African Nature Notes and Reminiscences

by Frederick Courteney Selous

The tse-tse flies spread with the buffaloes from the sea-coast all along the Limpopo to beyond its junction with the Maghaliquain, but were not able to accompany them to higher ground. The buffaloes, however, spread right up to near the sources of the Limpopo and its tributaries, crossed the watershed to the reed beds of the Molopo, and from thence spread through Bechwanaland as far south as the Orange river, hundreds of miles away from the nearest "fly"-infested area. Even in the midst of low-lying districts full of buffaloes, and, speaking generally, full of tse-tse flies as well, all open pieces of grass country, where there are neither trees nor bushes, and all reed beds of any size, will be found to be free from these insects. When buffaloes feed out into such places from the surrounding forests, the "flies" soon leave them and return to the shelter of the trees. Similarly, if one side of a river be covered with bush and forest down to the water's edge, and if, along this forest-covered bank, tse-tse flies swarm, these insects will never cross even a narrow channel to open reed beds or grass land on the other side. Dr. Livingstone has mentioned how, though he found tse-tse flies swarming along the southern bank of the Chobi river in 1853, his oxen were perfectly safe from these insects in the open grass lands on the other side of the river; and in my own experience, although I have often crossed this same part of the Chobi by canoe, and seen numbers of "flies" on meat, or on the natives or myself, as we left the southern bank, I never knew one of them to cross the river with us. As soon as we got to a short distance from the southern bank, they all left us and flew back to the shelter of the trees and bushes. But the most extraordinary thing about the tse-tse fly is, that in certain low-lying countries away from the wooded banks of the larger rivers, these insects were not found everywhere, but only in certain forest areas, known to the early South African pioneers as "fly" belts. I am speaking now, of course, of the time when natural conditions and the balance of nature had not been upset by North Europeans; for no charge of this kind can be made against the Portuguese, who were always poor hunters.

No one, I think, has ever been able to explain why the tse-tse flies never spread from the "fly" belt which was crossed by the old waggon road to the Zambesi, a few miles to the south of Daka, to the "fly"-infested forest, which lay across the same road a little to the north of Pandamatenka. The country between these two "fly"-infested areas was exactly similar in its vegetation, its altitude above the sea, and in every other particular, as far as one could see, to the "fly" belts which bounded it to the north and south, and during the rainy season buffaloes must have wandered through the intermediate country, as well as through the two "fly" belts. That tse-tse flies used to be found in the greatest numbers along the wooded banks of rivers such as the Chobi, the Zambesi and many of its tributaries, was owing, I think, to the fact that buffaloes had become excessively plentiful in the same districts, not because the near neighbourhood of water was necessary to them; for many "fly" belts, e.g. those extending across the road to the Zambesi, were absolutely destitute of water during several months of every year.

The tenacity with which tse-tse flies cling to certain tracts of country, or even narrow belts of forest, is wonderful, but they sometimes move beyond their usual limits nevertheless. About forty years ago, a waggon track was made by elephant hunters from Matabeleland to Hartley Hills in Mashunaland. Not more than ten miles to the north of the points where this waggon road cut the Umzweswe and Umfuli rivers, the country was always frequented by buffaloes and infested with tse-tse flies. In my own experience, I have often known large herds of buffaloes to come south along the Umfuli river up to and beyond the waggon road. I hunted and shot them there on horseback for the last time in 1885, and used my waggon and oxen to bring the meat and skins to my camp; and as my cattle did not suffer in any way, there could not have been any "flies" about. The tse-tse flies, however, used always to come with the buffaloes for several miles beyond their usual boundary, but gradually left them, and in my own experience I never knew them to quite reach the waggon road.

It will thus be seen that although "fly"-infested areas are, as a rule, well defined and well known to the natives, the movements of large herds of buffaloes may carry these insects—sometimes in great numbers—for a short period of time, for a few miles beyond their usual limits. Within a large area of country throughout which tse-tse flies exist, such as the level forest country in the valley of the Zambesi intersected by the lower courses of the Sanyati and Panyami rivers, or the country near the east coast, in the neighbourhood of the Pungwe river, tse-tse flies used to move about, so that in a place where they were found in great numbers on a certain date, hardly any would sometimes be met with in the same place a month later. In my experience, in such cases the tse-tse flies always moved about with the buffaloes, within these areas, where all other conditions were suitable to their existence.

In "fly"-infested areas where these insects are not very numerous, comparatively few or possibly none at all will be seen during the months of May, June, and July, when the days are short and not excessively hot and the nights are bitterly cold. In fact, it is quite possible to pass through a good deal of "fly" country during these months without ever becoming aware of the existence of these insects. But as the days get longer and hotter, and the nights less cold, if there are any tse-tse flies in a district at all they will be found to increase very rapidly in numbers. They become most numerous and most troublesome, I think, in October and November, just before the commencement of the rainy season. During the rainy season they are perhaps not quite so exasperating, but my experience has been that they were both numerous and troublesome at that season too. They are not so active in cloudy weather as in bright sunshine, and if a strong wind is blowing they hardly show themselves at all.

It is perhaps worth mentioning that the fact of the disappearance of the tse-tse fly from all countries to the south of the Zambesi, very soon after the complete extinction of buffaloes in the same regions, cannot be attributed to the settling up and cultivation of the land by Europeans; for the tse-tse fly has never existed in any part of Africa south of the Zambesi where malarial fever was not and is not still rife. Whatever may be the case to-day, up to 1896, long after the disappearance of both buffaloes and tse-tse flies, the Boers had never been able to establish themselves and live all the year round in the Northern Transvaal along the valley of the Limpopo, although they used to graze their cattle there during the winter; nor, as far as I am aware, although mining operations have been carried on for nearly twenty years within what was once "fly" country to the north of Hartley Hills in Mashunaland, has there been any settlement of families on the land in that district.

The word "tse-tse" (pronounced by the natives "tsay-tsay" and by colonists "tetsy") is simply the word used by natives of the Bechwana clans for the deadly fly known to scientists as Glossina morsitans. The Matabele—as well, I believe, as the Zulu—name for the same insect is "impugan." With the Matabele any kind of fly is an "impugan," but it is the only word they ever employ for the tse-tse.

As is well known, the tse-tse fly, when with its long proboscis it "sticks," as the Boers say, a domestic animal, introduces into the blood of the latter certain minute blood parasites (Trypanosoma), which, though constantly present in the blood of wild animals living in the "fly"-infested regions of Africa, does them no harm. These Trypanosomes, if introduced into the blood of domestic animals in any quantity, at once set up a disease, which almost always ends fatally. Cattle when "fly-stuck" soon begin to run at the eyes, and the glands behind the ears and in the throat swell. Although continuing to feed well, they become thinner and weaker day by day, and should they be exposed to cold or wet weather, their coats stare, as if they were suffering from lung sickness. According to the number of Trypanosomes in their blood, cattle will live a shorter or longer time. They will succumb within a month if kept constantly in country where tse-tse flies are numerous during that time. On the other hand, they will sometimes live for nearly a year if only "stuck" by one or a few flies whilst passing through a "fly"-infested belt of forest of small extent. I have known a young ox, though it showed every sign of having been impregnated with the "fly" disease—possibly it had only been "stuck" by one "fly"—to recover completely after remaining very thin for more than a year. Horses and donkeys, when "fly-stuck," run at the eyes and swell at the navel, and soon get thin and lose all their strength.

In 1877 I took three donkeys with me up the Chobi. They lived in a swarm of tse-tse flies day after day and all day long. The first of them to succumb only lived a fortnight; the second died in five weeks; but the third lived for nearly three months, and carried a buffalo head back to my waggons at Daka—some eighty miles from the Chobi.

For about ten days before the second donkey died I remained in the same camp. By this time it had grown very thin and was too weak to carry anything, but it did not seem to suffer in any way, and whenever I could observe it, was always feeding on the young green grass at the river's edge. I never tied it up at nights, but every evening it used to come and roll in a large heap of ashes behind my camp. One evening it came and rolled in the ashes as usual, but was too weak to get on its legs again, and on the following morning was dead. Apparently it enjoyed its life to the very last.