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and decaying wood or other vegetable matter so as to make it light. 

 In nearly every instance the breeding places have been situated 

 beneath a fallen and well-decaying tree, which has been prevented by 

 some of its limbs from actually touching the ground, and is of such girth 

 as to keep an area beneath it shaded and free from moisture. The 

 soil in such a place, being leavened by humus, becomes light and friable, 

 so that the larva can have little difficulty in making its way into it. 



" Very few pupae have been found in hard clayey soil beneath trees, 

 and as it has been found experimentally that the larvae have very 

 weak boring powers, being unprovided with bristles, their occurrence 

 in such situations is probably purely accidental, the parent fly having 

 possibly failed to find a suitable place in time for the birth of its 

 offspring. Such soil, moreover, in the dry season dries almost as hard 

 as stone, needing such considerable force to break the top crust as 

 would render it almost impossible for the newly emerged fly to break 

 its way to the surface. 



" Some few pupae have been found under trees in accumulations of 

 dead leaves on the surface of the ground, but so few, that this, again, 

 is probably purely accidental." 



" As has already been pointed out by workers in Rhodesia, pupae 

 may be deposited in cavities in dead limbs of trees, a certain amount 

 of soil, the result of the admixture of earth originally brought by 

 termites with wood debris, being invariably found in such situations. 



" The question of soil in the various breeding places has been studied, 

 but no special sort seems to be favoured, the chemical constitution 

 being immaterial, so long as the soil is friable. All the trees also, in 

 relation to which pupae have been found, have been carefully examined 

 with a view to ascertaining whether one species more than another is 

 favoured by the fly. In the majority of cases decay has been so far 

 advanced that the determination has been out of the question, but in 

 48 instances specimens of the foliage, representing at least fourteen 

 species, have been obtained and are available. In five cases a few 

 pupae have been found under the shelter of a fallen Borassus palm. 



" Further study of the question has shown that the presence of a 

 dead tree is by no means essential, for in certain parts of the Monkey 

 Bay district breeding grounds sheltered by overhanging rocks have 

 been found, each yielding from two or three to as many as ten pupae. 



" Attention has been paid to the orientation of all these places, the 

 conclusion arrived at being that this is immaterial, all that is apparently 

 required being that the breeding places should be sheltered from the 

 overhead sun. 



" The conclusions arrived at from my study of the question are 

 that the only essentials inducing a female tsetse to select a particular 

 spot are looseness of the earth and shelter. In Nyasaland, as in 

 Rhodesia, the situations most favoured are near game and native paths, 

 and near water-holes, whereby the newly emerged fly is in the most 

 favourable situation for obtaining food in the shortest possible time 

 after emergence. Beyond this, the choice of a site by the parent fly is 

 not, in my opinion, influenced by any special type of soil or of vegetation. 

 The insect fauna in breeding places has been studied as digging has 

 proceeded. It is never very numerous, the only frequent occupants 

 of such places being small blackish Myrmicine ants [Pheidole mega- 

 cephala, F.] and the larvae of ant-lions. Small cockroaches and their 

 oothecae are not uncommonly found, and also the pupa-cases of the 

 large Ponerine ant, Paltothyreus tarsatus, F. . . . . 



