Water scavenger beetles

Code QC119999

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.

A majority of Hydrophilidae are aquatic. They range in size from 1-40 mm. Most are smoothly oval and drab-coloured but the family includes also the Sperchinae, small (2mm) brown beetles with coarse elytral punctation, and Georissinae, minute (1mm) black, tuberculate beetles with a deflexed head concealed from above.

Antennae 7-9 segmented with a 3-segmented club. The segment before the club forms a transverse, concave cupule and is used in replenishing the air supply. The mandibular palps often are long and sensory, and may exceed the length of the head, but in some genera are short. Tarsal segmentation 5-5-5 or 4-4-4.

Some hydrophilids resemble the adephagan Dytiscidae (diving beetles) or some Carabidae (ground beetles). They can be separated by the antennae, by the mandibular palps (if long), by lack of a notopleural suture on the prothorax, and by the possession of moveable as opposed to fixed hind coxae.

Separation of Hydrophilidae from polyphagan family Hydraenidae may be difficult. Hydraenids can have similar body shape, similarly elongate palps, 6-7 visible sternites (against 5-6 in Hydrophilidae), an identical range of tarsal segmentation, and be of similar size. The chief external difference between a small hydrophilid and a large hydraenid is in the antennal club. The club is 3-segmented preceded by a cup in Hydrophilidae, 5-6 segmented and not always preceded by a cup in Hydraenidae. A majority of the species in each family can, however, be more readily identified on other combinations of characters.

Hydrophilidae (Polyphaga: Hydrophiloidea) occur throughout Australia in a range of damp to watery habitats. Most adults are phytophagous or saprophagous; by contrast, larval hydrophilids are mostly voracious predators. Hydrophilids occur in all Australian states, with approximately 175 species currently recognised.

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.