478 
THE STUDY OF INSECTS. 
form except that the female (Fig. 585) has the end of the 
abdomen elongate and bent forward under the body. It is 
most often seen flying about horses, which 
have an instinctive fear of it. The eggs are 
attached to the hair, chiefly on the legs and 
shoulders of the horse. The larvae are licked 
off by the horse and swallowed with its food. 
Fig * 5 8 5- When the larvae reach the stomach they fasten 
themselves to the inner coat of it, and remain there until 
full-grown. Then they pass from the animal with the dung, 
and crawl into some protected place, where they transform 
within a puparium. 
The Oxwarble, Hypoderma lineata (Hyp-o-der'ma lin- 
e-a'ta).—The larva of this species is the common pest that 
lives in the backs of cattle just beneath the skin. The adult 
lays its eggs on the backs of cattle ; and it has been supposed 
that the young larvae penetrate the skin, thus reaching the 
place where they are commonly found. But Dr. Cooper 
Curtice has recently shown that the larvae are licked off 
from the back by the cattle and swallowed. He found the 
larvae in large numbers in the walls of the oesophagus in 
November; later, about Christmas-time, they appeared sud¬ 
denly, and in large numbers under the skin of the back. 
The course of their migration from the oesophagus to the 
skin has not yet been traced. The greater part of the 
growth of the larva is made within the tumor beneath the 
skin. When full-grown it passes out through a hole in the 
skin and undergoes its transformations on the ground. Dr. 
Curtice has also shown that the most common oxwarble of 
this country is Hypoderma lineata and not Hypoderma bovis , 
as has been supposed. 
The Sheep Bot fly, CEstrus ovis (CEs'trus o'vis).—The 
eggs of this species are laid in the nostrils of sheep. The 
larvae pass up into the frontal sinuses and into the horns 
when they are present. Here they feed upon the mucus. 
They are very injurious to sheep, causing vertigo or the 
