THE TSETSE PROBLEM IN NORTH MOSSURISE. 3~)5 



In general it does not seem likely that the country west of the Sitatongas, at any 

 rate north of a line drawn through the middle of the '' Oblong " and parallel 

 to its greatest length, is in any danger of being invaded by tnorsitans. Occasional 

 flies might be carried over the hills by Kafirs or game, and the latter would probably 

 happen more frequently were the kraals on the eastern foot of the hills to be removed. 



(2). The mountains of and near the British border. These constitute the western 

 and northern boundaries of the pallidipes-brevipalpis areas, and for a clear idea of 

 them the map should be consulted. Generally speaking they form more or less 

 of an escarpment, abutting on to the fly country on these two sides. 



The great rise in elevation seems at first sight an adequate reason for the existence 

 of the fly boundary, which, it should be repeated, appears always to have stood 

 approximately where it is now, except when pushed east by Kafir settlement. No 

 doubt the British hills north of the Lusitu (6,000 feet) and the Chimanimani (much 

 higher) would act in this way as a direct barrier, but it is more than doubtful 

 if, from the Lusitu southwards, the elevation (with maximum heights of a little over 

 4,000 feet) is sufficient to act as a direct deterrent to the fly. On 

 the contrary, a glance at the map shows clearly that it is the great continuous 

 pieces of wooding of the right types that really delimit the fly. AYhere these 

 ascend mountains, the fly ascends equally ; where they stop short in low-lying 

 valleys (Inyamadzi, Chiredza, Buzi, Lusitu), the fly stops short too. It happens that 

 these great pieces of wooding cross the British border for a short distance only 

 where they touch it. With regard to the wet season fly, which is capable of being 

 established temporarily by game in occasional pieces of wooding such as exist 

 abundantly enough even on the British side of the border, another factor must be 

 mentioned — ^the white settlers on the border and such native kraals as are present. 

 Our experience shows that these do act quite considerably as a deterrent to the passage 

 of the wandering big game, and that where a white man shoots much or native 

 kraals are numerous a useful " guard " against the fly is thereby established. 



In general, however, the summing-up of old Inyabangwa, who long ago herded 

 cattle for the Zulus on the edge of the escarpment, fits the case. " They are barred, 

 sir," he exclaimed, "barred (zi-vimbekile, 'nkosi, zi-vimbekile). They fear the 

 open country (izimbaya) of the mountains and they fear its cold winds." 



XII. — Notes on Habits. 

 Waiting Habits. 



I have referred to the tick-like habits of tsetse. I came across no evidence that 

 the flies wander to any extent in search of their prey, though a good deal of local 

 activity is shown by male brevipalpis after sunset, and females then attack from a 

 greater distance. That some of the stray flies found in the country generally are 

 carried, I had evidence in the sudden appearance of my marked flies in native 

 villages inmiediately after parties of reed-cutters had passed through them from my 

 vleis. 



G. brevipalpis may be found in the day-time scattered through all the little 

 thickets in the bush it frequents, two or three or more to each. Just at sunset the 

 males emerge from the thickets in the neighbourhood of game and other paths and 

 (where plentiful) distribute themselves at short intervals along them, sometimes 



