THE DIPTERA OR FLIES 



43 



passages connected with the nose and sometimes produce 

 fatal results. 



The larvae of hot flies commonly inhabit the stomach or 

 intestine of horses, cattle and sheep, attaching themselves 

 to the mucous membranes of the walls and often causing 

 great distress to the afflicted animal. The eggs of the 

 horse bot fly are laid usually upon the hairs of the fore 

 legs of the horse and gain access to the stomach when the 

 horse licks itself. The larvae remain in the alimentary 



FIG. 33. Larvas of bot flies attached to the walls of the stomach of a 

 horse. (After Osborn.) 



canal during the fall and winter and pass out in the spring 

 when they go through their pupa stage in the ground. 

 The related warble flies cause much discomfort to cattle 

 since the larvae spend most of their life just beneath the 

 skin. The full grown larva may reach a length of an inch. 

 When ready to pupate it gnaws a hole through the skin 

 of its helpless host and drops down and burrows in the 

 ground. In this country the damage done to hides is 

 estimated at $50,000,000 per year. 



