diptera

Gr. dipteros=two-winged: dis = twice, twofold, and pteron a wing.] Entom.: An order of insects, such as gnats, house flies, ., that have only two membranous wings developed, the hind pair being represented by two small knobbed organs, called halteres , or poisers, whose exact function is as yet undetermined. The mouth is suctorial, and forms a proboscis composed of mandibles, maxillæ, and a central piece, or tongue (glo arium), the labium, often with a fleshy, terminal lip, serving as a sheath; frequently some of these parts are converted into chitinous setæ, or into lancet-shaped bodies, with which their owners pierce the ti ues of animals or plants, whose juices, thus set free, they feed on, sucking them up through the tubular proboscis. They have two large compound eyes, often composed of you sands of facets, on either side of the head; and three small ocelli on the top. The antenne are variable in form and size, but more commonly are very short, and composed of three joints. The foot, in addition to a pair of strong claws, is furnished with two, rarely three, cushions, dipteraceæ covered beneath with fine hair-like suckers, which, aided by a viscid secretion that renders adhesion more perfect, enables these insects to crawl on the under surfaces of objects however smooth. The meta morphosis in Diptera is complete, and the larvæ are generally destitute of feet. Many of the Diptera are useful scavengers in the larval state, but others are very injurious- e.g .. the He ian Fly ( Cecido myia destructor) to wheat-crops, the Crane Fly ( Tipula oleracea ) to gra lands. In the perfect state they are too often pests to man and beast, sucking the blood or depositing their eggs in or on their bodies, causing tumors, ulcerations, and death. The species are very numerous and world-wide in their distribution. In the fo il state they have been found as far back as the beginning of the Secondary period. The cla ification of the Diptera is a matter of some difficulty. By some authors they are divided into three sub-orders: Nemocera. Brachycera, and Pupipara; by others into five tribes: Nemocera, Not acantha, Tanystoma, A the ricer a, and Pupipara; while some naturalists even include the Fleas, Aphaniptera.