PROPOSED NEW METHOD OF DESTRUCTION 63 



experiments on Tavu and Ngamba in 1914. When I 

 returned to the islands after the war this question was 

 much in my mind. It had seemed probable that in 

 order to prevent the fly making use of natural breeding 

 grounds and loci it would be necessary to clear them, 

 but a most enlightening observation on Kimmi in 

 December 1918 made it seem probable that clearing 

 would be unnecessary. On a sand bank or raised beach 

 the boys were set to find pupae, but found only a few 

 except at one spot. This was under a little pent-house 

 roof formed by roots of a tree that had been torn up by 

 the wind but had been prevented from falling by its 

 neighbours. The earth embraced by the roots formed a 

 roof at an angle of forty-five degrees protecting from the 

 sun and rain loose dry soil, and in an area a few feet square 

 one boy found pupae at the rate of 104-5 per boy-hour. 

 This proves that although there may be a large area of 

 well sheltered sand apparently suitable for pupae, the 

 fly will carefully search for the best spot and deposit 

 pupae there in numbers rather than scatter them along 

 the larger area. 



I also found numerous other examples of the same thing : 

 moreover, an experiment has been cited earlier which 

 shows that the female fly does circulate round an island, 

 partly no doubt in search of food but also no doubt to 

 look for the best place for her young. Indeed, I feel sure 

 that the mother fly searches as carefully as does a parent 

 butterfly for the right plant on which to lay her eggs. 

 That being so, there is no need to cut down the bush, 

 if the artificial breeding place is made tempting enough. 

 The construction is very simple. All roots are pulled 

 up out of the loose dry soil. The roof covers an area 

 some twelve by four feet ; at its back it is just high enough 

 to allow a boy to creep under in search of pupae, in front 

 it just clears the ground. There are no walls, to allow 

 the free ventilation required. Creepers such as the 



