INSECTS AND OTHER ORGANISMS 



421 



The botflies are representative of a large group of insects 

 that are often injurious to horses and cattle (see Fig. 223). 



Fig. 222. The codling moth [Caf-pocapsa pomonella) 



a, where the egg is laid on the apple ; /', larva, the " worm " of the apple ; c, cocoon ; 

 fl', pupa; <", adults. (About natural size) 



The OX tvarble lays its eggs on the cow. It is not certain 

 whether the larvae work their way through the skin or from the 



Fig. 223. The horse botfly [Gastrophilus eqici). (Somewhat enlarged) 



The egg, a, is laid on the hair of the horse and is swallowed, together with the larva, h, 

 in the saliva. In the stomach the larvae attach themselves, often causing serious irri- 

 tations and incapacitating the animal for work. The larvae escape from the host with 

 the excrement, and then pupate in the ground, c, pupa; (/, adult 



alimentary canal. They finally lodge under the skin and thus 

 ruin millions of dollars' worth of hides, besides making the 

 animals sick and reducing their milk and beef values. 



