ANIMAL PAEASITES AND PABASITIC DISEASES 329 



entrance to the mouth, and eventually to the stomach. Once 

 here they attach themselves to the mucous lining and rapidly 

 develop into the full-grown bot. Most horses harbor a few, 

 some as many as two or three hundred (Fig. 83). 



The bots remain in the stomach for about ten months, or until 

 May or June, sucking blood for their sustenance. Then they 

 loosen their hold, pass along through the bowels with the ingesta, 

 and escape in the feces. If conditions are favorable they burrow 

 into the soil and form a pupa. Some four or six weeks are passed 

 in this stage, after which a perfect fly emerges ready to lay eggs. 



Fig. 83. — Bots attached to the lining of the horse's stomach. Full-grown larva 

 of the Gastrophilus equi. (U. S. Dept. of Agric, Division of Entomology.) 



Many different remedies have been used to free horses from 

 bots, but all are of little or no value. Drugs strong enough to 

 cause the bots to loosen their hold will injure the walls of the 

 stomach, so cannot be used. Bots seldom cause serious injury, 

 but may produce irritation and lack of thriftiness if present in 

 large numbers by interfering with gastric secretion. In view of 

 the fact that bots and many other internal parasites pass from 

 the host as soon as the animals are turned out in the spring, treat- 

 ment should be given in early winter to be effective. Prevention 

 is easiest and most satisfactory. Clip off all eggs, found attached 

 to the hair, with a sharp razor or destroy them by singeing with a 

 flame. 



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