Dragon Fly (libellula, Linn.), an insect of the family siibulicornes of Latreille, or odonata (Fabr.), and the order neuroptera. The insects of this genus, called in this country " devil's darning needles," in the perfect form are light and graceful fliers, of the most brilliant and beautiful colors, with four large, shining, delicate wings of nearly equal size; the mouth is provided with strong horny mandibles and spiny maxillae; the eyes are lateral, large, and brilliant, with three stemmata on the top of the head; the antennae consist of from three to six joints; the legs are short, six in number, directed forward, arising from a firm thorax of three united segments; the abdomen is very long, a flattened cylinder, soft, without sting or piercer, and in the males terminated by two lamellar appendages. In some genera the male sexual organs are placed in the second abdominal ring, and those of the female in the last ring; the female deposits her eggs on aquatic plants beneath the surface of the water. From their lightness and beauty the French call them demoiselles. They are among the most voracious and cruel of insects, darting with swiftness and ferocity upon gnats, mosquitoes, butterflies, and almost any soft-bodied winged insect, eating even their own species.

They are in no way injurious to man, but are directly beneficial in destroying many noxious insects. They hover over pools in search of prey, or dart from a post or fence upon insects coining near. They are equally carnivorous in the larva state, which they pass in the water. The larvae have six feet, and a very complicated arrangement of the parts forming the under lip, which covers the face like a mask, concealing the mouth; they crawl stealthily along the bottom, and spring their jointed mask upon insects and even small fishes with great precision. By a valvular apparatus at the end of the tail, they draw in and expel water, as a means of locomotion. They remain several months in the water, and change their skins several times. The nymphs have rudimentary wings, and when they are ready to assume their final change the brilliant eyes of the future fly may be seen through the envelope; they crawl out of the water upon some bank or aquatic plant, where the pupa skin becomes dry and crisp and hursts open on the back. During the drying of the wings the insect bends the body into a crescent, that the delicate tissue may not be disturbed by contact with any foreign substance.

The anterior nervures of the wings must bo very strong, though light, to permit the rapid vibrations of these organs; their section, as in the butterfly, presents the form found by engineers to be that of the beam of greatest strength and lightness, viz.: the greatest amount of material thrown into the oval flanges, connected by the thinnest possible median support. According to Drury, these insects are two years in reaching the perfect form from the egg; after flying about a few weeks, and having performed the act of reproduction, the wings become ragged, the strength fails, and they soon die. M. Poey says that at certain seasons the north winds sweep hosts of them into the neighborhood of Havana; in Belgium in 1854 a swarm was seen extending three quarters of a mile, the lowest individuals flying at a height of about six feet. - The restricted genus libellula, of which nearly 20 species inhabit New England, has a flattened, moderately long body, an almost globular head, the eyes contiguous or approximate, and the wings horizontal when at rest. The larvae are short and thick, rough and of a dirty color; they have five appendages to the tail.

The genus oeshna (Fab.) includes the large species, with long slender bodies, which keep the wings expanded when at rest; the larvae are larger, long and slender, with the abdomen flat below and rounded above; this includes the L. grandis (Linn.), the largest and most predaceous of the British genera; there are about a dozen species in Massachusetts. In the genus agrion (Fab.) the wings are perpendicular during repose, the head transversal, and the eyes far apart; this includes the species with the slender and filiform abdomen, sometimes of extraordinary length; the larvae are small, with round slender bodies terminating in three feathery appendages; there are about ten northern species well known, many of them delicate and beautiful; among the foreign species are some of the most brilliant of insects. Many of the finest American species of this family are described and figured by Drury.

Libellula trimaculata.

Agrion.