THE TSETSE PROBLEM IN NORTH MOSSURISE. 347 



A fact that is possibly of interest is that in my first week spent at the Kanyezi 

 morsitans centre (28th June-6th July) I saw and secured numbers of morsitnns 

 but relatively few 2)allidipes, though a good sprinkling of this fly was present. Dur- 

 ing my second stay there (27th July-lst August) pallidipes had apparently been 

 heavily reinforced and was now taken (both males and females) in greater numbers 

 than morsitans. It did not seem that emergences could account for this difference ; 

 the puparia, living and empty, taken in large numbers on each visit, contained 

 an extraordinarily small proportion of those of ^aMtpes— perhaps one per cent. — 

 though the bush generally was well searched. On the other hand the adult flies 

 of both sexes, which at my first arrival were scattered more through the country 

 generally, had latterly, with only two or three exceptions (these being on the basalt 

 where moisture would be harder fco find), been taken only at streams. There was 

 a difference now in the fact that the country was drier, and that leaf-fall had com- 

 menced and was in places appreciable at the time of my second visit, so that the 

 evidence suggested in a remarkable manner that pallidipes, previously to a larger 

 extent scattered sparsely over the face of the Brachystegia area, had now congregated 

 at the inorsitans centres. It is perhaps difficult to disentangle this conclusion 

 with certainty from the fact that the cattle always drew, and were now drawing, 

 pallidipes in much larger numbers than natives working without them ; but on 

 this occasion the latter were themselves securing a larger proportion of pallidipes 

 than previously. I should say that on the granite-gneiss the presence of pallidipes 

 was in no way dependent on that of woody undergrowth. 



West of the Sitatongas, where morsitans does not appear to occur at all, stray 

 individuals of pallidipes were taken in very open bush^ — and in every type of bush — 

 but it was never taken even two or three together except in Brachystegia and the 

 less tall of the " dense secondary " types. It certainly occurs in small numbers 

 in the dry season throughout the " Oblong " and its northward extension to the 

 Buzi. It is even possible that this great Brachystegia block may be its main per- 

 manent habitat here, and it is notable that my cattle sustained a severe attack 

 from pallidipes on 27th July in a limited piece of Brachystegia wooding just north 

 of the Dysart Concession — a wood that had previously supplied a pallidipes or two 

 daily to Dr. LaA\Tence's grass-cutters just outside it. I also took a few pallidipes 

 between this station and Gogoyo's kraal at a series of small vleis in very dry sandy 

 country carrying a type of Brachystegia bush equal only to the poorest on the 

 granite-gneiss and already losing leaf somewhat heavily, and was informed by a 

 native formerly resident that this fly was exceptionally bad here in the rains. Apart 

 from these instances my only real and repeated successes with this species in the 

 " Oblong " area were in and near the piece of coppice shown in PL xvii, 'fig. 1 and 

 representing a type of wooding that, resulting from native cultivation, is more 

 abundant north of the Mtshanedzi. Here (north of this river) on a few occasions 

 up to half a dozen — even a dozen — together showed themselves in such types 

 as are illustrated in PL xi (rather low thicket) and PL xvii, fig. 2 (coppice). 

 Largely on account of this predilection, partly no doubt on account of the 

 greater scarcity of brevipalpis and absence of morsitans, pallidipes west of the 

 Sitatongas appeared to be specially associated with the Puizisi-Mtshanedzi area, which 

 carries a very great deal of wooding of these types. The coppice or fern-entwined 

 (737) Q 



