(= LIMNEBIIDAE)

Code QC139999

A family of Polyphaga - the large suborder of beetles in which the prothoracic pleuron is entirely concealed and the hind coxae are motile, not dividing the first abdominal sternite.

Hydraenidae are small (1-3 mm), elongate to rounded beetles. All members of the family are aquatic. Antennae 8-9 segmented with a somewhat loose, 5-6 segmented club. The club preceded by a cup-shaped segment or else the pedicel cup-shaped. Mandibular palps often long and sensory, sometimes exceeding the length of the antennae. Tarsal segmentation 5-5-5 or 4-4-4, with the apical tarsal segment always the longest.

On the underside: Six-seven visible sternites with sternite 1 visible as a median intercoxal process as well as laterally.

The most likely misidentification for Hydraenidae is with Hydrophilidae. The chief external difference between a small hydrophilid and a large hydraenid is in the antennal club: 5-6 segmented and not always preceded by a cup in Hydraenidae; 3-segmented and preceded by a cup-like antennal segment in Hydrophilidae.

Hydraenids (Polyphaga: Staphylinoidea) are found in a variety of riparian and littoral habitats including streams, waterfalls, wet rock faces, ponds, marine rock pools, seabird nests and inland salt lakes, however larvae tend to be less truly aquatic than the adults, favouring damp riparian habitats. Most hydraenids are phytophagous, though some larvae may be more detritivorous or even predacious. The Australian fauna, distributed through all states, comprises 55 species in seven genera and two subfamilies.

Reference:

Lawrence, J.F. and Britton, E.B. (1991) Coleoptera. pp. 543-683. In: CSIRO, Insects of Australia. Volume 2. Melbourne University Press, Carlton, Victoria.