DRAGON-FLY, Libellula, a Linntean genus of neuropterous insects, now constituting the family libellulidce. They are in general very beautiful, rivaling butterflies in their hues, and like them loving the sunshine. They are, however, easily distinguished from butterflies, even at a distance, by their more slender form and comparatively narrow gauze-like wings; and differ from them still more widely in their habits, as they do not feed on the nectar of flowers, but prey on other insects, which they pursue with rapid flight. Dragon-flies have a large head; the mouth is formed for mastication, and its parts, especially the mandibles, possess great strength.—See the article COLEOPTERA for an explanation of the structure of the mouth in masticating insects, and the names of its parts.—The antennte are short, awl-shaped, and of few joints. The eyes are large, lateral, and projecting. The wings—four in number—are equal in size, or nearly so, long, very t'-in, and very much reticulated. The legs are short. The abdomen in some is compresseu, in others slender and cylindrical, in some remarkable for its extreme slenderness. The French name demoiselle, given to these insects, seems to be due to their beauty. They are, however, equally remarkable for their voracity. The great dragon-fly (aeshna grandis), an insect aJout 4 in. long, the largest of the British species, has been seen to dart upon a large which passed as it was flitting up and down in search of prey; and then wattling on a twig, it bit off the wings, and in less than a minute devoured the body.
Dragon-flies are usually most abundant in the vicinity of lakq, rivers, and marshes. They deposit their eggs in water, and the larvw and pupae are entirely aquatic, living chiefly at the bottom of the water, and creeping on the submerged parts of aquatic plants. They are as ravenous as the perfect insect, which in general form they pretty much resemble; aquatic insects are their food. The pupm, unlike those of the greater number of insects, are active. They are provided with the means of drawing water into their bodies to supply air for respiration, and expel it again by the same orifice at the extremity of the abdomen, with such force, that they thus propel themselves through the water, whilst their legs are at rest. When the final transformation is about to take place, the dragon-fly pupa crawls out of the water on a stick, rush, or other object; fixes itself by hooks, with which its legs are furnished; and the skin then splitting at the back, the perfect insect comes forth, but with body and wings quite soft and moist, and the wings still folded up into small compass. In the sub-family of agrionidce, the wings arc elevated vertically in repose: in the true lthellulidas aeshna, etc.), they are extended horizontally.
Dragon-flies extend even into very northern regions, but are most abundant in warm climates.