212 BOT-FLIES. 
that begins at the posterior end and progresses toward the 
head enables them in a few minutes to free themselves, which 
they usually do in the morning hours. Upon the ground 
they creep about until they meet some obstruction, when 
they burrow from one to two inches below the surface, and 
remain as in the gastrophilus species.” 
The bot-flies which infest domesticated animals have 
been transported with their hosts to nearly all parts of the 
globe; others are found in wild animals. These flies can be 
divided into three groups, according to their mode of exis- 
tence: 1, Gastric, or grubs that live in the stomach of their 
host; for example the Bot-flies of the horse (fig. 175). 2, 
Cephalic, or grubs that live in the nostrils and frontal sinuses 
of their host; for example, the Sheep Gad-fly (fig. 181). 3, 
Cutaneous, or grubs that cause and live in tumors just below 
the skin; for example the Ox Warble-fly (fig. 183). 
The Bot-flies belonging to the genus (Gastrophilus are 
well-known parasitic insects, most of which live in their 
larval stages in the stomach of horses. Atleast threespecies 
are found in Minnesota, but as all possess a very similar life- 
history only that of the best known species will be given. 
THE COMMON BOT-FLY. 
( Gastrophilus equi Fab.). 
The illustration (fig. 175) shows this wooly insect which 
resembles in many ways a common honey-bee. It has a 
fawn-colored face, which is covered with a silky down; the 
thorax is covered with reddish hairs, and has, very fre- 
quently, a black transverse band. The abdomen is yellow- 
ish or reddish-brown with irregular darker spots; that of 
the female ends in a long ovipositor bent around, as seen to 
the left of the figure, while that of the male is obtuse. The 
wings in this species are transparent, and have near their 
middle a transverse smoky bar and two spots of the same 
color near the tip. The fly measures from 12 to 14mm. 
During the whole summer these insects can be found, but 
principally during July and August, when the females are 
most active during the warmer part of the day; they 
may be seen buzzing about horses, asses and mules, balanc- 
a 
