(derived from ὑμέν, membrane, and ἀπόστρωσις, wing), in the Linnean system of natural history, is an order of insects, having four membranaceous wings, and the tails of the females are furnished with stings, which in some are used for instilling poison, and in others for merely piercing the bark and leaves of trees, and the bodies of other animals, in which they deposit their eggs. See ENTOMOLOGY Index.