GORDIUS, the HAIR-WORM, a genus of insects belonging to the class of vermes intestina. There are two species, 1. The aquaticus, with a filiform body, of equal thickness, and smooth. It hath a pale colour, with both the ends black; and inhabits boggy places, and clay at the bottom of water. 2. The argillaceus is of an uniform yellow colour, twisted spirally, and lying flat. It is common in the intestines of herring, and other sea-fish. Aristotle remarks, that the ballerus and tillo are infested in the dog-days with a worm that torments them so much, that they rise to the top of the water, where the heat destroys them. To these worms also may probably be owing the agonies to which the bleaks are at certain times subject. See CYPRINUS.