Family BOLBOCERATIDAE

<I>Blackburnium cavicolle</I> (Macleay, 1873)

Blackburnium cavicolle (Macleay, 1873)

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Family BOLBOCERATIDAE

Compiler and date details

1 December 2002 - Gerasimos Cassis & Tom A. Weir; updated by Andrew A. Calder, CSIRO Entomology, Canberra, Australia

Introduction

The Bolboceratidae are a large family of 40 genera and 400 species known from all biogeographic regions (Zunino 1984; Scholtz & Browne 1996). More than half of the world's fauna occur in Australia where they are mostly found on the coastal fringe, although a number occur in the dry interior (Howden 1981). Krikken (1984) revised the genera of the Bolboceratidae (as Bolboceratini) of the Afrotropical subregion. The family has previously been treated as a subfamily of Geotrupidae (Lawrence 1982; Lawrence & Newton 1982; Lawrence & Britton 1991; Lawrence & Newton 1995), but Browne & Scholtz (1995, 1999) and Scholtz & Browne (1996) presented evidence showing that the Geotrupidae sensu Lawrence & Newton (1995) are clearly polyphyletic consisting of two distinct lineages, the Bolboceratinae (including Athyreini) and another consisting of the Geotrupinae, Taurocerastinae and Lethrinae. Thus, the subfamily Bolboceratinae should be accorded family status as it is in this Catalogue.

The Australian fauna has high generic endemicity. The extralimital genera Gilletinus Boucomont, Australobolbus Howden & Cooper and Blackburnium Boucomont are shared with New Guinea (Howden 1990) and the genus Eucanthus Westwood is known also from the Western Hemisphere (Howden & Cooper 1977). Originally, almost all the Australian species were placed in the genus Bolboceras Kirby; Blackburn (1904) described 27 species and Macleay (1864, 1871, 1873, 1888) described 16 species. Howden & Cooper (1977) revised the Australian genera, described a number of new genera, recognised new synonymies and new combinations, and discussed the possible relationships of the Australian fauna. Howden (1974, 1979, 1985) revised the species of Stenaspidius, Blackburnium and Bolboleaus Howden & Cooper, Blackbolbus Howden & Cooper and Bolborhachium Boucomont. The New Guinea species of Australobolbus were revised by Howden (1990) and include the new species A. cruciatus from the Torres Strait Islands. Howden (1992) revised the Australian mainland species of Australobolbus. Carne (1965) revised the genus Elephastomus W.S. Macleay, which includes the first described Australian geotrupid, Elephastomus proboscideus (Schreibers). The Walford-Huggins collection of Geotrupids was sold to R. Mignani, Rome, Italy (Howden, pers. comm.).

The most recent world catalogue of the family is by Boucomont (1912).

BIOLOGY
The biology of the Bolboceratidae is very poorly known and some published statements are misleading. Many of the species are known to dig deep burrows and are thought to feed on fungi or plant material (Howden & Cooper 1977). As a general rule, dung feeding is not thought to occur in this tribe (Howden & Cooper 1977). Carne (1965), however, records that the adults of Elephatsomus meraldus Carne bury large quantities of dung in their oviposition burrows. Howden (1955) reported that the larvae of the American members of this family feed on packed humus, an activity apparently shared by the Australian species. This is confirmed by Howden (1985) who noted that the brood balls of Bolborhachium recticorne and B. anneae are composed of finely divided humus. Many of the species, particularly the larger ones, are found in sandy habitats (Howden 1981).

Adults of most species are nocturnal, but Stenaspidius and Gilletinus species are diurnal (Howden 1976). The adults are known to stridulate by rubbing the abdomen against a file on the hind coxae (Moore 1986).

Diagnosis

The Australian bolboceratids are medium to large-sized beetles (5–24 mm) and are usually black to brown. They are strongly convex, almost hemispherically shaped beetles, the elytra cover the abdomen, the antennae are 11-segmented with a circular, biconvex 3-segmented club, and males usually have large cephalic and pronotal horns (Lawrence & Britton 1991). Adults have asymmetrical, sclerotised mandibles with a prostheca and mesal tuft; the tentorium is of the single-foramen-type; the second axillary (2Ax) has the anterior margin of the dorsal-distal lobe concave and the dorsal surface of this lobe is very strongly convex; seven abdominal spiracles are present; the male has a well-defined tegmen but membranous penis; a well-developed genital capsule is present; female genitalia are without styli; 6 ovarioles present per ovary; karyotype 9+Xyp, and adults only provision food for their brood (Browne & Scholtz 1995, Scholtz & Browne 1996).

The larvae have 3-segmented antennae with the third segment reduced and the second with sensoria, and the legs are 3-segmented. The labrum is trilobed and the maxillae are divided into a separate galea and lacinia (Lawrence 1982). The fronto-clypeal suture is absent; galea and lacinia are separate; maxillary palpi are 4-segmented; maxillary and mandibular stridulatory areas are present; spiracles are biforous (Scholtz & Browne 1996). Howden (1985) described the larvae of Bolborhachium recticorne and Bolborhachium anneae.