47$ 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. 

 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 a.re 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 



