190 SCHOOL ENTOMOLOGY 



adjacent woodwork should be liberally treated. Another 

 application should be made in about two weeks. Unless 

 the walls and woodwork have become very badly infested, 

 thorough and persistent treatment will be effective, but in 

 such a case the building should be fumigated with hydro- 

 cyanic acid gas (see page 336). 



117. Horse Bots.* Horses running in pasture are com- 

 monly infected with bots. They are the maggots of a large, 

 brown, hairy fly, looking much like a bee, with a wing ex- 

 panse of about three-fourths of an inch. Horses instinct- 

 ively become nervous upon the approach of these flies, 

 which lay their small yellowish eggs, sometimes called "nits," 

 on the hair of the fore legs, shoulders and flanks. When the 

 horse licks these parts the eggs hatch and the little maggots 

 attach themselves to the tongue and then work their way 

 down the alimentary canal to the stomach. Here they 

 attach themselves to the walls, often occurring in such num- 

 bers as to form large patches. They continue growth during 

 the winter and the next spring they pass out through the in- 

 testines with the excrement and burrow into the ground, 

 where the pupal stage is passed. The adult flies emerge 

 a month or so later, there being but one generation a year. 

 The exact amount of damage which the bots do is a matter 

 of some dispute, but it is evident that when present in 

 large numbers they must irritate the lining of the stomach 

 and must absorb considerable nutriment both from the 

 stomach wall and the food in it. Cases have been observed 

 in which they have penetrated the wall of the stomach 

 and caused death. 



During late summer horses kept in pasture should be 

 examined every two weeks and the eggs destroyed or re- 

 moved. This may be effected by washing the eggs with 

 * Gastrophilus equi Fab. Family CEstridx. See page 139. 



