100 . 



cases mentioned the spread of the fly was believed by Jack to have 

 been due to the movements of game. 



In a paper published three and a half years later (74), Jack stated 

 that all data collected by him tended to confirm the dependence of 

 G. morsitans on the presence of wild ungulates ; at least there was 

 every reason to believe that the fly feeds upon them by preference 

 and thrives best in their company. 



According to Dr. H. L. Duke (49), whose experience has been gained 

 in Uganda, in no case has prolonged existence of G. morsitans been 

 discovered in an area where game is entirely and permanently absent. 

 The fly is generally found associated with game in considerable numbers 

 and variety, though it may occur in localities where wild ungulates 

 are apparently scarce. The theory regarding buffalo as essential to* 

 the subsistence of the fly has been found untenable. 



Lloyd (91), in the Ngoa area, Northern Rhodesia, in 1915, where 

 game was plentiful, collected four times as many pupae of G. morsitans 

 as in the Kashitu area, where game was relatively scarce (see above, 

 p. 41). He therefore thinks that the flies themselves are more 

 numerous in districts in which game is abundant. Man was frequently 

 attacked where game was scarce or non-resident, while the flies were 

 rarely seen where game was present in large numbers. Lloyd considers 

 that the reduction of game in a fly area would lead at first to an apparent 

 increase in the numbers of the fly, owing to increased hunger. The 

 number of females which approach man with the deliberate intent 

 of feeding, unlike the males, which chiefly do so as a means of meeting 

 and mating with the opposite sex in a capture would increase to about 

 50 per cent., while pupae would occur in fewer numbers, thus showing 

 that an actual reduction had taken place. 



On the other hand Christy (29) states that large areas of country 

 may swarm with Tsetse, and yet contain scarcely any game ; such 

 areas, according to this author, are found in the Upper Bahr-el-Ghazal, 

 where tall spear-grass is a conspicuous feature. In some districts, 

 both there and in the Eastern Welle basin, G. morsitans occurs in 

 millions, apparently irrespective of whether game or human beings are 

 present at all. The presence or absence of game depends upon grazing 

 facilities, but these have no relation to the presence or absence of 

 Tsetse-flies ; nor has the prevalence of sleeping sickness any relation 

 to the number of G. morsitans, or to the number of game in any given 

 area. Wild animals may act as hosts for the trypanosome of sleeping 

 sickness, but Christy considers it a dangerous assumption to conclude 

 that they are the chief reservoir of the disease. Even if this were 

 the case, he regards the extermination of all the wild animals in any 

 part of Tropical Africa as quite impracticable, nor does he think that 

 such a measure would have the effect of eliminating the disease. 

 Though excluding the majority of wild animals as a danger in the 

 transmission of sleeping sickness to man, this author is inclined to 

 suspect one or two. Of these, pigs are considered the most dangerous, 

 and not only the wild bush-pig and wart-hog, but, as has already 

 been stated (see p. 93), more especially the semi-domesticated pigs 

 frequently seen in native villages. 



In an attempt to collect evidence in the Bahr-el-Ghazal and the 

 Congo for or against the theory that wild animals are an important 

 reservoir of sleeping sickness, Christy made a microscopic examination 

 of the blood of many animals as soon as possible after each was shot. 

 Of 160 animals examined in this way, only five were found to have 

 trypanosomes in their blood, and of these only one, a wart-hog, 



