60 



GENERAL ZOOLOGY 



The famous tsetse fly of South Africa (Crlossi'na mor'sitans), 

 whose bite is almost certainly fatal to the ox, horse, and dog, 

 belongs to the same family as the species just mentioned. It 

 has been found almost impossible to build up certain sections 

 of South Africa, owing to the prevalence of this insect. An 

 English army surgeon has lately discovered that by its bite 

 it introduces disease germs from sick animals into the blood 

 of healthy ones. 



Bot-Flies. The bot-flies are parasites in the larval stage ; 

 that is, they live in the bodies of other animals. There are 



B D 



FIG. 38. Metamorphosis of Horse Bot-Fly. (After Osborn, Bulletin No. -5, N.S., 

 United States Department of Agriculture, Division of Entomology) 



A, egg on hair of horse (natural size) ; B, egg on hair of horse (enlarged) ; 

 C, young larva (enlarged) ; D, young larva (much enlarged) ; E, spines ; 

 F, full-grown larva (twice natural size) ; G, female (natural size) 



nearly one hundred species known, infesting various animals, 

 living either under the skin, in the nostrils, or in the stomach. 

 The bot-fly of the horse (G-astroph'ilus e'qui, Fig. 38) attaches 

 its eggs singly by means of a sticky substance to the hairs of 

 the legs, where the larva is pretty sure to be swallowed when 

 the animal licks or bites its legs to remove the irritation. 



