14 
HORSE. 
Horse Bot Fly; Horse Bee. Gastrophilus equi, Fab. 
Gastrophilus equi. —1, male ; 2, curved extremity of abdomen of female ; 3, 
maggot; 4, mouth hooks ; 5, spiracles at extremity of tail of maggot— all greatly 
magnified, after Brauer; nat. size given in descriptions. 
In the case of the “ Horse Bot Fly,” sometimes also called the 
“Horse Bee,” the method of infestation may be shortly described 
as follows. The female fly lays her eggs for the most part on the 
hairs of the mane, shoulders, or on the fore legs, where they can 
be reached by the tongue of the horse. By this means the eggs, 
or the maggots hatching from them, can be readily licked into 
the mouth, and thence the maggots pass down into the stomach. 
There they fix. themselves by their mouth hooks, and feed by 
suction, till after three-quarters of a year or more, when they are 
full grown, they loose hold, and pass out of the horse with the 
rejectamenta. In these, or in the ground, they bury themselves 
and turn to a hard dark-coloured chrysalis, in which the fly forms, 
and from which it comes out (in summer) in about six or eight weeks. 
This is the method of life-history given shortly, but the following 
details describe the chief points of the infestation, of which the 
knowledge is commonly needed for practical use. 
The flies are from half an inch to somewhat more in length, 
and clothed with wool or hair. The body between the wings with 
reddish or olive brown hair and some black or dark markings; 
abdomen yellowish brown, also with dark or black markings, but 
the mixture of black, whitish, yellowish, and brown hairs makes it 
very difficult to describe the colouring clearly, and the descriptions 
by different writers vary much. The two wiugs are transparent 
