; subclass Pterygota, order Coleoptera)
Family of highly convex water beetles, found in muddy ponds. They possess several primitive features—including, in the adult, swimming by means of alternate leg movements—and very prominent eyes. Adults produce high-pitched squeaks by rubbing the tip of the abdomen against the underside of the elytra. Larvae are club-shaped, with a large head and thorax and a three-pronged tail, and feed on insect larvae. There are four species, with notably discontinuous distribution, occurring in Australia, Asia, and Europe.
Subjects: Zoology and Animal Sciences.