FLIGHT HABITS OF THE TSETSE 33 



multiply. In some of the most fertile areas the 

 thick scrub that fringes the margin of the streams 

 and lakes, and so affords cover for myriads of flies 

 and breeding-grounds for their young, has been 

 destroyed. Already much good has been done by 

 the compulsory clearing of wide strips of bush along 

 the streams, and the lack of cover for the flies has 

 led to a decrease in the number of fresh cases of 

 sleeping sickness. In some cases a quite secondary 

 result has been obtained. The cleared strip has 

 been extended farther from the water, and part of 

 it planted with low-growing food-plants. This vege- 

 tation is not dense enough to afford cover to the 

 tsetses, and the increased quantity of food thus 

 available for the use of the natives has proved a 

 valuable addition to the supply obtained by their 

 somewhat primitive methods. 



The flying habits of the insects also are worthy 

 of note* When the atmosphere is humid, then the 

 insects sally forth in search of prey. Again, during 

 the hotter parts of the day, when the temptation to 

 expose the limbs to whatever slight breeze is avail- 

 able is almost irresistible, the Glossinse are alert and 

 active, and for safety's sake comfort must be sacri- 

 ficed by European and native alike. As many of 

 the natives reduce their clothing to a minimum, they 

 are naturally more liable to insect-bite than are 

 clothed men. However, Glossina palpalis has been 

 proved to be able to bite through clothing, though 

 they rarely attempt it. Further, G. palpalis is known 

 to have a strong preference for a dark-skinned victim, 

 and hence whites accompanied by natives are rela- 

 3 



