Tsetse Fly.—Confined to particular Spots.—Its Size.—Its
Destructiveness.—Fatal to Domestic Animals.—Symptoms in the Ox
when bitten by the Tsetse.
During my hunting excursions along the Teoge, I encountered, for the
first time, that most extraordinary of insects, the tsetse (_glossina
morsitans_, Westw.).[89] 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.
[Illustration: TSETSE FLY.]
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.[90] 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.[91]
“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,[92] 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?”