354 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



four months or more of infecting any person or other animal 

 that it bites. 



G. pal palls is found only in tropical Africa and is limited in its 

 distribution there to certain very definite, narrow, brushy 

 areas along the water's edge. If these places can be avoided 

 there seems to be little danger. Those who are fighting the 

 disease have found that if the brush in the vicinity of watering- 

 places and ferry-landings is cleared away such places become 

 comparatively safe. These flies do not lay eggs but produce 

 full-grown larvae which soon pupate in the ground. 



Trypanosoma cruzi is another species that causes a serious, 

 often fatal, disease in Brazil. It is transmitted by the bug 

 Conorrhinus megistus, belonging to the family Reduviidce, order 

 Hemiptera. This bug has habits very similar to those of the 

 bedbug, inhabiting houses and biting sleeping persons. Kala 

 azar, a chronic disease occurring in the Mediterranean region 

 and in many places in Asia, is caused by a parasite, Leish- 

 mannia donovani, somewhat resembling the trypanosomes. 

 The infection is probably acquired by the bite of an insect, 

 perhaps a bedbug. A similar disease, called Delhi boil, occurs 

 in the same region and also in Brazil, and it is thought that 

 infection may be carried to a wound by house-flies. 



There are several diseases of domestic animals caused by 

 trypanosomes. Tsetse-fly disease, or nagana, is one of the 

 most serious scourges of domestic animals in Central and 

 Southern Africa. In some sections it is almost impossible to 

 keep any kind of imported animals on account of this disease, 

 which is caused by Trypanosoma brncei. This parasite is to 

 be found in several different kinds of native animals which seem 

 to be themselves practically immune but are always a source 

 of danger when non-immune animals are introduced. The 

 tsetse-fly, Glossina morsitans, one of the most dreaded insect 

 pests of Southern Africa, is largely responsible for the trans- 

 mission of this disease, but one or two other species of tsetse- 

 flies may also act as hosts for the parasite. All through Asia, 

 in parts of Africa and in the Philippines there is a very serious 

 disease of horses and cattle known as surra. This disease, 

 which also affects camels, elephants, buffaloes and dogs in 



