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DIPTERA. 79 
forelegs, under side of body, and sometimes even the mane and other 
parts of the body, most commonly, however, on the forelegs and shoul- 
ders. The method of deposition has been frequently observed. The 
female hovers near the horse in a position which appears to be nearly 
vertical, since the body is bent downward, and the extended abdomen 
is thrust forward under the body to its full extent. The fly then darts 
toward the horse, the egg is glued to the hair in an instant and the fly 
retreats a yard or two to hover till another egg is ready to be deposited. 
The operation is repeated at very short intervals, so that hundreds of 
eggs may be deposited upon a horse in a comparatively short time. 
The eggs are held by a sticky fluid, which quickly dries and thus glues 
them firmly to the hairs. They are about one-sixteenth of an inch in 
length, and taper a little toward each end, though the attached end is 
the smaller. The outer end is provided with a little cap (operculum), 
which is set quite obliquely to the axis of the egg, though some authors 
represent it aS cutting the egg square off at the end. This cap or 
operculum breaks or is pushed off when the grub hatches. Bracy 
Clark wrote that the eggs do not hatch until twenty-five to thirty days 
old, while Joly found them to hatch in tour or five days. Verrill says: 
The eggs contain more or less perfectly developed larve when laid; and when they 
are mature or have been a few days attached to the hair, they burst open and allow 
the young to escape almost instantaneously, when moistened. Thus, when the horse 
licks itself or its companions, the moisture hatches the eggs and the young larve are 
transferred to the mouth by the tongue or lips, and thence to the stomach, where 
they fasten themselves to the lining membrane by their two hooks. 
Evidently some such condition is essential to the hatching of the eggs, 
as we have removed hairs containing eggs from the horse and keeping 
them where not subject to moisture they failed entirely to hatch, and 
even after a year’s time do not appear greatly shriveled. Doubtless 
they must hatch in a comparatively short time or lose their vitality, 
for moisture does not effect a hatching in those long kept away from 
the horse. The empty egg shells may cling to the horse for some time 
after the hatching of the larve and give it the appearance of being 
coated with eggs. Examination, however, will readily disclose the 
absence of the operculum in the hatched eggs. 
In order to determine more certainly as to the exact condition of 
hatching and the time involved, I undertook in [893 some observations 
which were reported in Bulletin No. 32 of the Division of Entomology 
(pp. 46-49). Eggs collected from a horse while flies were depositing, 
and therefore probably not long laid, were opened at different times by 
rubbing them with a moistened finger, simulating as nearly as possible 
the action of the tongue in licking the body. While the larvie appeared 
to be fully formed during the first three or four days after deposition, 
the eggs hatched with difficulty and the larvie seemed quite inactive, 
and all larvee that were freed in this manner up to the tenth day were 
hatched with difficulty, though the larve at the end of this time were 
becoming fairly active. 
