346 C. r. M. SWYNNERTON. 



to find a more fitting description of this jnorsitans-pallidipes area than has been 

 given by Dr. Shircore of the " proclaimed area " of Lake Nyasa (Bull. Ent. Res. 

 V, pp. 87 and 88) ; although, owing to the lateness of the season in 1918 and the fact 

 that grass-fires had now barely begun, I am not in a position to judge of the complete- 

 ness and duration of the stripping of the drier country of the stray fly of which 

 I seemed to have seen the beginning. This type of wooding comes back into leaf 

 again very readily after the weather has warmed up, and it possesses an early 

 element in the mutsatsas. The return of the leaf does not await the rains and the 

 country is sometimes already very shady when it is otherwise absolutely at its 

 driest. The relative value of these two factors — shade and moisture — in relation 

 to the fly's fresh redistribution should be interesting to study. * 



I did not find that G. inorsitans appeared to be at all dependent on the presence of 

 undergrowth. The bush in which it occurred was for the most part devoid of such 

 growth, though some of it was itself low. I may add here that in consequence of the 

 very late fires of 1918, and of the fact that I worked the normally late-burning 

 areas last, the whole investigation was carried out in unburned country (except 

 for a few odd patches). Nevertheless I obtained no evidence in favour of the view, 

 but much against it, that any of the flies concerned will live in open grass-country 

 devoid of bush. Even the attacks of morsitans on the basalt were always in or beside 

 shade, were it only that of a large shrub or a semi-leafless tree, and when noted 

 definitely resting, either in my experimental net or in the field, this fly was always 

 iu the shade — ^under a log, on the shady side of a trunk, etc. A replete resting 

 7norsitans female that I disturbed repeatedly always settled again on the shady 

 side of trees. I have seen waiting male clusters furthest from bush in large vleis, 

 but there was some reason to suppose that the individual flies did not stay with 

 the cluster indefinitely. 



Glossina jmllidipes is distinctly more catholic here in its general tastes than either 

 of the other two. It occurs both in the country favoured by brevipalpis and avoided 

 by morsitans and in that favoured by morsitans and avoided by brevipalpis, as 

 well as in wooding of its own ; nor do the stray individuals, at any rate, avoid the 

 extremes. Males were taken on the sparsely shaded basalt (PI. x, fig. 2) in dry 

 windy weather and with the leaf falling freely, and occasional individuals of both 

 sexes were taken in primary forest dominated by Khaya nyasica in full leaf (PI. ix). 



I do not feel that I disentangled its habits sufficiently from those of G. morsitans 

 on the granite-gneiss. Here, in the Brachystegia bush, it appeared to occur in every 

 place in which we found morsitans (PI. xiv, fig. 2 ; PI. xv, fig 1). It was in great numbers 

 only where morsitans was also numerous — namely at particular vleis and glades ; 

 it was very sparse elsewhere, but less so than morsitans, and both flies (and once 

 brevipalpis too) were on us or the cattle together. When pallidipes puparia were 

 taken at aU, they were under the same log as those of morsitans, 



* Mrs. Lawrence, writing for her husband well on in November and sending me flies, 

 speaks of the pleasant and cooling effects of the first light rains — " but " (she adds) 

 " the tsetses ! they are abundant." Tsetses had reappeared with the return of the shade, 

 but the advent of the rains would seem to have led either to their freer breeding out or 

 (as I think, by making more general the conditions under which they could exist in 

 comfort or safety) to their freer dispersal from their breeding centres. 



