Q10770073

Hydrochus is the only living genus of beetle in the family Hydrochidae, which belongs to the superfamily Hydrophiloidea, and was formerly treated as a subfamily of Hydrophilidae. Hydrochus includes about 180 species, which are found worldwide. The name "Hydrochus" has also been used for a fly genus in the family Dolichopodidae, but this is a junior subjective synonym of the genus Rhaphium.

They are found in slow moving streams or stagnant water bodies, where they are associated with dense vegetation. In adults air is stored in a bubble on the underside of the body, with the antennae used to transfer atmospheric air to the bubble. The larvae live at the bottom of water bodies, indicating that they can breathe underwater. The diet is only known for the larvae of one species, H. japonicus, which feed on annelid worms belonging the family Naididae. The larvae also burrow into crevices, such as hollow dead grass, including to pupate. The adults are sluggish crawlers along surfaces, and are thought to consume algae and plant detritus. Eggs are laid in silk cases, often attached to (usually plant) substrates.