"BULLETIN No. 597

TS Contribution from the Bureau of Boteniokouy
hy 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

Page Page
| Introduction... . 2. 2. se ees 1 | Natural Protection of Horses .... tI4
' Brief Life Eistory of Gastrophilus . . 2 | Seasonal History cf Gastrophilus. . . 15
eee my) ei Siw, ety eve oes © 2 | Gastrophilus haemorrhoidalis Linn . 16
' Species Differentiation . ...... 3 Gastrophilus nasalis Lim... . « 30
- Distribution in the United States and . Gastrophilus intestinalis DeGeer. . 32

| Probable Dispersion. . . . + = - 5 | Effect of Death of Host upon Guastro-
/} Larval Collections and Rearing Tech- philus Larve ..2 00 6 cies © © « 34
Naina!) & 8a ge einer wales, e 5: :| Control: Stidies 5; 20°) sf ee a 0) eae 35
>) Earval Infestation and Injuries. .|. . 6 | Summary .....- 2. ee eee 48
| Bot-fly Annoyance. . ....... 3. bingy. a ba? Seis? 6 lo Sek 50

7

UF oes

WASHINGTON
~ GOVERNMENT PRINTING OFFICE
1918

aes aw

4 onagraph

4 CA

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. EH. Dove, Scientific Assistant, Insects Affecting Domestic Animals.

CONTENTS.

Page Page
HET UE DM GuIONef145--~ Ss ots cats cote esse eee ee 1 | Seasonal history of Gastropkilus............- 15
Brief life history of Gastrophilus...........-- 2 | Gastrophilus haemorrhoidalis (Linnaeus) .... 16
ERHOUAI et Mes — ee couse dc cae meamece sis 2 | Gastrophilus nasalis (Linnaeus) .............- 30
Species differentiation .................--.-- 3 | Gastrophilus intestinalis (De Geer) ........... 32
Distribution in the United States and prob- Effect of death of host upon Gastrophilus

PIO IS PCUSION sh thcs .5- scin stot pe eeeere = 5 WAR debe oss mee teas dude ac. Tee 34
Larval collections and rearing technique... DF COR UrOLShUCicseees, ro. haf <0 ed ee 35
Larval infestation and injuries..-.........-.- Gr Summary)... @eeocte sews 255.5520 ce See 48
Hotetiy AMMO VANCED ==... l-.2ic-02cecccdecece 13 Biplo graphy 2a. esate an < oles Solan veg ae 50
Natural protection of horses......... geaetoks 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

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
eggshells 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 G. intestinalis De Geer, while to Brauer it was @. 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.

~~ = ae

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 “ ¢ntestinalis” by Guyot,
“ Gastrophilus intestinalis” is given preference rather than “ Gastro-
philus equi.”

Aside from priority, the specific name “ equz” 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.
: - . (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.

Kry To WING VENATION OF GASTROPHILUS SPP.

i Discoidal cell not closed. by a cross vein__-_--—______---..-_— G. pecorum.
nr eecellAClLosed aby j27CrOSS, VEIN. 525-6 2s a ee 2
Scoot aicericwabin PGEOWM. 2-6 G. intestinalis.
ir ace pit MMi OLOW Ne 22 tS 33
3. Anterior basal cell nearly or quite equal to the discoidal cell in
(ECE E) pg ee ao.) Sy TE a en a Re Re ne praaen ac eee ee G. nasalis.
Anterior basal cell markedly shorter than the discoidal
CST So ae aT a IS ES ea ea ee se oe 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. intesti-
nalis and G. haemorrhoi-
dalis are often found await-
ing the approach of females
to the horses, and when they
arrive the flies copulate.
Pic, 2 actroius hamorteidela: Fenele, The species characteristies

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 Gastrophilus 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 lavee, as can be seen in the illustration (Pl. I), vary
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 larve.

KEY FOR THE IDENTIFICATION OF FULLY DEVELOPED LARVA oF GASTROPHILUS SPP.

1. Spines arranged in two alternating rows, the first more developed than the

Second. 2/2324. 820. Ji) OS Se ee ee 2
Spines in one row______ ask St eee ee bs G. nasalis.
2. Spines long and prominent, inekine ae ee o to three pairs on dorsal center
of themminth row: 222. = See te | ee G. intestinalis.
Spines short and segments promuaeale Dice cicly deprived or possessing
only two to three pairs of spines on either side of the dorsal center of

the: \ninth! rinte. ---4 i Sek eae ees eee 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. pecorum 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
depositing eggs indicate that

Fic, 3.—Gastrophilus eggs attached to hairs:
: : a, G. haemorrhoidalis and hair removed
little dispersion takes place by with root; b, G. intestinalis ; c, G. nasalis.

; Greatly enlarged. (Original.
actual flight. In the nose-fly Aiea yd pee

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 larvee 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 larvee 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 larvee 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 larvee, 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. i

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 larve,
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. egui 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
during the period that larvee are well developed and naturally drop
trom 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
light into the nostrils and may be found in the pharynx and other
locations in the throat.

Dr. Buffington (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 cesophageal mucous membranes were found to be gan-

lO on ee oe! ea Pe

Bul. 597, U. S. Dept. of Agriculture. PLATE 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. hacmorrhoidalis: 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.)

PLATE II.

Bul. 597, U. S. Dept. of Agriculture.

LARVA OF THE BOT FLIES, GASTROPHILUS.

Upper.—Attachment of last-stage larvee and alveolar lesions upon the mucosa of the left sae
of the stomach, Lower.—Infestation of 317 last-stage larve, with lesions in the center.

(Original.)

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 larve were determined as @. nasalis, and it
is reasonable to believe that the other larve, 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 larve 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 @. 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 I1.—Gastrophilus findings in post-mortem examinations of horses at Aber-
deen, S. Dak., 1915—16.

Larve in stomach. Larve in duodenum.

Horse
died.

Spent summer.

sp. small.

sp. small.
Larve in rectum, G.

haemorrhoidalis
Total number larve.

| G. intestinalis.

G. haemorrhoi-
dalis

| Gastrophilus

| G. intestinalis.

G. haemorrhoi-
dalis

| Gastrophilus

| G. nasalis.

| G. nasalis.

We

July |

duly, 24) || Imipasture-—= 5 22s 2. e =e CGT ee ol eee aie ae 149 shes sc Se eee eee 610
Ade.) (Si, Harm) Workee.-ssese eens 151 1 Ulisecd hal weeconiese ses) sane: Sees eee 153
UNG pee Tee AE Sao aanagaonsecessoacaece 39 16 Aaleseeee 4 30.) Socal aeons 93
ANIGin Vlas ee oe eee eeee eee eee 20 ils 25 ceri em te Pe eee eee 25 2: | eee 47
Ang, Gilets os eee cememeneseee sen lee cece seo eee eee 135 | Esse 1S ees eee Re es 14
JANIS. 1a ee cee ences Gee eee eee ece re 7): Gl etd Perens eer AS Sen lemme sera ea Ne ae 24
YX ble eee ye Be Arist Itc 29 14 1 es IS Ee a ANS 225 S106 Cee eee 48
Tb FEDS A Bees soe Smee nae acoceoe I. A seer ees Gules e EAs a | Sen ar 26: s2asee 33
Aes, 23) 53. 2a seco tecase seme BAS eee 8 Sieceene QE ine see yl Bere 102
tg OB | 25e2 ses. oe ee | Se os eee ae mall ae S| ees 12 36
Sept. LT |jc2c2 2 o2Gen se ote eeaen emer UR Seteeeees | ee DO) | eae nl oss. ee eee eee 21
Sepiayet|{2-25.tecbes eee Pfilliest ns 2 1 lig | 8 (os ee | 14) |e 18
Septs Lf... sos ce sai sete ens eee Di |b ekelloe a cecey eerste ae 1 |e. 2 Sse eee 4 eee 6
DEPU. 1G --->- cus acsncceemeeenoeeree 2. | ae eee Bib | ace 2 [ee | eee BY, | roe 70

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 larve 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 larve 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 larve 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 lesions 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 larve only pause to become accustomed
to air temperatures before dropping.

There is no definitely periodic larval migration of G. haemorrhoi-
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 larve
were found in the stomach, and on July 10, 1916, 3 larve; July 14,
1916, 16 larve; and August 18, 1916, 2 larve 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 @. 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 larvee
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 larvee. 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 larve
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 products of the gastric mucosa.

Tt would appear, from observations, that Gastrophilus larvee 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.
intestinalis 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. 13

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 I.)

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 larve 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 larvee 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-wive
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 fiy. 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 poin:ed 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
lips 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
for 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,

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 IIT.

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 G. 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, 8S. 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, G. 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 LARV:.

During the early spring and summer the fourth-stage larve 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. Larve, 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 slightly 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 13 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 Ill.

PROTECTION FROM BoT FLIES.

Upper.—Horses assembled for protection during ovipositions of Gastrophilus haemorrhoidalis.

Center.—A method of protecting lips from ov
ing under jaws from ovipositing G. nasalis. (

ipositing G. haemorrhoidalis. Lower.—Protect-
Original.)

Bul. 597, U. S. Dept. of Agriculture. 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 Hordewm jubatum. (Original.)

GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 17

X

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 es black and retains this color until the
adult emerges.

Taste I1—Some environmental effects on metamorphosis of Gastrophilus
haemorrhoidalis at Aberdeen, S. Dak.

Temperature, col- Lon-
lection to emer- gevi-
1 . Ses Num-|Num ty
arvee Pre- tb Ba 7 “| Number| of
eollected Environment. pupal aed Ls ae adults |larves
period. he = emerged.| not
rectum. ‘ &. | pe. pu-
Max. | Min. | Mean. |
pat-
ing.
1915 Hours. | Days.; ° F.| ° F. | ° F.. | Days
June 4) Fresh horse manurein tin box} 27-47 | 39-45 88 30 | 68.21 |- 14 14 iil Deine 2
Wines oa lees (10) oe OEE etn cees 24-72 | 46-54 88 35 | 64.76 33 31 22 4
A jive (: egy fon ane a Tie te Se Ree eee 34-52 | 37-44 88 35 | 64.93 16 13 8 8
Junecealbones Qe eee see Mertens 49 | 38-40 88 35 | 65.67 | 7 7 Dees
Juney (97) Clean tin’ box: 2... 22.-.--- | 35-55 | 36-48 88 35 | 65.02 12 11 OU tes aes
June 12] Glass jar and fresh horse ma-
TIGL Oe tes Foun see ces | 53-146 | 33-36 88 40 | 65.73 | 14 14 yd ease
Junerlon sry: Nara Soll. se--2 2 22 tena 75-122 | 28-30 85 40 | 62.40} 10 10 Baise ee
Do...} Moist horse manure.........- 122 | 29-31 85 40 | 62.56 10 8 7 | 15-22
ness) lean tins POR >. .22 2 <n -e52/=1-1 120 | 31-32 84 40 | 62.89 7 6 4 15
Terese 2s . COS: oot S58 ee ee 50-144 | 30-38 84 40 | 64.33 27 25 18 16
June 18+). 2. .* Oss ea ere eee 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 pl es See
July 12 Black loam in tin can.....-.. 23-39 | 34-35 85 40 | 64. 23 8 5 7 Nese
Aviegen foe OUPTASS SOG q--0 oe neck sae 19-26 | 58-68 88 | 132 | 60.59 7 7 = ee
1916.
Maye 22:|"Glean tin bOX...-c52025..2--- 68 41 94 42 | 62.62 5 4 Arles eaas
May 23 |.---- Oe ae eeesnc PaueenepoeEen 52-72 | 36-40 94 42 | 62.81 5 4 3 | il
May 30'|.-..- Chap eee epee meee = aera 141-170 | 34-35 94 42 | 64.79 2 2 Merce
Maya jeoene ue reese ca aeons Geers 35 94 42 | 60.08 1 1 1 eee
Dimer ape OMe oS cae ee nese ce 42-96 | 33-34 94 42 | 65.55 1l 8 5 5
June 5 With’ MMGISE SANG!) Sete sce e sn 75-100 | 32-35 94 42 | 66.69 17 17 MGR oe oo
June 10}..... G0 ee a eee ee 44 | 30-32 94 42 | 68.15 28 25 20 4
June 23 | Clean tin box and moist joam_| ETS Gd 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 salve 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 larve 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 larvee 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 larve possessing the greenish color indi-
cating exposure at the margin of the anus were used in experiments
recorded in the tables.

In Table II, 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 LARVZ DROPPING UNDER VARYING CONDITIONS.

The variety of conditions under which larve 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 IIT, larve placed upon the surface: of
the soil or media penetrated to a slight 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.

19

GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS.

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20 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

Questioning the fate of pupe if buried, a lot consisting of larve
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 larvee 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 pupz, 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
pupe from excessive heat. In one lot 32 adults emerged from 35
pupee, 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 LARV AND PUP.

Doubtless numerous larve and pupz 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. The results of some tests are given in
Table IV.

21

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92 * 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 larve 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. Pupz, 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 larvee than ordinarily would be expected. Larve 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 LARVZ AND PUP.

Although, as shown in Table III, excess moisture seems to have
had a destructive effect upon pupz, the effect of submergence upon
larvee is not so great. Larve submerged 51 to 74 hours pupated and
produced adults. (See Table V.) Larvae submerged for 80 hours
pupated, but failed to emerge when kept under favorable breeding
conditions. While it is difficult to submerge pups, 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 pupe during
wet seasons,

TABLE V.—Effect of submergence on larve and pupe of Gastrophilus haemor-
rhoidalis at Aberdeen, S. Dak., 1915-16.

|
| | Larval Temperature after
| | ne period of
gevity, submergence.

Date | | : Num- | 4 quilts | includ-| Colec-

sub- | Stage. | ple ee paee d ot emerged,| ing | “on to
merged. ee SINDEN SSE Say | (male.) | period | ¢™&- |

: of sub-| 2°2°e-
Max.) Min. Mean.

mer- |

gence.

1915. Days. | Days.| °F. | °F. it! den
July 5..| Larve... Sap 83 5 36} 85| 41 63. 93
July 14.4) edo. =.2 Tt Ae ee 38| 85| 41] 64.21

Dose do.ccs! 285) 20 "dayst ots es Al! 7 ee Oll eee eee UP—20 5 cia. = 2 85 41 62. 98
July 24.. dos.36) 2 bY 4adayst 2 eee ele Onl eee eye ees ae 80 40 58. 14
July: 222) Rupees sR WB Biday sec et eee ee ne ee RUE ee eens eee | me 82 40 59. 40

1916

June *7::| Larve..| - 989) Vidaysoes atone ae Os eee Lil acesiaee 76 43 64. 83
Do.. Goss e|¢ sl Sid tys ae oe eee ee | eee Sate’ | sa 8ee 76 43 64. 83
July 12 do. 16) “72 days. 222252255 eee ee le. eee +) Re ee 96 64 76. 50
Do.. do. sd) = 25-80 hourss< 255442. een se eee a ee eee sed 96 64 75. 90

Do.. G0esse)' . 56a). Sedaysce cee | oem te eecs hs Weer 96 64 76. 50

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. e

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 larve,
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 larve 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 larvae 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 pupe it
appeared within from 3 to 17 days after collection.

24 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

TasLteE VI.—Fungus development upon pupe of Gastrophilus haemorrhoidalis
in new tin boxes at Aberdeen, S. Dak., 1915-16.

ro : ; Temperature
| 3 5 ee el ess rane Adis collection to
bet S <j 2] s jm ected.|/emerge emergence
Larvee ai a Se |e | P
from Collection and environment.| 5 5 eal | late
rectum. & 2 ae SS : S
=] 5 ra 8 & & ® 7 s : rs
ry &, Be Be se NT etan eres + 3
2 SB Le TR/EIS Sie /8/E)8] &
ty a & jo lHlsel/Alal|slal/al| &
1915. re Hours.| _1915. | Days. MIS eA
June 11! | From perspiring horses. ...|79-220 | June 15 | 34-36] 13]10|]10/ 3] 2] 2] 88| 40] 65.54
TUNES Week aaese secs. hee ee eeeoee 75 | June 30] 35-38 | 10] 10 | 10|....) 5] 1 88} 40| 64.66
June 221 athe sao ceme aa eee 20-219 | June 25 | 30-32 | 34 | 29 | 29 5 a 6 | 85 | 41 | 63.88
July 6] With fresh horse manure. -| 6-25 | July 13 34/ 5] 3] 3j....| 1]...-| 85 | 41 | 63:85
Do...| From perspiring horse... . - DSt ihe, ees S04 | Ament Tele De] On) ced] ence seme. eee ee
MUliye v7 le cate eee cage aes eee 6-43 | July 13 |'33=386)) 3) 3) 3 i-.22) 2 1 | 85) aoe
July 10 | With moist loam.......... 5-18 |...do.....| 33-36 | 40 | 40 | 40 |....) 14 | 11 | 85 41 | 64.32
Sly 1S) | Cease ane sees scene eee 21-29 | July 16 | 33-85] 4] 4] 4 1] 1] 85 | 41 | 64.43
1916 1916
May 172) On blotting paper...._.... 22-32 | May 29 ]....... Giexd |S) ewe] 26.4 eels S2- Se ee
DUMO M2 2 ears ctare ore anemic ee ae 20-39 | June 14 }....... 133) V1) | VPs) sooo a| mes |> 226) sees eee
JUNG VED |leerate ete Sa Sd no eee Ti NO2euntew22) eae mel Dainese, 0| O!} 76) 42 | 59.14
Do.2..| With moist sand........__. ABE | dey es oo SPT | 7 | cectoss clacocls scl Sees eee
June 93| ae On sew go are ee eee 22=7 Oui merye | Goes 10:| 20) 1052. see alae] See ae ree
June 24 |..._. COE eee hoe 4-122 | June 29 | 21-25 | 62 | 59 | 59 |....| 24 | 15 | 96 | 48 | 74.67
JUNE 226 2a a sae cede eee eee 119-166 | July 1]....... 20) 17 | 16\}- cle -ee|<See lee see eee
DREN O G27) (eee eet soe nee eee }22-190 | July 3] 21-29) 15] 13) 12]....| 4] 6| 96 | 56} 75.73
Truly Lh 55-2 es a ee ee 3-64 | July 6 20 | 4) 45) 4.22). 222) 2 96el S8eladnaoi
July 182) With moist sand........__. D1 674 |edllve 250 eames Vey 17 ae (a SR cl oe Is = -
July HA oes eA eee co eee | 21-31 | July 28 29)) 19) | 18") 182-22) Ss) 239) 98) sole (ORES

1 Determined by Mrs. Flora W. Patterson as Sporotrichum minutum.
2 Determined by Dr. A. T. Speare.

Except the collection on May 17, 1916, lary 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 pups
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 larve produced 259
pup, 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. 25

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 pup were in
close proximity. In Tables II and VI, 630 larvee produced 578 pupe.
Of these 247, or approximately 48 per cent, developed a fungus. Of
the ones kept under observation 57 per cent emerged, so that only 43
per cent of the infected pupz were rendered inviable; 43 per cent
of 48 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 ITI it is shown that no infected pups 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@. intestinalis or G. nasalis, though with dead
larve of any Gastrophilus a long growth of fungus quite different
from that met upon living G. haemorrhoidalis pupe is frequently
found.

PREDATORS AND PARASITES.

The dropping of larve 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 @. haemorrhoidalis pupe, 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-HISTORY 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. A total of

11216°—18—Bull. 597-4

26 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

2954 males and 184 females were used in the experiments. All of
these emerged normally from reared material. While some adults
died on the first and second days the maximum longevity was 7 days.
The greater periods were always obtained when the cages were kept
out of the bright sunlight and provided with more or less foliage to
prevent adults from battering themselves against the sides of the
cage. Twenty-seven males and 15 females liberated in the insectary
(9 by 12 by 7 feet) died within 1 to 3 days and were found dead
at a sunny exposure with the wings battered. Cages admitting a
great amount of light and without foliage yielded similar periods of
longevity.

Adults in screen cages 18 by 18 by 18 inches or in a parasite-
rearing box (covered on two sides with glass and arm holes in the
ends) usually died within 3 days. This longevity was slightly ex-
tended when green twigs were frequently replenished.

The longest periods were obtained in wooden boxes 4 by 4 by 6
inches half filled with moist soil and provided with a green twig
and a glass cover. This lessened adult activity, and from the 51
longevity experiments it was observed that the greater periods were
always accompanied with the least activity, while the converse was
also true. These wooden boxes placed in the shade admitted enough
light to permit of activity and flies were often observed to fly about
with the head near the glass and would alight on the green twigs
and rest. The usual longevity under such conditions ranged from
3 to 6 days. Some adults captured in nature were kept under simi-
lar conditions and lived from 8 to 5 days.

Various flowers were supplied as food. for the adults, but in no
case was feeding observed. Sweepings were also made from flowers
blooming in pastures and from alfalfa in bloom, but adults were
never captured under such conditions.

ADULT HABITS.

Adult flies in cages copulate most frequently about noon, the
duration of the act ranging from 3 and 4 to 15 minutes. During the
act the flies usually remain quiet, except for the distinct abdominal
movements of the male. The male usually breaks from the female,
leaving her at the place of copulation, but within a few minutes may
be observed to return. One pair has been observed to copulate as
many as four times within an hour. Males will mate with a freshly
emerged female before her wings are dry, properly unfolded, or the
body of a normal color. In nature the one object of the male seems
to be copulation, and that of the female oviposition. Buzzing in
midair about the horse the male may be easily caught with the hand.
A female is only observed buzzing at a standstill in midair when

2 ai

GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 27

a horse is grazing or otherwise protected from ovipositions. She
usually comes from a distance and strikes at the lips. Her quick
flight seems to pe distinguished by the male, who attempts to mount
her before she oviposits, but the momentum of the two usually carries
the couple to some distant place so quickly that one can not tell
whether copulation actually takes place upon the wing or whether
they fall to the ground. At any rate, they fly for some distance. Ap-

parently the sexes always meet at the horse, the males awaiting the

approach of the females. At times the male encounters an adult
female of G. intestinalis about the horse, and these two may be ob-
served to fall upon the grass at the feet of the horse, usually separat-
ing within a few seconds.

PREOVIPOSITION PERIOD AND OVIPOSITIONS.

Just how soon after emergence copulation takes place is not
definitely known, but it is certainly less than 18 hours. Adults
emerging during the night copulate by noon of the following day
and will oviposit during that afternoon. They will not oviposit in
captivity. On five occasions in which flies emerged normally during
the night, males and females were kept in a box with glass sides and
with green foliage. By noon in each case some were observed to
copulate and when liberated in the afternoon would oviposit. Their
wings were colored with red ink, and when captured they could be
identified easily. Under favorable conditions ovipositions took place
as soon as adults were liberated, usually about 3 hours after copula-
tion. After a lapse of a few minutes they were never to be col-
lected about the same bunch of horses, which is probably due to the
migration of adults and to the movements of the various horses upon
which they oviposit.

A determination of the egg-laying period is important in that it
shows the value of destroying adults at different times during this
stage, but with such short preoviposition and longevity periods and
the inability of flies to feed, the indication is that the flies oviposit
throughout their existence. Dissections of females reared to adults
indicate that they develop from 134 to 167 eggs, the usual number
possibly being near 150.

Unlike G. intestinalis, which may stand in midair and consecu-
tively deposit 15 or 20 eggs at one time, often placing two or more
upon one hair, G. haemorrhoidalis deposits but one at a time and
only one upon a hair. dt leaves the animal for about one-half minute
or longer after ovipositing, but not for so long a time as does
G. nasalis. It never oviposits upon any other portion except the
lips, preferably the portions moistened by saliva. The stalk portion
of the egg is inserted in the pore of the skin at varying depths, but

28 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

the stalk has never been observed to be inserted for its full length.
Often it extends to such a slight depth that after a few days the egg
may be found lying lengthwise upon the lips, yet firmly attached to
the hair. The color, a jet black, so conceals the attachment to the
transparent hair that it appears that the hair extends through the
center of the stalk portion and through a portion of the side of the
ege. The extreme point, however, shows a folding about the hair
which may be attributed to the pressure when it is inserted in the
pore of the skin. Above the stalk portion the hair is attached to
the side of the chamber containing the larva in a similar manner to
the attachment of other Gastrophilus eggs upon the hair.

INCUBATION AND INGRESS OF LARVAE.

Having observed eggs upon both moist and dry portions of the
lips of horses, large numbers in various stages of incubation were
removed and placed in tubes for observation. About 100 were kept
in a test tube, with a moist cotton stopper, at the air temperature
of a hving room. While a variation in color was at first observed,
ranging from a black to a reddish color, after a few days the major-
ity were of a reddish brown. Some were placed upon a slide and
moistened, then by the use of two dissecting needles dead larvee were
removed. No larve had hatched of their own accord, but emerged
when subjected to moisture and friction. In similar tubes which
were kept dry three lots of eggs varying in os were observed and
not a single larva hatched.

Examinations of the inside of horses’ lips revealed numerous holes
accompanied by much soreness which appeared as though the young
larvee hatched and bad burrowed through the lips. Upon dissec-
tions in post-mortem examinations it was disclosed that the injury
was caused by “wild barley” or “ foxtail grass.” This grass was
determined by the Bureau of Plant Industry as Hordeum jubatum.
Its injuries are more noticeable upon lips of livery horses when fed
hay containing this grass. as pastured animals avoid eating it and
the injury is less noticeable. It is worthy of note that this grass,
in addition to its injury upon lips of horses, serves as a winter host
of the black rust which is so destructive to wheat in the Dakotas.

On August 24, 1915, a suckling colt, its mother (a crippled horse)
and another horse were carefully freed of eggs. Twenty-four hours
later a diagram was made showing the exact location of each egg
deposited during this time. Upon the following three days it was
too cloudy for other adults to oviposit, so the horses were not kept
in a barn to prevent further ovipositions, but were left to graze in
the pasture. This allowed ample time for development of the
embryo and of a distinguishing brownish-red color which greatly
aided in keeping track of the eggs.

GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 29

Upon the suckling colt the first egg disappeared upon the ninth
day; the eleventh day, two; the thirteenth, five; and the fourteenth,
_ six. Five other eggs about 1 inch from the mucous membrane and
upon the dry portions yielded dead larvee when examined.

Upon the lips of the cripple horse and within 1 inch of the mucous
membrane 15 eggs were deposited. The first 6 eggs disappeared
upon the seventh day from near the corners of the mouth. The last
ege disappeared upon the eighteenth day.

The normal horse in grazing received 14 eggs within 1 inch from
the mucous membrane. Upon the sixth. day 10 eggs disappeared
from near the corners of the mouth, which was probably five days
from deposition. The other 4 disappeared during the following
three days.

The striking feature of the above three cases is that those eggs
deposited where they received most moisture and friction were the
first to disappear. Prior to disappearance, the color changes, being
first brownish, then a brownish red, finally with a whitish tip, thus
clearly indicating embryonic development. It is also clearly seen
that the amount of grazing affects the incubation, as the normal
horse grazed practically the whole time, the cripple only at times,
while the suckling colt was not observed to graze. There were no
indications that the larve burrowed into the lips, and as well-incu-
bated eggs have produced larvee under moisture and friction when
removed, it is certain that the method of ingress of larve into the
host is not unlike that of G. intestinalis. It is true that eggshells
were never found attached to the hairs after the larve had emerged,
but it is believed the moisture and friction are sufficient to remove
these after the larve leave the eggs and enter with the food.

Incubation records are not confined to the above three cases.
Upon August 24, 1915, one other animal was freed of eggs and
allowed to receive depositions during 24 hours. Upon the moist
portions of the lips 17 eggs were found, while 6 were deposited
upon the dry portions 1 inch from the mucous membranes. Separate
notes give a comparative idea of the incubation. Upon the sixth
day, probably 5 days from deposition, 4 eggs disappeared from the
moist portions and others disappeared the following day. Upon
the dry portions all were present upon the twelfth day. Three of
these when removed contained dead forms and the other 3 disap-
peared from the eighteenth to the twenty-third day.

The day of oviposition in the above cases was favorably followed
by three cloudy days, which prevented other ovipositions. The de-
velopment of the embryo in eggs upon moist portions was quite in
contrast to those upon the dry portions, showing clearly the necessity
of moisture and friction. Such observations indicated that those

30 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

eggs upon the moist portions incubated in from 5 days to a slightly
longer period.

September 9 was preceded by two unfavorable days for oviposition
and was itself very favorable, but was followed by rain and cloudy —
weather until September 15. At this time black eggs were found
upon the dry portions of the lips, while upon the moist portions
the eggs were reddish with whitish tips. Due to the scarcity of
adults, the eggs were not plentiful at this time, and a few days
later one only could be found, upon the dry portions of the lips.

Due to the comparatively long period during which the eggs re-
main attached upon the dry portions of the lips of horses, which is
particularly due to the protection of the thick, coarse hairs surround-
ing them, it is believed that one could be misled easily as to the
most favorable places of deposition of the adults.

GASTROPHILUS NASALIS (Linnaeus).

SYNONYMY.

Oestrus nasalis Linnaeus, 1761.
Oestrus veterinus Clark, 1797.
Oestrus salutiferus Clark, 1815:
Oestrus clarkii Leach, 1817.
Gastrus nasalis Meigen, 1824.
Oestrus duodenalis Schwab, 1840.
Gastrophilus nasalis Schiner, 1861.

OVIPOSITIONS AND LONGEVITY.

The female Gastrophilus nasalis often appears from the grass
about the fore legs of a grazing animal, strikes under the jaws, re-
mains a few seconds, and during that time deposits an egg about
midway upon the hair. The adult then leaves, completely disap-
pearing in the distance, but within a minute or two a similar oviposi-
tion may occur, except that the adult approaches from a distance.
The presence of a person about the head of an animal does not inter-
fere with egg deposition, and the fly may be caught with the hand
when it alights upon the hairs underneath the jaws. It may also
be observed to deposit upon the fore legs or the flanks. Dissections
of the abdomen of reared females show that they are capable of
depositing from 480 to 518 eggs. The attachment of these, as may |
be seen by referring to figure 3, c, extends to almost the entire length
of the egg, and being attached about midway upon the hair, numbers
are concealed unless the hair is brushed aside in making examina-
tions. Often eggs may be observed near the end of the hairs, but
this usually occurs after great numbers have been deposited. ‘Then
it is possible to find two or more eggs upon one hair. As yet the
method of ingress of the larve has not been determined. Dr. C. H.
T. Townsend thinks that the larve burrow through into the mouth

' . GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. a.

and are swallowed. One author believes that a horse in eating will
rub the jaws upon the manger, which hatches the eggs, and that they
are taken into the mouth with the food. The fact that some eggs are
deposited upon the fore legs and portions accessible to the mouth
indicates that the ingress of larve may be similar to that of G. intes-
tinalis.

Longevity in this species seems to be increased over that of
G. haemorrhoidalis, as one reared adult kept under conditions similar
to those of the nose fly lived for 12 days.

LARVA AND PUPA STAGES.

Coincidentally with the appearance of G. haemorrhoidalis at the
anus of horses, the larvae of G. nasalis occasionally may be observed
to pass normally from horses and be found in their droppings. This
normally occurs when larve become fully developed and is often
attributed by farmers to “ a destructive effect of grass upon the bots.”

These larve seldom migrate a great distance, and apparently only
burrow under the droppings for protection. Larve which dropped
normally pupated in from 1} to 2 days, though the prepupal periods
in some cases in which larve were removed in autopsies and cited in
Table VII extended for 7 days. It was observed that the short pupal
periods were preceded by long prepupal ones, and that larve pupat-
ing within 2 days after dropping emerged in from 42 to 45 days.
At Victoria, Tex., Mr. J. D. Mitchell collected a larva under manure,
which pupated October 6, 1914, and emerged 20 days later. To
rear larve collected in autopsies is a difficult task, even though they
are well developed and appear normal, but during the late summer
a small percentage may be reared if they are collected from horses
immediately after death. The larve removed from dead animals
are capable of remaining alive and active for some time, some having
been kept as long as 25 days. Some larve have been observed to
live submerged in water for 12 days.

TaBLeE VII.—Pupal periods of Gastrophilus nasalis, Aberdeen, S. Dak., 1915-16.

od =
rt aes Number 5 eh | Temperatures.
fa = Be emerged. | 3-5
Larvie 2 Ball eee pS
col- Location. I Breeding environ- | | OB iiss - Eafe
lected. 2 ment. 3] of |} 2 sega -
z Ele s | gq | #6 a a3| 8
Ss Cs) 3 ow ga oO
Z, zie (sie ja AeA s
1915 Days. | Days.| ° F.| °F.) °
June 4 Fresh dropping........ 1 | With horse manure.| 1 4 b Ue See pe |= ee 88 | 35 | 65.30
1916.
May 29 }..... CAL ere re cee | Mae ee box; moist | 2 | 44-45 | 1 1S soe 94 | 42 | 67.93
sand. i
June 12 | Dropped from treat-| 4 |..... ADS :< i Str vente 1 SIRs ASS 4 sso. 7 | 94 | 42 }168.98
ment.
July, 107) Wuodenum............ 19 | Dry paperintinbox.} 3 | 25-33] 1 2 | 3-15 | 98 | 41 | 72.77
AP UN StOMACK. ..-..502..5.5 18 | Moist sand.......... 3 ASW Woes 3-8 | 98 | 28 | 60. 26
11 | Duodenum® ...:....... A ee Gone. tas: sce 3 Ea lhe al 1 11 | 95 | 28 | 59.97

1 Horse treated with carbon disulphid.

82 BULLETIN 597, U. S. DEPARFMENT 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 ave 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. 33

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 LARV2.

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 larve 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 larve were removed as late as December 1.

LARVA STAGES.

The attachment of voung larve frequently occurs in almost any
part of the stomach, but, as has been previously stated, they are
found as fourth-stage larve 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 larvee
molt during their development and that there are at least three
stages. No experiments have been reported as to the exact time that
jarvee 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 larvze 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 larvee 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 larve drop. .’

SUBMERGENCE OF LARVZ.

Last-stage larvee 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 larvee 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

GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 35

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
larve 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 larve.

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.

BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

36

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88 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

Some of the tznicides 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 larvee 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. <A list of
indorsements from many countries can be found in articles dealing
with this subject. Originally the disulphid was administered in
12-gram capsules surrounded by aloes, the whole contained in 48-
gram gelatine capsules. In the hands of various workers it has been
subjected to modifications, but each reports that large numbers of
larvee pass as a result of the treatment, and some remark upon the
beneficial effects of the removal of larve upon the animal.

The Bureau of Animal Industry, after employing this treatment
upon a number of horses, recommends the following procedure:

The day preceding the treatment a small amount of hay and a moderate
amount of oats is given in the morning; in the evening food is withheld and a
purgative given—Barbados aloes 1 ounce, or raw linseed oil 1 pint. The day of
the treatment, at 6 o’clock in the morning, give 3 drams of carbon disulphid in
~ a gelatin capsule; at 7 o’clock repeat the dose in the same manner; and at
8 o’clock give the third and last dose, making in all 9 drams of carbon disulphid
in three gelatin capsules.

The above treatment is for the adult horse. For a yearling colt half the
quantity of carbon disulphid used for a mature horse will give the desired
results. If properly administered the gelatin capsule reaches the stomach
intact, but soon dissolves and the carbon disulphid rapidly evaporates, suffo-
cating all bot larve and other parasites with which it comes in contact, but
not injuring the horse. Worms are quite often expelled as well.

The Bureau of Animal Industry calls attention to the fact that
the so-called 4-dram capsules hold about 3 drams of carbon disulphid.

Desiring to know the periods of time required to kill the larve in
the treatments, a number of experiments have been conducted in
fumigating stomach sections to which larve were attached. Only
larvee from those animals that could be secured shortly after the death
of the hosts were used, and the sections with larve in situ were placed
in wooden boxes tightly covered with glass after the box was well

Prey

GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 39

moistened. The sections came from both the stomach and duodenum,
and the tests include all three species of Gastrophilus. After the
short periods of fumigation, which were ineffective with last-stage
larvee, it was observed that the larve lived for some days. At the end
of fumigation tests it was impossible to determine the viability of
larvee except by observing them for a number of days. As will be
seen in Table IX, chloroform was not wholly effective at 4 hours,
but at a later date larve were killed with carbon disulphid within
3 hours. In no case did larve live after subjection to 34 hours of
carbon disulphid. These gases were liberated from absorbent cotton
in the corner of the box, and no larve came in direct contact with the
liquid, as would probably be the case within the stomach. The carbon
disulphid, being soluble in water, evidently reaches all portions of
the stomach, either as a gas or in solution.

BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE.

40

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42 BULLETIN 597, U. 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 disulphid gas is capable of
killing last-stage larve within 34 hours, the ideal time for treatment
of horses would be in the autumn when all larve 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 larvee 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
uot 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

ee

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
egg 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

4 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
flies 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 lips, 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 G. 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.)

++ (eae

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. There was also
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. Itseems 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.

KSEE

\

ASAssay

[ASR SRS al

~~

fra SESS

q
I

Fic. 4.—A bot preventive. 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 larve 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.
Dry tiniWOSsacs- cee -e-See eee 72 to 126 hours. Borax, saturated solution... .-.-.. 40 minutes.
Waiter 22 2 esik eo eccs: see eee 76 to 99 hours. 50 per cent alcohol. .-...-....--- 30 minutes.
Tincturelquassia ta e.---e a= sees 24 to 36 hours. Petroleum, refined .....--.-.---- 30 minutes.
Beta-naphthol in alcohol. ..-.--. 20 to 28 hours. DO eo wcietyack ace eerie 30 minutes.
10 per cent oil of tar emulsion... .| 41 to 48 hours, BORIC ACId pose oc meee Eero eer 13 minutes.
Borax, saturated solution. ....--- 28 to 41 hours. 334 per cent pine tar and 663 per | 1 minute.
DO eater eas c ie emcee comin ete 24 to 43 hours. cent kerosene.

Dr. Guyot’s results compare favorably with those herein reported.
His larvee 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 larve became submerged with the
exception of the posterior spiracles, which remained exposed at the
surface. They are capable of living in this manner for 76 to 99
hours.

. LARV 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-

pee ere Dene edt ae

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 larvee 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 larvee.

TABLE XI.—FXffectiveness of washes upon eggs of Gastrophilus intestinalis,
Aberdeen, S. Dak., 1915-16.

Num- Mortality of larvee.
Date Ex ber ;
Peer Insecticide. posure larvee ery Remarks.
eated. “| @X- as oubt-
amined. Dead. |Living. ful.
1915. Minutes’
Sept. 6 | Refined petroleum.......| 6-18 7 0 7 0 | Engine oil, No. 1.
LS eee MOE sleet ion. aa ata «55 18-31 8 4 4 0 Do.
1916. Hours. :
Sept. 7 |) Kerosene. 3.25.52 522-.0., 24 20 ioe a ee 1
Do...-| 1.35 per cent phenols! .... 24 38 38 0 0 | Reddish brown in color.
Do....| 2 per cent nicotine sul- 24 Wi) 12 5 0
phate.
Do....; Carbolic acid 2 per cent 24 20 19 1 0
pheno
LD) Ts | 0 Oe ee Se ee 24 20 0 20 0
Do....| Nitrobenzine gas. -...-..--- 25 38 38 0 0
Sept. 9 i la acid 2 per cent 5 28 23 0 0 | 2larvee yellow in color.
phenol.
Pesce al ISBLOSCHO= 2.4.52 cise es =m 29 22 5 Fie BAe ee 5 Si larve yellow in
color.
Do....| 0.135 per cent phenols 1... 29 23 23 0 0/3 See larvee yellow in
color.
Sept. 11 | Nitrobenzine gas. ........ 4 34 7 22 5
Peer | se (3 0) Ae Fee ree 10 40 By tal sata 3
100) Sa ee ats (SAR este eee Rae 25 42 42 0 0
Do....| 0.054 per cent phenols 1... 26 40 40 0 0
Wos=2))) kmerosene iS, .- S222 Jae. 25 28 5 p21 eee ae 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 .152|" Keresene.......+.-----24-- 24 55 11 38 6 | 38 larve very active.
Do.1. .| Carbolic acid 2 per cent 24 48 47 0 1
phenol.
Do.!. .| 0.054 per cent phenols !... 25 49 49 0 0
MOt st | KELOSCNO 5c )ce 13) Sas 25-1 147 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 larvae 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 larve were
more active than from any similar treatment. The kerosene seemed
to facilitate the emergence of the larve. 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-fly (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 fly (@. 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 iips, 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 71 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.

r
4
S
7.

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 14 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.
Carbolic acid containing 2 per cent phenols is satisfactory for de-
stroying eggs when applied to the infested parts of the host.

BIBLIOGRAPHY.

AutpricH, J. M. A Catalogue of North American Diptera. 680 pp. Washing-
ton, D. C. 1905. (Smithsn. Misc. 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, 1918.

Anonymous. Bots of horses. In Agr. Gaz. N. S. Wales, vol. 20, pt. 3, pp.
203-208, 6 figs., Mar. 2, 1909.

BRAUER, FrReDRICH. Monographie der Oestriden. 291 pp. Wein, 1868.

BuFFINGTON, G. L. Gastrophilus haemorrhoidalis in the pharynx of a horse.
In Amer. Vet. Rev., vol. 29, No. 1, pp. 37-88, 1905.

CARPENTER, G. H., and Hewirt, T. R. Some new observations on the life history
of warble flies. Jn Irish Naturalist, Dublin, vol. 23, No. 10, pp. 214—
221, Oct., 1914.

CLARK, Bracy. Observations on the genus Oestrus. Jn Trans. Linn. Soe.
London, vol. 3, pp. 289-329, col. pl. 238, 1797.

CLARK, Bracy. An Essay on the Bots of Horses and other Animals. 94 pp., 2
pl. London, 1815.

Crark, 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.). In Jour. Econ. Biol. vol. 5, No. 1, pp. 9-17, 1 fig.,
March 31, 1910. ;

DuaearR, B. M. Notes on the maximum thermal death-point of Sporotrichum
globuliferum. In Bot. Gaz., vol. 27, No. 4, pp. 181-136, Feb., 1899.

FreNcH, ©. The horse bot-fly. Jn Jour. Dept. Agr. Victoria, vol. 1, pt. 7, pp.
693-696, July, 1902. Page 697—Treatment for the bot fly, by J. R.
Weir.

Froggatt, W. W. The bot-fly (Gastrophilus equi). In Agr. Gaz. N. S. Wales,
vol. 19, pt. 3, pp. 229-2338, 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. xxvi—xxxiv and Rept.
8, 1895, pp. xtix—L. The throat bot-fly 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.

HutcHeon, D. Bots or “ Paapjes.” In Agr. Jour. Union South Africa, vol. 8,
No. 2, pp. 194-200, Aug., 1914.

KrOnNING, —. Die Gastruslarvenkrankheit der Pferde in ihrer Bedeutung fiir
die Fohlenaufzucht besonders veredelter Zuchten. Jn Ztschr. Veteri-
nirk., 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.

GASTROPHILUS HAEMORRHOIDALIS AND OTHER BOTS. 51

LucGcer, OTtTo. 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).

MacDoveatr, R. §. Insect pests of domesticated animals. Jn Trans. Highland
and Agr. Soc. Scot., ser. 2, vol. 5, pp. 187-190, 1899.

Macleay, W.S. On the insect called Oistros by the ancient Greeks and Asilus
by the Romans. Jn Trans. Linn. Soc. London, vol. 14, pp. 853-359,
1824. ;

MicHEneER, 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 larvee.

Moore, WittiAM. 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, E. P. Animal parasites IIl. Virginia Agr. Exp. Sta. Bul. 110, pp. 27-37,
fig. mv, March, 1900.

OrMeEROD, ELEANoR A. Report of observations of injurious insects. <
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 Oestridx. (Bot-flies, breeze flies.! Pages T6-
84, fig. 37, pl. 2, The horse bot-fly. (Gastrophilus equi Fab.)

Parker, R. R. Notes concerning Gastrophilus haemorrhoidalis Linnaeus
(Dipt.). Jn Jour. N. Y. Ent. Soc., vol. 24, No. 4, pp. 258-255, figs.
1-2, Dec., 1916.

PrrRoncito, E., and Bosso, G. Sul Metodo di Distruzione delle Larve G’Estro,
Gastrophilus equi, nel Ventricolo del Cavallo. 81 pp. Torino, 1897.
Traduction francaise, Bulletin veterinaire No. 67, 1900, pp. 569-590.

PreRrRonciro, EH. Importanza patologica delle larve d’estro nello stomaco del
eavallo. In Gior. Reale Soc. ed. Accad. Vet. Ital., vol. 51, No. 32, pp.
801-805, Agosto 9, 1902.

SEYDERHELM, K. R., and SEYDERHELM, R. Die Ursache der perniziédsen Animie
der Pferde. Jn Archiv fiir Experimentale Pathologie u. Pharmakolo-
gie, Bd. 76, Hft. 3 u. 4, pp. 149-201, May, 1914.

Swenxk, M. H. The bot-flies affecting live stock in Nebraska. Jn Ann. Rept.
Neb. St. Bd. Agr. for 1908, pp. 327-341, figs. 25-82.

TOWNSEND, C. H. T. On the so-called throat bot. In Ent. News, vol. 3, No. 9,
p. 227. Nov., 1892.

Ve.vu, 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.)

Verritt, A. HE. 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, Cecit. 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-WItstTER, W. Abtreibung von Gastru larven bei Fohlen durch Schwefel-
kohlenstoff. Jn Berliner Thieriirztliche Wochenschr., Jahrg. 1901,
No. 9;-p..156:

WILLISTON, SamurL W. Manual of North American Diptera, ed. 3. 405 pp.
New Haven, 1908.

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