116 J. STEVENSON HAMILTON — THE RELATION 



result can scarcely have been due to the reduction of its food supply. In the 

 absence of any other destructive cause, the fact that even a few buffalo, kudu, 

 and bushbuck survived, supposing these animals to provide the favourite food of 

 the insects, must surely have induced at least a partial survival of the latter, a 

 nucleus which in the course of years, would have increased with the increasing 

 herds. The buffalo had, for a long time, been so continuouslv hunted and per- 

 secuted, that they had become accustomed to adhere very rigidly to the large 

 extent of dense thorn bush, which coincided with the ily-belts, and seldom if 

 ever left it. This Sabi bush consists of very closely growing acacias (A. splro- 

 carpuides, A. aralnca var. kraussiana, &c., &c.) ; there is very little undergrowth, 

 and, though there are numerous small watercourses intersecting the country, they 

 are all dry sand-beds during the greater part of the year, and the only permanent 

 water is the Sabi River, to within 50 yards of which the bush grows. The soil 

 is shallow granite sand, imposed on a substratum of more or less solid rock. The 

 height varies from 500 to 1,000 feet above sea-level, and the mean night and day 

 shade temperature throughout the year is about 72° Fahr., with an average rain- 

 fall during the last few years of about 20 inches. The latitude is 25° 15' S. 



Seeing that the various fly-zones in the Sabi district, all very similar in nature, 

 ran more or less in parallel directions, and at no great distance apart, it appears 

 improbable that all the numerous animals which survived the rinderpest, or that 

 even the buffalo alone, would have 23rolonged their absence from one or the other 

 for so long as to account for the death of all the flies from starvation, supposing 

 this to be the logical outcome thereof. At present there are living within the 

 old fly-areas several herds of buffalo of considerable size, together with a very 

 large number of kudu, bushbuck, impala, waterbuck, duiker, wildebeest, zebra 

 and sable antelope, and I have personally spent a great deal of time camping 

 about there with my transport animals, dn order to observe the progressive 

 increase of the buffalo. 



Here then, seems to be a clear case of fly having from some cause become 

 extinct, although game of all kinds continued to exist in the areas formerly 

 occupied by it. 



I have also had a personal experience of the existence of G. morsitans in large 

 numbers where there was little or no sign of the larger mammals. 



In 1908 I travelled through the northern part of Portuguese East Africa from 

 Ibo on the coast to Lake Nyasa, roughly along the 13th parallel of latitude. 

 Tsetse-fly was met with in two places ; first, in a small belt near the Mwagidi 

 River, not far from the coast, and secondly, from the right bank of the Msalu to 

 the right bank of the Lujenda River — a distance of about 80 miles, as the crow 

 flies. No signs of any game were found until we had passed through the first 

 fly-area ; then, in one place, we came on a very few kudu, and in another, saw a 

 single waterbuck. In the fly-areas themselves there was no indication oi the 

 presence of big game, nor indeed of that of any of the lesser species of buck. 

 Hares were pretty numerous, monkeys not uncommon. The forest was full of 

 small birds, and judging by their " runs," smaller mammals probably abounded. 

 Throughout the larger area, fly was practically continuous, and though it was 

 then the coolest season of the year, was extremely troublesome, often biting 



