Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. aes: UNITED STATES DEPARTMENT OF AGRICULTURE | BULLETIN No. 597 Contribution from the Bureau of Entomology L. O. HOWARD, Chief Washington, D. C. PROFESSIONAL PAPER - April 9, 1918 SOME BIOLOGICAL AND CONTROL STUDIES OF GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS OF HORSES By W. E. DOVE, Scientific Assistant Insects Affecting Domestic Animals CONTENTS Introduction Brief Life Histery of Gastrophilus Histerical Species Differentiation Distribution in the United States and Probable Dispersion Larval Cellections and Rearing Tech- nigue Larval Infestation and Injuries. .. . Bot-fly Annoyance Natural Protection of Horses | Seasonal History of Gastrophilus . .. Gastrophilus haemorrhoidalis Linn . Gastrophilus nasalis Linn | Gastrophilus intestinalis DeGeer. . | Effect of Death of Host upon Gastro- philus Larvz | Control Studies Summary Bibliography WASHINGTON GOVERNMENT PRINTING OFFICE 1918 UNITED STATES DEPARTMENT OF AGRICULTURE Contribution from the Bureau of Entomology L. O. HOWARD, Chief Washington, D. C. PROFESSIONAL PAPER. April 9, 1918 SOME BIOLOGICAL AND CONTROL STUDIES OF GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS OF HORSES.’ By W. BE. Dove, Scientific Assistant, Insects Affecting Domestic Animals. CONTENTS. Page Page In ENOGUCtIONL Ss poe ees eee aes 1 | Seasonal history of Gastrophilus............- 15 Brief life history of Gastrophilus......--...-- 2 | Gastrophilus haemorrhoidalis (Linnaeus) .... 16 EM StOni Callie steer caer ae ae cle eee ose emt wer 2 | Gastrophilus nasalis (Linnaeus)..........--... 30 SPECles GiseremtIatiOMeo. ees seo e sss liar 3 | Gastrophilus intestinalis (De Geer) ........--. 32 Distribution in the United States and prob- Effect of death of host upon Gastrophilus Abledisperslomlaas sae <1 - oeeeeie eece cere 5 1 ETN oe are aac, A Re = ne ear aS 34 Larval collections and rearing technique... oF le Controlistudicssss20s) sso eee eee 35 Larval infestation and injuries..........-.-.- GS Summa nyt ee Shei se ae ets ieee ieee 48 iB Ob-tlys AN NOWANCE =. eee sai elo ice oa 1) |W" Jello) Wo yeiv2) 0) ON / Jes oee ppemosceealcoducnooocebos 50 Natural protection of horses.........-2------ 14 INTRODUCTION. In compliance with requests from farmers and horse breeders of the Dakotas and Montana regarding “ fly annoyance” to horses, a survey of conditions was made in the autumn of 1914 by Mr. F. C. Bishopp. Under the direction of Dr. W. D. Hunter and the super- vision of Mr. Bishopp, investigations were undertaken in the follow- ing summer upon the European Gastrophilus haemorrhoidalis, com- monly known in that section as the “ nose-fly.” The preliminary investigations in the summer of 1915 revealed the fact that the concentration of horses in pastures had rendered breeding conditions practically ideal for bot-flies, and that a most serious fly nuisance had developed which implicated three species of Gastrophilus. This concentration of horses in pastures may be attributed in part to the advent of gas engines, automobiles, and tractors, and to maximum prices, which has encouraged the breeder 1Mr. H. B. Bradford made the drawing illustrating the eggs of Gastrophilus, and Mr. W. N. Dovener made those illustrating the larve and dorsal aspects of the adults. Many of the photographs were made by Mr. A. K. Pettit. 11216°—18—Bull. 597 1 1 2 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. to meet the great demand for army horses. Within the nose-fly dis- trict is to be found one of the largest horse-sale points in the world. BRIEF LIFE HISTORY OF GASTROPHILUS. Our knowledge of the life histories and habits of these insect pests, which is always essential to successful control, is confined for the most part to the classical accounts of Bracy Clark in 1797 and subsequently, although later writers have added important details. When the female of Gastrophilus intestinalis (G. equi) becomes sexually mature it is most often observed hovering near the inside of the knee of a horse, where by preference the eggs are deposited. After a few days, when the larvee develop within the eggs, the horse by scratching the forelegs with the teeth provides sufficient moisture and friction to remove the operculum or small cap of the eggs and inadvertently the larve are taken within the mouth. The empty egoshells remain attached to the hairs of the legs, whereas the larve are carried with the food or water to the stomach, where attachment to the stomach walls takes place. Here they undergo development during the autumn, winter, and spring months, and later are passed from the horse with the manure. At this stage pupa- tion ensues and adult flies are produced. The other species of bots also spend similar larval periods in the animal, but have habits peculiar to the particular species. HISTORICAL. The literature containing historical references to the Oestridae carries one to a most remote time. The ancient Greeks and the Latins refer to “an unspeakable fright of cattle,’ though later writers are not agreed as to whether it was produced by an oestrid or a tabanid. It is certain, however, that Aristotle knew the forms found in the throats of deer. The Greek veterinarians Theomnestus and Absyrtus give us the earliest record which could be referred to Gastrophilus when they write of the “biting worms which fix themselves to the anus of the horse.” In order to destroy them it was recommended that they be torn from the anus with the fingers and covered with hot ashes and pulverized salt. Malpighi in 1697 gave the first description of a gastrophilid larva taken from the stomach of an ass. According to Joly, it belonged to the species @. intestinalis De Geer, while to Brauer it was G. flavipes Olivier. Gaspari published an erroneous opinion that G. haemorrho- idalis deposited its eggs in the rectum of the horse during def- ecation, and that the larve migrated to the stomach until about fully developed. Vallisnieri and Réaumur made the same erroneous diagnosis. GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 3 Linnaeus, Fabricius, and De Geer occupied themselves with the early classification, and not until 1797, with Bracy Clark, does the natural history of the Oestride truly commence. To this historical work of Bracy Clark a few additions, many of which are cited in the bibliography, have been made by subsequent writers. In conformity with the rules of nomenclature and following the reestablishment of the Linnaean designation “ éntestinalis” by Guyot, “ Gastrophilus intestinalis” is given preference rather than “ Gastro- philus equi.” Aside from priority, the specific name “ eguz” is not reliable, since there are several spe- cies of Gastrophilus which infest the horse; moreover “in- testinalis” has been adopted by a number of dependable au- thorities. SPECIES DIFFEREN- TIATION. The eggs, larve, and adults are so Fic. 1.—Gastrophilus nasalis: Female. Oviposits com- easily distinguishable monly under the jaws of horses. Greatly enlarged. 3 A 5 (Original.) in this genus that it does not require a study of detailed descriptions to enable a student to determine the species. (Figs. 1, 2,3.) Prof. Garman’s key to the wing venation, a reliable index to the species, is here quoted. KEY TO WING VENATION OF GASTROPHILUS SPP. ie OIscoiMalecellinot, closed, bya. Cross vein=__—=] 2-4) ee G. pecorum. PISCOMaAlacelAClOSCOL Dyas CLOSSaVeIN oe 20 es es a ee 2 POO Seti ee Ginilil MeO RON se es G. intestinalis. ant Senora ae heom with OEOWE se we Se ee Se eee 3 38. Anterior basal cell nearly or quite equal to the discoidal cell in SPOS ea ae a a a eae ee G. nasalis, Anterior basal cell markedly shorter than the discoidal Gece ee ee Se wee ee G. haemorrhoidalis. The cloudy wings of G. intestinalis and its habit of depositing upon any convenient portion of the horse where it is not disturbed, but most commonly on the forelegs, will enable one to distinguish it most readily. G. nasalis is smaller than G. intestinalis, densely hairy, with the thorax yellowish red or rust colored. Its most common place of oviposition is under the jaws, but it is sometimes observed to oviposit 4. BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. upon the flanks or forelegs of the animal. Unlike G. intestinalis, it does not remain near the animal prior to the deposition of a_ second egg. G. haemorrhoidalis is easily distinguished by the bright orange red on the tip of the abdomen. The thorax above is olive gray and! hairy, with a black band behind the suture. The base of the abdo- men is whitish and the mid- dle blackish, which is in strange contrast with the orange red of the end. It deposits only upon the small hairs on the lips of horses and mules. The males of G. itesti- nalis and G. haemorrhoi- dalis are often found await- ing the approach of females to the horses, and when they arrive the flies copulate. Bie ceeronting fama fete: Wael = hey of horses. preferably the portions moistened by of the eggs of the three saliva. Greatly enlarged. (Original.) species occurring in the United States can best be observed by referring to the illustration (fig. 3). While G. intestinalis is usually attached about one-half its length to the hair, G. nasalis is attached almost its entire length. G. haemorrhoidalis is always found attached to the base of a hair on the lips. These hairs are so small that one does not observe them with the naked eye. It is the only Gastrophiltis depositing here. The egg is black in color and the stalk is partially inserted in the pore of the skin at the root of the hair. Fourth-stage lave, as can be seen in the dinceoeon (Pl sb saany in size when fully developed. In all specimens the eleventh ring is completely deprived of spines, but upon the other rings the varia- tions are often misleading. However, the key given herein will assist in identifying fully developed larvee IKEY FOR THE IDENTIFICATION OF FULLY DEVELOPED LARV4: OF GASTROPHILUS SPP. 1. Spines arranged in two alternating rows, the first more developed than the Second ~~ 4-422 Se eS ce Be ae ee 2 SDiINeES' 11 ONE, WO We a a a ee epee G. nasdalis. 2. Spines long and prominent, lacking only two to three pairs on dorsal center of the ninth row 2 23 22 a ee ee G. intestinalis. Spines short and segments prominent. Completely deprived or possessing only two to three pairs of spines on either side of the dorsal center of the ninth “Tings 522224 2 eee 2 Se ea ee G. haemorrhoidalis. GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 5 DISTRIBUTION IN THE UNITED STATES AND PROBABLE DISPERSION. Recently Mr. F. C. Bishopp, in communication with a large num- ber of horse breeders, has determined some facts on the distribution -and other points, especially in regions adjoining the district where G@. haemorrhoidalis is known to occur. This information will be published later. It will suffice to say here that G. haemorrhoidalis occurs in sufficient numbers to warrant the adoption of control measures in the Dakotas, Montana, and northern Wyoming. Accord- ing to Dr. C. Gordon Hewitt, Dominion Entomologist, the species extends over a considerable area in the Dominion of Canada. Two of the species, G. intestinalis and G. nasalis, are found throughout the United States where horses are present. G. pecorwm is not known to occur in the United States. The constant migration of the larve of G. haemorrhoidalis to the region of the anus and their dropping, which occurs over a long period, indicates that the principal means of dispersion is through the movement of infested horses. During the past few years large numbers of horses, which have been purchased in the infested district for European army purposes, were concentrat- ed at certain points until more could be assembled for shipment. This. occurred at times when larvee were normally dropping and allowed ample time for this species to become established. Although the adults may not have appeared in sufficient num- bers to attract attention in new districts, this will undoubtedly occur in the near future. The comparatively short dura- tion of adult life and the func- tions of the adults restricted to ee : - Fie. 3. depositing eggs indicate that 7 a little dispersion takes place by with root; b, G. intestinalis ; c, G. nasalis. Gastrophilus eggs attached to hairs: haemorrhoidalis and hair removed . xreatly enlarged. (Original. actual flight. In the nose-fly Z y re roue district there has been a slow but gradual spread of the species each year, as verified by hundreds of statements from farmers and horse breeders. LARVAL COLLECTIONS AND REARING TECHNIQUE. An insectary was located in Aberdeen, S. Dak., where all types of farm and city operations concerned with the use of horses could 6 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. be observed, and at the same time easily accessible to a rendering plant where post-mortem examinations could be made. Horses in pasture were available in all directions, and livery barns were located within a mile and could be conveniently visited. Horses of many types, representing every locality in the imme- diate vicinity, could be observed in the livery barns, and it was from these horses that breeding material of G. haemorrhoidalis was obtained. While examinations of droppings were made, most of the larve utilized were removed from their places of attachment about the anus. These were sufficiently developed to pupate and produce adults, and did so even though they were not handled care- fully with the forceps in removal. The number of horses in the liveries varied, but usually from 30 to 100 were observed daily. In order to obtain an ample supply of larve additional collections were made when near-by farmers came in with teams. In rearing adults, the larvee were placed in tin boxes upon moist sand in California parasite-rearing boxes, or in bread trays upon grass sod. These were usually kept in cages 18 by 18 by 18 inches, each of which was fitted with a door of sufficient size to permit the removal of trays for examination. When adults emerged it was necessary to confine them in tightly fitted cages which excluded sun- light, and to keep them supplied with grass sod or green foliage to lessen activity. Sunlight has an unusually great attraction for adult flies. They are very active and will damage their wings against the screen or crawl into a cage crevice and die. More especially has this been noted with G. haemorrhoidalis. LARVAL INFESTATION AND INJURIES. REVIEW OF OPINIONS. In reviewing opinions on the economic importance of bot-flies, one naturally encounters the ideas of Bracy Clark, which have been passed from one to another since 1798. He believed that larve by irritating the membranes of the stomach and intestines often re- lieved a general disorder of the system, but mentions that, however useful a few of these natural stimuli may be, they result in large infestations which should at all times be prevented. He indicates in this paper that the infestations coming under his observation did not greatly exceed 100 larve, and for the most part not more than a half dozen were to be found. We find the following statement by R. S. MacDougal (1899) : Opinion differs a good deal as to the harmfulness of these bots. In conver- sations with veterinary surgeons I find there is a tendency to minimize the evils that may attend bot presence. There are authenticated records, however, which place the possibility of grievous harm beyond all doubt. Inflammation, ulcers, interference with digestion, interference with the free passage of food or exit of waste matters, loss of appetite and condition, have been frequently GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. ) 7 Warburton (1899) says: The irritation they set up can not fail, however, to be detrimental to the horse’s health even where no ill effects are obvious. The fact seems to be that a horse in good condition and well fed can endure the presence of numerous bots in the stomach without great inconvenience, but if the animal is in poor condition gastric enteritis, perforation of the stomach, and death may result. In Miss Ormerod’s report of 1890, Dr. Hy. Thompson, of Aspatria, Cumberland, England, says: {i have never seen the stomach entirely perforated, but the irritation induced by the development of the larva causes in many cases a great wasting of flesh in the horse. Perroncito (1902) describes lesions caused by Gastrophilus larvee, some of which resulted in perforation of the stomach walls and death of the animals. Cases of Flohill, Numan, Conti, and others, as well as cases coming under his personal observation, are mentioned. Kroéning (1906) reports having observed cachexia accompanied with colic in young colts during the previous five years, and at- tributes this to infestations of bots. Lahille (1911) makes mention of larve causing death of animals and cites the possibility of infection in the lesions. Velu (1913) reports that a drought greatly favored attacks in Morocco and more than 1,000 larve were usually found in post- mortem examinations. All three of the more common species were present, but G. nasalis caused lesions which resulted in death of the animals. The universal distribution of G. equi and G. nasalis has familiar- ized persons in every locality to some extent with bots of horses, yet their opinions are naturally varied as to the economic importance of the larve. There are some who believe that there are no ill effects; others think that they are beneficial; while some even believe that a horse will die if the bots are removed. Such conceptions are most prevalent among “horse doctors” who are not in possession of an ef- fective treatment for the removal of bots. On the other hand, it is a difficult matter to convince a horse breeder that bots are bene- ficial when his yearling colts kept in pastures have a rough coat, fail to grow or fatten, show no symptoms of disease, and at the same time possess a good appetite. Many breeders have made post-mortem examinations of horses for their personal satisfaction. The finding of hundreds of well developed larve with conspicuous lesions con- veys vivid impressions and greatly emphasizes the importance of bots. Others, without a knowledge of the development of bots within the horse, often make examinations after numbers have been passed and the lesions healed; or when the larve are small and probably not observed by an untrained eye they are regarded as less detrimental. It is only by careful post-mortem examinations of large numbers of 8 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. horses that conclusions can be drawn, and these may be erroneous if one is not familiar with the various species, their usual points of at- tachment, and phenomena peculiar to each. SPECIES IMPLICATED. Gastrophilis intestinalis, “the common bot,” attaches ordinarily in the stomach, has been taken in the duodenum, but has never been found permanently attached in any other regions (Table I, p. 10). Rarely it may become temporarily attached in the rectum, but is not present with an alveolus or lesion. G. nasalis, “the throat bot,’ attaches by preference in the duo- denum, is often found in the stomach, and is the only known species which attaches in the pharynx. Due to the attachment in the throat, it not only becomes a species of vital importance when the bots congregate in sufficient numbers to hinder or cut off the breathing ot the horse or cause an infection, but in this location they can not be removed by an internal treatment. In the duodenum the infestation may be sufficient to hinder or stop the passing of excreta. Table I (p. 10) shows the comparative abundance in the stomach and duodenum curing the period that larvee are well developed and naturally drop from the host. ) Various cases are on record in which this species has been removed from the pharynx, in all of which the authors considered it a serious detriment to the horse. While larve which were not sufficiently de- veloped to be determined with authenticity have frequently been removed from the pharynx, 8 larvee of G. nasalis were collected in the throat of a dray horse by J. L. Webb at Reno, Nev., on August 29,1916. In numerous cases, both at Aberdeen, S. Dak., and at Dal- las, Tex., the author has found lesions present in the pharynx, indi- cating that the larvee had become fully developed and had passed out of the horse. In making post-mortem examination of horses to de- termine the attachment of young larve in the pharynx extreme care should be exercised, as young meat-infesting larvee may be con- fused with Gastrophilus. Upon hatching they migrate from the hght into the nostrils and may be found in the pharynx and other locations in the throat. Dr. Buflington (1905), of Brooklyn, Iowa, gives a valuable history of a case in which a mare died as the result of an infestation of G. nasalis in the pharynx. This animal had experienced difficulty in eating for more than a month, and was unable to take food for a week prior to November 26, 1908. At this time she would drink water, but after masticating food a very little, would drop it out. The symptoms were those of paralysis of the muscles of deglutition and there was a very offensive odor about the head. Four days later, when the animal died, the nasal, pharyngeal, laryngeal, and upper portion of the esophageal mucous membranes were found to be gan- Bul. 597, U. S. Dept. of Agriculture. PLATE lI. Ye, 4, e Sd ote ites acai, bist ‘ ties Oe 4 this je OO PCI ey, tiki ¢T% pete NO ag AP Cm, pyats ua di i J : i ‘895% Cy J ayes aaa, ae gt? “A tx £. de as Zs VY LEG ge. vet | % % 3h SOUL hes © 4 a vad | ay + ; “ptr CHENG & ¢ y y Bene oI" aso i ¥ STAGES OF THE BOT FLIES, GASTROPHILUS. Upper left.—Gastrophilus haemorrhoidalis: Female, side view. Upper right.—G. haemorrhoidalis. Larve attached to margin of anus of horse. Left of center.—G. haemorrhoidalis: Last-stage larva. Center.—G. intestinalis: Last-stage larva. Right of center.—G. nasalis: Last-stage larva. Lower left.—G. intestinalis: Puparium, showing cap split off by fly inemergence. Lower right.—G. haemorrhoidalis: Male, side view. (Original.) Bul. 597, U. S. Dept. of Agriculture. PLATE II. LARV4 OF THE BOT FLIES, GASTROPHILUS. | Upper.—Attachment of last-stage larvee and alveolar lesions upon the mucosa of the left sac °0 the Storey. Lower.—Infestation of 317 last-stage larvee, with lesions in the center. riginal.) GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 9 grenous and the source of the offensive odor. From the pharyngeal walls 12 or 15 larvee were removed, 6 of which the present author obtained. Three of these larvae were determined as @. nasalis, and it is reasonable to believe that the other larvae, which were not suffi- ciently developed for identification, were of the same species. The larve of G. haemorrhoidalis, “ the nose-fly,” as is shown in Table I, may be found in the stomach, duodenum, or rectum, and also attached about the margin of the anus, where they change in color from pink to a greenish, become accustomed to the atmosphere, and later drop to the soil for pupation. During the early stages they attach within the stomach and duodenum, but later loosen them- selves and reattach in the rectum, from which they gradually move to the anus. The attachment of clusters of these larvee in the rectum has been known to stop the passage of excreta and to cause abnormal protrusions accompanied by much suffering. About June 1, 1915, a horse breeder in Montana experienced a case of obstruction of the rectum in a yearling colt. On three different occasions within one week the animal was observed lying down in the pasture with the rectum greatly protruded. Each time it was washed with warm water and replaced, but the larve causing it were not observed until the third time. The exact number of bots removed by hand was not ascertained, but upon their removal and replace- ment of the rectum the animal gradually recovered. Table I records a maximum of 1,032 bots removed from a 2-year- old colt. The infestation consisted of 695 G. intestinalis, 248 G. nasalis, and 89 G. haemorrhoidalis. This was the greatest number obtained during any of the autopsies. Colts are always the most heavily infested, especially when they come from summer pastures, and in this case the animal was greatly emaciated, possessed a dull coat, and, in spite of a good appetite and an abundance of food dur- ing the previous winter, failed to grow or fatten. It had suffered from a broken shoulder, the result of a kick, which ordinarily would have healed promptly at this age, but instead it remained for months a cripple. The owner, believing that it would never thrive, caused the animal to be killed, and the post-mortem examination revealed no abnormal condition, except the bot infestation and the broken shoulder. It appeared that so much vitality was sapped through the inroads of bot infestation that the colt had no recuperative surplus. At the date of the post-mortem examination 89 G. haemorrhoidalis larve had migrated to the rectum and attached. They were not suffi- ciently developed to pass out and were attached at this point with lesions characteristic of those usually found in the stomach. In Table I many of the infestations noted were comparatively small when the post-mortem examination was made, and attention should be called to the fact that all of these examinations were made 11216°—18—Bull. 597 2 10 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. during the time when larve were naturally dropping with excreta. The numbers do not show the maximum infestations of larve that may have been present. Many of the dead horses examined had been subjected to various environments prior to the autopsies and are not representative of infestations found when horses have spent the entire previous summer in pastures. TABLE I.—Gastrophilus findings in post-mortem examinations of horses at Aber- deen, S. Dak., 1915—16. Larve instomach. | Larveinduodenum. | © S | =o > == 5 == | po n | 1 | 3s = S| VB Bi | Se | ee ee S |" re 3 = pS) Ss oe Spent summer. E Peeve estat Oe = | Beles tre = 3 | 3 e288 |e be ea enema $ B eg|/”| 8 2 l|es|”|e@& a Pepe cee = 2@|es| 3 | cad _~ — ms. re == == = ae rs —_— — | : | | | 1915 | j TFT LCC: Beaey Go Peeper Sn ew oaeaa ce SS 295 11 We 5 ee | eRe | eed rene 9 1337 Saly 87.25. ee eee LOS Se 9B eee Pram rae pee ae 14 184 Suily 4 fee eae eee eee 1033/8 ris eee 11 dj lates eee 116 July 21 | es eye oa engi ira 58 41-290 |B VERS a eee ee ee ee 351 July 26 | Driven on streets.........-- a panes locos Bseee aan pe a ae ees eciod | 34 Age oA 2a e Onss asst seset ee | atin eee lEeoeoe aware eats jescees = | Beate [es eet 18 Aug. 23 |-.--. dole et Uy ase [ESS = LOS pana 2 lbeesee Eee Bae es aes 16 Aug: 23°)-In-pasture, 1915. = eee AS Ie pa es Bere eae ieee = Gare oe 67 5 45 76 42 217 17 22 18 138 145 7 67 111 71 42 17 3 21,032 237 138 241 aeote oe Sees eee ee ee 610 Aug. 3 | Farmtwork2:2~ 225-222-232 52] 5 150 2 a ae ee ee ee 153 Aug: 45) See ee 304s jasees ee. 93 AUS EL |= eee ee eee 25 | 24° Ses [E= ee 47 Aug, 6 |)... eee ee ee ie ees: bees == 14 Ang. V1 |... SSeS a A ee eS pe eS eee 24 ‘Aug. 11 |. 25 ees gs nee 4 ee bates eae ce Avge DR |o-22y ee el l eees |e eeee eee ee 26 |------ 33 AUG. 23). 25S sea ae ee oe ee 26: | 525-23 16.J522322 102 Aug. 26 |.-20 Se ee eee epee i Pag Peeese 36 Sept. &.].--2-- 522 2S ee a a a a0 ye ee ee eee 21 Sept. $4.22 6 a ea te ee ee eee Bese Sie ee 18 Sept. UU |... - <2 5 5p ae ee ea esd ee ee [cee [ae Ea > 6 Sept. 16 |S). 22 a eee | Lee =a jee as By ee as 70 | 1 } j j 1 Includes 1 G. intestinalis temporarily attached in colon. 2 Includes 1 G. intestinalis temporarily attached in rectum. LARVAL MOVEMENTS WITHIN THE HORSE. When a post-mortem examination is made. the larve usually are found quiescent, although occasionally some may be observed to move the posterior end slightly. The smaller larve show more activity than do well-developed ones. GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 11 Other than G. nasalis, which sometimes attaches in the pharynx, the first-stage larvee attach to various portions of the stomach and duodenum. In the stomach young larve have been removed from various locations, including both the cardiac and pyloric portions. The last-stage larvee of all three species are found in the various por- tions. Gastrophilus intestinalis is confined for the most part to the mucosa of the left sac, though this species has been taken in the right sac and in the duodenum (see Table I). In the early stages some of the larvee either change places of attachment or pass out of the horse undeveloped. With last-stage larve the indications are that, excepting G. haemorrhoidalis, they remain attached at one place continuously during feeding, as in early spring the number of larvee and Jesions upon the mucosa is the same. During the early spring or perhaps even in winter the larve of G. haemorrhoidalis move from the stomach and duodenum to the rectum where they may be found permanently attached in clusters. It is evident that they feed in this position, as lesions are sometimes present. Later when they move to the margin of the anus no lesions are present and apparently the larvee only pause to become accustomed to air temperatures before dropping. There is no definitely periodic larval migration of G. haemorrhot- dalis, as some last-stage larve are found in the stomach and duode- num until early fall. Through the courtesy of Dr. L. Van Es, of the North Dakota Experiment Station, some post-mortem examinations were made at Fargo, N. Dak., and larve preserved according to their location within the animal. During the winter these larvee were found in the stomach, and on July 10, 1916, 3 larve; July 14, 1916, 16 larve; and August 18, 1916, 2 larvee were fully developed and in the same regions. This coincides with the findings at Aber- deen, S. Dak., although one last-stage larva was found in the stomach on September 8, 1916. POINTS OF LARVAL ATTACHMENT. | When an opened stomach of a horse is examined, one is impressed by the contrast in the left and right portions. Around the entire organ a line of demarcation is represented by a prominent sinuous crest. In the left portion, which is often called the left sac, the mucosa is white, dry, resistant, and covered by a thick layer of epithelium. This covering is identical with that of the esophagus and may be considered as a widening of the esophageal canal. Dr. Guyot, in describing the mucosa of the left sac, says the struc- ture is analogous to that of the skin. It is dermo-papillary, with epithelium of the Malpighian type, but possesses a muscle, the muscularis mucosae, which is peculiar to it. The structure of the 12 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. right sac differs in having a soft membrane with an epithelium formed by a single layer of cells. G. intestinalis larvee are practically always found attached in the left sac, and it is the opinion of Dr. Guyot that this portion affords the most stable point for larval attachment. He thinks that cases are exceptional in which larve maintain themselves in the right sae. This, however, does not explain the attachment of G. nasalis in the duodenum and to the walls of the pharynx, nor does it account for the attachment of G. haemorrhoidalis in the right sac of the stomach, in the duodenum, or in the rectum. As has been mentioned by Dr. Guyot, the reason for attachment in certain regions of the diges- tive tract will remain a mystery until the manner in which larve are nourished is ascertained. | Various investigators have been unable to discover white or red corpuscles of the horse in the pharynx and other alimentary portions of the larve. Clark believed their food was probably the chyle, but Guyot rejects this explanation, as larve in the pharynx are located where this could not possibly be utilized. As Oestrus ovis larvee nourish themselves with the mucus secreted by the mucosa of the nose and frontal sinuses of sheep, and as those of Hypoderma utilize the pus of the abscesses which they create by their presence in cattle, he believes it permissible to suppose that those of Gastrophilus find nutriment in the inflammatory preducts of the gastric mucosa. It would appear, from observations, that Gastrophilus larve some- times feed upon the blood of the animal, although they are not de- pendent upon it for subsistence. The red and maroon color of G. entestinalis and G. hemorrhoidalis, with their attachment upon points other than the mucosa of the left sac, would bear out this hypothesis, which is further supported by the fact that G. haemor- — rhoidalis when fully developed in the rectum still retains a pinkish color. | THE ALVEOLAR LESIONS OF THE STOMACH. In Dr. Guyot’s examinations of lesions caused by the attachment of larve to the mucosa of the left sac, the muscular coat was not damaged. The condition found was merely a localized inflammation around the point of larval attachment, in which the derma had been invaded by leucocytes. He assumes that this is only the common inflammatory reaction which would be normally produced around any foreign body. In following these studies Perroncito found that the bottom of the alveolus varied in size and became the seat of a more or less remark- able inflammatory process. This produced a thickening of the walls of the stomach and finally the disappearance of the muscular tissue, which becomes hard and compact, preventing the normal functions of GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 1b} the stomach. He mentions cases of perforations, lacerations, and ruptures of the stomach observed by Flohill, Numan, Conti, and Brusasco, and calls attention to alveolar lesions which are naturally more predisposed to induce various infective diseases. (See Plate IT.) GASTROPHILUS AND SWAMP FEVER. Aside from the lesions which may induce the entrance of organisms of infectious diseases, the Seyderhelms, of Strassburg (1914), report results which they think implicate Gastrophilus larvee in the causa- tion of swamp fever. It is believed by them that the larve excrete a specific toxin which is the cause of the disease, for by administer- ing extracts of these larve symptoms typical of swamp fever have been observed. The coincidental distribution of Gastrophilus with that of this disease would appear to bear out the hypothesis. It is said that the most virulent reactions were obtained in these experi- ments with G. haemorrhoidalis larvee. BOT-FLY ANNOYANCE. In those portions of the country where the nose-fly does not occur, horses are seldom sufficiently annoyed to require protection. ‘The persistence of the common bot-fly and the repeated stamping of the animals are evidence that it is annoying, but when the throat bot- fly “strikes” the action of the horse becomes more violent. The throat bot-fly is less persistent but more determined in de- positing, and the horse usually responds with a violent nod or jerk, the violence depending upon the nervousness of the individual. In plowing it is sometimes necessary to place a strip of cloth or a small branch of a tree underneath the throat latch and extending to the bit rings. | In the nose-fly section the annoyance is produced by the two gener- ally distributed species in addition to G. haemorrhoidalis. Upon the approach of this fly the horse moves the head backward and forward to prevent its darting on the lips, but this only seems to arouse its determination, for it quickly alights on the lips and within a second or two deposits a black egg. It apparently occasions a most annoy- ing sensation, and a horse will most often snort and rub violently against the ground, a bowlder, a tree, barb-wire fence, or any con- venient object. The effects of ovipositions on pastured animals are worry, loss of flesh, and mechanical injuries. If the lips are examined barb-wire lesions will be found which resulted from the rubbing of the horse following an oviposition. (See Plate IV.) With an unprotected work animal one may be suddenly confronted with a jerk or a similar violent action of the animal at each oviposi- tion of the fly. When a few eggs have been deposited the animal 14 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. proceeds from infuriated shaking of the head, sometimes accompanied by loud snorts, to complete loss of self-control, and will use any means for self-protection. Numerous runaways naturally occur and serious accidents have also occurred when horses were being used for mowing. The majority of farmers and breeders contend that “the fly stings the horse in the nose.” ‘The reactions of the animals are often so violent that at first it seemed that the horses really experienced pain. Dr. Parker, of the Montana State Board of Entomology, has published some notes? to the effect that the eggs were thrust into the skin. but he failed to recognize the minute hairs to which the eggs are attached. The pointed portion of the egg is merely a device by which it is attached to the hair. A horse does not experience any pain, as the ovipositions do not puncture the skin. Neither do the flies deposit in the nostrils. Careful search has failed to disclose a single egg in such locations, and it would appear that the snorting of the animal has given rise to this “ popular opinion.” It is believed, however, that annoyance is largely due at first to an instinctive fear and later to a tickling sensation when the eggs are attached to the minute hairs, as the lips are the most sensi- tive portions of the horse. Practically all horses in this section have sore lips from eating a “ wild barley” or “ foxtail grass” (Hordeum jubatum) and there is no doubt that this soreness contributes to the annoyance. NATURAL PROTECTION OF HORSES. The flies show no preference as to type, breed, color, or age, but naturally oviposit upon unprotected animals. Horses seek protection in pastures, the individuals gathering in a bunch and resting their ~ lps upon one another. Colts and young animals not high enough to protect their lips in this way receive an abundance of eggs. A horse will sometimes hold the lips upon the ground as if grazing, upon detecting the presence of the fly, and when held in such posi- tion the adult fly is rarely observed to oviposit. Often the annoyance of biting flies and other depositing Gastrophilus will cause a horse to walk, holding the lips near the ground. Frequently other horses will follow and protect themselves by placing their lips upon his back or the backs of other animals in the line. Usually they search tor the highest elevation where the breeze is blowing, or for standing water, but if an open stall is convenient they will use it to good advantage. If protection is not found an unconfined animal will often wander a great distance from home. Upon a bright still day ovipositions occur from 8 a. m. until about sunset, and the group of horses may be observed to shift from place 1 See “‘ Bibliography.” page 50. BNE Naty, Gils A eae Sib GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 15 to place without eating, their lips resting upon one another, or they may congregate with cattle, which are not subject to attack. The horses spend such days in awaiting darkness, after which feeding takes place. Characteristic positions of the animals are shown in Plate III. Wind with a velocity of 15 miles an hour or more greatly relieves the animals, and persons driving horses about thrashing machines often stop them so that they face the breeze. Cloudiness is also a protection to horses, and if only a light cloud conceals the sun a bunch of horses may be observed to disperse and begin grazing. Often their feeding will have only begun when the sunlight returns, causing them again to seek protection in a group. Horses in standing water are not annoyed by nose flies and fre- quently they seek this protection in order to eat, despite the fact that hundreds of mosquitoes feed upon each animal. This standing or feeding upon grass in water is excellent for a foundered horse, and the mud which adheres to his legs prevents G. intestinalis from ovipositing upon them, While the wind and cloudiness are especially protective against G. haemorrhoidalis, the other two species of bot-flies are not much affected thereby. G. intestinalis may be observed to oviposit on windy and cloudy days. G. nasalis deposits under more adverse conditions than does @. haemorrhoidalis, but seems to be more sensi- tive to natural agencies than is G. intestinalis. In barns the species of Gastrophilus never have been observed to oviposit. On numerous occasions ovipositing adults have been ob- - served to pursue the animal only until it reaches the stall door. Post-mortem examinations of horses which had been confined in stalls failed to reveal a single larva. One of our correspondents ‘reports that the annoyance of G. haemorrhoidalis was greatly re- duced when he constructed a simple shed in the pasture where the horses could congregate. SEASONAL HISTORY OF GASTROPHILUS. At Aberdeen, S. Dak., the larve of G. haemorrhoidalis are ob- served attached to the margin of the anus of horses as early as May 5 to 10, and if suitable temperatures occur adults may be expected a little prior to June 15. From June 21 to 27, 1915, @. haemorrhoidalis adults appeared at Lodge Grass, Hardin, Billings, Miles City, and Custer, Mont. At the same time they appeared at Aberdeen, S. Dak., and neighboring points. They have been observed at Aberdeen, S. Dak., as late as October 10, though they are seldom found after a killing frost, which is usually about September 15. 16 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. The other two species appear at Aberdeen, S. Dak., about the same time as G. haemorrhoidalis, but are most abundant just before a killing frost. The G. haemorrhoidalis are least abundant at this time, and are present in greater numbers during the early half of the season. After a killing frost one seldom finds a Gastrophilus except when warm temperatures prevail during a few days. | In the “ nose-fly ” district one must bear in mind that the period during which flies oviposit is that when farmers are most busy, and the most favorable time for fly ovipositions is when the weather is most favorable for working horses. The adults appear during the plowing of corn and sorghum, and the annoyance continues during the mowing of hay, the harvesting and thrashing of grain, and the marketing of farm products, GASTROPHILUS HAEMORRHOIDALIS (Linnaeus). SYNONYMY. Oestrus haemorrhoidalis Linnaeus, 1761. Gastrophilus haemorrhoidalis Leach, 1817. Gastrus haemorrhoidalis Meigen, 1824. ATTACHMENT IN RECTUM AND DROPPING OF LARVA. During the early spring and summer the fourth-stage larvee are normally concealed within the rectum, where lesions have been noted in post-mortem examinations. Later they effect a temporary attach- ment to the margin of the anus, where they become accustomed to the air temperatures, assume a greenish color, and apparently increase their motility. Larvee, normally exposed to the air at the rectum, after dropping seem to conceal themselves at grass roots so as to be protected from the heat of the sun much more easily than those unexposed at the margin of the anus. When a larva is attached so that only the posterior end is exposed at the rectum one will find the anterior end a pinkish color, while the posterior will be greenish. Larve exposed at the rectum have been observed for the length of time they remain attached, and the shortest period was shghtly more than 40 hours, while the longest was 71 hours. The heat of the sun for a few minutes was sufficient to cause larvee to drop when an attempt was made to photograph a larval attachment at the anus. At various times during the day larve appear at the anus, as many as 183 sometimes being visible at one time. The larve are likely to drop under most any condition, but do not drop with manure, as is supposed. When manure is dropped during their attachment they seem to use more effort in clinging and are only pushed aside during its passage. (See Plate I, figure at upper right.) PREPUPATION AND PUPAL PERIODS. In the normal pupation of a larva which has been exposed at the margin of the anus there is a gradual change from greenish to yel- Bul. 597, U. S. Dept. of Agriculture. PLATE III. PROTECTION FROM BoT FLIES. Upper.—Horses assembled for protection during ovipositions of Gastrophilus_hacmorrhoidalis. Center.—A method of protecting lips from ovipositing G. haemorrhoidalis. Lower.—Protect- ing under jaws from ovipositing G. nasalis. (Original.) Bul. 597, U. S. Dept. of Agriculture. 7 PLATE IV. SECONDARY INJURY FROM BOT FLIES. Upper.—Horses rubbing following ovipositions of Gastrophilus haemorrhoidalis. _Lower.—Lower lip of horse showing barbed wire cut at the lower extremity which resulted from rubbing. The small holes are injury from the grass Hordeum jubatum. (Original.) GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. We lowish, the larva contracting and assuming the form of a pupa.. As the puparium becomes more hardened a reddish tinge appears, but after a few days it becomes black and retains this color until the adult emerges. TABLE I1.—Some environmental effects on metamorphosis of Gastrophilus haemorrhoidalis at Aberdeen, S. Dak. Temperature, col- Lon- lection to emer- gevi- 1b ari Num-|Num ty anv e& Pre- 5 ‘|Number| of collected Environment. pupal Pupal ber | ber | adults |larve from : period. lar- | pu- period. emerged.| not rectum. ; ve. | pe. pu- Max. Min. | Mean. pat- ing. 1915 JEQOUR \\ JOCOR NS J05.)) M3g8, | Jae) Days June 4 Fresh horse manurein tin box; 27-47 | 39-45 88 30 | 638.21 | 14 14 LO). eee Ayutavey 8) Ie Sbe COREE eeee nc sci sesimisie 24-72 | 46-54 88 39 | 64.76 3D 31 22 4 Yung 7 lesace GIO) Aen Ree ee ee 34-52 | 37-44 88 35 | 64.93 16 13 8 8 jumer 8) Gee 22 CON ease es oe 49 | 38-40 88 35 | 65.67 7 7 DiS aera Muleee ose CleametinibOxt ae. eee == | 35-55 | 36-48 88 35 | 65.02 12 11 ies see, June 12} Glass jar and fresh horse ma- | INDORE: 5 cnr i Ake R eo aaa | 58-146 | 33-36 88 40 | 65.73 14 14 ty feels ler Junew! On| pO myalardasOtlessese esse ase | 75-122 | 28-30 85 40 | 62.40 10 10 a eee Do-...| Moist horse manure.....----- | 122 | 29-31 85 40 | 62.56 10 8 7 | 15-22 IDO; <6} Clieanai iin lores GasoaecousdSoce Veet 20n|eok—32 84 40 | 62.89 G 6 4 15 June l4s ees: ORs scree eine ctyseisl | 50-144 | 30-38 84 40 | 64.33 27 25 18 16 june L842... GO eee ces Sete ee 27 |} 32-42 84 40 | 63. 23 34 30 26 12 June 17 | Moist manure in tin box..... 18-47 | 34-40 84 40'| 62.06 33 33 28h Peete July 12 | Black loam in tin can........ 23-39 | 34-35 85 40 | 64. 23 8 5 Dh lareene ADE, 7 |! Oral Pare WOO ls oGeeeeeedasedede 19-26 | 58-68 88 | 132 | 60.59 d 7 Sileuee 1916. | Wey 24 |) Oleznavinholoyoy:<5 35 Gononosnoecee 68 41 94 42 | 62.62 5 4 rN ees Wleny PAY |e ooce GON ee arco emcee 52-72 | 36-40 94 42 | 62.81 5 4 3 11 Mays 30) 22222 Oa eer snk steleks Siete 141-170 | 34-35 94 42 | 64.79 2 2 Ds eer anys Wien; Bildscose (OKO) ees aco Boao eters Ee aeaeeee 35 94 42 | 60.08 1 tt ile kes tage: JUNE; Saleen OR Be sere aes eather 42-96 | 33-34 94 42 | 65.55 11 8 5 5 June so) Withimoist sandiso5.2 4.24... 75-100 | 32-35 94 42 | 66.69 17 17 Gi ate Repay) WO) Nos oee GIONS eae cetas Gale eet 44 | 30-32 94 42 | 68.15 28 25 20 4 June 23 | Clean tin box and moist loam.)......_. 21-24 96 48 | 74.08 46 44 38 5 1 Minimum, Sept. 21. In rearing larve to adults a most convenient and efficient method was utilized by placing them in clean tin saive boxes upon moist sand in bread pans. Table II gives some results of rearing under such conditions, using various media within the tin boxes. The period of collections extends from June 4 to August 7, which includes prac- tically the entire season during which larve appear at the anus of horses in Aberdeen, S. Dak. It will be observed that the prepupal stage, the period from removal of larvee until pupation, varies from 18 to 170 hours. This is a much greater range of time than is normal and may be attributed to the fact that larve were removed before the critical period of dropping. In some instances under varying con- ditions they did not pupate, and, while some larve died within a few days, one is recorded as living for 22 days. The removal of larve from the rectum prior to their normal ex- posure to the air at the margin of the anus has a pronounced effect. upon rearing. A small percentage have been reared which were fully 11216°—18—Bull. 597——3 18 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. developed and concealed within the rectum, but larve less than normal size, which were not exposed at the margin of the anus, did not produce adults. Only larvee possessing the greenish color indi- cating exposure at the margin of the anus were used in experiments recorded in the tables. | In Table IT, of 347 larvee collected, 319 pupated and produced 236 adults, the pupa period varying from 21 to 68 days. The greater portion emerged during the shorter periods indicated in the table. FATE OF LARV4 DROPPING UNDER VARYING CONDITIONS. The variety of conditions under which larvee are dropped naturally suggests the question of their ultimate fate. In an effort to deter- mine this point by experiments, the most striking phenomenon ob- served was the larval “ migration ” which precedes pupation.. In ex- periments recorded in Table II, larvee placed upon the surface of the soil or media penetrated to a shght depth for protection of the pup. With larve buried in loose soil, as would ordinarily occur when they are dropped by plow horses, they moved upward to near the surface for pupation. . iene. MOS ey 19 n HH e) aa) or ia sn H © a -errednd [eV1dAos JO $1U91U09 918 OSNOT ¢ ‘pokvoop wdnd 19440 {porp BAIR] 6 z *pokvoop wdng _; S Sit =< OOH 5 (26S 86 Po-&B_ | ST 06 oh 7G tls a ee ems yoga OQBJINS VON | 7 qsrour AT} YSTTS yoy | ce a pepe ee pos ssvig UQ |" " "~~ or Ainge : “govyans 2 PEL | SF 96 T-4% | ST FI Ee 8e MOTOq soyoUr g poowjd adng |-------- qstour ATWYSITg |° ~~ urvOy soyouT g JepuN pearing |*----** LT oune 4 PL OL GP 96 VEaGS) |G IT 61 Gaia | eae aes ee ar ee SEA TONS CHASING Po ee es ASTO Uli Cosyiia |neaieaiiann beans cee eas pos sstid UO |*~"""e GT oung A “OT6T 5 G6 "9 OF Gs 9e-se | I I 8 UTS SopUniee ae i aetee Ee spe SOCTI SAGO Nig lan eeatese aaa ee almaranal qom 4dox | peigphe scar baie UOT YORI JOM UGQ | ---- 76 Ayng ae 18 “9 OF C8 Tr-rE | ST 61 cE cg --Q0VJINS IVIU PUV SOOTADIO Uj | --- qstour AT ATG HY | Apion yal pos ssvis UG |~~-7 >> od “TUIVOT = T6 “#9 IF cg ce-08 | 6 9 ce GORI inate gece Serge dOVJANS IVOU fF |~ ~~~ qovduroo pur ysrow ATM ; YORV[G soyour FE Japun porimg |-~~-~- 161 eung *pox Tul © -10]UI OINULU PUB MIS SUT a 99 “$9 OF ¢8 Ofacoeslar 9 GT GTS hy Spa ee ee OOLJINS VOU MOT |e ystou Ape | -Avoop soyour F Jopun poling |--~~ ~~~ od sa *poxTurs0} Ur < BAIR] dINULUI OS1OY YSo1J pUw UIBOT aa €0°F9 OF ¢8 OF-1E | F P FI (FS: ab S| laaicn yaw ae sovjins y@ poyednd ¢ | vusoysouyoer’y Aq pozrtioATng | WoRlq soyour p Jopun poling |-----~" 9I oung pie eevee |n0Y c8 ge-7e | ¢ j 8 OTe |e ees ae IS] OSU OWI CUS IS ge ee TSTOUL COST een oINUVUL YSTOU WO |* ~~" ~*~ od 5 ¥6 F9 OF ¢8 SESLen (6 te, OT Oe esr pr SaaS SSeS Fog eees SOBRINS ivi: || mage tent wearer leerlaas Uke GOVULO ES EPRI Ie See [los paey ‘Aip ug |--"" 77> gi ounr “UILOT JO SOYOUI Z IOAO 4 90°99 OF 88 OF-GE | 8 OI Piles ee | Soames Stage dovjins eou pue uody |-----" ~~ emmuru osi0y AIp AOA | oINUvUI osIOY AIp soyoUT Z UO |--~* ~~ od ae ‘ornueti yord *pjour “MIBOT JO SOYOUT Z 19AO oINU Oy OT 99 OF 88 TP-GE | ¢ L fay LI -W100 ULI YOU T 01 = pemoring | @ podo[vasp oinuru ysIop | -eU eSIOY YSoij soyoUr g UC |°-~* ~~” OT oune ) ‘To Wo ‘Ho “shod “GIGI a = Z H op) “uvoyW | “Ul | “xB | ‘o0u0s |-oremroy| “ole < -I0Ul9 ‘poyed | “warty *uIn4oe1 o 0} HOT} -nd 1oq} req ‘poyednd yydoq *[1OS JO WOTJIpuoD *JUIMIUOITAU WO1J Poo] "9003100 0} 59@T[09 | *posi0ule “WN | -UINN -[00 BAIC'T TOT99T[00 ‘oinyerodurey, | POMd | synpVy ‘9I-GI6L “Yo *S ‘vaapsaqy 7 sypproyssoany snyrydousnsy fo sppring jowifysp puv uoyndnd pounoyy—'T I] ATAV, 20 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. Questioning the fate of pupe if buried, a lot consisting of larvee that had moved near to the surface before pupating were replaced in moist loam to a depth of 5 inches. The adults had no difficulty in penetrating this soil, as 29 emerged normally from 32 pupe. A lot of 15 larve buried 4 inches under black loam and fresh horse manure produced 14 pupz, many of which were located near the surface. Lachnosterna larve were present and during their develop- ment kept the soil well pulverized. Of the 14 pups, 8 produced normal adults. The experiments cited in Table III, with the exception of the lot of puparia eaten by a field mouse, show that the greater emer- gence percentage occurred when larve were placed upon grass sod. By this method sufficient moisture was supplied, and at the same time the movement of the larve to the roots of the grass protected the pup from excessive heat. In one lot 32 adults emerged from 35 pupe, and in another, under similar conditions, 38 adults emerged from 42 pupe. It is also noted from other experiments that excessive moisture or dryness is less favorable for the metamorphosis. EFFECT OF HEAT ON LARVZE AND PUPZ. Doubtless numerous larve and pup are subjected to heat, in barren places, when dropping from work horses driven upon the roads. This may not be confined to the heat of the sun, for horses standing in stalls may drop larve which are placed with the manure in piles that generate heat. 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(. . 4 . . . } Y fo Ll} 22, BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. Upon hard soil the larve are seldom observed to move more than a foot, and this sometimes requires 15 minutes. The tendency seems to be confined almost wholly to burrowing, and it is only when dropped on unsuitable places that they migrate. When exposed upon hard, barren soil to the heat of the sun during the summer it seems certain that only a few find protection and eventually produce adults. Certainly those not finding suitable protection from the sun’s heat die within a short time. On black loam at a mean temperature of 122.9° F., 8 to 12 minute exposures caused 100 per cent mortality. Yet some larvee seem to withstand even higher temperatures, for adults were produced after having been exposed from 5 to 17 minutes at a mean of 129° F. Pupe, being unable to accommodate themselves by moving for protection, seem to be very susceptible to heat. Ex- posures of from 30 to 137 minutes at 116.6° F. were sufficient to render them inviable. The heat generated in a manure pile produced greater mortality upon larve than ordinarily would be expected. Larvee buried with- out protection at a mean temperature of 151.7° F. were dead within 15 minutes, having become soft and white. EFFECT OF SUBMERGENCE ON LARVA AND PUPZ. Although, as shown in Table III, excess moisture seems to have had a destructive effect upon pupe, the effect of submergence upon larvee is not so great. Larvee submerged 51 to 74 hours pupated and produced adults. (See Table V.) Larve submerged for 80 hours pupated, but failed to emerge when kept under favorable breeding conditions. While it is difficult to submerge pupe, as they float and expose a portion of the posterior spiracles, three normal ones kept in water for 5 days failed to emerge. In view of the results in Table III, it is apparent that great mortality occurs among pup during wet seasons, TABLE V.—Effect of submergence on larve and pupe of Gastrophilus haemor- rhoidalis at Aberdeen, S. Dak., 1915—16. Late Petipersaue after on- period of + gevity, = submergence. Date tage. Num-| Period —_—| er |, Adults |nelud| tron to merged. | | ber. submerged. ~ EPG (male.)’ period au Z of sub-| | E | mer- Max. Min. Mean. | | gence. 1915. Days.:\2 Deys.}-° eas hfe ae July 5..) Larve 6p obhourss se -eee 4 3 5 36} 85] 41 | 68.93 July 14. do 3:| 74 noursee eae 2 | od Eee 38 85 4] 64. 21 Do.. do Sal 20 dayse== seems Osha V7=20) |e ee 85 41 62. 98 July 24. do 5 1aidays a ee (Ii Pe saeeet 9-14e eee 80} 40| 58.14 J une Pupe Saloidaysees ae eee 0: eee ELE Shearer ee eee 82} 40] 59.40 June 7..| Larve Oo) 7 daysss sss ones Ou) ce ers 1 OA ee ied 76 | 43 64. 83 Do.. do 5.) 26 dayss aon ee | are ae SATO et seme 76| 43 64. 83 July: 12:2) dos! 15,| 75 days-26.c ce lees [eae eee Silene 96} 64| 76.50 Doz do 5)| SQhours-s7.5- 4-2-2 Shi Sze 75a DE see ly 96 64 75. 90 Do...| do 53) (bk dayssese. cue ssc ee ol ened 96 | 64| 76.50 ARGH Nee» ‘3 j " GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 23 Larve have been observed to remain alive during submergence for from 14 to 20 days; those submerged 6 and 7 days live for some few days after removal. NATURAL CONTROL. FUNGUS DEVELOPMENT. Under conditions the same as those upon which adults were reared in Table II apparently two species of fungi developed upon living material. The first mentioned in Table VI occurred upon three larvee, to one of which a particle of horse manure adhered. They were collected from the rectum of perspiring horses, and it appeared that the fungus developed from the manure and spread to the larvee and pupe. The larve giving promise of fungus development were placed in a clean tin pill box with three well-washed G. haemor- rhoidalis larvee, which had been exposed to the air at the anus of a horse for about 24 hours preceding the washing. The fungus de- veloped upon all the larve and death ensued. This fungus was determined by Mrs. Flora W. Patterson, Mycologist of the Bureau of Plant Industry, as Sporotrichum minutum. This, with one ex- ception, was the only lot in which fungi appeared on living larve. As this fungus had developed upon larve collected from perspiring horses, it seemed possible that such larvee as were not washed might have developed a superficial growth. Later collections were made from work animals which were perspiring during the time of collec- tion, and they were kept under similar conditions, but no fungus ap- peared. In collections of larve kept under normal rearing condi- tions, as given in Table VI, a fungus appeared on the pupa stages which apparently spread to other pupe in the same lot. In some lots pup remained without becoming infected, but in others it even developed upon various parts of the tin boxes. The collections and rearing methods used in these experiments were not unlike those in which no fungus appeared, as new, clean, but unsterilized tin boxes were used in each breeding experiment, and sterilized forceps were used in handling.. The soil or medium was different in the various boxes, but since these various conditions were also present in lots which developed no fungi, there appears to be no reason for attrib- uting it to the type of soil or to the medium. Upon the pupz it appeared within from 3 to 17 days after collection. 24 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. TABLE VI.—Fungus development upon pupe of Gastrophilus haemorrhoidalis in new tin boxes at Aberdeen, S. Dak., 1915-16. : z : : Temperature BE | = [gg amber Aduts) collection to larve S oe = E 1 2 5 emergence. from (Collection and environment.| = = Fe eS —a rectum. Bs 2 Ne 2 ee . Ss =} = R & R Q ° 3 4 ra] = a Se eels albenl Bal Saecee iie 3 2 = 5 s|S8i5s/eieisisial s ow & See Neel ee Sie el eee eee ee ees 1915, Hours.| 1915 Days. gs Oe hes em ae June 111 | From perspiring horses. ...|79-220 | June 15 | 34-36 | 13] 10| 10) 3] 2} 2] 88) 40 | 65.54 Dime sbi See see eee eee eee 75 | June 30 | 35-38 | 10] 10 | 10 5 1 | 88 | 40 | 64.66 JUNG 2 | He ea ee cee ee eee 20-219 | June 25 | 30-32 | 34 | 29 | 29 5 7 6 | 85 | 41 | 63.88 July 6 | With fresh horse manure. .| 6-25 | July 13 34} 5] 3] 3]....) 1]----| 85 | 41 | 63.85 Do...| From perspiring horse..... Eo eter ta aire A a De [pee se dO Ya eee Me oe ya ee eee al a ees a bl clean] fr SE REA ne ase eS aS eae é 6-43 | July 13 | 33-36] 3] 31] 3) 1| 1] 85) 41 | 62.12 July 10 | With moist loam.........- aS eee Oseeee 33-36 | 40 | 40 | 40 14 | 11 | 85 | 41 | 64.32 Say 15 | pose ae Set ee ee 21-29 | July 16| 33-35] 4| 4| 4 1| 1| 85] 41 | 64.43 1916 1916 | May 172) On blotting paper........- 22-32 | May 29 |.......- Vol did legere| 2 oo: len el eee JUNC 5a ees os ees eee eee 20-39) sume 14s eases wa es Os ss HM ele eel ee suas = bla eal (eee an sec eee es Een oe Ti—10QE June) 225s QA 2 tA S| 20) a= Oe OnE Aaa goO see: Do2=|" With moist sand=—-2 | sas 48-72 June 12 |------- Soe TE Te tee ee | ee ee eee June 29215--=- On Sec =s eee eee 22-70:| June 17 |. -..=.- | 10s) cL O aE Bees ens ee eee [soca lbsos=e June 24 |.._.. O22 ee eee 4-122 | June 29 | 21-25 | 62 | 59 | 59 24 | 15 | 96 | 48 | 74.67 MUM C1263 xs oo ee en eee 19-166: duly: j=. Se (e202 ela | ll Geeta [Ses clizcmpleneese VON C2275 eee ser eee eee eee 22-190 | July 3 | 21-29 | 15 | 13 | 12 4) 6/96 56} 75.73 Sully teases = ace ees 8 Gane yee On|. 20) \eial eet a) 1 | 96 | 58 | 77.07 July 182, With moist sand..-......_.| PIE67 | Jullyaca eae aa | DS ee lee el ee Pees Sete, Ful ye 20 eS ee Gs eee 91-31 | July 28/ 29] 19|18|18|--.-| 5| 3 | 98 >t | 70. 19 1 Determined by Mrs. Flora W. Patterson as Sporotrichum minutum. * Determined by Dr. A. T. Speare. Except the collection on May 17, 1916, larve were not washed. Several lots were sent to Dr. A. T. Speare, Mycoentomologist of the Bureau of Entomology, who made cultures and determined the characters showing that all the infestations were of one species and were not Sporotrichum. According to Dr. Speare about 50 per cent of the pupe sent to him produced adults. He reported that the fungus seemed to be restricted in its development to the chitinous wall of the puparium, and that death, if caused by the fungus, must have been brought about in some unusual way, as, for example, by closing the spiracles. However, the fungus seems to develop best at the rings of the segments and is seldom observed upon the posterior spiracles. In Table IV it will be observed that a fungus appeared upon pup which had been subjected to heat tests, and this was apparently the same as has been observed in other experiments. A comparison of results and mortalities due to the fungi indicates that there is little hope of controlling the Gastrophilus by encouraging natural develop- ment of the fungus. Eighteen lots containing 283 larvee produced 259 pupe, of which 247 became infected with fungus in rearing experi- ments. Twelve of the lots, containing 194 pups, were retained for observations on mortality. Of these, 64 males and 47 females emerged as normal adults, giving 57 per cent emergence. The adults GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. De possessed a normal longevity as compared with others in rearing experiments. The above percentage of mortality is based upon those experiments in which the fungus occurred. As there seems to be no reason for attributing the fungus to soil or media it is well to base this per- centage upon all experiments in tin boxes and where pupe were in close proximity. In Tables II and VI, 630 larvee produced 578 pupee. Of these 247, or approximately 48 per cent, developed a fungus. Of the ones kept under observation 57 per cent emerged, so that only 48 per cent of the infected pupe were rendered inviable; 48 per cent of 43 per cent would approximate 18.5 per cent, or the percentage of loss in rearing experiments where numbers were kept in close prox- imity, which probably allowed the infection to spread over indi- vidual lots. In Table III it is shown that no infected pupz were found, and should a fungus develop in such conditions the single location of pupe would prevent its spreading. This fungus has never been ob- served upon normal G@. zntestinalis or G. nasalis, though with dead larvee of any Gastrophilus a long growth of fungus quite different from that met upon living G. haemorrhoidalis pup is frequently found, PREDATORS AND PARASITES. The dropping of larvee under varying conditions and in locations where they do not pupate in close proximity renders the situation such that very little could be expected of predators and parasites in control. In rearing experiments some field mice devoured pup on grass sod, but even though they feed upon these in nature it is not likely that a great many are devoured. Chickens probably do not feed upon many larve when they drop, though a single hen has been known to devour about 40 dead G. intestinalis removed from a_ horse by a carbon disulphid treatment, and without any noticeable ill effects upon the chicken. Desiring to know if the widely distributed Nasonia brevicornis, which parasitizes various species of dipterous pups, could be reared upon G@. haemorrhoidalis pupee, repeated efforts were made, but with- out success. The indications are that the flycatchers feed very little upon Gastrophilus adults. On account of the danger in shooting such birds in pastures very few examinations of stomachs have been made. LIFE-HISTOKY NOTES. ADULT LONGEVITY. The life of adults appeared so short at the beginning of expevi- ments that it was attributed to abnormal conditions, but various cages and environments did not materially increase the periods. s | 3 emerged. | 5.8 SG (er) Wises AG || Sige Larvie & al) cae bs col- Location. | Breedingenviron- | . | °F (aves os 3) lfc jected. £3) ment. ee Dials enlaces aoe = tia civeticl [aie 8 See SES Nei ea oles ae lacs 5 3 es a ee) ey fsl e q SS co) Z ya! (= =| | fe Pepin |e | 1915. Days. | | Days: Snare June 4/ Fresh dropping........ 1 | With horse manure.| 1 AQT lis Reoseaea | erase 88 | 35 | 65.30 1916. . | iMay.29" | 2.2.2 CORES Saupe cenriee 2 | Clean a box; moist | 2 | 44-45 | 1 ie eet 94 | 42) 67.93 sand. June 12} Dropped from treat-| 4 |..... WO Bes. er 1 Sie ape eee 7 | 94 | 42 /168.98 ment. TilyelO) |MOwodenumes.5-.2..--- 19 | Dry paperintinbox.| 3 | 25-33 | 1 2 | 3-15 | 98 | 41 | 72.77 Petree | SStOMaCchs 5.0503 .- 52 lelSei Morstisande. 292.0): 3 CVS 0 oe Te Ee 3-8 | 98 | 28 | 60. 26 Tia wodentima =.=. 5. i veo] leek Oke oe pomee ae 3 4) il 1 11 | 95 | 28 | 59.97 1 Horse treated with carbon disulphid. 30, BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. GASTROPHILUS INTESTINALIS (DeGeer). SYNONYMY. Oestrus bovis Linnaeus, 1761. Oestrus intestinalis De Geer, 1776. Oestrus equi Clark, 1797. Gastrophilus equi Leach, 1817. Gastrus equi Meigen, 1824. Oestrus gastricus major Schwab, 1840. OVIPOSITIONS AND LONGEVITY. The universal distribution of the common bot-fly, the familiarity of innumerable persons with its oviposition habits, and the numerous publications dealing more particularly with ovipositions and ingress of the larve into the host since Bracy Clark (1797), leave little to be desired. It is probable that there is no other insect whose eggs come so directly under the observation of farmers as does the common bot- fly. The common names of this Gastrophilus vary with the locality, but farmers are usually aware of the fact that this insect produces the bots in horses. Some authors contend that the eggs are deposited upon those places most accessible to the horse’s mouth, while others hold that the fly will deposit upon any portion where it is not disturbed. It has always been observed that these flies give preference to the forelegs, and, after these have become well covered with eggs, depo- sitions occur at other points where the fly is not disturbed by the horse’s tail. Very few eggs are deposited upon the hind legs or upon the backs of the animals, but when adult flies are in numbers the mane may become heavily infested, especially near the shoulder. Large numbers of eggs may be found upon the sides of the animals, and these are concentrated at points accessible to the mouth, as in cases of depositions upon the inside of the forelegs. It seems that the fly oviposits on the forelegs instinctively. and, after the legs become heavily infested, adults may be observed to deposit one or two eggs on them and then seek other portions of the body. At times iwo or more eggs may be found upon a single hair on the inside of the forelegs, but seldom has this been noted upon other portions. How- ever, the length of the mane often permits adults to deposit large numbers upon a single hair. With the exception of the forelegs, the © sides below and to the rear of the shoulder blades probably harbor most eggs. The longevity of 14 reared adults in 9 tests, in which the flies were kept under conditions similar to those employed in rearing G. haemorrhoidalis varied from 7 to 21 days. The longer periods oc- curred during early fall, when lower temperatures were experienced. These adults, like those of other species of Gastrophilus, were never GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 30 observed feeding upon flowers, but green twigs were favorable resting places in rearing cages. A female taken while ovipositing was placed within a tube contain- ing a male, and they were observed to copulate for 5 minutes. Dissections of 5 females showed the following egg capacity: Maxi- mum, 770; minimum, 397; average, 541. INCUBATION AND INGRESS OF LARVZ. While making observations in pastures, on four occasions large numbers of eggs were collected. which had been deposited upon the author’s horse. The eggs were kept in tubes at air temperatures of a living room and none hatched without friction and moisture. By placing the infested hair upon a microscope slide and moistening it the larvee were most easily removed by rubbing the lot with a dis- secting needle. In such tests the eggs remained attached to the hair, while the operculum was removed, allowing the larva to emerge. Very good results were also obtained by rubbing a moistened finger over the lot. When eggs were less than 7 days old it was found diffi- cult to obtain living larve, though at 9 and 11 days active larve were removed. When they were slightly older than 11 days they emerged without difficulty when attended by moisture and friction, and one living larva was found as late as the forty-eighth day. This seemed to be an exception, as in the other lots all were dead after 40 days. In general, all experiments tended to confirm those of Osborn. Ac- cording to Guyot, with various lots placed in paper bags and kept in a pasteboard box at room temperatures, some emerged without moisture and friction. On December 28, 1900, Guyot obtained quite agile larve as late as 96 days after collection of the eggs. In another case, with eggs collected on October 6, he succeeded in obtaining larve from January 7 to 13 following, a period of 92 to 98 days. Due to this fact, Guyot concludes that the larve are capable of withstanding comparatively low temperatures after the eggs have been removed from the host. From eggs collected on horses in the open, active larvee were removed as late as December 1. LARVA STAGES. The attachment of young larve frequently occurs in almost any part of the stomach, but, as has been previously stated, they are found as fourth-stage larvee upon the mucosa of the stomach, more especially on the left sac. If living larve are removed from an animal during a post-mortem examination a great tendency for re- attachment will be observed. During such examinations they have been frequently separated into lots according to species, and in a short 34 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. time they would attach to a piece of paper or stomach section or even to one another. This is only a temporary attachment, however, and apparently no attempt at feeding takes place. The studies of Brauer, Numan, and Guyot indicate that the larve molt during their development and that there are at least three stages. No experiments have been reported as to the exact time that larvee remain within the body of the horse, although apparently they spend about 10 months in this parasitic stage. On some occasions, as will be observed in Table I, well-developed larvee were disclosed on post-mortem examinations in early fall. The indications are that some larve are not sufficiently developed to pass out in time to pro- duce adults and that they succumb to low temperatures. ‘There are various factors that apparently tend to influence the extension of lar- val periods. When gross infestations occur the development is markedly slower than in those horses containing only a few larve. Laxative foods have a greater tendency to discharge well-developed larve than foods of anon-laxative nature, as is observed In comparing autopsies of livery and pastured animals. Since there is such a wide range of variation in the ages of larve within the eggs at which they are capable of being ingested it is possible that this may tend to prolong the period during which the last-stage larvee drop. SUBMERGENCE OF LARVZ. Last-stage larve removed from horses immediately after death remained alive and active from 21 to 33 days when submerged in water, but when submerged for only 6 days they would not attempt pupation. These periods are considerably decreased if larve are not removed shortly after the death of the animal. PUPA PERIODS. The larve drop naturally with manure, burrow only enough for protection, and normally pupate within a day.or two. The periods of dropping extend over a long time and very few larve are found in droppings. It is a difficult matter to rear larve taken in post-mortem examinations, and this is best undertaken in the late summer or early autumn, when the greatest number of larve are fully developed. With such larve, used in the experiments, the pu- pa periods have been observed to vary from 27 to 43 days, with an average of 38 days. EFFECT OF DEATH OF HOST UPON GASTROPHILUS LARVA. The resistance of larve and the death of horses from infectious diseases naturally suggest the fate of larve during the period when they normally drop. In experiments larve were not kept with the animals during the decay, but were removed in autopsies, separated tN A hd 0 tal Bip tt Ps el als SALI tg SUPA ech win MNase nsiains oad wpb ite pptsenorbec cee. “Dene toe 11 Gl Spot irae 2.5 Peer laee and at RDA Beal TA there Se : a 7 = - & 4 GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. itd) according to species, and placed under favorable rearing conditions. It is evident that larve within the stomach and duodenum are not capable of withstanding the internal processes which accompany the decomposition of animal tissues, especially during warm periods. There is excessive gas formation with the breaking down of the tis- sues, and the larve apparently become asphyxiated, since they are found bloated and when crushed become flat. During cool periods larvee are affected very little for a number of hours, and in stated cases as long as 30 and 48 hours after death of the host larve have been reared to adults. Low temperatures hold back that period of decay in the carcass which normally would cause the death of larvee. From post-mortem examinations, as will be seen in Table I, G. haemorrhoidalis larve are seldom found in the rectum. In all probability they drop shortly after death, and during the normal period of dropping are capable of producing adults. CONTROL STUDIES. REMOVAL OF G. HAEMORRHOIDALIS LARVZ FROM RECTUM. The effectiveness of the extraction of Hypoderma larve as advocated by various authors suggests a mechanical removal of G. haemorr- hoidalis larve. While they appear at the margin of the anus daily, studies show that they remain visibly attached from 40 to 71 hours. This would necessitate much work during a busy season with farm- ers, but extractions at feeding time would greatly reduce the number in work animals. In practice this periodical detaching caused much discomfort and soreness about the anus. The attachment of clusters of larve within the rectum and the recommendation of tobacco decoctions, by the Bureau of Animal Industry (1911), for larve lodged in the rectums of horses, indi- cated the need of information as to the effect, on this species of Gastrophilus, of substances used as enemas. This necessarily re- quired a detailed study of the effects of various substances upon larvee, and these are reported in Table VIII. 4 ope ai ae cle cee nde mee Qracenaines ones Gn g [ve tht teint sata ccsoescedeanseesdeacanns ses S. DEPARTMENT OF AGRICULTURE. PEN RY obra Sigs teteen s O [O ie eneieeal | ste oeeee aeaeener Os) NUCL | --ayeydns ourpooru ye aed Fe ese pels ALohels pyres Gielen Sefton ake © SORTA TLS [le nae ietens © apcaeltti joa ae ala igre Bae pce C0} OF SAE “SO TMU PLE Glencoe eit os atin ge asia tees Se cone. 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SO RELULMUL Gia lying ier Mer tiem at ae 7 i Saran TOL Saati) Mei Shee Vicia oie ois he a oneal | eager | eters eal ay ‘IV ie Oe ee er OD eo ae eae ot, OTOL GDy | peace: avai ace ee 1 ri ainsi amen RRB, Be eek tas fe ee eal Ae erie e (Ua eaenme eI wate atten (cy 404 ‘TIV Eee ee ie PODS aaa 5S oye oy? FeSO TUL UD Gs | geen sore at trey a ar Ot ORM Lea | Daa ee apes et chegeha ey | Ragen SNC eM aC sear ce ale 6-% ‘ILV ables eng trae en) Veal ite abana N0N OCC eh cate Geemee ns MR UW NMR TE bree hheres Co Deg re ah 09 ne oie 2 Jes-eecreee|-eeeeecree|eeeeseseeefesecoreeee €I-F ‘TLV TE com aan OD Rie ee Paes Ae a A SOCUTULL Coal Sua een cae gt aie See Ler ais ieee uae ONIN |G DOC SCH Nc mk a | Parana mene \eaeeneaaeessiltaneean ie COsG ILV deere r ces = (prac sc bes Se OdUTE [yl Gorece ns ee OLBUCI NO aM OTUs Ome Crs alg Ra tie |ooeeestcee|eeeeesecee)seeeeeeeee| sense seen 6-% ILV DOF SO 0} 0 Laatatarel a OSI TSI j\aqusedtsiline eioma ore meta ilefoh aay:yer ide) gornocpy Chelsie tay 38 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. Some of the teenicides and larvicides which have been successfully used upon insects, as well as soapy enemas, were tested upon detached larve in tin boxes. As with other Gastrophilus larve, remarkable resistance was noted. It will be observed that negative results were obtained by using the common tenicides, that soap solutions seemed more effective, and that nicotine sulphate gave good results. LARVAL TREATMENTS. Experimenters have been impressed with the resistance of Gastro- philus larve to various contact substances, and it is practically agreed that any contact substance capable of killing the larva would seriously injure the stomach membranes of the horse. The internal method for use must necessarily be in the form of a fumigant. The use of carbon disulphid internally, as brought out by Perroncito and Bosso, has been tried and indorsed by many veterinarians. 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S. DEPARTMENT OF AGRICULTURE. The G. intestinalis are the most resistant of the Gastrophilus to treatments, but these, being found in the stomach, are in the most fa- vorable place for treatment. No immediate effects of the gas upon last- stage Gastrophilus larve are observed, as they remain motionless for some time. Finally they contract so as to conceal the hooks of attach- ment and then drop from the stomach section. This sometimes occurs within 30 minutes after the fumigation begins, but most often it is after 1 or 2 hours. Occasionally the contraction is not so great and larvee remain attached but drop at the slightest touch. A number of observations were made upon animals treated by local veterinarians. During the spring and early summer records were kept on 23 of these horses, which were treated when they contained only last-stage larvee. The treatment was given as recommended by the Bureau of Animal Industry. Within 36 to 48 hours the first bots appear in the feces, though if the physic acts well they may be found after 24 hours. The writer observed bots to pass for a period of 5 days, beginning about 36 hours after the treatment. With the first droppings a few living larve may be found which detached from the stomach before the treatment, and in one case G. nasalis was reared from such larve. G. haemorrhoidalis may appear at the anus as usual if this treat- ment is given in the spring, as by this time numbers have previously migrated to the rectum. While Table IX shows that carbon dicilpivd gas is capable of killing last-stage larvee within 34 hours, the ideal time for treatment of horses would be in the autumn when all larvee are young and the G. haemorrhoidalis are still within the stomach and duodenum. The last-mentioned experiments in Table IX show some fumigation re- sults with small Gastrophilus. It will be observed that 1 hour was an amply sufficient time, though a few last-stage larve were present as late as September 18. If not caused to detach these would possibly drop during the winter and succumb to low temperatures. In Dallas, Tex., 45 minutes was sufficient to kill young larve on December 9, 1916. The fact that G. nasalis attaches in the throat, where the larve are not in a position to be affected by the carbon disulphid treatment, em- phasizes the fact that “an ounce of prevention is worth a pound of cure.” REPELLENTS. The rubbing of horses upon posts, bowlders, and other convenient objects suggested a device for use in pasture whereby horses could rub their lips upon a repellent. The short period of effectiveness of repellent substances and the inability to obtain one that will remain on the lips during grazing are difficulties which would seem to be overcome by such a device. A keg reservoir was devised whereby a GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 43 flow of repellent, which was regulated by a stopcock, moistened a padded plank by means of a small pipe perforated with holes. This was placed at a salting and resting place of the horses and the amount of rubbing noted was very encouraging. Unfortunately, the horses did not rub the corners of the mouth, which are favorable places of ege deposition, and the scheme was abandoned. Dr. Van Es suggested the use of a repellent upon the forelegs of horses and other portions of the body accessible to the mouth, so as to cause the common bot fly to deposit eggs upon places where they could not be reached by the horse’s mouth. A marked repellent quality was observed in equal parts of pine tar and lard, no adults having been observed to oviposit during the following 4 days. There was apparently no injury to the animal, and 1 part of tar to 2 parts of lard was effective during 3 days. The disadvantage in some of the treat- ments was the fact that animals would walk through mud and water and cause a decrease in the repellent qualities of the mixture applied. Very good results were obtained with pine tar 3% ounces, kerosene 14 ounces, laundry soap 1 ounce, powdered resin 1 ounce, and hot wa- ter to make 14 ounces. The pine tar was thinned with kerosene, the soap and resin dissolved in hot water, and the two mixtures poured together. There was not only great repellent action observed, but the resin caused the hair to stick together in small bunches and pre- vented the adult flies from ovipositing. There was apparently no injury to the skin of the animal, and these same repellents pre- vented G. nasalis from ovipositing under the jaws. A successful repel- lent that would not require renewal over a reasonable period is de- sirable, since the loss of time due to the renewal of repellents is a great loss. MECHANICAL PROTECTIVE DEVICES FOR WORK HORSES. The protective devices found upon work animals vary, but there are none used in the Dakotas on pastured animals. (See Plate V.) Various forms of fringes are most frequently found and may consist of leather, burlap, or a portion of the leg of trousers. These are probably the least effective of the devices, as examination of teams wearing such fringes developed the fact that they are often found infested with eggs. Leather seems to be the most efficient of the fringes, as it is not so easily blown aside by the wind and does not hinder the horses in breathing. Those extending completely around the head retail for 50 cents each, while those covering only the face sell for 25 cents. Baskets which are used extensively in nose-fly districts serve as muzzles during the last plowing of corn, but are not very effective nose-fly protectors. The mesh is of sufficient coarseness to permit files to oviposit if the lips can be touched. They do not always fit well at the top and occasionally a nose fly will get on the inside, 44 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. producing great annoyance by its buzzing. During thrashing moisture collects within the basket and, when the dust settles upon this, creates a condition which greatly handicaps the animal’s breath- ing. These baskets retail for 35 cents each when fitted with two snaps. While protection of any description about the lips will prevent many ovipositions and annoyance by flies, by far the most effective de- vice consists of a simple strip of leather extending over the lips and fastened at the bit rings. This actually covers the portions of the lips upon which the flies lay their eggs and upon horses thus pro- tected an absence of eggs and annoyance has been noted. During the movement of the horse’s head in walking, especially when working, this protection not only covers the lps, but swings to and fro and tends to repel the flies. The nostrils being exposed, it does not hinder breathing. Due to the cost of leather, very few of these are in use, but if one obtains an old belt from a thrashing machine great num- bers can be made. It requires only a strip which will extend from one bit ring to the other and be from 4 to 6 inches in width. The size of the strip will depend upon the size of the horse’s head. A snap placed at each end near the center facilitates handling, and the pro- tector can be snapped onto the harness when not in use. PROTECTORS FOR PASTURED ANIMALS. Studies of efficiency of halter appliances for pastured horses have been made, and while conclusive results have not been obtained, a type has been designed which promises to meet the demand. At first halters were used with a piece of leather covering the jaws and hanging so as to flap against the lips when the animal walked. The front of the halter was provided with a face net which swung over > the nostrils and lips. This proved unsatisfactory, as the flap, if long enough to protect the animals during depositions, was too long during grazing. The horses would step upon them with the fore feet, causing them to break. A variation from the most efficient work-horse protector was devised by using a piece of duck on the rear, so as to cover the jaws and prevent G. nasalis from depositing in this location (see fig. 4). A block of wood under the center and below the lips enables a horse to graze with ease and at the same time be protected from flies when the head is held above the ground. The cloth on the rear also pre- vents ingress of @. intestinalis larve by preventing the horse from scratching portions infested with eggs. When the head is placed upon other animals the device occasions such discomfort that almost immediately the horses move and prevent the protected animal from becoming infested from their bodies. For pasture uses the leather becomes soft and at times exposes the corners of the mouth, but excellent results have been obtained by sub- Bul. 597, U. S. Dept. of Agriculture. PLATE V. — DEVICES IN USE TO PROTECT WORK HORSES FROM OVIPOSITING G. HAEMORRHOIDALIS. Upper left.—A leather frings is fairly effective. Upper right.—A burlap fringe hinders breathing. Lower left.—A wire basket often permits ovipositions on account of coarse mesh and ill fitting. Moisture and dust collect and hinder breathing. Lower right.—A strip of leather actually covers oviposition places and allows the horse to breathe easily. (Original.) asset alates Mideshmaniaaie veh GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 45 stituting a hard wood. The weight in either case will compare with the weight of blind bridles. Horses using these in experiments be- came free of G. haemorrhoidalis eggs during the summer of 1916, whereas unprotected animals were heavily infested. .a marked difference in the feeding, as protected animals grazed nor- mally in bunches. While the device in- dicates a favorable preventive measure, before its adoption tests of durability should be made and minor points in the construction deter- mined. It seems pos- sible that the con- struction could be made so simple that farmers could make the protectors at a nominal price. A halter attach- ment would permit horses to graze dur- ing times that are favorable for depo- sitions of flies, and would prevent even- tual infestations by all three species of Gastrophilus. A shed constructed in the pasture would protect animals from nose flies, al- though it would not prevent infestations by the other species of Gastrophilus. Fie. 4.—A bot preventive. There was also The box prevents ‘nose flies” from ovipositing when the head is held upright, while the block of wood underneath the box allows the horse to graze easily. ‘The canvas prevents normal ovipositions of the ‘“‘ throat bot-fly,’ and does not permit the horse to bite the portions infested with eggs of the ‘‘ common bot- fly.”” (Original.) such a shed would keep the animals from grazing during times that were favorable for depositions, and could be used for storage of feed during the winter. EFFECTIVENESS OF WASHES UPON EGGS. Regardless of whether horses are treated internally for bots, which is best during the autumn, when larvee are small, or whether they 46 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. wear halter appliances during the summer, it is necessary to treat the eggs during the autumn to prevent a late infestation from the well-incubated eggs after the protectors have been removed. ‘Then, too, the ease with which places so accessible to the horse’s mouth can be washed makes the use of washes a practical prevention in regions where bots are not so numerous. LARVZ REMOVED FROM EGGS PRIOR TO TREATMENT. Active larvee were removed from well-incubated eggs and subjected to substances reported in Table X. Only larve in excellent condition were used, and these were observed in watch glasses, small tin boxes, and test tubes at short intervals until dead. When in doubt they were removed with a drop of the liquid to a microscope slide, and the warmth of one’s breath was sufficient to cause living ones to move. Larve were killed instantly when placed in volatile liquids or gases of carbon disulphid and in absolute alcohol. TABLE X.—Resistance of first-stage larve of Gastrophilus intestinalis, Aberdeen, S. Dak., 1916. Larve placed in— Longevity. Larve placed in— Longevity. DD ryebingbOXs oe oe eee eee 72 to 126 hours. || Borax, saturated solution... _.._- 40 minutes. Wie GOT tere te Sess Sek ose hepa pee 76 to 99 hours. oO percentialcoholea sae 30 minutes. MMncturei@uassiaess eee ee 24 to 36 hours. Petroleum, refined .--.:-.. 22222. 30 minutes. Beta-naphthol in alcohol........ 20 to 28 hours. DOS soe icincrn eee eee see ee 30 minutes. 10 per.cent oil of tar emulsion... .] 41 to 48 hours. IB OLiCiacid=tieere-eeee eee ...-| 13 minutes. Borax, saturated solution.......- 28 to 41 hours. 334 per cent pine tar and 663 per | 1 minute. DOs ree SA eee eee 24 to 43 hours. cent kerosene. Dr. Guyot’s results compare favorably with those herein reported. His larve remained alive in water for 4 days, nearly a day in olive oil, and more than 14 hours in bichlorid of mercury solution 1 to 1,000. The movement of freshly emerged larve is very rapid upon moist surfaces, but upon a dry surface they seldom move from the original location, although they have been observed to live for 72 to 125 hours. When placed in water the larva became submerged with the exception of the posterior spiracles, which remained exposed at the surface. They are capable of living in this manner for (6 to 99 hours. LARVE REMOVED AFTER TREATMENT OF EGGS. Hundreds of eggs were collected from horses in pastures during the latter part of August and the early half of September. At this time the activities of adults of G. intestinalis were being directed to the manes of horses for oviposition, as in most cases the inside of the forelegs and sides immediately behind the forelegs were very grossly infested. These hairs were of sufficient length to render handling easy, and the eggs were about the same age. Except as otherwise in- Sit ag her Aah BE aan GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 47 dicated in Table XI, infested hair was placed in tubes at air tempera- tures of a living room and allowed to remain until larve were well formed and ready for emergence. Some of the eggs were then tested and the viability determined. A check was not kept, as the brownish color of the dead larve easily distinguished them from the trans- parency of the active larve. TABLE XI.—Hffcectiveness of washes upon eggs of Gastrophilus intestinalis, Aberdeen, S. Dak., 1915-16. Num- Mortality of larvee. Date Bae ber eggs Insecticide. Satire larvee Remarks. treated. Pp ‘| ex- Weel. eS Doubt- amined. : 8-1 ful. 1915. | Minutes Sept. 6 | Refined petroleum.......| 6-18 7 0 7 0 | Engine oil, No. 1. Dor slesee- GOS eaee eet se ee 18-31 8 4 4 0 Do. 1916. | Hours. Septe. val Kerosenews.so-se eee see 24 20 LOR Rasa teat: 1 Do..--| 1.35 per cent phenols! ...- 24 38 38 0 0 | Reddish brown in color. Do...-| 2 per cent nicotine sul- 24 17 12 5 0 phate. Do....| Carbolic acid 2 per cent 24 20 19 1 0 phenol. Dorsal Wander tress eee Aes 3 24 20 0 20 0 Do....| Nitrobenzine gas. ....---. 25 38 38 0 0 Sept. 9 Caubolic acid 2 per cent 5 28 23 0 0 | 2larvee yellow in color. phenol. . WOR sere WCTOSCNE gt can. ae aoe oe 29 22 5 iL fal ete 5 card larvee yellow in color. Do...-| 0.185 per cent phenols 1... 29 23 23 0 Ones gerd larvee yellow in color. Sept. 11 | Nitrobenzine gas......... 4 34 7 22 5 DOs: |= GOR aero Neraties orseeiats 10 40 iti [a laesmaeeters 3 DO ae GOS tee Sg 25 42 42 0 0 Do....| 0.054 per cent phenols 1... 26 40 40 0 0 1D) Oars | PKCCrosene ses: saee mers rics 25 28 5 D3 hes Sees 18 larvee very active. Do....| 2 per cent nicotine sul- 26 26 9 14 3 phate. Do....| 2 per cent carbolic acid. . . 26 38 38 0 0 Sept l5-|s Wwerosenes sana eeece ooo 24 55 11 38 6 | 38 larvee very active. Do.1..| Carbolic acid 2 per cent 24 48 47 0 | 1 phenol. Do.!. .| 0.054 per cent phenols 1... 25 49 49 0 0 DON EIMCLOSENC se aoe eae ae 147 24 3 19 2 Do.!..| Carbolic acid 2 per cent 146 27 27 0 0 phenol. Do.‘ . .| 0.054 per cent phenols!- - - 147 21 21 0 0 1 A proprietary compound of cresol in combination with resin soap. 2 Eggs not well incubated were treated and larvee removed Sept. 21. In the tests with larve removed from the eggs it was observed that the minimum period causing death by contact was 1 minute with pine tar 1 part and kerosene 2 parts. The ease with which either of these can be obtained suggested a study of these and similar substances. It will be observed that kerosene, which is commonly reported to be in use by farmers, even at an exposure of 147 hours, had prac- tically no effect upon larve. When eggs upon hair were rubbed they more readily yielded to hatching and apparently the larvee were more active than from any similar treatment. The kerosene seemed to facilitate the emergence of the larvae. While it was ineffective against well-developed larve, it was thought that upon freshly 48 BULLETIN 597, U. S$. DEPARTMENT OF AGRICULTURE. deposited eggs it would probably prevent development of the embryo, as is the case with hens’ eggs during incubation; but even a test of this kind was onty slightly effective. A 2 per cent nicotine-sulphate solution was only partially effective. Nitrobenzine gas, which has recently been brought to our attention as a fumigant for external parasites of animals by Prof. William Moore, of the University of Minnesota, yielded good results at 25. 24, and 10 hours’ exposure, but only a small percentage was killed at 4 hours. The fumigation was conducted in a common glass fruit jar into which a strip of cloth, impregnated with a few drops of nitrobenzine, was suspended. The phenol compounds, by a contact application, seem to be most effective in destroying young larve and preventing the further de- velopment of embryos. It will be observed that carbolic acid con- taining 2 per cent phenol yielded as good results as higher per- centages, and that this substance was most effectively used. With carbolic acid as a wash it will be well to be cautious of its effects upon the hands. If used at too great strength. the exposed skin of the hand will become white and peel off, although it does not affect the skin of the horse, which is protected by the hair. SUMMARY. Three species of horse bots—the common bot-fly (Gastrophilus intestinalis ), the throat bot-fily (G. nasalis), and the nose fly (G. hae- morrhoidalis)—occur in the United States, and each is a source of considerable injury to horses. This injury is produced through worriment caused by the flies at the time the eggs are laid and by the attachment of the larve, or bots, in the alimentary tract. Gastrophilus intestinalis and G. nasalis are widely distributed in the United States but G. haemorrhoidalis is confined to the North- Central and northern Rocky Mountain States. The nose fiy (G. haemorrhoidalis) is by far the most annoying to horses at the time its eggs are laid. The adults appear early in June and reach the maximum of abundance during the first half of the season, disappearing with killing frosts. The eggs are deposited on the minute hairs on the lips, and those near the edges which are kept moist and receive friction hatch in from 5 to 10 days. The larve are taken in with food or water and attach themselves to the walls of the stomach. Here they remain until the following winter or spring and then migrate to the rectum, where they reattach. Before leaving the host they usually attach close to the anus and protrude from it. They remain in this position from 40 to 7i hours. After dropping to the ground the bots seek protection and pupate in from 18 to 170 hours later. The pupa stage lasts from 21 to 68 days. The adults are GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 49 very active, and as they deposit only one egg at a time they are not so frequently seen about horses as are the adults of the common bot- fly. They take no food in the adult stage. Their length of life is from 1 to 7 days. The throat bot-fly (G. nasalis) deposits its eggs on the hairs under the jaws and to some extent on the shoulders and other parts of the host. The larve of this species attach themselves to the walls of the pharynx and also to those of the stomach and duodenum. They do not reattach in the rectum or at the anus as do the bots of the nose fly. Pupation occurs in from 1% to 2 days after the larve have passed from the host, and adults emerge in from 20 to 56 days later. The adults are somewhat longer lived than those of the nose fly. The flies cause considerable annoyance to horses during oviposition but not as serious as in the case of the nose fly. The common bot-fly (G. intestinalis) usually appears later in the season than the nose fly and becomes most abundant just before kill- ing frosts. The eggs are deposited on all parts of the body, but preferably on the fore legs. They hatch upon the application of moisture and friction. From 9 to 11 days after oviposition appears to be the most favorable period for hatching, although some may hatch as early as 7 days and others as late as 96 days after oviposi- tion. The larve attach in any part of the stomach, but the last-stage bots are found mostly in the left sac. They continue to drop from the host for a long period of time. Pupation takes place in protected places on the surface of the soil and the pupa stage lasts from 40 to 60 days. All Gastrophilus larve are surprisingly resistant to chemicals. The treatment of horses with carbon disulphid in three doses followed by a physic is satisfactory if administered in the late fall. Spring treatment is less effective, as the full-grown larve are more resistant, and many of the nose-fly bots have left the stomach and passed back to the rectum at that time. Larve of G. haemorrhoidalis may be removed from the rectum mechanically, but this is laborious. The use of enemas containing insecticides is ineffective. As a repellent, pine tar mixed with other material gave good re- sults against the common bot-fly and the throat bot-fly. Such mix- tures may be utilized to cause the flies to lay eggs on parts of the body less accessible to the horse’s mouth. Various nose protectors are in use against G. haemorrhoidalis, but there are objections to many of them. A piece of leather suspended below the lips from the bit rings is simplest and best. For animals on pasture a halter with a box-like arrangement and throat cover has been devised to protect horses against infeetation by all three species. 50 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. Kerosene oil used as a wash is ineffective in destroying the eggs of Gastrophilus, but certain other substances have given good results. Carbolie acid containing 2 per cent phenols is satisfactory for de- stroying eggs when applied to the infested parts of the host. BIBLIOGRAPHY. AupRicH, J. M. A Catalogue of North American Diptera. 680 pp. Washing- ton, D. C. 1905. (Smithsn. Mise. Coll., vol. 46, No. 1444.) Pp. 413-415, Gastrophilus. ANoNYMoUS. Bots harmful to the horse. Jn U. S. Dept. Agr. Weekly News Letter, vol. 1, No. 5, p. 4, Sept. 10, 1913. ANONYMOUS. Bots of horses. In Agr. Gaz. N. S. Wales, vol. 20, pt. 3, pp. 203-208, 6 figs., Mar. 2, 1909. BRAUER, FREDRICH. Monographie der Oestriden. 291 pp. Wein, 1868. BurFincton, G. L. Gastrophilus haemorrhoidalis in the pharynx of a horse. In Amer. Vet. Rey., vol. 29, No. 1, pp. 37-838, 1905. CARPENTER, G. H., and Hewitt, T. R.. Some new observations on the life history of warble flies. Jn Irish Naturalist, Dublin, vol. 23, No. 10, pp. 214- 221, Oct. AGt4- CLARK, Bracy. Observations on the genus Oestrus. Jn Trans. Linn. Soc. London, vol. 3, pp. 289-829, col. pl. 23, 1797. CLARK, Bracy. An Essay on the Bots of Horses and other Animals. 94 pp., 2 pl. London, 1815. CLARK, Bracy. Of the insect called Oistros by the ancients and of the true species intended by them under this appellation. . . . Jn Trans. Linn. Soc. London, vol. 15, pt. 2, pp. 402-410, 1827. CoLLINGE, W. E. Some observations on the eggs of the horse bot fly Gastrophi- lus equi (Fabr.). Jn Jour. Econ. Biol. vol. 5, No. 1, pp. 9-17, I fig., March 31, 1910. Dueear, B. M.. Notes on the maximum thermal death-point of Sporotrichum globuliferum. In Bot. Gaz., vol. 27, No. 4, pp. 131-136, Feb., 1899. FRENCH, C. The horse bot-fly. In Jour. Dept. Agr. Victoria, vol. 1, pt. 7, pp. 693-696, July, 1902. Page 697—Treatment for the bot fly, by J. R. Weir. Froeeatr, W. W. The bot-fly (Gastrophilus equi). In Agr. Gaz. N. S. Wales, vol. 19, pt. 3, pp. 229-238, pl., Mar., 1908. GARMAN, H. The bot-flies of the horse (Gastrophilus equi and G. nasalis). In Kentucky Agr. Exp. Sta. Rept. 7, 1894, pp. xxvuI—xxxiv and Rept. 8, 1895, pp. xLix—L. The throat bot-fiy of the horse (G. nasalis). Guyot, J. Contribution 4 1 étude des larves de gastrophiles (Oestrides) para- sites de l’estomac du cheval. Jn Arch. Par., vol. 4, pp. 169-221, 11 figs., 1901. HutTcHEon, D. Bots or “ Paapjes.” Jn Agr. Jour. Union South Africa, vol. 8, No. 2, pp. 194-200, Aug., 1914. Die Gastruslarvenkrankheit der Pferde in ihrer Bedeutung fiir die Fohlenaufzucht besonders veredelter Zuchten. Jn Ztschr. Veteri- nark., Jahrg. 18, Hft. 5, pp. 201-211, May, 1906. LAHILLE, F. Los gastréphilos en la Reptiblica Argentina. Jn Bol. Min. Agr. Argentine Republic, vol. 18, num. 12, pp. 886-856, 8 fig., col. pl., Dec., 1911. LOcHHEAD, W. Some notes regarding nose and other bot flies. Jn Forty-sixth Ann. Rept. Ontario Ent. Soc., 1915, pp. 102-108, 1916. KKRONING, ati ed serio | | 4 | ; ] GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. HAL LuGeER, OTTO. Insects injurious in 1896. Jn Second Ann. Rept. Agr. Exp. Sta. Univ. Minn., 1896, pp. 31-257, fig. 2-187, 16 pl., 1897. Pages 235- 245. B. Bot-flies, Gad-flies (Oestride). MAcDovucGatt, R. 8S. Insect pests of domesticated animals. Jn Trans. Highland 3 and Agr. Soc. Scot., ser. 2, vol. 5, pp. 187-190, 1899. MaAcLray, W.S. On the insect called Oistros by the ancient Greeks and Asilus by the Romans. Jn Trans. Linn. Soc. London, vol. 14, pp. 353-359, 1824. MicHENER, C. B. Diseases of the digestive organs. In U. S. Dept. Agr. Bur. An Indus. Spec. Rept. on Diseases of the Horse, 1911, pp. 34-74, 3 pl. Page 61, pl. II. Bot-fly larve. Moorr, WILLIAM. Fumigation of animals to destroy their external parasites. In Jour. Econ. Ent., vol. 9, No. 1, pp. 71-80, fig. 5-6, Feb., 1916. Nites, HK. P. Animal parasites III. Virginia Agr. Exp. Sta. Bul. 110, pp. 27-387, fig. mm—v11I, March, 1900. . ORMEROD, ELEANOR A. Report of observations of injurious insects. Paha 14th, 1890. 144 pp. London, 1891. Pages 64-71, Horse bot fly; horse bee, Gastrophilus equi Fab. OSBORN, HERBERT. Insects affecting domestic animals. . . . U.S. Dept. Agr. Div. Ent. Bul. 5, new ser. 302 pp., 170 figs., Washington, D. C., 1896. Pages 72-114, Family Oestridse. (Bot-flies, breeze flies. Pages 76- 84, fig. 837, pl. 2, The horse bot-fiy. (Gastrophilus equi Fab.) Parker, R. R. Notes concerning Gastrophilus haemorrhoidalis Linnaeus (Dipt.). Jn Jour. N. Y. Ent. Soc., vol. 24, No. 4, pp. 2538-255, figs. 1-2, Dec., 1916. PrerRoncitTo, E., and Bosso, G. Sul Metodo di Distruzione delle Larve d’Estro, Gastrophilus equi, nel Ventricolo del Cavallo. 31 pp. Torino, 1897. Traduction francaise, Bulletin veterinaire No. 67, 1900, pp. 569-590. PERRONCITO, E. Importanza patologica delle larve d’estro nello stomaco del cavallo. In Gior. Reale Soc. ed. Acead. Vet. Ital., vol. 51, No. 32, pp. 801-805, Agosto 9, 1902. SEYDERHELM, K. R., and SEYDERHELM, R. Die Ursache der pernizidsen Animie der Pferde. Jn Archiv fiir Experimentale Pathologie u. Pharmakolo- gie, Bd. 76, Hft. 3 u. 4, pp. 149-201, May, 1914. SwENK, M. H. The bot-flies affecting live stock in Nebraska. Jn Ann. Rept. Neb. St. Bd. Agr. for 1908, pp. 327-841, figs. 25-32. TOWNSEND, C. H. T. On the so-called throat bot. Jn Ent. News, vol. 3, No. 9, Dp. 227. -Nov., 1892. VeLu, H. Note sur une lesion de myase intestinale chez le cheval. Jn Recueil Med. Vet. Alfort, vol. 92, No. 13, pp. 408-410, 1916. (Rev. App. Ent., ser. B, vol. 4, No. 10, p. 164, Oct., 1916.) . VerRRILL, A. E. The external and internal parasites of man and domestic ani- mals. . . . Hartford, Conn. [1870]. 140 pp. (From Fourth Ann. Rept. Sec. Conn. Bd. Agr., 1869-70. ) WARBURTON, CreciIL. Annual Report for 1899 of the zoologist. Jn Jour. Roy. Agr. Soc. England, ser. 3, vol. 10, pt. 4, pp. 667-678, 1899. Pages 668-669, Horse bot-flies. WESSEL-WItstTErR, W. Abtreibung von Gastru larven bei Fohlen durch Schwefel- kohlenstoff. Jn Berliner Thierirztliche Wochenschr., Jahrg. 1901, INGOs) OF pe 136: WILLISTON, SAMUEL W. Manual of North American Diptera, ed. 3. 405 pp. New Haven, 1908. PUBLICATIONS OF THE UNITED STATES DEPARTMENT OF AGRI- CULTURE RELATING TO INSECTS AFFECTING THE HEALTH OF MAN AND DOMESTIC ANIMALS. AVAILABLE FOR FREE DISTRIBUTION BY THE DEPARTMENT. Remedies and Preventives Against Mosquitoes. (Farmers’ Bulletin 444.) Some Facts About Malaria. (Farmers’ Bulletin 450.) The Sanitary Frivy. (Farmers’ Bulletin 463.) How to Prevent Typhoid Fever. (Karmers’ Bulletin 478.) The Stable Fly. (KFarmers’ Bulletin 540.) The Yellow Fever Mosquito. (Farmers’ Bulletin 547.) Harvest Mites, or ‘‘ Chiggers.” (KFarmers’ Bulletin 671.) The Bedbug. (KFarmers’ Bulletin 754.) Mites and Lice on Poultry. (KFarmers’ Bulletin 801.) The House Fly. (armers’ Bulletin 851.) Screw-Worms and Other Maggots Affecting Animals. (Farmers’ Bulletin 857.) 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