4 USUAL HAUNTS OF TSETSE-FLIES. 



also somewhat tectiform, i.e. they meet together at the base Hke 



the roof of a house (Fig. 3). The antennae, too, afford a further 



means of distinction. While the antennae of Tsetse-flies, as 



of all other Muscidae, are drooping, those of Haematopota 



project horizontally in front of the head, and being of some 



length are readily seen. 



In those parts of Africa in which Tsetse-flies 



Where Tsetse-flies Q^^ur they are not found everywhere, but are 

 are usually found. •' . . 



generally confined to particular tracts, which 



are known as " Fly-belts," and are often of very limited 

 extent. We are still somewhat in the dark as to the 

 factors that determine the limits of these " belts," but, 

 although Tsetse are undoubtedly dependent upon the blood 

 of vertebrates for their continued existence, all recent 

 evidence goes to show that the most important element is 

 the physical character of the locality, and, probably, its suita- 

 bility as a breeding-ground. As a general rule it may be said 

 that Tsetse-flies are usually met with in damp, hot localities, 

 either on the borders of rivers or lakes, or at any rate not far 

 from water ; this, however, applies more especially to the species 

 belonging to the Glossina paljjaUs group ; other Tsetse-flies, 

 especially those of the Glossina morsitans group, are often found 

 at a considerable distance from water. Cover in the shape of 

 more or less thick bush or forest, shady trees, or reeds, is 

 essential, and Tsetse-flies are absent from open grass plains. 



The mode of reproduction in Tsetse-flies — first 

 Reproduction. ,. , , c<- t\ • i t? j ■ i • 



discovered by oir David Bruce, during his 



classical investigations in Zululand in 1895-96 — is extremely 



remarkable, since, instead of laying eggs as do the majority of 



Diptera, the pregnant female produces at each birth a single 



full-grown larva, which, while retained within the oviduct of the 



mother, is nourished by the secretion of special glands, and on 



being born crawls away into some hiding place and immediately 



changes into a pupa. Observations show that, under normal 



conditions as regards temperature and humidity, the extrusion of 



larvae takes place at intervals of from about eight to eleven days. 



The Tsetse-fly larva is a yellowish, footless maggot, nearly as 



large as the abdomen of the mother, with a shagreen-like 



integument, and the anal extremity (twelfth segment) produced 



into a pair of large, black, granular prominences (the tumid lips), 



separated by a pit-shaped depression containing the stigmata or 



respiratory apertures. 



