HEMEROBIUS, in natural history, a genus of insects of the order Neuroptera. Mouth with a short horny mandible, the jaws cylindrical,istraight, cleft ; feelers Sour, unequal, filiform ; wings deflected, not folded ; antenna setaceous, project ing, longer than the thorax, which is con vex. There are nearly forty species, in two divisions ; A. lip cylindrical, mem branaceous, annulate B. lip horny, rounded at the tip, vaulted. The insects belonging to this genus are, like the ephemera, very short-lived, and in every state of their existence prey, with un ceasing avidity, upon plant-lice. The larva is six-footed, generally ovate and hairy ; the pupa mostly folliculate ; the eggs are deposited in clusters on the leaves of plants, each placed on a small gummy pellicle. When touched, many of them have an excrementitious smell. The most common species is the H. perla, an insect of great beauty, seen chiefly in the middle, and towards the decline of sum mer ; and is a slender-bodied fly, of a grass-green colour, with bright gold-co loured eyes, and four large, transparent oval wings, finely reticulated with pale green veins. The eggs of this insect are
supported each one on a delicate stem, of more than half an inch in length, which is attached to the surface of a leaf or twig, and by some persons, unacquainted with their nature, they have been taken for a small species of the fungus. From the eggs are hatched the larva, which in a few days become fitted to undergo their change into the chrysalis state. For this purpose the animal draws a fine silk from the extremity of the body, and in a short space envelopes itself in a round ball, of the size of a small pea, affixed to a leaf or twig of the tree it frequents, and divesting itself of its skin commences a chrysalis ; in about three weeks it be comes a complete insect. The hemero bios takes its name from the shortness or its life, as it seldom lives more than two or three days.