890; 48 specimens. Hcematobia serrata, Desv. Sept. 17, 2 specimens. FAMILY ANTHOMYHXS Hydro fcea armipes. Fallen. Issued Sept. 27, 30, Oct. 4, 1889; Jan. 2, 6, 7, 8, 9, 10, April 24, 1890; 38 speci- mens. 284 THE HOUSE FLY— DISEASE CARRIER Ophyra leucostoma, Wied. Issued Sept. 6, 1889; u specimens. Limnophora, sp. Issued Aug. 30, 31, 1889; 5 specimen^. Cccnosia lata, Walker. Issued April 25, 1890; i specimen. Ccenosia ftavicoxa, Stein. Issued Aug. 31, 1889; 4 speci- mens. Phorbia, sp. Issued March 29, 1890; I specimen. FAMILY SEPSID^E Sepsis violacca, Meigen. Issued Aug. 28, 1889; 8 speci- mens. FAMILY BORBORID^ Sphfcrocera siibsultans, Fabr. Issued Aug. 30, 1889; 7 specimens. Limosina albipennis, Rondani. Issued August 28, Dec. 23, 1889; 2 specimens. APPENDIX III REGULATIONS OF THE HEALTH DEPARTMENT OF THE DISTRICT OF COLUMBIA RELATING TO HOUSE FLIES EXTRACT from An Ordinance to Revise, Consol- idate, and Amend the Ordinances of the Board of Health, etc., as Amended by Commissioners' Orders. SEC. 3. That manure, accumulated in great quan- tities; manure, offal, or garbage piled or deposited within 300 feet of any place of worship, or of any dwelling, or unloaded along the line of any railroad, or in any street or public way ; cars or flats loaded with manure, or other offensive matter, remaining or stand- ing on any railroad, street or highway in the cities of Washington or Georgetown, or in the more densely populated suburbs of said cities, are hereby declared nuisances injurious to health; and any person who shall pile or deposit manure, offal, or garbage, or any offensive or nauseous substance within 300 feet of any inhabited dwelling within the limits of said cities or their said suburbs, and any person who shall unload, discharge, or put upon or along the line of any rail- road, street, or highway, or public place within said cities or their said suburbs any manure, garbage, offal, or other offensive or nauseous substance within 300 feet of any inhabited dwelling, or who shall cause or allow cars or flats loaded with or having in or upon them 285 286 THE HOUSE FLY— DISEASE CARRIER any such substance to remain or stand in or along any railroad, street, or highway within the limits of said cities or their suburbs within 300 feet of any inhabited dwelling, and who shall fail, after notice duly served by this board, to remove the same, shall, upon convic- tion thereof, be fined not less than five nor more than twenty-five dollars for every such offense. ******* SEC. i8^4. No person owning, occupying or hav- ing use of any stable, shed, pen, stall, or other place within any of the more densely populated parts of the District of Columbia, where animals of any kind are kept shall permit such stable, shed, pen, stall, or place to become or to remain filthy or unwholesome. SEC. 1 8 B. No person shall use any stable, nor shall any person having the power and authority to prevent permit any person to use any stable, within any of the more densely populated parts of the District of Columbia, after the first day of July, 1907, unless the surface of the ground beneath every stall and for a distance of four feet from the rear thereof be covered with a water-tight floor laid with such grades as will cause all fluids that fall upon it to flow as promptly as possible, if a public sewer be available, into the public sewer, and, if a public sewer be not available, to that portion of the premises where they will cause the least possible nuisance. SEC. 1 8 C. Every person owning or occupying any building or part of a building within any of the more densely populated parts of the District of Columbia, APPENDIX III 287 where one or more horses, mules, cows, or similar ani- mals are kept, shall maintain in connection therewith a bin or pit for the reception of manure, and, pending the removal from the premises of the manure from the animal or animals aforesaid, shall place such ma- nure in said bin or pit. The bin or pit required by this regulation shall be located at a point as remote as prac- ticable from any dwelling, church, school or similar structure, owned or occupied by any person or persons in the neighborhood of said bin or pit, other than the owner or occupant of the building or part of building aforesaid, and as remote as practicable from any pub- lic street or avenue; shall be so constructed as to ex- clude rain water, and shall in all other respects be watep-tight except as it may be connected with the pub- lic sewer or as other definite provision may be made for cleaning and flushing from time to time; shall be provided with a suitable cover, and constructed so as to prevent in so far as may be practicable the ingress and egress of flies. No bin or pit shall be constructed the bottom of which is below the level of the surface of the surrounding earth unless it be of substantial masonry and connected with the public sewer. The provisions of this paragraph shall take effect from and after the expiration of three months immediately fol- lowing its promulgation. SEC. i8Z). No person owning or occupying any building or part of a building located within any of the more densely populated parts of the District of Colum- bia, in which building or part of a building any horse, 288 THE HOUSE FLY— DISEASE CAKRIKR mule, cow, or similar animal is kept, shall keep any manure, or permit any manure to be kept, in or upon any portion of the premises other than the bin or pit provided for that purpose; nor shall any person afore- said allow any such bin or pit to be overfilled or to be needlessly uncovered. SEC. i8E. The provisions of paragraphs C and D shall not apply to the keeping of manure from horses when such manure is kept tightly rammed into \\c-ll covered barrels for the purpose of removal in such bar- rels. SEC. i8F. No person shall permit any manure to accumulate on premises under his control in such a manner or to such an extent as to give rise to objec- tionable odors upon any public highway or upon any premises owned or occupied by any person other than the person owning or occupying the premises on which said manure is located. Every person having the use of any manure bin or pit and every person keeping manure, in any of the more densely populated parts of the District of Columbia, shall cause all such ma- nure to be removed from the premises at least twice every week between June first and October thirty- first, inclusive, of each year, and at least once every week between November first of each year and May thirty-first of the following year, both dates in- clusive. SEC. 1 8 G. Every person using within the District of Columbia any building, or any portion of a building, in the city of Washington, or in any of the more APPENDIX III 289 densely populated suburbs thereof, as a stable for one or more horses, mules, or cows, shall report that fact to the health officer in writing, within thirty days after this regulation takes effect, giving his or her name, and the location of such stable, and the number and the kind of the animals stabled therein ; and thereafter every person occupying any building, or any portion of a building, in the city of Washington, or in any of the more densely populated suburbs thereof, for the purpose aforesaid, shall report in like manner his or her name and the location of said stable, and the num- ber and kind of animals stabled therein, within five days after the beginning of his or her occupancy of such buildings; provided, that stables recorded at the Health Office as parts of dairy farms in the District of Columbia need not be so reported. SEC. iSH. No person who has removed manure from any bin or pit, or any other place where manure has been accumulated, shall deposit such manure in any place within any of the more densely populated parts of the District of Columbia without a permit from the health officer authorizing him so to do and then only in accordance with the terms of such permit. The provisions of this paragraph shall not apply to the dis- tribution of manure over lawns and parking when such manure has been so thoroughly rotted or decomposed that its distribution gives rise to no offensive odors on adjacent properties or on public thoroughfares. SEC. 1 87. Any person violating any of the pro- visions of this section shall upon conviction thereof be 290 THE HOUSE FLY— DISEASE CARRIER punished by a fine of not more than forty dollars for each offense. Extract from Article IX, Police Regulations ARTICLE IX SEC. 10. No person shall remove or transport any manure over any public highway in any of the more densely populated parts of the District of Columbia except in a tight vehicle, which if not enclosed must be effectually covered with canvas so secured to the sides and ends of the vehicle as to prevent the manure from being dropped while being removed, and so as to limit as much as practicable the escape of odors from said manure. SEC. 20. Manure may be deposited in pits below the surface of alleys that are not less than fifteen feet wide, but the pit must not extend more than four feet beyond the building line. The walls must be substan- tial and water-tight, with stone or iron coping, bedded in cement, set fair with the surface of the alley. They must be covered with heavy wrought-iron doors, flush with the alley pavement or surface, sufficiently strong to carry heavily loaded carts or other vehicles, and pro- vided with ventilation by means of a flue inside of the stable and extending above the roof of the same, and they must be drained by sewer connections, as directed by the Inspector of Plumbing. APPENDIX III EXECUTIVE OFFICE COMMISSIONERS OF THE DISTRICT OF COLUMBIA ORDERED: WASHINGTON, April 11, 1908. That, Pursuant to the authority vested in the Commis- sioners by the "Joint Resolution authorizing the Commis- sioners of the District of Columbia to alter, amend, or repeal certain health ordinances" approved February 28, 1899, "An ordinance to prevent the sale of unwholesome food in the cities of Washington and Georgetown" as amended by Commissioners' orders of January 2, 1902; April 21, 1903 ; October 6, 1904; April 24, 1906; May 31, 1907, and June 10, 1907, is hereby further amended by inserting after the word "effectually" in section 13 thereof the phrase "or effectually protected by a power-driven fan or fans," so that said section shall read as follows : SEC. 13. Every manager of a store, market, dairy, cafe, lunch room, or any other place in the District of Columbia, where a food, or a beverage, or confectionery, or any similar article, is manufactured or prepared for sale, stored for sale, offered for sale, or sold, shall cause it to be screened effectually, or effectually protected by power-driven fan or fans, so as to prevent flies and other insects from obtaining access to such food, beverage, confectionery, or other article, and shall keep such food, beverage, confectionery, or other article free from flies and other insects at all times. Any person violating the provisions of this regulation shall, upon conviction thereof, be punished by a fine of not more than twenty- five dollars for each and every such offense. This regu- lation shall take effect from and after the expiration of thirty days immediately following the date of its promul- gation. Official copy furnished Health Department. By order: WM. TINDALL, Secretary. Officially published in the Washington Herald April 1 6, 1908. 292 THE HOUSE FLY— DISEASE CARRIER EXECUTIVE DEPARTMENT COMMISSIONERS OF THE DISTRICT OF COLUMBIA • WASHINGTON, December i, 1909. ORDERED : That Section 60 of "An Ordinance to prevent the sale of unwholesome food in the cities of Washington and Georgetown" as amended by orders of the Commissioners of the District of Columbia, be, and the same is hereby amended so as to read as follows : SEC. 60. No person shall expose for sale on any pub- lic highway or in any uninclosed market, store, shop, stand, or stall, or in any open lot, or transport over any public highway to any place for sale there or elsewhere, in the District of Columbia, any meat, fish, plucked poultry or game bird, dressed rabbit or squirrel, butter, butterine, oleomargarine, lard, lard compound or sub- stitute, cheese, candy, cake, bread, dates, figs, or any food whatsoever of a kind not commonly washed, peeled, shelled or cooked, before eaten, unless the same be then and there effectually and in a cleanly manner wrapped, or covered and enclosed, so as to protect it from dust and insects. No person shall expose for sale in any place aforesaid between April ist and October 3ist, inclusive, of any year, any fresh meat or fresh fish unless said meat or fish, while thus exposed, be kept at a temperature not exceed- ing fifty-five degrees Fahrenheit. Official copy furnished. By order : WM. TINDALL, Secretary. Officially published in the Washington Post, December 3, 1909- APPENDIX IV DIRECTIONS FOR BUILDING A SANITARY PRIVY* IN order to put the construction of a sanitary privy for the home within the carpentering abilities of boys, a practical carpenter has been requested to con- struct models to conform to the general ideas expressed in this article, and to furnish estimates of the amount of lumber, hardware, and wire screening required. Drawings of these models have been made during the process of construction (Figs. 36, 37) and in completed condition (Figs. 38, 39). The carpenter was requested to hold constantly in mind two points, namely, (i) economy and (2) simplicity of construction. It is be- lieved that any fourteen-year-old schoolboy of average intelligence and mechanical ingenuity can, by follow- ing these plans, build a sanitary privy for his home at an expense for building materials, exclusive of recep- tacle, of five to ten dollars, according to locality. It is further believed that the plans submitted cover the es- sential points to be considered. They can be elaborated to suit the individual taste of persons who prefer a more elegant and more expensive structure. For in- stance, the roof can have a double instead of a single slant, and can be shingled ; the sides, front, and back can be clapboarded or they can be shingled. Instead Taken from Public Health Bull. No. 37, U. S. Public Health and Marine Hospital Service. By C W. Stiles, Ph.D., Washing- ton, 1910. 293 294 THE HOUSE FLY— DISEASE CARRIER of one seat or six seats, there may be two, three, four, or five seats, etc., according to necessity. A SINGLE-SEATED PRIVY FOR THE HOME Nearly all privies for the home have seats for two persons, but a single privy can be made more econom- ically. Framework (Fig. 36). — The lumber required for the framework (Fig. 37) of the outhouse shown as completed in Fig. 38 is as follows: A. Two pieces of lumber (scantling) 4 feet long and 6 inches square at ends. B. One piece of lumber (scantling) 3 feet 10 inches long; 4 inches square at ends. C. Two pieces of lumber (scantling) 3 feet 4 inches long; 4 inches square at ends. D. Two pieces of lumber (scantling) 7 feet 9 inches long; 2 by 4 inches at ends. E. Two pieces of lumber (scantling) 6 feet 7 inches long; 2 by 4 inches at ends. F. Two pieces of lumber (scantling) 6 feet 3 inches long; 2 by 4 inches at ends. G. Two pieces of lumber (scantling) 5 feet long; 2 by 4 inches at ends. H. One piece of lumber (scantling) 3 feet 10 inches long ; 2 by 4 inches at ends. /. Two pieces of lumber (scantling) 3 feet 4 inches long; 2 by 4 inches at ends. /. Two pieces of lumber (scantling) 3 inches long; 2 by 4 inches at ends. K. Two pieces of lumber (scantling) 4 feet 7 inches long; 6 inches wide by I inch thick. The ends of K should be trimmed after being nailed in place. L. Two pieces of lumber (scantling) 4 feet long; 6 inches wide, and I inch thick. APPENDIX IV 295 1 \ 1! \ \ 296 THE HOUSE FLY— DISEASE CARRIER First lay down the sills marked A and join them with the joist marked B; then nail in position the two joists marked C, with their ends 3 inches from the outer edge of A; raise the corner posts (D and F), spiking them at bottom to A and C, and joining them with L, 1 2, G, and K; raise door posts E, fastening them at /, and then spike 7X in position ; H is fastened to K. (Fig. 37.) Sides. — Each side requires four boards (a) 12 inches wide by i inch thick and 8 feet 6 inches long; these are nailed to K, L, and A. (Fig. 37.) The corner boards are notched at G, allowing them to pass to bottom or roof; draw a slant from front to back at G-G, on the outside of the boards, and saw the four side boards to correspond with this slant. (Fig. 39.) Back. — The back requires two boards (b) 12 inches wide by i inch thick and 6 feet 1 1 inches long, and two boards 12 inches wide by i inch thick and 6 feet 5 inches long. The two longest boards (b) are nailed next to the sides ; the shorter boards are each sawed in two so that one piece (c1) measures 4 feet 6 inches, the other (c2) i foot n inches; the longer portion (c1) is nailed in position above the seat; the shorter portion (c2) is utilized in making the back door. Floor. — The floor requires four boards (d) which (when cut to fit) measure I inch thick, 12 inches wide, and 3 feet 10 inches long. (Fig. 38.) Front. — The front boards may next be nailed on. The front requires (aside from the door) two boards (E) which (when cut to fit) measure i inch thick, 9 APPENDIX IV 297 37-— The framework for a single-seated privy. (Redrawn from Stiles.) 298 THE HOUSE FLY— DISEASE CARRIER inches wide, and 8 feet 5 inches long; these are nailed next to the sides. (Fig. 38.) Roof. — The roof may now be finished. This re- quires five boards (/), measuring (when cut to fit) i inch thick, 12 inches wide, and 6 feet long. They are so placed that they extend 8 inches beyond the front. The joints (cracks) are to be broken (covered) by laths one-half inch thick, 3 inches broad, and 6 feet long. (Fig. 39.) Box. — The front of the box may be made with two boards, i inch thick, 3 feet 10 inches long. One may measure 12 inches wide, the other 5 inches wide. These are nailed in place, so that the back of the boards is 18 inches from the inside of the back- boards. The seat of the box may be made with two boards, I inch thick, 3 feet 10 inches long; one may measure 12 inches wide, the other 7 inches wide. One must be jogged (cut out) to fit around the back corner posts (F). An oblong hole, 10 inches long and 7^2 inches wide, is cut in the seat. The edge should be smoothly rounded or beveled. An extra (removable) seat for children may be made by cutting a board I inch thick, 15 inches wide, and 20 inches long; in this seat a hole is cut, measuring 7 inches long by 6 inches wide ; the front margin of this hole should be about 3 inches from the front edge of the board; to prevent warping, a cross cleat is nailed on top near or at each end of the board. A cover (K) to the seat should measure i inch thick by 15 inches wide by 20 inches long; it is cleated on APPENDIX IV Fig. 38. — Front view of single-seated sanitary privy. (Redrawn from Stiles.) 300 THE HOUSE FLY— DISEASE CARRIER top near the ends, to prevent warping; it is hinged in back to a strip i inch thick, 3 inches wide, and 20 inches long, which is fastened to the seat. Cleats may also be nailed on the seat at the sides of the cover. On the inside of the backboard, 12 inches above the seat, there should be nailed a block ( i ) , 2 inches wide, 6 inches long, extending forward 3*4 inches; this is intended to prevent the cover from falling backward and to make it to fall down over the hole when the occupant rises. On the floor of the box (underneath the seat) two or three cleats are nailed in such a position that they will always center the tub; the position of these cleats depends upon the size of the tub. Back door. — In making the back of the privy the two center boards were sawed at the height of the bottom of the seat. The small portions (c2) sawed off (23 inches long) are cleated (O) together so as to form a back door which is hinged above; a bolt or a button is sufficient arrangement to keep the door closed. Front door. — The front door, Fig. 38, is made by cleating (/>) together three boards (Q) i inch thick, 10 inches wide, and (when finished) 6 feet 7 inches long; it is best to use three cross-cleats (/>) (i inch thick, 6 inches wide, 30 inches long), placed on the inside. The door is hung with two hinges (6-inch "strap" hinges will do), which are placed on the right as one faces the privy, so that the door opens from the left. The door should close with a coil spring (cost APPENDIX IV 301 about 10 cents) or with a rope and weight, and may fasten on the "inside with a catch or a cord. Under Fig. 39- — Rear view of single-seated sanitary privy. (Redrawn from Stiles.) the door a crosspiece (R) i inch thick, 4 inches wide, 30 inches long (when finished) may be nailed to the 302 THE HOUSE FLY— DISEASE CARRIER joist. Stops may be placed inside the door. These should be i inch thick, 3 inches wide, and 6 feet 6 inches long, and should be jogged (that is to say, cut out) to fit the cross-cleats (/>) on the door. Close over the top of the door place a strip i inch thick, 2 inches wide, 30 inches long, nailed to I. (Fig. 37). A corre- sponding piece is placed higher up directly under the roof, nailed to G. A strap or door-pull is fastened to the outside of the door. Ventilators. — There should be five ventilators (w). One is placed at each side of the box directly under the seat; it measures 6 to 8 inches square. Another (12 inches square) is placed near the top on each side of the privy. A fifth (30 inches long Sl/2 inches wide) is placed over the door, between G and I (Figs. 37, 38). The ventilators are made of 15-mesh copper wire, which is first tacked in place and then protected at the edge with the same kind of lath that is used on the cracks and joints. Lath. — Outside cracks (joints) are covered with lath one-half inch thick by 3 inches wide. Receptacle. — For a receptacle, saw a water-tight bar- rel to fit snugly under the seat; or purchase a can or tub, as deep (17 inches) as the distance from the un- der surface of the seat to the floor. If it is not pos- sible to obtain a tub, barrel, or can of the desired size, the receptacle used should be elevated from the floor by blocks or boards so that it fits snugly under the seat. A galvanized can measuring 16 inches deep and 16 inches in diameter can be purchased for about $i, or APPENDIX IV 303 even less. An empty candy bucket can be purchased for about 10 cents. Order for material. — The carpenter has made out the following order for lumber (pine, No. i grade) and hardware to be used in building a privy such as has been described : i piece scantling, 6 by 6 inches by 8 feet long, 24 square feet. 1 piece scantling, 4 by 4 inches by 12 feet long, i6"square feet. 5 pieces scantling, 2 by 4 inches by 16 feet long, 54 square feet. 3 pieces board, i by 6 inches by 16 feet long, 24 square feet. 2 pieces board, i by 9 inches by 9 feet long, 14 square feet. 3 pieces board, i by 10 inches by 7 feet long, 18 square feet. 15 pieces board, i by 12 inches by 12 feet long, 180 square feet. 12 pieces board, /^ by 3 inches by 16 feet long, 48 square feet. 2 pounds of 2O-penny spikes. 6 pounds of lo-penny nails. 2 pounds of 6-penny nails. 7 feet screen, I5~mesh, copper, 12 inches wide. 4 hinges, 6-inch "strap," for front and back doors. 2 hinges, 6-inch "T," or 3-inch "butts," for cover. i coil spring for front door. According to the carpenter's estimate, these materials will cost from $5 to $10, according to locality. There is some variation in the size of lumber, as the pieces are not absolutely uniform. The sizes given in 304 THE HOUSE FLY— DISEASE CARRIER the lumber order represent the standard sizes which should be ordered, but the purchaser need not expect to find that the pieces delivered correspond with mathe- matical exactness to the sizes called for. On this ac- count the pieces must be measured and cut to measure as they are put together. ESTIMATE OF MATERIAL FOR SCHOOL PRIVY The following estimate of building materials has been made by a carpenter for the construction of a six-seated school privy. The estimated cost of these materials is $25 to $50, according to locality ; this does not include the pails, which ought not to cost over $i apiece. 3 pieces scantling, 6 by 6 inches by 20 feet, 180 square feet. I piece scantling, 6 by 6 inches by 8 feet, 24 square inches. Scantling, 2 by 4 inches, 165 square feet. Boards, I by 12 inches, 600 square feet. Boards, I by 10 inches, 185 square feet. Boards, I by 8 inches, 100 square feet. Boards, I by 6 inches, 80 square feet. Boards, l/2 by 3 inches, 100 square feet. Flooring, 80 square feet. 40 feet 15-mesh copper wire screen, 12 inches wide. 12 pairs of hinges, 6-inch "strap." 6 pairs of hinges, 6-inch "T." 3 pounds of 2O-penny spikes. 15 pounds of lo-penny nails. 8 pounds of 6-penny nails. 6 coil springs for front doors. 6 knobs or latches. APPENDIX V A SIMPLE APPARATUS FOR USE IN THE SAFE DISPOSAL OF NIGHT-SOIL* proper disposal of human excreta is recog- 1 nized by sanitarians as the most important single measure needed to prevent the spread of typhoid fever, hookworm disease, the dysenteries, and certain other widely prevalent diseases. Where large numbers of people are gathered to- gether, as in cities, the removal of dejecta from per- sons becomes, from an esthetic standpoint at least, a necessity, and practically all modern cities have ex- pended large sums of money to install sewerage sys- tems, which, though usually removing the sewage in such a way as to prevent it from becoming an intoler- able nuisance to sight and smell, yet frequently fall short of safety from a sanitary standpoint. Though a city may dispose of its own sewage prop- erly, its people are exposed to excreta-borne infections brought in on various food supplies from farms. Thus the sanitation of the farm is vastly important, not only to the rural population, but also to the urban, and there- fore the farm as the fountain head of various and far- flowing streams of infection is the logical point to *From Public Health Report No. 54. Preliminary Note on a Simple and Inexpensive Apparatus in Use in Safe Disposal of Night-Soil. By L. L. Lumsden, Norman Roberts, and Ch War- dell Stiles. 305 306 THE HOUSE FLY— DISEASE CARRIER attack in campaigns of prevention against many of the communicable diseases.* Among the obstacles in progress in farm sanitation one of the chief has been the difficulty of convincing the farmer that the benefits which would accrue from proper disposal of excreta would justify the expense of constructing, and the disagreeable labor of main- taining, the sanitary devices proposed. Therefore, whatever can be done in simplification and in lessen- ing expense and labor in the installation and mainte- nance of an efficient disposal system will increase the chances of its adoption. The apparatus described in this note has been in use in one of the work rooms of the Hygienic Laboratory since July 12, 1910. It has been seen by a number of sanitarians from different sections of the country, and several of them have expressed a desire to test it for themselves. The details of construction are presented at this time in order to place them at the disposal of any persons who may desire to test the apparatus in ques- tion. Starting point of studies. — Starting out on the prin- ciple that the forces of nature in fermentation should, if possible, be utilized, we have sought to meet the ob- jections that have thus far occurred to us in respect to the wet system. Further, the importance of economy and of simplicity of construction has been constantly held in mind. An effort has also been made to reduce *Freeman, Allen W., The Farm the Next Point of Attack in Sanitary Progress. Jour. A. M. A., August 27, 1910. APPENDIX V 307 to a minimum the labor and skill involved in taking care of the privy, and, finally, while sanitary safety has been the chief object in mind, we have not ignored the widespread demand that human excreta be turned to economic account. Fig. 40. — The Lumsden, Roberts and Stiles apparatus for the safe disposal of night-soil. (Redrawn from Lumsden, Roberts and Stiles.) 308 THE HOUSE FLY— DISEASE CARRIER Construction. — The apparatus under consideration consists of the following parts : 1. A water-tight barrel, to be used as a liquefier. 2. A covered water-tight barrel, can, or other con- tainer to receive the effluent. 3. A connecting.pipe about two and one-half inches in diameter, about twelve inches long, and provided with an open "T" at one end, both openings of the "T" being covered by wire screens. 4. A tight box, preferably zinc lined, which fits tightly on the top of the liquefying barrel ; it is pro- vided with an opening on top for the seat, which has an automatically closing lid. 5. An anti-splashing device consisting of a small board placed horizontally under the seat and one inch below the level of the transverse connecting pipe; it is held in place by a rod, which passes through eyes or rings fastened to the box, and by which the board is raised and lowered. The liquefy- ing tank is filled with water up to the point where it begins to trickle into the effluent tank. As an insect repellent a thin film of some form of petroleum may be poured on the surface of the liquid in each barrel. Practical ivorking of the apparatus. — When the privy is to be used, the rod is pulled up so that the anti- splashing board rises to within about one inch below the surface of the water. The fecal matter falls into the water, but this board prevents splashing, and thus meets one of the greatest objections thus far raised to the wet system. After defecation the person sinks the anti-splashing board by depressing the rod, and the APPENDIX V 309 fecal matter then floats free into the water. We are now working on an improvement whereby the rod will connect with the automatically closing lid, and the anti- splashing board will rise and sink as the lid is opened and closed. Although some of the fecal matter floats, it is pro- tected both from fly breeding and fly feeding in the following ways : First, by the automatically closing lid ; second, by the water; third, by the film of oil; and, fourth, for additional safety, the apparatus should be located in a screened place. The film of oil also pre- vents the breeding of mosquitoes in the barrel. Ac- cordingly, so far as the privy as a breeding or feed- ing place for flies and mosquitoes is concerned, the model in question completely solves the problem. The fecal material becomes fermented in the water and gradually liquefies ; the addition of excreta natu- rally raises the level of the liquid, and the excess flows into the effluent tank, where it is protected from in- sects by the cover and by the film of oil. This effluent may be allowed to collect in the tank until it reaches the level of the connecting pipe, when it may be safely dis- posed of in various ways to be discussed later. From July I2th to October 26th there have been 246 defecations (with urination) into the model in question, making about two and one-third defecations a day. The effluent has amounted to about twelve gal- lons of manageable fluid. It has not been found neces- sary to add water to the liquefying barrel since the ap- paratus was put into operation. 310 THE HOUSE FLY— DISEASE CARRIER Although the period in question included the hottest part of summer, the odor, when compared with that of the average privy, has been negligible. It is thus seen that this device appears to meet the following requirements : 1. It solves the fly and mosquito problems, so far as the privy is concerned. 2. It liquefies fecal matter and reduces its volume so that it may be safely disposed of more easily and cheaply than night-soil. 4. It reduces odor. 4. It reduces the labor of cleaning the privy and makes this work less disagreeable. 5. It is of simple and inexpensive construction. The effect of the fermentative changes in the ap- paratus upon the viability of typhoid bacilli and hook- worm eggs has not been determined, but other experi- ments tend to show that under such conditions the vast majority of typhoid bacilli and of hookworm eggs in- troduced would die within six weeks' to two months' time. While the time of storage can be prolonged ac- cording to the capacity of vessels provided for the pur- pose, we believe at present that it is safer and more practical not to depend upon storage alone to destroy infectious organisms in the effluent, but to consider the effluent infectious and to dispose of it accordingly. Disposal of effluent. — ( i ) Heat : If a suitable (metal- lic) vessel is provided to receive the effluent, a fire may be built under the vessel and the effluent heated to boil- ing. Or if a wooden or concrete effluent tank is used, APPENDIX V 311 the effluent may be transferred to some other vessel for boiling. After boiling, the fluid may be safely used for fer- tilizer under any conditions. Heat disinfection is the only measure which can to- day be recommended unreservedly. (2) Burial: Burial wilt unquestionably decrease the dangers of spreading infection, but in the present state of our knowledge this method of disposal cannot be relied upon as safe. If burial of the effluent is prac- tised, the fluid should be disposed of not less than 300 feet from and downhill from any neighboring water supply and not less than two feet underground, and then only provided the soil itself is a good filter. Bur- ial in a limestone region may contaminate water sup- plies miles away. (3) Chemical disinfection: Chemical disinfectants, such as chlorinated lime and certain coal-tar deriva- tives, have the great advantage of cheapness and can be relied upon to destroy pathogenic bacteria. Our knowledge regarding the action of chemical disinfec- tants upon the eggs and spores of the various animal parasites is at present very rudimentary, but so far as results are known, their practicable use does not seem to be so efficient in the destruction of the zooparasitic as of the bacterial infectious organisms. Therefore, pending further investigations, the use of chemically treated excrement as fertilizer should not be regarded as unqualifiedly safe. (4) Chemical disinfection with subsequent burial : THE HOUSE FLY— DISEASE CARRIER Inasmuch as chemical disinfection can be relied upon to destroy pathogenic bacteria, and inasmuch as burial greatly reduces the danger from animal parasites, a suitable combination of the two methods (chemical dis- infection and burial) can be used with reasonable safety. (5) Sewers: In partly sewered towns, the effluent from these privies may be emptied into the sewers. If conditions are such that the addition of this material to the sewage is dangerous, then the entire sewerage system needs correction. Paper. — Only toilet paper so far has been used, and the septic action seems to digest it. Other experiments indicate that newspaper would be disposed of by septic action in the tank, but perhaps some increase in the size of the tank would be required. Cleaning. — Although no water has been added since the model was put into operation, the contents of the liquefying tank have remained fluid, and it is prob- able that in a tank having the capacity of an oil bar- rel, the amount of sludge from the dejecta of a family of five people would not be sufficient to require the cleaning of the liquefying tank oftener than once in six months to a year. 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