Family TROGIDAE

<I>Omorgus australasiae</I> (Erichson 1842)

Omorgus australasiae (Erichson 1842)

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Family TROGIDAE

Compiler and date details

1 December 2002 - Gerasimos Cassis & Tom A. Weir

Introduction

The Trogidae are a cosmopolitan family, comprising three genera and about 325 species. Scholtz (1986b) excluded the genera Glaresis Erichson, Afroglaresis Petrovitz, and Cryptogenius Westwood from the family, leaving three recognised genera, Trox Fabricus, Omorgus Erichson and Polynoncus Burmeister. Scholtz (1982) catalogued the Trogidae of the world. The Trogidae are now considered to be most closely related to the Hybosoridae and Ceratocanthidae (Howden 1982; Scholtz 1986b). Strümpher et al. (2014) analysed the phylogeny of the family, based on mitachondrial and nuclear ribosomal DNA sequence data.

The genus Trox is found in the Holarctic and Afrotropical Regions and is represented in Australia by the introduced species, Trox (Trox) scaber (Linnaeus). The remainder of the Australian fauna, comprising 52 species, are assigned to the genus Omorgus (Omorgus) which is known also from the southern Nearctic and Neotropical Regions. Macleay (1864, 1871, 1888) and Blackburn (1892, 1895, 1896, 1904) described a number of the trogid species and Haaf (1954, 1957, 1958) revised the Australian fauna and added 11 new species. Scholtz (1986a) monographed the Australian fauna, recognised new synonymies and described ten new species. He placed all Australian species, except for Trox scaber, in Trox (Omorgus), but later elevated Omorgus to generic status (Scholtz 1986b). Barbero & Palestrini (2003) gave new records for eight species of Omorgus.

BIOLOGY
The biology of this family is characterised by keratinophagy, with the larvae and adults of most species being facultative necrophages. They have been taken from a wide variety of animal remains, such as carcasses, skin, carnivore faeces, regurgitates of predatory birds, locust eggs and fly maggots. The adults are usually among the last of the succession of insects to invade carcasses. Eggs are laid in the soil beneath carcasses under which the larvae form vertical burrows. Some species are also known from the nests of birds and mammals (Lawrence 1982). Leefmans (1932) recorded Omorgus (Omorgus) costatus (Wiedemann) feeding on bat guano in caves in Sulawesi; this behaviour is suspected for two other Australian species, O. brucki (Harold), O. alatus (Macleay), and the Oriental species O. mollis (Arrow). Wing polymorphism is common in the Australian trogids, e.g. O. tatei (Blackburn) and O. gigas (Harold) are micropterous while O. aphanocephalus (Scholtz) and O. ovalis (Haaf) are brachypterous. The alate species are attracted to light at night. Trogids are well adapted to arid regions and are common in the interior regions of Australia.

Diagnosis

The Trogidae or carcass beetles are medium to large-sized (7–20 mm) and are heavily sclerotized, with embossed or tuberculate sculpture (Moore 1986). They are moderately to strongly convex, dull in colour, and usually glabrous. The head is deflexed, the antennae are 10-segmented, the mesocoxal cavities are broadly closed, and the abdomen is entirely covered by the elytra. The larvae have 3-segmented antennae, a bilobed labrum, a darkly pigmented head, and abdominal terga with transverse folds and short spines (Lawrence 1982). Scholtz (1991) described the larvae of some Australian Omorgus species and discussed implications for the phylogeny of the family.