60 NATURAL HISTORY OF GLOSSINA PALPALIS 



the beaches were found the optimum conditions. But a 

 recent observation, I think, disposes of that argument. 

 On Kimmi Isle in 1914 was a broad flat strip of low lying 

 marshy land, soft and waterlogged, that obviously owed 

 its origin to the level of the lake having fallen and the 

 water having receded from the real shore marked at 

 the edge of the forest by the usual raised beach, which 

 was thus separated from the water by a hundred yards 

 of marshy grass land. 



This raised beach satisfied aU the requirements of pupae 

 except proximity to the open water, but no pupae were 

 found in 1914. In December 1918, however, there having 

 been an exceptionally wet season in 1916, the water 

 had returned to a former height and had covered the 

 former marsh land, so that it came right up to the old 

 beach, which thus formed a typical " fly beach." It 

 was now used by the fly as a breeding ground, and pupae 

 were found there. 



It may be said, then, that the ideal requirements of 

 the fly for its pupae are found on the beaches near the 

 water, well shaded, and composed of dry sand or gravel, 

 and that where these occur palpalis is found in maximum 

 numbers. But in their absence the fly makes use of such 

 scattered nooks as can be found, so that it can exist 

 in some number in the absence of " breeding grounds " 

 on rocky coasts. I consider this to be very important, 

 for it has been thought that it would be possible to 

 destroy the fly by merely cutting down and clearing the 

 low shade producing vegetation on the beaches so as to 

 spoil the breeding grounds. This would doubtless lessen 

 the numbers of the fly, perhaps by half, but would not 

 exterminate it. 



In order to exterminate Sleeping Sickness two animals 

 must be kept from each other — the Situtunga antelope 

 from which the fly obtains the Trypanosome, and the 

 fly, which inoculates the Situtunga with the Trypanosome. 



