Hydraenidae

Hydraenidae is a family of very small aquatic beetles in the order Coleoptera, commonly called minute moss beetles, with a worldwide distribution and body lengths of about 0.8 to 3.3 millimeters. Adults store air beneath the body and elytra, allowing them to crawl underwater, often on the underside of the surface tension, though they cannot swim, and some species have gills letting them remain submerged indefinitely; larvae range from fully terrestrial to aquatic in their earliest stages. The family comprises about 1,300 species in 42 genera, whose diet is thought to consist of algae, spores and other plant matter, and at least some adults communicate by stridulation.