248 ENTOMOLOGY 



(Fig. 272) instead of being separated at the tips. The proboscis projects 

 forward, and is stout, owing to the ensheathing palpi; the base of the 

 labium forms a prominent bulb. These are the moie conspicuous char- 

 acters that serve to distinguish tsetse flies from other blood-sucking flies 

 with which they might be confused. 



The mode of reproduction as described by Brauer is similar to that 

 of the group of parasitic flies known as Pupipara. The fly produces a 

 full-grown larva, which at once creeps to some resting place and forms a 

 black puparium. 



Tsetse flies frequent hot, humid regions, near bodies of water, and 

 are restricted to shaded situations, never occurring on the open plains. 

 Both sexes are bloodthirsty but bite only during the daytime as a rule; 

 though they may bite at night when the moonlight is bright. Travelers 



take advantage of the habits of the fly to 

 journey by night; spending the day in an open 

 uninfested place. 



Nagana. The colonization of South Africa 

 has been greatly retarded by nagana, a disease 

 invariably fatal to the horse, donkey and dog, 

 and usually fatal to cattle, but not affecting 

 man. Livingstone and other explorers in re- 

 gions where nagana is prevalent record their 

 having been bitten by tsetse flies thousands 

 of times with no result other than a slight 



irritation. 



FIG. 272. Tsetse fly, Glossina ~. . ~ , . , . . 



morsitans. X2>. Bruce was the first to prove the identity of 



nagana and tsetse-fly disease and to demon- 

 strate the role of the fly in the transmission of the disease. His investi- 

 gations, begun in Zululand in 1894, are of fundamental importance and 

 have given an immense stimulus to the study of trypanosomes. 



After finding that no bacteria were concerned in nagana, Bruce dis- 

 covered trypanosomes in the blood of cattle affected with the disease. 

 He inoculated their blood into healthy horses and dogs and in a few days 

 the blood of these animals was teeming with trypanosomes. Then he 

 took healthy animals from the mountain on which he had located down 

 into the "fly country"; there they contracted the tsetse-fly disease and 

 showed in -their blood trypanosomes indistinguishable from those of 

 nagana. 



Horses taken into the fly country but not allowed to eat or drink 

 there, took the disease; furthermore, supplies of grass and water brought 



