DISTINCTIVE CHARACTERS OF TSETSE-ELIES. .'] 



carrying the wings) when at rest, that it is impossible to speak 

 of a particular species as "the Tsetse" or "the true Tsetse-fly "• 

 ia~contra-distinction to the others. It follows, therefore, that 

 the designation Tsetse, in default of a vernacular term for; 

 each species of Glossina, must be taken as the equivalent of' 

 the genus rather than of any one species, even the one which is 

 best known. ; 



. ' » 

 ^ . . ^ A technical description of the genus Glossina 



General Characters , j. , . f . f , 



of Tsetse : how ^^^ c>i the species (seven m number) at present 

 to distinguish them known will be found in Chapter IV., so that 

 from other flies. ., • , , , ■ m, 



it IS here only necessary to characterise i setse- 



flies in simple language, in such a way as to enable a non- 

 entomological reader to recognise a specimen at sight. Tsetse, 

 then, may be described as ordinary-looking sombre brownish or 

 greyish-brown flies, varying in length from 3^ to 4^ lines {7h to 

 10 millimetres) in the case of Glossina morsitans, to about 5^ lines 

 {11-^- millimetres) in that of Gl. fusca or longipennis* with a 

 prominent proboscis in all species. The hinder half of the body, 

 or abdomen, in the best-known species, though not in all, is of a 

 paler colour and marked with sharply defined dark brown bands, 

 which are interrupted on the middle line ; the abdomen, however, 

 is invisible when the insect is at rest, as it is then concealed 

 by the wings. The sexes of Tsetse-flies can readily be distin- 

 guished when specimens can be examined, since in the male the 

 external genitalia form a conspicuous knob-like protuberance 

 (hypopygium) beneath the end of the abdomen (see Figs. 12 and 

 13, p. 94), which is absent in the feuiale. 



It is probable that only those who have suffered from the 

 attacks of Tsetse can recognise them when, on the wing, but in 

 the resting position their identification is easy. In this attitude 

 they can be distinguished from all other blood-sucking Diptera,f 

 especially from those belonging to the genera Stomoxys (Fig. 3) 

 and Haematopota (Fig. 4), which are inost likely to be mistaken 

 foi* them, by the fact that the brownish loings lie closed flat over 

 one another dotvn the back, like the blades of a pair , of scissors, 



* These measurements are only from the head to the end of the body', 

 &nd are exclusive of the proboscis, which projects horizontally in front of 

 the head, and has a length of about a line to a line and a half, according 

 to the species. In the crossed lines on the coloured plates, however, the 

 vertical line indicates the average length of the whole insect, including the 

 proboscis, the transverse line showing the wing-expanse. 



t Except midges, which, however, need not be considered since they 

 cannot be confused with Tsetse-flies. 



B 2 



