71 



RESTING SURFACES. 



In Nyasaland it was found by Lamborn that G. morsitans displays a 

 preference for baobab trees as resting places, although large trees of 

 any kind are utilised. The predilections of the species mentioned, as 

 well as of G. brevipalpis and G. pallidipes, as regards actual resting 

 surfaces were tested experimentally in Portuguese East Africa by 

 Swynnerton (145), who writes : " When studying morsitans, and later 

 brevipalpis, I erected a large mosquito net, 9 ft. 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 

 lies. 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 6 ft. 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. Diplorhynchus mossambicensis was a favourite 

 with the large tsetse, and a distinct colour-harmonisation took place 

 also, the blacker tsetses (morsitans] choosing blacker bark, the greyer 

 grey bark, the brown ones (brevipalpis) brown bark and the underside 

 of rough or knobby lianas, on which they easily passed as one of the 

 knobs. 



"For the morsitans experiment, in 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 con- 

 ditions 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 brown grooves, and this was at 3-4 ft. from 

 the ground. Below this area the bark was uniformly black, above it 

 rather more uniformly pale and uncharred. The females also settled, 

 the colours being right, mainly on the lower side of a branch or log, 

 the males settling as frequently on the upper sides. A raised stone and 

 clods of earth were also used for resting under in the brevipalpis 

 experiment. Leaves and thin twigs were used by active, not resting 

 flies ; these flies were readily disturbed . . . The hiding flies 

 were mostly, but by no means entirely, females. From my observations 

 in the field also, it seemed clear that in Glossina, as in so many other 

 animals, the female trusts mainly to concealment for defence against 

 enemies, the male more largely to activity, and that the difference in 

 the requirements of the sexes and their methods of meeting them is 

 the chief reason for the female's special seclusion, though Lamborn's 

 factor (avoidance of males) may be operative also." 



PROPORTION OF THE SEXES. 



As regards the apparent disproportion of the sexes in the case of 

 G. palpalis, reference may be made to certain observations and experi- 

 ments by Dr. J. W. Scott Macfie (93) at Zungeru in Northern Nigeria, 

 during December 1911 and January 1912. " These months," writes 

 Dr. Macfie, " cover the height of the dry season, when the Tsetse-flies 



