492 



OTHER BLOOD-SUCKING FLIES 



tsetse fly. 

 Alcock.) 



mouthparts when the latter are not in use, and it is thus the palpi 

 alone that are seen when the long blunt-tipped proboscis is ob- 

 served. The characteristic form of the antennae is shown in 

 Fig. 229. The thorax is relatively large and 

 (juadrangular, with a characteristic pattern 

 which is, however, inconspicuous in some 

 species. The abdomen may be nearly uniform 

 dark brown, or pale brown banded with a 

 dusky color. The male has a large oval swell- 

 ing on the under side of the last segment of 

 pyKium'o'f m^uTe the abdomeu, the " hypopygium " (Fig. 230), 

 (.\fter which forms a good distinguishing mark be- 

 tween the sexes. 

 Distribution, Habits, etc. — Tsetse flies, fortunately, are lim- 

 ited in their distribution to the middle portion of the African 

 continent from south of the Sahara Desert to the northern borders 

 of British South Africa (Fig. 

 231, = ). One species occurs 

 in the southwestern corner 

 of Arabia. Tsetses are b>- 

 no means evenly distributed 

 over this great area, )jut aic 

 limited locally to "fly-belts." 

 chiefly along rivers and at 

 the edges of lakes. All the 

 factors which cause the 

 " patchy " distribution of 

 tsetses are not known; there 

 are cases where close limita- 

 tion to certain areas cannot 

 l;e explained by any known 

 requirements of the flies. 

 Different species vary in 

 their choice of habitats; 

 (rlossinn jmlpalis (Fig. 230), 

 the carrier of CJambian ami Nigerian sleeping sickness, is 

 seldom fouml iiioic than 'M yards from the cdfic of water 

 where a sandy bottom and overhanging vegetation is abun- 

 dant, though it follows animals and man for a few hundred 

 yards from such positions. This species is found onl>' in shady 



Fig. 231. 

 flics. 



\\\ 

 /// 



.\pproxiinatt' r:iiin<'S of tsetse 

 (Conipilfd from Austen.) 



ranKe of entire genus glossina 

 r;incc of fj. morsituns 

 rannf of o- iMlfxili" 



