Family THROSCIDAE

Aulonothroscus sp.

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Family THROSCIDAE

Throscids

Compiler and date details

31 August 1996 - Andrew A. Calder, CSIRO Entomology, Canberra, Australian Capital Territory, Australia

Introduction

The Throscidae (= Trixagidae) are a small family of five genera and about 190 species, occurring in most faunal regions (Lawrence 1982). The family originally comprised two very distinct subfamilies, Lissominae including the genera Drapetes Dejean, Paradrapetes Fleutiaux, Lissomus Dalman, Hypochaetes Bonvouloir, and now the newly erected Osslimus Calder, and the Throscinae including Aulonothroscus Horn, Cryptophthalma Cobos, Pactopus LeConte, Potergus Bonvouloir and Trixagus Kugelann. Crowson (1955) added the Thylacosterninae with the genera Cussolenis Fleutiaux, Thylacosternus Bonvouloir, Balgus Fleutiaux and Pterotarsus Guérin-Méneville (= Lissothyreus Bonvouloir) from the Eucnemidae. In this Catalogue, the family Throscidae is defined in its narrowest sense to include only the subfamily Throscinae. Both the Lissominae and Thylacosterninae are here considered to belong to the Elateridae (Calder et al. 1993; Calder 1996, 1998). However, Muona (1996) includes the subfamily Lissominae in the family Throscidae. The genus Potergus was originally described in the family Eucnemidae, but Cobos (1961) demonstrated that it belongs in the Throscidae.

The Australian fauna consists of 10 described species in three genera, arranged as follows: Aulonothroscus with seven species; Potergus with two species; and Trixagus with one species (CALDER 1998). None of these genera is endemic to Australia. Australian throscids are poorly known and ever since Bonvouloir (1859, 1871) described the first two Australian species, the only other worker to describe new Australian taxa has been Cobos (1963, 1967). The Australian fauna has never been revised systematically and the limits of Aulonothroscus and Trixagus have yet to be defined satisfactorily.

The biology of the Australian throscids is unknown but adults are known to occur in leaf litter, decaying wood, under bark on trees and on flowers, and in Australia come readily to light. The larvae of the European Trixagus dermestoides (Linnaeus) feed in the soil on ectomycorrhizal fungi on the roots of various trees (Burakowski 1975) and North American throscid larvae have been collected in brown-rotten conifer wood and in grass tufts (Lawrence 1982). Throscids are able to jump by means of a click-jump mechanism involving the prosternal intercoxal process and mesosternal cavity (Yensen 1975; Lawrence & Britton 1994).

Diagnosis

Throscids are oblong to elongate, slightly flattened, finely pubescent beetles, 1.6–3.5 mm in length. The labrum is visible, the hind pronotal angles are acute and fit closely against the elytra, all five ventrites are connate, the tarsi are usually without membranous appendages although tarsomere 4 is lobed ventrally, and the antennae, except in Potergus, usually have a distinct 3-segmented club. The larvae are lightly sclerotised and grub-like with head small and legs reduced. The antennae are very short; mandibles flattened, rounded and fused to the head; prothorax with supporting rods and the abdominal segment 9 has a pair of minute, fixed spines (Lawrence & Britton 1994).