Family HYDRAENIDAE

Hydraenidae

Museums

Museum list

Regional Maps

Family HYDRAENIDAE

Compiler and date details

2007 - Updated by ABRS, with input from P.D. Perkins

26 June 2002 - Andrew A. Calder, CSIRO Entomology, Canberra, ACT, Australia

Introduction

The Hydraenidae are a cosmopolitan group of small aquatic or subaquatic beetles ranging in length from 0.5 to 3.0 mm and numbering nearly 40 genera and 1163 species (Hansen 1998). The described Australian fauna contains 9 genera and 221 species.

The family is a member of the Staphyliniformia lineage of polyphagan beetles (Lawrence & Newton 1982). Opinions vary on its exact relationship within the lineage. The Hydraenidae have been placed either in the Staphylinoidea or in Hydrophiloidea. Hydraenids were previously considered to be closely related to the Hydrophilidae, indeed they had earlier been included in that family. However, Böving & Craighead (1931) proposed an association of the Hydraenidae (as Limnebiidae) with the staphylinoid families Leiodidae (as Anisotomidae and Leptinidae) and Ptiliidae rather than with the Hydrophilidae, based on larval characters. Hydraenids appear to show a relationship with the Hydrophilidae based upon adult antennal structure, elongate maxillary palpi of Hydraena Kugelann, metendosternite structure and aquatic habits (Crowson 1955) or to the Staphylinoidea (Ptiliidae) based upon hind wing venation, absence of an aedeagal basal piece and larval characters (Dybas 1976; Hansen 1997). A phylogenetic analysis by Hansen (1997) confirms the monophyly of Hydraenidae plus Ptiliidae and thus a placement of the family within the superfamily Staphylinoidea.

The first Australian species were described by Macleay (1871), Blackburn (1888, 1896, 1898) and Lea (1926). Deane (1931, 1933, 1937) described another 23 species, mostly in the Ochthebiinae, and Zwick (1977) revised and described 23 new species of Hydraena but did not provide any key for their identification. Janssens (1967) noted that several species previously described in Ochthebius Leach by Deane and other authors actually belonged to two other genera: Meropathus Enderlein, previously only known from the subantarctic islands Kerguelen and Prince Edward, and a new genus, Tympanogaster Janssens. Hansen (1991) revised the hydraenid genera on a world-wide basis and provided a key to the genera. Jäch et al. (2000) discuss the subgeneric classification of the genus Hydraena and give a checklist of the species of the world. The subfamily arrangement in this catalogue follows Perkins (1997) who also provides keys to subfamilies, tribes and genera. The most recent catalogue of the world fauna was published by Hansen (1998), and was based on Perkins' classification. Matthews (1982) gives an illustrated key to the hydraenid genera of South Australia, while P.D. Perkins (Harvard University) has been revising the Australian fauna.

Hydraenidae live in a wide variety of aquatic habitats. In general they inhabit submerged vegetation, leaf packs in billabongs, stagnant pools of mountain streams or slow-moving water bodies. Meropathus inhabits moss in the spray zone of waterfalls and cascades; Tympanogaster adults and larvae also live in the splash zone beneath waterfalls and sometimes on rocks in mountain streams, especially near the air-water interface which is always wet; Ochthebius inhabits algal crusts of mud and sand in marginal areas of fresh or saline waters (Zwick 1977; Lawrence & Britton 1994). Hughleechia occurs in rock crevices in the high tide splash zone and intertidal rock pools of Western Australia (Perkins 1981). Adults are able to breathe underwater by using hydrofuge hairs on their ventral surfaces as a plastron, but most larvae have no aquatic modifications except for Tympanogaster, which possesses a pair of dorsally projecting thoracic spiracular tubes (Spangler 1991; Perkins 1997). All known North American larvae are essentially terrestrial, being found in moist situations beside water bodies (Spangler 1991). Information on the immature stages and biology of most Australian species is lacking; illustrations of larvae can be found in Bertrand (1972) and Spangler (1991).

P.D. Perkins (2004a,b,c, 2005, 2006) recently reviewed several genera that include Australian species, and several Australian genera (Perkins 2007a,b).