in zoology; a genus of insects of the coleoptera order. The generic characters are: The antennae are cylindrical, stiff, and shorter than the plate head; and the eyes are four, two on the upper and two on the under part of the head. Mr Barbut, however, says that the eyes only appear on the upper and under parts of the head, but that they are not four. The natator, or common water-flea, is of a bright black colour; the feet are yellow, flat, and large; the insect is in length one-third of an inch. It runs with great celerity in circles on the surface of the waters, and is very difficult to catch, plunging down instantaneously when attempted to be taken. There are eight other species, which frequent the waters in different parts of the globe.