BOT-FLIES. 213 
ing themselves in the air with the telescopic ovipositor 
directed downwards and forwards. When not disturbed by 
the animal the female deposits an egg upon those parts of 
the horse most accessible to that animal’s tongue, or upon 
the fore-limbs, knees and shanks, and this operation is re- 
peated so that many hundreds of eggs can be found upon 
the same animal. Horses in stables are not molested. The 
egg, one of which is shown on a hair in the illustration, is at 
first white, but soon becomes yellowish-white, is conical, 
about 1.25mm. long, finely transversely striated and provided 
at the upper end with a peculiar cap obliquely truncated. 
Such eggs are fastened to the hairs at their narrower end by 

Fig. 175.—Bot-fly of horse; male; abdomen of female, and egg. Greatly en- 
larged. Original. 
means of a sticky material, which secures them so well in 
position that they can not be removed simply by brushing, 
as has been frequently stated. These eggs soon hatch, the 
time varying greatly according to the climatic conditions, 
into very active larvee, which, crawling over the skin, cause 
an itching that-induces the horse to lick such places. In 
some cases the eggs themselves are removed by licking, and 
thus reach the stomach; in other cases the very young larvee 
crawl into the mouth, being enabled to do so by two 
black hooks in the head, which are bent almost at right 
angles. In this manner the larve reach the interior of the 
horse, where they fasten themselves to the mucous membrane 
of the stomach. This is accomplished by means of hooks 
found upon the head of the larve; the head gradually sinks 
