Sometimes called halicns. — Ed. 59

very much; and the formation of the sucker is regulated by it. Some imbibe blood, others live on the secretions of animals. Their chief nourishment, however, consists of the juices of flowers, on whose brilliant corollas the Diptera abound, either plundering from every species indiscriminately, or attaching themselves to some particular kind. They display the most wonderful instinct in their maternal care, and employ the most varied and ingenious precautions to preserve their progeny. The Diptera, besides their variety and the number of their species, are remarkable on account of their profusion. The myriads of flies which rise from our meadows, which fly in crowds around our plants, and around every organised substance from which life has departed, some of which even infest living animals, are Diptera.

The profusion with which they are distributed over the face of the globe, causes them to fulfil two important duties in the economy of Nature. On the one hand, they furnish to insectivorous birds an inexhaustible supply of food; on the other, they contribute to the removal of all decaying animal and vegetable substances, and thus serve to purify the air which we breathe. Their fecundity, the rapidity with which one generation succeeds another, and their great voracity, added to the extraordinary quickness of their reproduction, are such that Linnaeus tells us that three flies, with the generations which spring from them, could eat up a dead horse as quickly as a lion could.

These Diptera, which are worthy of so much attention, and deserve so much study with regard to the part they play in the general economy of Nature, are an object of fear and repulsion when one considers their relations to us and other animals. Gnats and mosquitoes suck our blood; the gad-fly and the species of Asilus attack our cattle. The order Diptera is composed of a great number of families, which are again divided into tribes, each comprising several genera. We shall only notice the more remarkable genera of Diptera. M. Macquart, the learned author of "L'Histoire Naturelle des Dipteres,''''' divides this great class of insects into two principal groups.In one of these groups, the antennae are formed of at least six joints, and the palpi of four or five: these are called Nemocera. In the other, the antennae consist only of three joints, and the palpi of one or two: these are the Brachycera.

The Nemocera may generally be distinguished from the other Diptera, independently of the difference in the antennae and palpi, by

" Suites a Buflon." 2 vols. 3vo.

DIPT ERA.

35 the slenderness of the body, the smaUness of the head, the shape of the thorax, and the length of the feet and wings. The result of this " organisation is a graceful, light, and aerial form

Nemocera.

Abounding everywhere, the Nemocera live, some on the blood of ' man and animals, some on small insects, and others on the juices of fragrant flowers. From vr\ii.(x, thread; /c^pos, horn.

In all climates, in every latitude, in the fields and woods, even in our dwellings, they may be seen fluttering and plundering. The Nemocera are divided into two families, that of the Cii/icidce, of which the gnat {Culex), which has a long, thin trunk, and a sucker provided with six bristles, is a member; and that of the Tipu/idcE, which have a short thick trunk, and a sucker having two bristles.

We will begin our examination with the Gnat {Culex pip lens), of

Figs. 19 and 20. — The Gnat {Culex pi^iens).

which Re'aumur, in his "Memoires pour servir a I'Histoire des Insectes," has given such a curious history (Figs. 19, 20). ''The gnat is our declared enemy," says Re'aumur, in the introduction to his memoir, "and a very troublesome enemy it is. However, it is well to make its acquaintance, for if we pay a little attention we shall be forced to admire it, and even to admire the instrument with which it wounds us. Besides which, throughout the whole course of its life it offers most interesting matter of investigation to those who are curious

THE INSECT WORLD.

36 to know the wonders of Nature. During a period in its life the observer, forgetting that it will at some time annoy him, feels the greatest interest in its life- history."

As this is the case, let us explain the history of these insects, which excite so much interest. The illustrious naturalist we have just mentioned will be our guide.

The body of the gnat is long and cylindrical. When in a state of repose one of its wings is crossed over the other. They present a charming appearance when seen through a microscope, their nervures, as well as their edges, being completely covered with scales,

Fig. 21.— Antennse of Gnat, magnified. Fig. 22. — Head of Gnat, magnified.

shaped like oblong plates and finely striated longitudinally. These scales are also found on all the segments of the body.

The antenn?e of the gnat, particularly those of the male, have a fine feathery appearance (Fig. 21).

Their eyes, covered with network, are so large that they cover nearly the whole of the head. Some have eyes of a brilliant green colour, but looked at in certain lights they appear red. Fig. 22 shows the head of, the gnat with its two eyes, its antenn?e, and trunk.

The instrument which the gnat employs for puncturing the skin, and which is called the trunk (Fig. 23), is well worthy of our attention. That which is generally seen is only the case of those instruments which are intended to pierce our skin and suck our blood, and in which they are held, as lancets and other instruments are held in a surgeon's case. The case (Fig. 24) is cylindrical, covered with scales, and terminates in a small knob. Split from end to end that

it may open, It contains a perfect bundle of stings. Reaumur tried to observe, by allowing himself to be stung by gnats, what took place during the attack. He forgot, in watching the operations of the insect, the slight pain caused by the wound, soliciting it as a favour, his only regret being not to obtain it when he wished.

Reaumur observed that the compound sting, which is about a line in length, enters the skin to the depth of about three-quarters of a line, and that during that time the case bends into a bow, until the two ends meet. He noticed besides, that the trunk-case of certain

Figs. 23 and 24. Figs. 25, 26, 2.7. Trunk of Gnat, magnified. Lancets of the Gnat.

gnats was even more complicated than that which we have described. But we will not dwell any longer on this point.

Let us now try to give an idea of the construction and composition of this sting, which, after piercing the skin, draws our blood.

According to Reaumur, the sting of the gnat is composed of five parts. He acknowledges, however, that it is very difficult to be certain of the exact number of these parts, on account of the way In which they are united, and of their form. At the present day we know that there are six. Reaumur, as also Leuwenhoek, thought he saw two In the form of a sword blade with three edges. These have the points reversed, and are serrated on the convex side of the bend (Fig. 25). To form an idea of the shape of the other points, the reader should look at Figs. 26 and 27. He will then see that the gnat's sting is a sword in miniature.

The prick made by so fine a point as that of the sting of the gnat

THE INSECT WOni.D.

ought not to cause any pain. " The point of the finest needle," says Reaumur, '' compared to the sting of the gnat, is the same as the point of a sword compared to that of the needle." How is it thenthat so small a wound does not heal at once? How is it that small bumps arise on the part that is stung? The fact is, that it is not only a wound, but it has been imbued with an irritating liquid.

This liquid may be seen to exude, under different circumstances, from the trunk of the gnat, like a drop of very clear v/ater.

Reaumur sometimes saw this liquid even in the trunk itself. " There is nothing better," he observes, " to prevent the bad effects of gnat bites than at once to dilute the liquid they have left in the wound with water. However small this wound may be, it will not be difficult for water to be introduced. By rubbing, it will be at once enlarged, and there is nothing to do but to wash it. I have sometimes found this remedy answer very well."

The gnat is not always in the form of a winged insect, greedy for our blood. There is a period during which they leave us in repose. This is the larva period. It is in water, and in stagnant water in particular, that the larva of the insect which occupies our attention is to be found. It resembles a worm, and may be found in ponds from the month of May until the commencement of winter. If we desire to follow the larva of the gnat from the beginning, we have only to keep a bucket of water in the open air. After a few days this water will be observed to be full of the larvae of the gnat (Fig. 28). They are very small, and come to the surface of the water to breathe; for which purpose they extend the opening of a pipe, A, which is attached to the last segment of the

body, a little above the surface. I'hey are, consequently, obliged to hold their heads down. By the side of the breathing-tube is another tube, b, shorter and thicker than the former, nearly per-

Fig. 28. pendicular to the body, its orifice being the exterior

Larva of the Gnat. termination of the digestive tube. At the anus it is fringed with long hairs, having the appearance, when in the water, of a funnel. At the end of the same tube, and inside the hair funnel, are four thin, oval, transparent, scaly blades, having the appearance of fins. They are placed in pairs, of which one emanates from the right side, the other from the left. I

Fig. 28. of the G Fig. 28. Larva of the Gnat.

These four blades or fins have the power of separating from each other. Each segment of the abdomen has on both sides a tuft of hair, and the thorax has three. Hie head is round and flat, and is provided with two simple brown eyes. Round the mouth are several wattles, furnished with hair, of which two of crescent-like form are the most conspicuous. These tufts move with great quickness, causing small cuiTents of liquid to flow into the mouth, by means of which the necessary food, microscopic insects and particles of vegetable and earthy matter, is brought to the larva.

They change their skin several times during their continuance in this state. This latter fact has been remarked by Dom Allou, a learned Carthusian, '• whose pleasure," says Reaumur, " consisted in admiring the works of the Almighty, when not occupied in singing His praises." We think it will be interesting to repeat the fe\v lines which accompany the mention made by Reaumur of this worthy Carthusian. They appear to us to be well worth reading, even at the present day. " If the pious monks who composed so many societies, possessed, like Dom Allou, the love of observing insects, we might hope that the most essential facts in the history of those little creatures would soon be made known to us. What enjoyment more worthy of the calling they have chosen could these pious men pursue than that which would place before their eyes the marvellous creations of an Almighty Power? Even their leisure would then incline them to adore that Power, and would furnish them the means to make others do so who are occupied by too serious or too frivolous employments.'' After having changed its skin three times in a fortnight or three weeks, the larva of the gnat throws off its covering for a fourth time, and is no longer in the larva state. It is changed both in shape and condition. Instead of being oblong, its body is shortened, rounded, and bent in such a way that the tail is applied to the under part of the head. This is the case when the animal is in repose; but it is able to move and swim, and then, by bending its body and straightening it again, propels itself through the water.

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