GEOGRAPHICAL DISTEIBUTIOX. 29 



Limpopo in 1836. For reasons which have already been ex- 

 plained, however,* it does not necessarily follow that the Tsetse 

 is to be found to-day in the precise localities coloured red on the 

 map, and this applies more especially to regions south of the 

 Zambesi. In this portion of the Continent, owing to the advance 

 of civilisation and the retreat or disappearance of the big game, 

 many tracts in which the fly formerly abounded are now entirely 

 or to a large extent free from it ; so that in order to learn what 

 is known of the extent of the fly-belts in South Africa at the pre- 

 sent time, the latter portion of the first part of the Bibliography 

 must be consulted, in addition to the records of the localities of 

 specimens given in Chapter IV. 



With this reservation, therefore, it may be stated that so far 

 as can be ascertained at present, either from the examination of 

 actual specimens or from records in literature, the genus Glossina 

 ranges from the Gambia in the west (approximate latitude 

 13° 66' N.) to Somaliland in the east, extending south from this 

 line until it reaches its southernmost limit in the northern 

 portion of Zululand, near St. Lucia Lake (approximate latitude 

 27° 60' S.). Quite recently it has been recorded from the regioti 

 of Lake Tchad [171], but as yet we do not know whether it 

 occurs in the Egyptian Sudan or in the river valleys and ravines 

 of Abyssinia ; although from what we are told as to the mortality 

 among horses and mules during the Abyssinian Expedition of 

 1867, it is probable that it is indigenous in the latter country, 

 at any rate [c/. 171]. There is, however, a doubtful record 

 from Sennaar [47], and, should this be confirmed, the northern 

 limit of the Tsetse would be represented by a line running from 

 that country through Lake Tchad to the Gambia, or roughly by 

 the 13th parallel of north latitude. But it is almost certain 

 that the genus Glossina will ultimately be found to extend 

 farther north than this, and whether it occurs or not on the 

 White and Blue Nile up to the latitude of Khartum, it can 

 scarcely fail to do so on the Senegal River and throughout the 

 valley of the Niger. 



It will be seen from the map that records of localities north of 

 the Equator are at present very scanty, but that they become far 

 more numerous in the eastern half of the southern portion of the 

 Continent. On the western side, although the Tsetse no doubt 

 occurs throughout Portuguese West Africa, there appear to be 

 no records whatever of its having been met with south of the 

 * See pp. 10, 11. 



