TSETSE IN BEITISH CENTEAL AFEICA. 229 



could run and huge numbers of pack-animals — horses, 

 mules and oxen — might convey goods which at present 

 are carried on men's heads. Undoubtedly the Tsetse-fly 

 has checked the southward range of the Muhammadan 

 raiders from the north. But for the presence of this 

 insect in the Congo Basin and in Equatorial East Africa, 

 the Muhammadanised negroes and Arabs of the Sudan 

 would have spread much farther south than they have done 

 already on their sturdy little ponies " (p. 377). 



" Fortunately the Tsetse-fly is not present in all parts 

 of British Central Africa, Roughly speaking, it may be 

 said that it is absent from any district that is above 

 3000 feet in altitude, and is not found in many of the low- 

 lying lands for some hitherto unexplained reason, no 

 doubt connected with human settlement. It is present 

 throughout the whole valley of the great Luangwa River 

 from the Zambezi to the verge of the Nyasa-Tanganyika 

 plateau. It is found on part of the upper course of the 

 River Luapula and on the shores of Lake Mweru, but is 

 absent from the greater part of the country round 

 Bangweolo. It is most abundant on the south coast of 

 Tanganyika, disappearing, however, as soon as the slopes 

 of the Nyasa-Tanganyika plateau are reached. On Lake 

 Nyasa it is absent from almost the entirety of the east 

 coast. On the west coast it is met with between Deep 

 Bay on the north and the River Bua on the south, some 

 patches in between, however, being free from it. From 

 about Kotakota and the Marimba district it is absent. It 

 reappears again south of the Marimba in the northern 

 part of the coastlands of the Central Angoniland district. 

 From the south coast of Lake Nyasa it is almost entirely 

 absent, but it is found again on a small portion of the 

 Upper Shire. 



" In the low-lying country round Lake Chilwa up to 

 the slopes of Mlanje and the hills near Zomba it is present. 

 On the Central Shire at Chikwawa and Katunga there is 

 no Tsetse, but in the Elephant Marsh below it abounds, 

 as also in much of the Ruo district and in the district of 

 the Lower Shire. Always, however, when the land rises 

 to 3000 feet and beyond the Tsetse disappears. This 

 insect has a great dislike to water and a still stronger 

 dislike to a congeries of human habitations. In conse- 



