PARASITES OF ANIMALS. 29 
horses. They change to pupx beneath the manure, and the 
flies appear from June to September. It also infests the ass 
and mule, and some authors say that it lives even in cattle. 
The Gastrophilus pecorum is densely covered with yellow | 
hairs, with a band of black hairs on the thorax behind the 
suture, in the male. The female is yellowish brown, the 
abdomen black, with yellowish hairs at its base, as well as 
on the thorax. The wings are grayish or light brownish, 
clouded with yellowish brown. The larve are similar to 
those of the more common G. equt, and have similar habiis. 
The flies appear at the same time. 
The Gastrophilus hemorrhoidalis, or red-tailed bot-fly, is 
a small species, easily distinguished by the bright orange-red 
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 middle blackish, in strange contrast- 
with the orange-red of the end. The larve have the same 
habits and are found in the same situations with those of 
the common bot-fly, which they much resemble, except that 
they are whiter and smaller, their length not exceeding one- 
half or five-eighths of an inch. They change to pupe within 
two days after leaving the horse, and the pupe are deep red. 
They remain in the pupa state about two months, and the flies 
appear from the last of June till the cool weather of autumn. 
In depositing the eggs, the female fly differs in habit from 
the common bot-fly, for she selects the lips and nose of the 
herse as the most suitable place for this purpose. In deposit- | 
ing her eggs she therefore causes the horse much trouble and 
uneasiness. Mr. Clark described the operation as follows: 
“ At the sight of this fly the horse appears much ayitated, 
and moves his head backwards and forwards in the air to 
baulk its touch and prevent its darting on the lips; but the 
fly, waiting for a “favorable opportunity, continues to repeat 
the operation from time to time ; till at length, finding this 
mode of defence insufficient, the enraged animal endeavors 
to avoid it by galloping away to a distant part of the field. If 
it still continues to follow and tease him, his last resource is 
in the water, where the @strus is never observed to follow 
Digitized by Microsoft® 
