THE FLIES: DIPTERA 71 



Flesh Flies. Equally well known are the blowfly (Calliph'- 

 ora vomito'ria) and the bluebottle (Lucil'ia cse'sar), which 

 deposit their eggs on fresh and decaying meat. These flies 

 hatch within a day, and the larvae greedily devour the de- 

 caying material, not hesitating, when that task is finished, 

 to devour each other. 



The history of South Africa has been very largely con- 

 trolled by the biting flies known as the tsetse flies of the 

 genus Glossi'na. There are several species of these flies. 

 By their bite they infect man and domestic animals with 

 minute disease-producing protozoa known as trypanosomes. 

 African sleeping sickness, one of the most deadly human 

 diseases known, is produced by the bite of the tsetse fly. In 

 large parts of South Africa practically all horses and cows 

 are killed off by a disease known as nagana. Like human 

 sleeping sickness this also is produced by trypanosomes, 

 carried by the tsetse flies. The native game animals have 

 recently been found to harbor the protozoa without suffer- 

 ing any apparent ill effects. 



Botflies. The botflies are parasites in the larval stage; 

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

 nearly one hundred species known, infesting various ani- 

 mals, living either under the skin, in the nostrils, or in the 

 stomach. The botfly of the horse (Gastroph'ilus e'qui, 

 Fig. 48) attaches its eggs singly by means of a sticky sub- 

 stance 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. The larva then attaches itself to the 

 lining of the stomach by means of hooks which encircle its 

 mouth, and for nearly a year feeds on the substance of the 

 stomach wall. The pupal stage is passed in the earth, which 

 is reached through the alimentary canal. A few of these 

 parasites do no particular harm, but a large number may 

 cause death. 



