DIPTERA 



49 



FIG. 28. Botfly of the horse, 

 larva and adult. Natural size. 

 After Selenka. 



Later these are licked off by the animal and taken into 



the stomach, where they develop into grublike larvae. 



After attaching themselves to the 



walls of the stomach, they are 



nourished by the blood and lymph 



of the host until the following 



spring, when they pass on through 



the canal, burrow into the ground, 



and transform into the adult 



about two weeks later. Bots 



are sometimes fatal to the 



horse. 



The ox warble or heel fly (Hypoderma lineata) is a 

 pest to cattle raisers. The eggs deposited in the hair 

 are licked off by the cow, and immediately hatching pene- 

 trate the esophagus to wander several months among 



the tissues, finally 

 reaching their des- 

 tination beneath 

 the skin on either 

 side of the back- 

 bone. The lumps 

 in these regions in 

 spring and early 

 summer reveal the 

 presence of the in- 

 sect. In late sum- 

 mer the maggot 

 emerges, drops to 

 the ground, and transforms to the adult. Stratton estimates 

 that this parasite in the United Kingdom causes a loss of 



FIG. 29. Ox warble or heel fly. a, adult ; i, larva 

 removed from beneath the skin of the cow. Nat- 

 ural size. From Insect Life. 



