Taxonomy and biology of the bromeliad-inhabiting genus Lachnodacnum (Coleoptera: Hydrophilidae: Sphaeridiinae)

Abstract: The water scavenger beetle genus Lachnodacnum Orchymont, 1937 sensu Hansen (1991) is revised. The three species that had previously been placed in the genus, L. luederwaldti Orchymont, 1937 (southern Brazil), L. saundersi Orchymont, 1937 (northern Brazil) and L. urichi (Scott, 1912) (Trinidad and Tobago), are redescribed in detail and illustrated with habitus photographs, line drawings, and SEM micrographs of relevant diagnostic characters. Lachnodacnum urichi is found not to be congeneric with the remaining two species. It is transferred to the genus Phaenostoma Orchymont, 1937 (as P. urichi (Scott, 1912) comb. nov.) and the genus Psilodacnum Orchymont, 1937 previously erected for this species is removed from the synonymy with Lachnodacnum and placed to synonymy with Phaenostoma. The preimaginal stages of Lachnodacnum luederwaldti, including the egg case, all three larval instars and pupa, are described. Basic information on the biology of the species is provided based on field observations and rearing in the laboratory. The species is found to be aquatic, living in water tanks of terrestrial and epiphytic bromeliads. An updated identification key to adults of the Neotropical genera of the Coelostomatini is also provided.

Key words: Coleoptera; Hydrophilidae; Coelostomatini; Lachnodacnum; Phaenostoma; Psilodacnum; new synonymy; new combination; taxonomy; morphology; biology; immature stages; bromelicolous taxa; Atlantic forests; Brazil; Trinidad and Tobago; Neotropical Region