Rediscovery of Coelostoma thienemanni (Coleoptera: Hydrophilidae): the first record from continental Asia and correction of its subgeneric assignment

Abstract

Abstract We are reporting a recent discovery of Coelostoma ( Lachnocoelostoma ) thienemanni Orchymont, 1932 (Coleoptera: Hydrophilidae: Sphaeridiinae: Coelostomatini) from northern Vietnam, which represents the first record of the species since 1929 and its first record from continental Asia. The species is redescribed and illustrated, and transferred from the subgenus Holocoelostoma Mouchamps, 1958 to Lachnocoelostoma Mouchamps, 1958. The species is unusual among Asian Coelostoma by its complex three-dimensional shape of the median lobe of the aedeagus, in which it is only similar to C. tangliangi Jia et al ., 2017 in Asia. The species is also unusual by its very long dorsal tarsal swimming hairs, indicating that it is an aquatic species.