220 SHEEP GAD-FLY. 
detected, hence few persons have ever seen it, and judging 
from the fact that it is not represented in most of the larger 
collections in this country even entomologists have not fre- 
quently observed it. Fig. 181 was made by J. W. Folsom 
from a specimen in the Cambridge museum. It resembles a 
very large house-fly; the upper parts of the head and thorax 
are of a dull-yellow color and are covered with little elevat- 
ed, round, black spots and still smaller brown specks. The 
five-jointed abdomen is velvety and variegated with brown 
and yellow colors; the feet are brown; the swollen underside 
of the head is white; the eyes are purplish-brown; three eye- 
lets are found upon the top of the head, and two very min- 

Fig. 180.—Sheep Gad-fly; @, adult; b, larva; c, puparium. After Brauer. 
ute feelers in front. As the fly possesses no mouth it can 
take no food; and it is only active during the warmer days 
of summer, when it attempts to deposit the young larve in 
the nostrils of sheep. Ofcourse these larve come from eggs 
that were already hatched in the oviduct. Both sexes are 
nearly of the same size, measuring from 10 to 12mm. in 
length. 
This parasite is found throughout Europe, Asia, Africa, 
and the Americas. Very likely it was introduced into the 
United States with the earliest flocks of sheep; more recently 
it has been introduced into Chili. 
The Sheep Gad-fly flies only during dry and warm 
