EEPEODUCTION IN ZULULAND TSETSE. 271 



" Two theoi'ies are held. 



" A. — That the disease is caused by the bite of the Tsetse-fly. 

 This is the European theory, and, as everyone knows, has been 

 popularly prevalent ever since white men first landed in South 

 Africa. 



" B. — That the disease is caused by the presence of large 

 game, the wild animals in some way contaminating the grass or 

 drinking-water by then- saliva or excretions. This may be called 

 the native theory " (p. 2). 



A, — The Tsetse-Fly. — The Tsetse "acts as a carrier of a 

 living virus, an infinitely small pai^asite, from one animal to 

 another, which entering into the blood stream of the animal 

 bitten or pricked, there propagates and so gives rise to the 

 disease " (p. 2). 



Position of the tvings ivJien the fly is at rest. — " When the 

 Tsetse is at rest the wings fold over one another like the blades 

 of a pair of scissors, and give the fly an elongated appearance 

 (Plate I., figs. 1 and 4) " (p. 2). 



Mode of reproduction. — " The Tsetse-fly does not lay eggs as 

 do the majority of the Diptera, but extrudes a yellow-coloured 

 larva nearly as large as the abdomen of the mother. This larva 

 is furnished with a black hood at one pole and two minute spikes 

 at the other. It is annulated and consists of ten segments. 

 Immediately on being born the larva creeps about with a good 

 deal of activity, evidently searching for some cover or hole in 

 which to hide. Having found a resting-place, it immediately 

 begins to change colour, and after a few hours has turned into 

 a jet-black hard pupa or nympha (Plate I., figs. 2 and 3). 



" If these pupal cases are placed in a perfectly dry place, as 

 in a wooden box, the perfect insect hatches out in about six 

 weeks. From this it would appear that the life-history of this 

 species of fly is very simple, it only being necessary for the 

 female insect to deposit the larva on the surface of the soil or in 

 the grass, when the larva creeps into the nearest shelter, in a 

 few hours becomes hard and black, and in five or .six weeks 

 hatches out into the fully-developed Tsetse-fly. 



" It has often been surmised that this fly is bred in buff"alo 

 dung, but from a consideration of the foregoing facts it is evident 

 that nothing is wanted except any moderately dry place " 

 (PP- 2-3). 



Habits of Tsetse-flies. — " It is astonishing with what rapidity 

 the flies fill themselves ; in as small a space of time as twenty or 

 thirty seconds a fly will become swollen out like a balloon with 

 bright red blood. 



" On entering ' Fly Country,' one is not left long in ignorance 

 of the presence of the Tsetse. The natives may be seen slapping 

 their naked legs, the dogs bite round, and the hoi'ses kick. The 

 Tsetse, however, may be said to be somewhat local in its distribu- 



