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 continuously 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 fly-belts, and seldom if 
ever left it. This Sabi bush consists of very closely growing acacias (A. spiro- 
carpoides, A, arabica var. kraussiana, &c., &e.) ; there is very little undergrowth, 
and, though there are numerous small watercourses intersecting the country, they 
are alldry 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 buftalo alone, would have prolonged 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, in 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, ina 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 of 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 
