96 



it is by no means certain that the disappearance of the fly at the time 

 of the rinderpest was due to the diminution of its food-supply. While 

 on the one hand we have no information as to the climatic conditions 

 prevailing at the period in question, experiments have shown that low 

 or high temperatures have a considerable influence upon the life of 

 Tsetse-flies, and consequently the disappearance of Glossina morsitans 

 at the time of the rinderpest may have been nothing but a simple 

 coincidence. 



It would seem that trypanosomes have never been recorded as 

 occurring in the blood of the elephant or hippopotamus. It has 

 indeed been asserted by certain big game hunters and travellers that 

 G. morsitans evinces a special predilection for the latter animal, and 

 it is said that wherever there are buffalo these flies are found to be 

 infected with trypanosomes. 



In 1914 a study of the relation between Glossina morsitans and big 

 game in Southern Rhodesia was published by Mr. R. W. Jack (68), to 

 whose interesting investigations repeated reference has been made in 

 the course of the present work. We give below some extracts from 

 Mr. Jack's paper. 



After mentioning the sources of his information, which was derived 

 not only from personal observation but also from the testimony of 

 other Europeans especially qualified to express an opinion, Mr. Jack 

 writes : " It may be stated at once that the case built up is considered 

 strongly in favour of a vital association between the prevalence of big 

 game and the continuance and increase of the fly .... During the 

 last four and a half years the writer has visited the great majority of 

 the fly-belts in the territory, and the main belts repeatedly, and, 

 broadly expressed, the results of observations on game and fly are to 

 the effect that in most cases game is more or less abundant all the year 

 round in fly-infested country, and that in no instance is the larger 

 animal life altogether absent, even during a portion of the year. 



" Turning now to broader considerations, the evidence in favour 

 of the necessity of big game to the tsetse in Southern Rhodesia and 

 adjacent territory may be summed up under four heads : 



" (1) Tsetse retired before the advance of civilisation in the Trans- 

 vaal, the only known modification of conditions being the destruction 

 of the game. 



" (2) Tsetse disappeared from large tracts of country immediately 

 after the rinderpest epizootic in 1896. 



" (3)r Tsetse has increased and spread since the rinderpest only 

 in those parts of Southern Rhodesia where big game has increased. 



" (4) Tsetse has greatly decreased of late years in the Hartley district 

 in those parts where the big game has been most effectively destroyed 

 or driven away." 



With regard to the possibility that big game is not necessarily the 

 only source of the requisite blood-supply, and dealing in the first place 

 with reptiles and amphibians, the author remarks : " As a matter of 

 fact, in the case of G. morsitans such a supply is rarely available, as 

 the fly is not often found on the banks- of the larger rivers where 

 crocodiles abound, and the belts in the dry season are frequently far 

 removed from water of any sort, in which case water-loving reptiles, 

 such as Varanus and fresh-water Chelonia, as well as most amphibians, 

 are not available. The smaller lizards, including chameleons, are 



