61 



Manyema. In Manyema the banks of the Lualaba are at the 

 present time to a large extent denuded of arborescent growth ; conse- 

 quently in this section G. palpalis is relatively rare, or even in many 

 cases absent (e.g., at the Nyangwe post). This is in no way due to the 

 climatic conditions of the country, since wherever there is a dense and 

 luxuriant growth of trees along the watercourses Tsetse-flies reappear. 



Katanga. In Katanga, so far as regards Belgian Congo, the range 

 of G. palpalis attains its most southerly limit ; the latter has been 

 determined with great exactness by Dr. S. A. Neave, who mentions 

 the following localities as the southernmost points at which this species 

 is found : 



Kapepwe's Village, on the Luapula (11 30' S.) ; Gombela's Village, 

 on the Kafira (10 50' S.) ; Tsinika's Village, on the Lufira (10 50' S.) ; 

 Shara's Village, on the Dikuluwe (10 30' S.) ; Koni's Village, on the 

 Kalule (10 S.) (Dr. Goessens) ; Nzilo Gorges, on the Lualaba 

 (10 30' S.) ; Ndzimina's Village, on the Lufupa (10 25' S.) ; and 

 Chianda's Village, on the Lubudi (10 40' S.). 



It will be noticed that the most southerly points at which G. palpalis 

 occurs are usually situated about 10 30' S., except on the Luapula, 

 where the fly reaches 11 30' S. Dr. Bequaert was able to satisfy 

 himself by personal observation that the limit mentioned is in accord- 

 ance with facts ; nevertheless he states that there is no reason why 

 G. palpalis should not one day invade Upper Katanga, and even 

 penetrate into the basin of the Zambesi. 



In the valley of the Dikuluwe and its affluents, M. M. Vermeesch, 

 who in 1914 was entrusted by the Government of Belgian Congo with 

 the task of surveying and examining the region in question, ascertained 

 the presence of G. palpalis on the Lower Pande, the Dikuluwe, the 

 Lower Kabango, the Luvilombo and the Lufira, where it is found 

 especially in the scrub, as well as beneath certain thorny trees and 

 bushes with very dense foliage. 



Valley of the Lukuga and the shores of Lake Tanganyika. According 

 to Dr. J. Schwetz, all the western affluents of Lake Tanganyika come 

 from the mountains, with the result that in this region Tsetse-flies are 

 not met with until within quite a short distance of the lake shore. 

 This, however, does not apply to the valley of the Lukuga ; the river 

 contains much water, and its banks are covered with luxuriant 

 vegetation, affording excellent cover. Consequently G. palpalis is to 

 be found all along the valley, albeit close to the river and its banks, 

 while G. morsitans occupies the remainder of the valley and the margins 

 of Lake Tanganyika. Between the western shore of the latter, where 

 G. palpalis exists, and the rivers Lualaba and Luvira, where it is 

 likewise found, the intervening district is very mountainous and free 

 from human trypanosomiasis. 



DISTRIBUTION OF G. morsitans. According to Dr. Bequaert, little 

 is yet known as to the northern limits of G. morsitans, which is very 

 common in Katanga. Dr. Bequaert found that this species does not 

 exist at Kongolo (Lat. 5 30' S.), but he met with a number of specimens 

 of it at Kabalo (Lat. 6 S.), further up the Lualaba. On the other 

 hand, we know from Dr. Schwetz's observations that G. morsitans 

 occurs in abundance in the region of the Lukuga near Lake Tanganyika, 

 but we are absolutely ignorant as to how far the range of this Tsetse- 

 fly extends towards the north, in the country lying between Lake 

 Tanganyika and the Lualaba. 



