6 GEOGEAPHICAL DISTEIBUTIOK 



Tlie shape and appearance of the piqm * will, it is hoped, be 

 readily understood from Figs. 4, 5, and 6. Tsetse-fly pupae are 

 dark brown or clove-brown in colour, with a slight sheen which 

 produces somewhat the effect of the bloom on a black plum. The 

 tumid lips seen in the larva are equally conspicuous in the pupa, 

 and the shape of the notch between them, in conjunction with 

 the size and shape of the lips themselves, affords a valuable means 

 of identifying and distinguishing pupae belonging to different 

 species (see Fig. 6). 



Although, since the discovery of Glosshat 



DlsfStion' (((cMnoidex, Westw., in Southern Arabia,! the 

 generalisation that existing Tsetse-flies are con- 

 fined to Africa no longer holds good, it is nevertheless trvie that 

 the genus GJossina at the present day occurs only in the Ethiopian 

 Region, inasmuch as the southern portion of Arabia belongs 

 zoo-geographically to the region in question. | In the African 

 continent Tsetse-flies have a very wide distribution in the tropical 

 and sub-tropical zones. Roughly speaking, so far as our present 

 knowledge goes, the northern boundary of the genus may be 

 represented by a line drawn from the mouth of the Senegal 

 River across the middle of Lake Chad to the Nile, just south of 

 the twelfth parallel of north latitude, and thence to the east 

 coast at about 4** N. ; while its southern limit may similarly be 

 shown by tracing a line from the mouth of the Cunene River, 

 the southern boundary of Angola, to the north-eastern extremity 

 of St. Lucia Lake, in Zululand. Within this area Tsetse-flies, 

 as already explained, are not found continuously, but are 

 restricted to " belts " or " patches " of forest, bush, banana- 

 plantation, or even reeds. The accompanying map must not be 

 regarded as afibrding anything more than an approximate idea 

 of the distribution of Glossina. Since the necessary cover is 

 mainly found in the valleys of rivers and watercourses, and on 

 the shores of lakes, it is chiefly the river-systems that are marked 

 on the map. In a map on so small a scale it is, however, almost 

 impossible to convey any idea of the actual extent of fly-belts or 

 fly-areas. Since it is practically certain that Glossina p)alp)aUii 



* What is seen is really thepuparium, or chitiuous pupa-case, consisting 

 of the hardened and contracted skin of the adult larva ; the true, soft- 

 bodied pupa lies within this protecting envelope. Puparia of this character 

 are invariably found in the IMuscidae, and other families of Diptera 

 belonging to the same division of the Order. 



t Cf. p. 41. X Cf. p. 41, note f. 



