are divided into two sections-Land-bugs and Waterbugs. To the former section belong the Bedbugs before referred to. Of the Water-bugs there are only two families the Boat-flies and the Water Scorpions. The former are good swimmers, always swimming on the back. They can fly well, but rarely do it.

499. The Diptera, or two-winged insects, constitute one of the most extensive orders, both in the number of species and in the number of individuals. None of them are large, and some are exceedingly small. For the most part they are dull in color. On the head are two very large compound eyes, and two short antennæ near together. In some there is a soft proboscis, as the common House-fly; in others, a hard, pointed, sucking tube, as in the Musquito; and in others still, simply a mouth. They have three pairs of feet, and two thin wings, which, in most cases, give out a humming sound in flying. Their larvæ are generally maggots, white, and having no feet, but instead thereof fleshy tubercles or warts, on which they crawl. Most of the larvæ live in dirt, or dung-hills, or spoiled meat, or cheese, etc. The metamorphosis is complete, but in some cases very peculiar.

500. The species of Flies are very numerous. There are about seventeen hundred known in Europe. The larvæ of Flies, the maggots, generally live in some kind of filth; but the Flies themselves live, for the most part, on dainty food. The wing of a common Fly, examined under the microscope, is a beautiful object. Although to the naked eye it has a very plain appearance, it is covered with little pointed projections of curious shape regularly arranged.

501. The larvæ found in cheese come from eggs deposited by a small Fly. From their great power in leaping they are called Cheese-hoppers. The manner in which the leap is performed is very singular, and is thus described by Carpenter: "When preparing to leap, it first raises itself upon its tail, in which position it is enabled

to balance itself by means of some prominent tubercles on the last segment of the body. It then bends itself into a circle, and having brought the head toward the tail, it stretches out the two hooks of the mouth, fixing them into two cavities at the other extremity of the body. It then contracts the body from a circular to an oblong figure-the contraction extending in a manner to every part of the body. It now suddenly lets go its hold, and straightens the body with such violence that the noise produced by its hooks is very perceptible. The height of the leap is often from twenty to thirty times the length of the body, exhibiting an energy of motion which is par ticularly remarkable in the soft larva of an insect. A Viper, if endowed with similar powers, would throw it self nearly a hundred feet from the ground."

A

Fig. 227.-Wriggler.

502. The Musquito family are remarkable in many respects, but chiefly for the peculiar mode of their metamorphosis. The common Musquito, when first hatched, is an inhabitant of the water, and is, from its antic and rapid motions, called a Wriggler. In Fig. 227 you see the animal of its natural size, and also as it looks when magnified. Though it lives in the water, it is not like a fish, for it has no gills. It is more like a whale, for it is obliged to come occasionally to the surface to breathe. Its breathing apparatus is near its tail. The air is taken in through a tube made of hairs, represented at A. After the insect arrives at its proper size it comes to the surface with its back upward, which gapes open, as in the case of the Cicada (§ 493), and the winged insect emerges, as seen in an enlarged representation in Fig. 228. It

Fig. 228.

rests upon its cast-off skin as a boat, while it unfolds and expands its wings, and then flies off. Great care is required in this operation, as there is danger that the in

sect will be plunged into the water before it expands its wings.

503. The eggs of the Musquito are deposited on the surface of stagnant water to the number of about three hundred, fastened together as you see in Fig. 229. They thus make a sort of raft which swims on the surface.

Fig. 229.

The large ends of the eggs are downward, and it is out of these that the larvæ come, diving down into the water. There is a lid at the blunt end of the egg which is opened to let the larva out. Some species do not have this mode of arranging their eggs.

504. The proboscis which is visible to us, and which the insect so deliberately adjusts upon the skin when it alights, is not the stinging apparatus, but the sheath or scabbard of it. It incloses some bristles with lancetshaped points. When the skin is pierced by these, the blood is sucked up through the sheath. It is supposed that the irritation attending the bite is occasioned by the saliva of the insect introduced into the wound to dilute the blood that it may more readily be sucked up. In Fig. 230 you have at A the sheath closed, both of the natural size and magnified. In the lower figure you have the whole instrument opened at B the sheath, at C three lancets, and at D protectors. At F you see these parts of their natural size. This is the arrangement of the proboscis of the common American Musquito. It is different, however, in the different species of this insect.

505. The different species of Musquitoes, of which there are many, are quite widely diffused in the earth.

D

B

Fig. 230.

They are generally most troublesome in warm climates, and in the tropics they are present throughout the year. But there are some cold countries in which, during their brief but hot summers, they are not only extremely annoying, but occasionally very destructive. This is the case with parts of Russia, both in Europe and in Asia. Even such animals as horses, oxen, sheep, goats, and hogs, are so severely stung by them as to die, some meeting their death by drowning, having run into water to escape the swarms of their small but formidable enemies. At some periods it seems in that country to be the grand business of life to devise and put in execution expedients for guarding man and beast against these insects.