366 C. r. M. SWYNNERTON. 



stems, under which the pigs had been lying. The ground (shale) was in two cases 

 exceedingly hard and compact, but humus was present in the situations in which 

 the pupae were found. There seemed to be no such localisation of the breeding 

 centres as I found with morsitans. 



Glossina pallidipes. 



1 have referred to the puparia of this species elsewhere (p. 346). They w^ere 

 taken with those of G. morsitans and under the same logs, but in very small 

 numbers indeed. None were found west of the Sitatongas. 



Glossina austeni. 



I have already given some details of this species (p. 348). The very distinctive 

 puparia were all under four logs. One, more or less rotten — with only two 

 puparia — was beside a game path used by bushbucks and waterbucks. Another 

 with 30, showed many blue duiker " forms " about it , but these were too recent ; 

 leaf-carpet does not preserve traces well. The third, with 23 puparia, was also in 

 dense shade and exactly at the junction of the primary- type forest and some heavy 

 Marhhamia bush (mubfeya). Right up to the log, in the latter bush, were the old 

 tramplings and lying places of elephants. A similar log in similar shade lay 18 

 yards away ; it was away from the tramplings, etc., and covered no puparia. The 

 fourth log is described sufficiently elsewhere (p. 349). 



XV. — Net Experiments. 

 Resting Surfaces. 



When studying mom^a?^5, and, later brempalpis, I erected (PI. xv, fig. 2) a large mos- 

 quito net, 9 feet high, over cut-back tree-trunks, shrubs, etc., and furnished it 

 with stems having different kinds of bark, stones, etc., in order to study the resting 

 habits of the flies. These I turned into the net in some numbers — well over a 

 hundred in the case of brevipalpis. Some pallidipes were also included in each 

 experiment, and each was continued for from three to four days. None of the three 

 species used confined themselves to the few feet next the ground ; they settled, 

 colour conditions being correct, up to the full height available. I have noticed 

 unconfined morsitans resting up to at least six feet from the ground. 



The rough-barked stems were selected in preference to the smooth, and large 

 and small holes in the trunk and grooves in the bark were freely utilised for hiding 

 in. A completely smooth-barked trunk was entirely neglected. Diplorhynchiis 

 mossambicensis was a favourite with the large tsetse, and a distinct colour-harmoni- 

 sation took place also, the blacker tsetses {morsitans) choosing blacker bark, the 

 greyer grey bark, the brown ones (brevipalpis) brown bark and the imderside of 

 rough or knobby lianas, on which they easUy passed as one of the knobs. 



For the wxyrsitans experiment, iu pyrophytic wooding in which the trees always 

 show, on one side especially, blackening by the grass fires, the Diplorhynchus trunks 

 were specially selected on account of the strong contrast between the colours of 

 their two sides. Shade conditions were about equal (as the result of overhead shade) 

 and, the position of the branch being also suitable, the female flies in particular 

 always tended on settling to select the blackened side. On this side, furthermore, 

 they settled chiefly where the black of the raised cork ridges alternated with pale 



