60*

owner. Awoke by the pain, the beggar was taken to the H6tel- Dieu, where he expired. Who would suppose that one of the causes which render the centre of Africa difficult to be explored is a fly not larger than the house-fly? The Tsetse fly (Fig. 53) is of brown colour, with a few transverse yellow stripes across the abdomen, and with wings longer than its body. It is not dangerous to man, to any wild animals, or to the pig, the mule, the ass, or the goat. But it stings mortally the

Fig- 53- — The Tsetse Fly {Glossina morsitans).

ox, the horse, the sheep, and the dog, and renders the countries of Central Africa uninhabitable for those valuable animals. It seems

to possess very sharp sight. " It darts from the top of a bush as quick as an arrow on the object it wishes to attack," writes a tra veller, M. de Castelnau. Mr. Chapman, one of the many travellers who have explored the middle region of Southern Africa, relates that he covered his body with the greatest care to avoid the bites of this nimble enemy; but if a thorn happened to make a nearly imperceptible hole in his clothing, he often saw the Tsetse, who appeared to know that it could not penetrate the cloth, dart forward and bite him on

the uncovered part. The sucker of blood secretes — in a gland placed at the base of his trunk — so subtle a poison, that three or four flies are sufficient to kill an ox.

The Glossma morsitans abounds on the banks of the African river, the Zambesi, frequenting the bushes and reeds that border it. It likes, indeed, all aquatic situations. The African cattle recognise at great distances the buzzing of this sanguinary enemy, and this fatal sound causes them to feel the greatest fear.

Livingstone, the celebrated traveller, in crossing those regions of Africa that are watered by the Zambesi, lost forty-three magnificent oxen by the bites of the Tsetse fly, notwithstanding that they were . carefully watched, and had been very fittle bitten. " A most remarkable feature in the bite of the Tsetse is its perfect harmlessness in man and wild animals, and even calves so long as they continue to suck the cows. We never experienced the slightest injury from them ourselves personally, although we lived two months in their habitat, which was in this case as sharply defined as in many others, for the south bank of the Chobe was infested by them, and the northern bank, where our cattle were placed, only fifty yards distant, contained not a single specimen. This was the more remarkable, as we often saw natives carrying over raw meat to the opposite bank with many Tsetses settled on it.

"The poison does not seem to be injected by a sting, or by ova placed beneath the skin, for, when one is allowed to feed freely on the hand, it is seen to insert the middle prong of three portions, into which the proboscis divides, somewhat deeply, into the true skin. It then draws it out a little way, and it assumes a crimson colour, as the mandibles come into brisk operation. The previously-shrunken belly swells out, and, if left undisturbed, the fly quietly departs when it is full. A slight itching irritation follows, but not more than in the bite of the mosquito. In the ox this same bite produces no more immediate eflects than in man. It does not startle him, as the gad-fly does; but a few days afterwards the following symptoms supervene: the eyes and nose begin to run, the coat stares as if the animal were cold, a swelling appears under the jaw, and sometimes on the navel; and, though the animal continues to graze, emaciation commences, accompanied with a peculiar flaccidity of the muscles, and this proceeds unchecked until, perhaps months afterwards, purging comes on, and the animal, no longer able to graze, perishes in the state of extreme exhaustion. Those which are in good condition often perish, soon after the bite is inflicted, with staggering and blindness, as if the brain were

affected by it. Sudden changes ot temperature produced by falls of rain seem to hasten the progress of the complaint; but in general the emaciation goes on uninterruptedly for months, and, do what we will, the poor animals perish miserably.

"When opened, the cellular tissue on the surface of the body beneath the skin is seen to be injected with air, as if a quantity of soap bubbles were scattered over it, or a dishonest awkward butcher had been trying to make it look fat. The fat is of a greenish-yellow colour, and of an oily consistence. All the muscles are flabby, and the heart often so soft that the fingers may be made to meet through it. The lungs and liver partake of the disease. The stomach and bowels are pale and empty, and the gall-bladder is distended with bile. These symptoms seem to indicate, what is probably the case, a poison in the blood; the germ of which enters when the proboscis is-inserted to draw blood. The poison-germ contained in a bulb at the^ root of the proboscis, seems capable, although very minute in quantity,-, of reproducing itself. The blood after death by Tsetse is very small Ij in quantity, and scarcely stains the hands in dissection....

"The mule, ass, and goat enjoy the same immunity from die Tsetse as man and game. Many large tribes on the Zambesi keep no domestic animals except the goat, in consequence of the scourge existing in their country. Our children were frequenth bitten, yet suffered no harm; and we saw around us numbers o^ zebras, buffaloes, pigs, pallas and other antelopes, feeding quietl] in the very habitat of the Tsetse, yet as undisturbed by its bite as oxen are when they first receive the fatal poison. There is not so much difference in the natures of the horse and zebra, the buftalo and ox, the sheep and the antelope, as to afford any satisfactory explanation of the phenomenon. Is a man not as much a domestic animal as a dog? " The curious feature in the case, that dogs perish though fed on milk, whereas the calves escape so long as they continue sucking, made us imagine that the mischief might be produced by some plant in the locality, and not by Tsetse: but Major Vardon. of the Madras army, settled that point by riding a horse up to a small hill infested by the insect, without allowing him time to graze, and though he only remained long enough to take a view of the country and, catch some specimens of Tsetse on the animal, in ten days afterwards the horse was dead."'^ ■. ' '.. '

*' Missionary Travels and Researches in South Africa, "by David Livingslonc, LL.D., D.C.L. V.%i,ctseq. London, John Murray, 1857. (The extract in the

The inhabitants of the Zambesi can, therefore, have no domestic animal but the goat. When herds of cattle driven by travellers or dealers are obliged to cross these regions, they only move them during the bright nights of the cool season, and are careful to smear them with dung mixed with milk; the Tsetse fly having an intense antipathy to the dung of animals, besides being in this season rendered dormant by the lowness of the temperature. It is only by such precautions that they are able to get through this dangerous stage of their journey. The large blue Meat-fly, the familiar representative of the genus ^ Ca/h'f/iora, is known to all by its brilliant biue-and-white-reflecting abdomen. This fly, which is common everywhere, is the Cai/i-phora voinitoria on which Reaumur has made many beautiful observations, which we will make known to our readers.

If we shut up a blue meat-fly in a glass vase, as Reaumur did, and place near the insect a piece of fresh meat, before half a Fi§, 54 -Eggs of the Meat-fly. day is passed, the fly will have deposited its iCaiupkora vomitoria). eggs thereon one after the other, in irregular heaps, of various sizes. The whole of these heaps consist of about two hundred eggs, which are of an iridescent white colour, and four or five times as long as they are brOad. In less than twenty-four hours after the Qgg is laid the larva is hatched. It is no sooner born than it thinks of feeding, and buries itself in the meat with the aid of the hooks and lancets with which it is provided.

These worms do not appear to discharge any solid excrement, but they produce a sticky liquid, which keeps the meat in a moist state and hastens its putrefaction. The larvae eat voraciously and continually; so much so, that in four or five days they arrive at their full growth. They then take no more nourishment until they are transformed into flies. They are now about to assume the pupa state. In this condition it is no longer necessary for them to remain on the tainted meat, which has been alike their cradle and their

larder, and where until now they were so well ofl". They therefore leave it and seek a retreat under ground.

The larva then assumes a globular form and reddish colour, loses

original of this work is from a French translation: "Explorations dans I'lnterieur de I'Afrique australe, et voyages a travers le continent Sainte-Paul de Loanda a rEmbouchure du Zanibeze, de 1840 k 1846, traduit de 1' Anglais." Pages 93— 95. 8vo. Paris, 1859. —Ed.

JS THE INSECT WORLD.

all motion, and cannot any longer either lengthen or shorten, or dilate or contract itself. Life seems to have left it. " It would be considered a miracle," says Reaumur, "if we were told there was any kind of quadruped of the size of a bear, or of an ox, which at a certain time of the year, the beginning of winter for instance, disengages itself completely from its skin, of which it makes a box of an oval form; that it shuts itself up in this box; that it knows how to close it in every part, and besides that it knows how to strengthen it in such a manner as to preserve itself from the effects of the air and the attacks of other animals. This prodigy is presented to us, on a small scale, in the metamorphosis of our larva. It casts its skin to make itself a strong and well-closed dweUing."

If one opens these cocoons only twenty-four hours after the metamorphoses of the worms, no vestige of those parts appertaining to a pupa is to be found. But four or five days afterwards, the cocoon is occupied by a white pupa, provided with all the parts of a fly. The legs and wings, although enclosed in sheaths, are very distinct; these sheaths being so thin that they do not conceal them. The trunk of the fly rests on the thorax; one can discern its lips, and the case which encloses the lancet. The head is large and welJ formed, its large, compound eyes being very distinct. The wings appear still unformed, because they are folded, and, as it were, packed up. It is a fly, but an immovable and inanimate fly; it is like a mummy enveloped in its cloths.

Nevertheless, it is intended this mummy should awake, and when the time comes it will be strong and vigorous. Indeed, it has need of strength and vigour to accomplish the important work of its life. Although its coverings are thin, it is a considerable work for the insect to emerge, for each of its exterior parts is enclosed in them as in a case, much the same as a glove fits tightly to all the fingers of the hand. But that for which the most strength is necessary is the operation of forming the opening of the cocoon, in which as a mummy it is so tightly enclosed.

Page 13 of 88