ORDER VII.—TW0-WINGED INSECTS, OR FLIES. 297 
Bot-fly (@Zstrus veterinus), which deposits her eggs under the 
throat of the horse. The maggots then enter the mouth 
of this animal, are carried into the stomach, and go through 
the intestines like the former ones, producing the same ef- 
fects. 
The Ox Bor-rry (@strus bovis) is nearly one inch long, 
has a yellow breast, with a black band across it, while the 
hind body is white and yellowish red, covered with hair, 
and resembling that of the bumble-bee. The female of 
this insect, with its long, horny ovipositor, pierces the skin 
of the ox or cow, generally on the back of the body, and 
deposits therein her egg, which is hatched by the caloric 
of the animal. The maggot, as soon as hatched, finds its 
nourishment in the cavity where it was born, and, as it de- 
velops, causes the skin to swell, forming a protuberance 
like that caused by gall-wasps on plants, and finally pro- 
ducing a running sore. In the month of May there may 
frequently be seen on the backs of young cattle from four 
to twenty such boils, each an inch thick, with an opening 
from which flows a purulent discharge. These maggots 
live about four weeks under the skin, when they come out 
from their disgusting and filthy abode, fall to the ground, 
change into pupz, and a week after are transformed into 
the perfect fly. The female of this insect is so prolific that 
a single one may infest a whole drove of cattle with its 
egos. 
The Surep Bot-rry (@strus ovis) has transparent wings 
spotted at the lower margin, a brown spotted hind body, 
with yellow and brown lateral lines, sparingly covered with 
hairs. This insect dces not show much inclination to fly 
or to walk, and is very slow in its motions. The female 
lays its eggs on the nostrils of sheep, whence the hatched 
maggots creep into the frontal cavity, and there develop 
until fully grown, when they come out, fall to the ground, 
and change into pup, in which state they remain about 
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