III.—Sheep attacked by Cephalemyia ovis.

grey, sometimes brown, bristling with small black turbercles; the abdomen white, spotted with brown or black; and the wings hyaline.

The Cephakmyia (CEstriis) ovis is to be found in Europe, Arabia, Persia, and in the East Indies. It lays its eggs on the edges of the animal's nostrils, and the larva lives in the frontal and maxillary sinuses. It is a whitish worm, having a black transverse band on each of its segments. Its head is armed with two horny black hooks, parallel, and capable of being moved up and down and laterally. Underneath, each segment of the body has several rows of tubercles of nearly spherical form, surmounted by small bristles having reddish points, and all of them bent backwards. "These points," says M. Joly, " probably serve to facilitate the progress of the animal on the smooth and slippery surfaces of the mucous membranes to which it fixes itself to feed^ and perhaps also to increase the secretion of these membranes by the irritation occasioned

by the brisdes with which they are furnished."''

Fixed by means of these hooks to the mucous membrane, which it perforates, the larva nourishes itself with mucus, and lives in this state, according to M. Joly, during nearly a whole year. At the end of this time it comes out, following the same course by which it entered, falls to the ground, and burying itself to the depth of a few inches, is transformed into a pupa. The cocoon is of a fine black colour. Thirty or forty days after its burial it emerges in the perfect state, and de- Fig. 5o.-Conops. taching the lid at the anterior end of the cocoon by the aid of its head, which has increased considerably in size, takes flight. Notwithstanding the formidable appearance of their trunks, the habits of the perfect Conopes (Fig. 50) are very quiet. In the adult state they are only to be seen on flowers, of which they suck the honeyed juice. But with their larvae the case is otherwise. These latter live as parasites on the humble-bees {Bombi). Latreille saw the Conops rufipes issue in the perfect state from the body of a humblebee, through the intervals of the segments of the abdomen.

" Recherches sur les (Estrides en general, et particulierement sur les CEstres ! qui attaquent I'homme, le cheval, le boeuf, et le mouton." Par N. Joly, Pro- I f(?sseur a la Faculte des Sciences de Toulouse. P. 63. Lyons, 1846.

THE INSECT WORLD.

70 The MuscidcE form that great tribe of Diptera commonly known as flies, which are distributed in such abundance over the whole world. Faithful companions of plants, the flies follow them to the utmost limits of vegetation., At the same time they are called upon-by Nature to hasten the dissolution of dead bodies. They place their eggs in the carcases of animals, and the larvce prey upon the corrupt flesh, thus quickly ridding the earth of those fatal causes of infection to its inhabitants. The organs of these insects are also infinitely modified, in order to adapt them to their various functions. M. Macquart divides the MuscidiC into three sections ■ — the Creophili, the Anthomyidce^ and the Acalyptera. The Crcophiii \d,'^ the strongest organisation; their movements and their flight are rapid. The greater |mrt feed on the juices of flowers, some on the blood or the, humours of animals. Some I deposit their eggs on diflerent kinds of insects, others on bodies in a state of decomposition, some again are viviparous. The insects of

Fig. 51. — Echinomyia grossa. the genus Echinomyia^ for instance (Fig. 51), derive their nourishment from flowers. They deposit their eggs on caterpillars, and the young larvae on hatching penetrate their bodies and feed on their viscera. How surprised, sometimes, is the naturalist, who, after carefully preserving a chrysalis, and awaiting day by day the appearance of the beautiful butterfly of which it is the coarse and mysterious envelope, sees a cloud of flies emerge in place of it!

But there is another singular manoeuvre performed by some of the species of the Diptera with which we are at present occupied, to

DIPT ERA. yi

prepare an abundant supply of provision for their laivae as soon as •hey are hatched. The following are the means they employ. It is vitW known that certain fossorial Hymenoptera carry their prey — Dther insects which they have caught, weevils, flies, &c., and which they intend should serve as food for their own larvae — into their subterranean abodes. These Diptera, spying a favourable moment, 'slip furtively into their retreats, and deposit their eggs on the very food which was intended for others. Their larvae, which are soon hatched, make great havoc among the provisions gathered together in the cave, and cause the legitimate proprietors to die o.f starvation.

" This instinct," says M. Macquart, " is accompanied by the greatest agility, obstinacy, and audacity, which are necessary to carry on this brigandage; and, on the other hand, the Hymenoptera, seized with fear, or stupefied, offer no resistance to their enemies, and although they carry on a continual war against different insects, and particularly against different Muscidce, they never seize those of whom they have so much to complain, and which, nevertheless, have no arms to oppose them with."

The Sarcophagce are a very common family of Diptera, and are chiefly to be found on flowers, from which they steal the juice. The

females do not lay* eggs, but are viviparous.

Re'aumur, with his usual care, observed this remarkable instance of viviparism proved in a fly, which seeks those parts of our houses where meat is kept to deposit its larvae. This fly is grey, its legs are black, and its eyes red. When one of them is taken and held between the fingers, there may often be seen a small, oblong, whitish, cylindrical worm come QUt of the posterior part of the body, and shake itself in order to disengage itself thoroughly. It has no sooner freed itself than the head of another begins to show. Thirty or forty sometimes come out, in this manner, and, on pressing the abdomen of the fly slightly, niore than eighty of these larvae may sometimes be made to come out in a short space of time. If a piece of meat be put near these worms, they quickly get into it, and eat greedily. They grow rapidly, attaining their full size in a few days, and make a cocoon of their skin, from which in a certain time the imago issues. If the body of one of these ovoviviparous flies (for the eggs hatch within the parent) be opened, a sort of thick ribbon of spiral form is soon seen. This ribbon appears at first sight to be nothing but an assemblage of worms, placed alongside of and parallel to one another.

. Each worm has' a thin white membranous envelope, similar to

THE INSECT WORLD.

those light spiders' webs which float about in autumn, which the French callyf/s- de la vierge, and we dtnominditQ gossamer.

The fecundity of this fly is very great, for, in the length of a quarter of an inch, the envelope in which these small worms are enclosed contains 2,000 of them. Therefore this ribbon, being two inches and a half long, contains about 20,000 worms.

The members of the genus Stof?ioxys, though nearly related to the house-fly, differ from it very much in habits. They live on the blood of animals. The Sto?noxys calcitrans is common in northern climates. Its palpi are tawny yellow, antennae black, thorax striped with black, abdomen spotted with brown, and its trunk hard, thin, and long. It deposits its eggs on the carcases of large animals.

The Golden Fly, Lucilia Ccesar, lays its eggs on cut-up meat, or

Fig. 52.— Lucilia hominivorax.

on dead animals. It is only three or four lines in length, of a golden green, with the palpi ferruginous, antennae brown, and feet black.

A species of this genus, the Lucilia hominivo7'ax, has obtained a melancholy notoriety. We are indebted to M. Charles Coquerel, surgeon in the French Imperial navy, for the most exact information concerning this dangerous creature, and the revelation of the dangers to which man is liable in certain parts of the globe. But let us first describe the insect, which is very pretty and of brilliant colours.

Fig. 52, taken from M. Charles Coquerel's Memoir, represents the larva and the perfect insect, as well as the horny mandibles with which the larva is provided. It is rather more than the third of an inch in length, the head is large, downy, and of a golden yellow.

DIPTERA.

The thorax is dark blue; and very brilliant, with reflections of purple, - as is also the abdomen. The wings are transparent, and have rather the appearance of being smoked; their margins, as well as the feet, are black. .This beautiful insect is an assassin. -M. Coquerel has informed us that it sometimes occasions the d^ath of those wretched convicts whom human justice has transported to the distant penitentiary of Cayenne. When one of these degraded beings, who live in a state of sordid filth, goes to sleep, a prey to intoxication, it happens sometimes that this fly gets into his mouth and nostrils; it lays its eggs there, and when they are changed into larvae,. the death of the victim generally ifollows.'' These-larvae are of an opaque white colour, a little over half an inch in length, aiid have eleven segments. /'They are lodged in theinterior of the nasal orifices and the fron.tafl sinuses, and their mouths

are armed with two very sharp horny'mandibles. They have been known to reach the ball of the eye, and to gangrene the eyelids. They enter the mouth, corrode and devour the gums and the entrance of the throat, so as to transform those parts into a mass of putrid flesh, a heap of corruption.

Let us turn away from this horrible description^;ioti observe that this hominivorous fly is nqt-, properly speaking, a parasite of man, as it only attacks him accidentally, a^'i't would attack any animal thatwas in a daily state of uncleanliness.

In many works on medicine may be found mentioned a circumstance which Occurred many years ago at the surgery of M. J. Cloquet. The story is perhaps not very agreeable, but is so interesting as regards the subject with which we are occupied, that we think it ought to be repeated here. One day a poor wretch, half dead, was brought to the Hotel-Dieu. He was a beggar, who, having some tainted meat in his 'wullet, had gone to sleep in the sun^ under a tree. He must have slept long, as the flies had time enough tQ deposit their eggs on the tainted meat, and the larvae time enough

to be hatched, and to devour the beggar's meat. It seems that the larvae enjoyed the repast, for they passed from the dead meat to the living flesh, and after devouring the meat they commenced to eat the

. - * " The majority of convict^ attacked by the Lticilia hominivorax,"' says M. F. ^C)uyer, captain of the frigate, in " Un Voyage a la Guyane Fran(;aise,'' "have succumbed, despite the assistance of science. Cures have been the excej^fion: in a dozen cases three or four are reported." — Tour dii Mondc^ 1866, ur Semestre^

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