gnat; a genus of insects belonging to the order of diptera. The mouth is formed by a flexible sheath, including bristles pointed like stings. Plate CLI. The antennae of the males are filiform; those of the females feathered. There are seven species. These insects, too well known by the severe punctures they inflict, and the itchings thence arising, afford a most interesting history. Before they turn to flying insects, they have been in some manner fishes, under two different forms. You may observe in stagnating waters, from the beginning of May till winter, small grubs with their heads downwards, their hinder-parts on the surface of the water; from which part arises sideways a kind of vent-hole, or small hollow tube like a funnel, and this is the organ of respiration. The head is armed with hooks, that serve to seize on insects and bits of grass on which it feeds. On the sides are placed four small fins, by the help of which the insect swims about, and dives to the bottom. These larvae retain their form during a fortnight or three weeks, after which period they turn to chrysalids. All the parts of the winged insect are distinguishable through the outward robe that surrounds them. The chrysalids are rolled up into spirals. The situation and shape of the windpipe is then altered; it consists of two tubes near the head, which occupy the place of the stigma, through which the winged insect is one day to breathe. These chrysalids, constantly on the surface of the water in order to draw breath, abstain now from eating; but upon the least motion are seen to unroll themselves, and plunge to the bottom, by means of little paddles situated at their hinder-part. After three or four days strict fasting, they pass to the state of gnats. A moment before, water was its element; but now, become an aerial insect, it can no longer exist in it. He swells his head, and bursts his inclosure. The robe he lately wore turns to a ship, of which the insect is the mast and sail. If at the instant the gnat displays his wings there arises a breeze, it proves to him a dreadful hurricane; the water gets into the ship, and the insect, who is not yet loosed from it, sinks and is lost. But in calm weather, the gnat forsakes his slough, dries himself, flies into the air, seeks to pump the alimentary juice of leaves, or the blood of man and beasts. The thing which our naked eye discovers, is but a tube, containing five or six spicula of exquisite minuteness; some dentated at their extremity like the head of an arrow, others sharp-edged like razors. These spicula, introduced into the veins, act as pump-fuckers, into which the blood ascends by reason of the smallness of the capillary tubes. The insect injects a small quantity of liquor into the wound, by which the blood becomes more fluid, and is seen through the microscope passing through these spicula. The animal swells, grows red, and does not quit its hold till it has gorged itself. The liquor it has injected causes by its fermenting that disagreeable itching which we experience; and which may be removed by volatile alkali, or by scratching the part newly flung, and washing it with cold water; for later, the venom ferments, and you would only increase the tumor and the itching. Rubbing oneself at night with fuller's-earth and water, lessens the pain and inflammation. Gnats perform their copulation in the air. The female deposits her eggs on the water; by the help of her moveable hinder part and her legs, placing them one by the side of another in the form of a little boat. This vessel, composed of two or three hundred eggs, swims on the water for two or three days, after which they are hatched. If a storm arises, the boats are sunk. Every month there is a fresh progeny of these insects. Were they not devoured by swallows, other birds, and by several carnivorous insects, the air would be darkened by them.

Gnats in this country, however troublesome they may be, do not make us feel them so severely as the muleto-flies (culex pipiens) do in foreign parts. In the daytime or at night these come into the houses; and when the people are gone to bed they begin their disagreeable humming, approach always nearer to the bed, and at last suck up so much blood that they can hardly fly away. Their bite causes blisters in people of a delicate constitution. When the weather has been cool for some days, the mosquitoes disappear; but when it changes again, and especially after a rain, they gather frequently in such quantities about the houses, that their numbers are astonishing. In sultry evenings they accompany the cattle in great swarms, from the woods to the houses or to town; and when they are driven before the houses, the gnats fly wherever they can. In the greatest heat of summer, they are so numerous in some places, that the air seems to be quite full of them, especially near swamps and stagnate waters, such as the river Morris in New Jersey. The inhabitants therefore make a fire before their houses to expel these disagreeable guests by the smoke.