Lake Ngami/Chapter 37
CHAPTER XXXVII.
During my hunting excursions along the Teoge, I encountered, for the first time, that most extraordinary of insects, the tsetse (glossina morsitans, Westw.).[1]
TSETSE FLY. Among the several scourges to which the traveler is subjected in the South African wilderness, one of the greatest is this insect; not, it is true, as to the wayfarer's own person, for he himself escapes very nearly unscathed, but as regards the horses and cattle.
The tsetse is found chiefly in the bush or among the reeds, but rarely in the open country. It is confined to particular spots, and is never known to shift its haunts. Thus cattle may be seen grazing securely on one side of a river, while the opposite bank swarms with the insect. Should the natives, who are well acquainted with localities frequented by the fly, have occasion to change their cattle-posts, and are obliged to pass through tracts of country where it exists, they choose, I am told, a moonlight winter's night, as, during the hours of rest in the cold season, it does not bite.
In size the tsetse is somewhat less than the common blue fly that settles on meat, but its wings are longer. Yet, though so small and insignificant in appearance, its bite carries with it a poison equal to that of the most deadly reptile. Many is the traveler who, from his draft-oxen and horses having been destroyed by this pestiferous insect, has not only had the object of his journey completely marred, but his personal safety endangered by the loss of his means of conveyance.
Very lately, indeed, a party of Griquas, about twenty in number, who were elephant-hunting to the northwest of the Ngami, and who were provided with three wagons and a large number of trek, or draft-oxen, lost, prior to their return to the Lake, all their cattle by the bite of the tsetse. Some horses, brought with them to further their sport, shared a similar fate.
The very same year that this disaster happened to the Griquas, a party of Englishmen, among whom was my friend Mr. Frederick Green, attempted to reach Libèbé; but they had only proceeded seven or eight days' journey to the north of the Ngami when both horses and cattle were bitten by the fly in question, and the party were, in consequence, compelled to make a hasty retreat. One of the number, I am told, was thus deprived of as many as thirty-six horses, excellent hunters, and all sustained heavy losses in cattle.
There are large tribes which can not keep either cattle or sheep because the tsetse abounds in their country. But it is only fatal to domestic animals, as wild animals feed undisturbed in parts infested by the insect. Yet many of them, such as oxen and buffaloes, horses and zebras, dogs and jackals, &c., possess somewhat the same nature. Moreover, it bites man, and no danger follows. The sensation experienced has not inaptly been likened to the sting of a flea.[2] The problem to be solved is, what quality exists in domestication which renders domestic animals obnoxious to this poison? "Is man not as much a domestic animal as a dog? Is it the tsetse at all which kills the animal?"
Captain Vardon, of the Indian army, one of the earlier pioneers of the more interior parts of Southern Africa, was among the first to decide the point; for he rode his horse up a hill infested by tsetse, and in twenty days his doubts were removed by the death of his horse.
According to the statement of the celebrated explorers, Messrs. Oswell and Livingstone, who were severe sufferers by the tsetse, the following symptoms are observed in the ox when bitten: the eye runs, the glands under the throat swell, the coat loses its gloss, there is a peculiar flaccidity of the muscles generally, and emaciation commences, which proceeds unchecked until—perhaps months after the bite—purging supervenes, and the animal perishes of exhaustion. Some die soon after the bite is inflicted, especially if they are in good condition, or should rain fall; but, in general, the process of emaciation goes on for many weeks. In some cases the animals become blind before they die.[3]
"From what I have seen of the tsetse," writes Mr. Oswell to me, "I believe that three or four flies are sufficient to kill a full-grown ox. We examined about twenty of ours that were bitten and died, and the appearances were similar in all. On raising the skin, we perceived a glairy appearance of the muscles and flesh, which were much wasted. The stomach and intestines were healthy; heart, lungs, and liver, sometimes all, but invariably one or the other, much diseased. The heart, in particular, attracted our attention. It was no longer a firm and muscular organ, but collapsed readily on compression, and had the appearance of flesh that had been steeped in water. The blood of the whole carcass was greatly diminished in quantity. Not more than twenty pints (a small pailful) were obtained from the largest ox, and this thick and albuminous; the hands, when plunged into it, came out free of stain. The poison would seem to grow in the blood, and, through the blood, affect the vital organs.
"A curious feature in the case is, that dogs, though reared on milk, die if bitten,[4] while calves and other young sucking animals are safe as long as they suck. Man, and all the wild animals, escape with impunity. Can the poison be alkaline, and neutralized by the acid?"
- ↑ For a scientific description of this insect, see "Proceedings of the Zoological Society," No. ccxvii.
- ↑ When allowed to settle on the hand of man, all it is observed to do is to insert its proboscis a little farther than seems necessary to draw blood. It then partially withdraws the dart, which assumes a crimson hue. The mandibles now appear to be agitated; the shrunken body swells; and, in a few seconds, the insect becomes quite full, and quietly abandons its prey.
- ↑ "One of my steeds," says Gordon Gumming, "died of the tsetse. The head and body of the poor animal swelled up in a most distressing manner before he died; his eyes were so swollen that he could not see; and, in darkness, he neighed for his comrades who stood feeding beside him."
- ↑ A dog reared on the meat of game may be hunted in tsetse districts in safety!