Hydrochus


Hydrochus is a genus of water scavenger beetles in the monogeneric family Hydrochidae, sometimes placed in the Hydrophilidae as a subfamily Hydrochinae. The family Hydrochidae includes about 180 species, all of which are placed in the genus Hydrochus. Hydrochus has also been used for a fly genus in the family Dolichopodidae. This junior homonym is a junior subjective synonym of the genus Rhaphium.
Beetles in the genus Hydrochus are found in slow moving streams or stagnant water bodies. The club of the 7 segmented antenna consists of three segments with a cup-like basal segment. The number of tarsi on the legs are usually 5-5-5 or 4-4-4. The pronotum narrows towards the rear but is narrower than the base of the elytra. They walk around inside water or swim weakly in search of invertebrate prey. They hold air under the elytra. The larvae are also aquatic and predatory. An African species was formerly described under the genus Kiransus, but along with several other African species, they are now placed in Hydrochus. Hydrochids are considered to be an older branch of the Hydrophiloidea. Hydrochids have been suggested as a sister group of the Spercheidae+Hydrophilidae but the relationships are unclear. Molecular phylogenetic comparisons suggest that they are related as a sister group to Helophorus+Georissus.

Species

More than 180 species have been described in the genus. The following list includes some of the species in the genus:
Data sources: i = ITIS, c = Catalogue of Life, g = GBIF, b = Bugguide.net