62 NATURAL HISTORY OF GLOSSINA PALPALIS 



the pupa is all that remains to us. Can we then 

 destroy it ? 



This is theoretically easy since shade is a requisite. If 

 all the low bushes and creeper growing on dry sand near 

 the water were cut down, the " breeding grounds " would 

 be destroyed and the numbers of the fly might be reduced 

 by half. 



This would leave, however, all the " loci " that have 

 been discussed, and I see nothing for it but to clear all 

 the shore of low bush for at least fifty yards back from 

 the water, and probably a great deal further. This would 

 be a colossal task with a lake of such a size. But a better 

 way occurred to me in 1914, and an observation in 1918 

 on Kimmi that has been already quoted made it seem 

 very likely to succeed. 



The method is to provide for the fly all the conditions 

 that it requires in a concentrated form, in such a way 

 that it will deposit its pupae in the place chosen for it rather 

 than elsewhere. The pupae can then be easily collected 

 and destroyed. The conditions required by the fly 

 have been dealt with above, and they are provided by 

 building a low roof of thatch covered with green creeper 

 on a bank of sand or gravel near the water. In 1914, 

 I had commenced experimental work on these lines on 

 Tavu and Ngamba, which was cut short by the call of 

 active service, but I had satisfied myself that these 

 shelters were attractive to the fly. I also found that 

 although, as has been said before, a thick layer of dead 

 leaves on the surface is inimical to the pupae, yet the fly 

 prefers the surface to be lightly strewn with flakes of bark, 

 sticks or dead leaves. In the preliminary tests one half 

 of the sheltered area was strewn with bark or leaves and 

 the other half left bare, but there were always more 

 pupae found in the former half. 



The accompanying figures show the nature of the 

 " artificial breeding ground " thus provided in the test 



