Hydraenidae

Hydraenidae is a family of very small aquatic beetles, sometimes called "minute moss beetles", with a worldwide distribution. These beetles are generally 1–3 mm in length (although some species reach 7 mm) with clubbed antennae. They do not swim well and are generally found crawling in marginal vegetation. Most are phytophagous but a few saprophagous and predatory species are known.

Hydraenidae Temporal range: Early Jurassic–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Coleoptera
Suborder:	Polyphaga
Infraorder:	Staphyliniformia
Superfamily:	Staphylinoidea
Family:	Hydraenidae Mulsant, 1844
Subfamilies
Hydraeninae Mulsant, 1844 Ochthebiinae C. G. Thomson, 1860 Orchymontiinae Perkins, 1997 Prosthetopinae Perkins, 1994

Wikispecies has information related to Hydraenidae.

The family consists of more than 2000 species belonging to over 50 genera. Genus Hydraena alone includes nearly 900 described species worldwide.

The beetles are semi-aquatic, riparian and can walk on water surface. They feed on algae, bacteria, protozoans and detritus on wet stones and plant matter.

The larvae, although preferring damp habitats near water, are non-aquatic and tend to drown easily. They have a distinct labrum and well developed galea of maxillae. 9th abdominal tergum has a pair of apical, re-curved ventral hook and 2-segmented urogomphi.[1][2]