(= HELMINTHIDAE, ELMINTHIDAE)

Riffle beetles

Code QC349999

A family of Polyphaga - the large suborder of beetles in which the prothoracic pleuron is entirely concealed and the hind coxae are motile.

Elmidae are small to minute (1-6 mm), dark-coloured beetles. The body either is glabrous or sparsely hairy above with tomentose tracts on the underside (Elminae), or else is densely pubescent above without ventral tracts (Larainae).

The head is deflexed and never rostrate. Antennae 11-segmented, moderately long, slender, and without a club. Metasternum with a transverse suture. Mid coxae not touching (widely separated in Elminae) and hind coxae without a deep cavity into which the femur may fit. Legs relatively long. Tarsal formula 5-5-5, the terminal tarsal segment as long as the other four segments combined.

Elmids (Polyphaga, placed in Byrrhoidea by Australian authors, Dryopoidea by American authors) live in clear, generally somewhat shallow, running water, and occur throughout Australia. Currently, around 150 species are recognised from over 8 genera. Adults live in clear, running water with a rocky bottom and high oxygen content. The hair tracts are used as plastrons, maintaining an air bubble by which the animal breathes. Adult elmids appear to be mostly generalist particulate detritivores.

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.