The genus Musca (fly), in which Linnaeus comprised the immense eries of Diptera, with the exception of the Tipulida, the Tabanidce^ he A si/ idee, the Bombylidcs, and the Empidce, is now reduced to the louse Fly and a few resembHng it. The habits of these trouble-ome companions are in conformity with the two great principles of .nimal life, that is, eating and propagating their species.

Flies feed principally on fluids which exude from the bodies of .nimals; that is, sweat, saliva, and other secretions. They also seek ege table juices; and they may be seen in our houses to feed eagerly m fruits and sweet substances.

The common flies deposit their eggs on vegetables, and particu-arly on fungi in a state of decomposition, on dung-heaps, cow dung, 5cc. They are essentially parasites, settHng on both man and beast, o suck up the fluid substances which are diftused over the surface of heir bodies. In our dwellings they eat anything that will serve to

Fig. 61.— Lancet of the Meat Fly. Fig. 62, -House ¥\y {Musca domestica).

nourish them. Generation succeeds generation with the greatest apidity. The House Fly {Musca domestica, Fig. 62) is about three lines in length, ash-coloured, with the face black, the sides of the head yellow, and the forehead yellow with black stripes; the thorax is marked with black lines; the abdomen is pale underneath, and a transparent yellow at the sides, in the males, and is speckled with black. The feet are black; the wings transparent, and yellowish at the base. This species is extremely plentiful throughout the whole of Europe. Every one knows how annoying it is towards the end of the summer, and especially so in the South of France during the hot season. The Ox Fly {Musca bovina\ a near relation of the house fly, is also very common. It setdes on the nostrils, the eyes, and thewounds of animals.

The Executioner Fly {Musca carnifex), which is not rare m France, also attacks oxen. It is of a dark metallic green colour

H THE INSECT WORLD.

with a slight ash-coloured down. Its forehead is silvery at the front and sides; the abdomen is edged with black; the wings hyaline, and yellow at the base. Section of the Antho?nyidce.—T\Q section of AnthomyidcE comprises insects which appear to be Creophili whose organisation has become weakened by almost insensible degrees. Their colours vary very much — black, grey, and iron-colour are everlastingly shaded and blended together. To that may be added reflections which are above the ground colour, and which change the hues of the little animal according to the incidence of the rays of light. The Antho-myidii resemble the genus Musca very closely in their habits as well as in their organisation. In this group of Diptera we will first say a few words about the Anthoviytcp. These flies are to be found in most gardens, and on all flowers, particularly on the heads of Compositae and Umbellifer^e. They often unite in numerous bands in the air, and indulge in the joyous dances to which love invites them. The females deposit their eggs in the ground, and their larvae are there quickly developed. The latter suspend themselves to certain bodies, the same as some lepidopterous chrysalides, in order to transform themselves intc

pupae.'W^ Anthomyia pluviaUs (Fig. 63) is from two to four lines in length, and of a whitisJi ash-colour. Its wings are hyaline, the thorax has five black spots, and the abdomen thret rows of similar spots. AVe will stop a moment with the Pego fnyicE, which are very interesting in the larva

Fig. 63.— Amhomyia pluvialis. state, and which excited the interest anc sagacity of Reaumur. The cradle of these Diptera is the interior of leaves. They work as the miners of the vegetable world, in the parenchyma or cellulai tissue of the leaf, between the two epidermal membranes Th( henbane, the sorrel, and the thistle, especially nourish them. If ont holds a leaf in which one of these miners has established itself againsl the light, one sees the workman boring the vegetable membrane Its head is armed with a hook, formed of two horny pieces, anc with this hook it digs into the parenchyma of the leaf. The eftect Oi

DIPTERA.

This digging is visible, as those places become by degrees transparent. Each blow detaches a small portion of the substance of the leaf. It is thus that these miners hollow out galleries for themselves, in which they find shelter, food, and security. Some are changed into pupæ in the gallery which they have hollowed out, others go out of the leaves when they are near their final transformation.

Section of Acalyptera.—The Acalyptera, which are the last of the great tribe of Muscidæ, comprehend the greater number of these insects. Their constitution appears to be peculiar and slow. They live principally in the thickest part of woods, on grasses, and aquatic plants. Fearing the lustre and warmth of the sun, they never draw the nectar from flowers. Their flight is feeble, and they never indulge in those joyous ethereal dances which we have mentioned when speaking of the preceding groups. Their life is generally melancholy, obscure, and hidden. Some of them seek decomposed animal and vegetable substances, others living vegetables.

We shall only be able in this immense group of Muscidæ to mention a few types which are interesting from various reasons, such as the Helomyzæ, the Scatophagæ, the Ortalidæ, the Daci, and the Thyreophoræ.

The Helomyzæ (Fig. 64) live in the woods. Their larvæ are developed in the interior of fungi. Réaumur studied the larvæ of the Truffle Helomyza. The head of this fly is ferruginous, its thorax is of a brownish grey, its shoulders of a brownish yellow, its wings brownish, the abdomen yellow and brown, and the feet red.

Fig. 64.—A species of Helomyza.

The larvæ of these insects commit depredations for which gourmands will never forgive them, destroying, as they do, their truffles. When one presses between one’s fingers a truffle that is in a too advanced state, one feels certain soft parts, which yield under pressure. On

opening the truffle, the larvae of the insect of which we are speaking will be found inside. These larvae are white and very transparent. Their mouth is armed with two black hooks, by means of which they dig into the truffle in the same way as other larvae dig into meat. The excretions of these little parasites cause the truffle to become decomposed and rotten. In a few days the larvae become full-grown. They then leave their abode and go into the ground, there to change; into pupae. j The Ortalidd! form a tribe which is remarkable for the upright carriage of the wings, which are generally speckled, by the vibratory movement of these organs, and especially for the cradle chosen by them for their progeny in fruits and grains. Nature seems to have assigned to each species its own particular vegetable.

We will only mention here the Cherry-tree Ortalis, whose larva lives on the pulp of that fruit. This fly is about a line and a half long. It is of rather a metallic black colour, its head light yellow, the edges of its eyes white, and the tarsi red. The wings have four broad black stripes. The Olive Dacus {Dacus oiece, Fig. 65) is a little fly, about half the size of the house fly, of ashy grey colour on the back, its head orange-yellow, its eyes green, and its forehead yellow, marked with two large black spots. The thorax is adorned with four lightish yellow spots, and its hind part, as well as its antennae and wings, are of the same colour. The wings are transparent, reflecting green,

Fig. 65.-Dacus oies. gold, pink, and blue, according as the rays of light fall upon them, and are remarkable for having a small black spot at their extremity. The abdomen is of a fawn colour or orange-yellow, spotted with black on each side. This fly performs sudden and jerking movements; it keeps its wings extended, and rather jumps than flies. It is a destructive insect, a perfect scourge, which causes every two or three years a loss of five or six millions of francs to French agriculture. M. Guerin-Meneville has made some valuable observations on

the Olive Dacus, and at the request of the Imperial Society ot" Agriculture of Paris, has indicated the way to preserve the olive from

DIPTBRA.

these rumous larvae, which generally destroy two crops out of three. We will borrow the following details from this learned entomologist:

Fig. 66. — Olives attacked by Dacus oleae.

" At the time when the olives are formed the Dacus proceeds to place an egg under the skin of each of the fruits. By means of a fetle horny instrument, with which the female is provided, and which

contains a small lancet, she pierces the skin of_ the olive; she nipves. her wings and lays hex egg. She afterwards cleans and rests herself, by passing her feet over her head, wings, and other parts of her body. She then flies away, and seeks another olive, to deposit in it another egg; she repeats this operation until she has placed on as many olives the three or four hundred eggs which she bears."

Fig. 66, taken from the Memoir published by M. Gue'rin- Me'neville, in the "Revue Nouvelle '' of the 15 th July, 1847, shows the Dacus laying its eggs on the olive, and the larvae that are already hatched in another of the same fruit. The larvae which succeed these eggs (Fig. 67) are whitish, soft, and without limbs. They pass fifteen or sixteen days in boring a gallery in the pulp of the olive, at

Fig. 67. Larvae of Dacus olese (magnified and natural size). Gallery formed byFig.larva68. of Dacus oleae.

first vertically, until they reach the stone, then on one side, and along the side of the stone. When they have reached the term of their development, they approach the surface, enlarging the first channel and leaving between it and the exterior air only a thin pellicle, in the middle of which may be perceived the first small opening by which the mother had introduced her tgg in the commencement.

Fig. 68, copied from a drawing in the Memoirs of M. Gue'rin- Me'neville, shows the gallery bored round the olive by the larva of the Dacus. The larva thus prepares an easy issue for the perfect insect. Its skin then contracts, its body diminishes in length, and is transformed into an ^val cocoon, which soon gets brown, and is the chrysalis of the insect. At the side of the head it shows a curved

line, 'a thin suture which marks a sort of cap or door, ^yhich, at- the time of its hatching, the insect will be easily able to force open with its head. The fly is hatched; twelve days after its inetamorphosis

from the larva to the pupa. It has thus taken the Dacus twenty-seven to twenty-eight days to arrive at this state, from the time the egg was laid; besides which, this species, in the warm cUmates of Provence and Italy, can reproduce itself several times from the beginning of July, the period at which the first flies begin to lay, till the end of autumn. In order to save a considerable portion of the olive crop of these countries, M. Guerin-Meneville has advised hastening the harvest sufficiently for all the olives to be pressed at a time when the larvas of the last generation, which would be preserved in the olives that are left, or in the earth, according to the climate, are still in the fruit. If a first operation were not sufficient to destroy them all, it should be repeated the following year. The sacrifice entailed by this practice would be amply compensated by a succession of good crops and the certainty of a sure and permanent profit. In fact, by an i early gathering at least half a crop of oil is still obtained; whereas, , by waiting for the usual period of gathering the olives, sufficient time [ is left for the larvae of the Dacus to devour their parenchyma, which \ deprives them of the little oil that they might have yielded if their destruction had been accomplished earher. This early gathering has the advantage of causing the destruction of a great number of larvae, which will be so much towards diminishing the means of reproduction of the flv.

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