Coelostoma

Distinguished from other Hydrophilidae genera by the combination of deeply excised eyes, arrow-head shaped mesoventral elevation, and the characteristic metaventral structure with anteriorly projecting raised median portion. The absence of serial punctures on elytra further separates Coelostoma from many related genera. Species-level identification requires examination of male genitalia and detailed morphometric analysis.

Body rather convex, brown to black in coloration. Eyes medium in size, deeply excised internally. Antenna with 9 antennomeres and loosely segmented antennal club. Mesoventrite with arrow-head shaped median elevation. Metaventrite longer than mesoventral elevation, with strongly raised median portion broadly projecting anteriorly and abutting mesoventral process. Elytra lacking serial punctures.

Aquatic and semi-aquatic environments including edges of ponds and streams with grass cover, muddy lands beside paddy fields, forest streams, and wet stone surfaces with running water. Adults occur under stones at stream margins, beneath grass roots on wet stones, in accumulations of rotten leaves, and in shallow vegetated standing water. Some species inhabit artificial water bodies such as reservoirs and agricultural fields.

Primarily Old World distribution encompassing Oriental, Afrotropical, and Palearctic regions. Limited presence in Australian region. Absent from Nearctic and Neotropical regions. Documented from China (Yunnan, Fujian, Guangdong, Xizang, Hunan, Guizhou, Chongqing, Shanxi, Zhejiang, Jiangxi, Guangxi, Hong Kong), Taiwan, India (Deccan Peninsula), Indonesia, Malaysia, Nepal, Vietnam, Himalayas, Myanmar, and Korea. North American records exist for at least one species (C. orbiculare).

Decomposing organic material, algae, and rotting aquatic plants. Specific feeding habits documented through association with these materials in habitat descriptions.

Adults are predominantly nocturnal and exhibit phototaxis, sometimes attracted to light sources. Activity patterns include both submerged and shore-zone border habitats. Some species demonstrate syntopic co-occurrence with congeners.

Water scavenger beetles inhabiting aquatic and semi-aquatic environments, contributing to decomposition processes through consumption of organic detritus and algae.

• Other Hydrophilidae generaCoelostoma differs in the unique combination of deeply excised eyes, arrow-head shaped mesoventral elevation, and anteriorly projecting metaventral process; related genera in Nearctic and Neotropical regions occupy similar ecological niches but are taxonomically distinct

• Hydrophilidae
• water scavenger beetle
• aquatic beetle
• nocturnal
• Old World distribution
• decomposer

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Additional fauna of Coelostoma Brullé, 1835 from China, with re-establishment of Coelostoma sulcatum Pu, 1963 as a valid species (Coleoptera, Hydrophilidae, Sphaeridiinae)
• Review of the genus Coelostoma of Taiwan with description of a new species (Coleoptera: Hydrophilidae)
• Coelostoma orbiculare (Fabricius) (Coleoptera: Hydrophilidae: Sphaeridiinae): New Records and Distribution in North America
• Review of the Chinese species of the genus Coelostoma Brullé, 1835 <br />(Coleoptera: Hydrophilidae: Sphaeridiinae)
• Occurrence of <i>Coelostoma</i> (<i>Lachnocoelostoma</i>) <i>horni</i> (Régimbart, 1902) (Coleoptera: Hydrophilidae) from Deccan Peninsular, India