Subfamily Dynastinae

<I>Xylotrupes gideon</I> (Linnaeus, 1767)

Xylotrupes gideon (Linnaeus, 1767)

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Subfamily Dynastinae

Compiler and date details

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

Introduction

The Dynastinae are a large cosmopolitan subfamily, comprising around 250 genera and 1,400 species. Endrödi (1985) reviewed the world fauna and provided keys to the genera and species. Six of the eight tribes recognised in his classification are present in Australia, although the only member of the Cyclocephalina is the accidentally introduced Cyclocephala signaticollis Burmeister.

The Dynastini is represented in Australia by two genera and five species, including the first described Australian insect, Haploscapanes barbarossa (Fabricius, 1775). The Oryctini, with 3 genera and 18 species is doubtfully native to Australia. It includes two species of Oryctes Illiger, which are widespread in the Oriental Region, recorded from a few specimens in Australia. The Oryctoderini, which is most species rich in New Guinea, is represented in Australia by two species, one in each of two genera.

The majority of the Australian dynastine fauna belong to the cosmopolitan Pentodontini which contains 32 genera and 150 species; genera with the largest number of species are Corynophyllus Carne and Tienogenys Sharp. The Phileurini is represented in Australia by two genera, Cryptodus and Eophileurus.

Endrödi (1985) does not regard the Australian fauna as a continuation of the Oriental and New Guinea faunas. Howden (1981) suggested that all the non-endemic genera, except for Cheiroplatys Hope, belong to a Torresian element. The majority of the species are found in northern and western Australia with the most depauperate area being south-eastern Australia.

Burmeister (1847) published the first worldwide account of the subfamily and Arrow (1937) listed the numerous regional works and catalogues for this group. Gemminger & Harold (1869) provided the first world catalogue and Arrow (1937) compiled the most recent catalogue. Burmeister (1847) described nine Australian species and Macleay (1871, 1887, 1888) described eight species. Blackburn (1888a, 1888b, 1889, 1890a, 1890b, 1892, 1894, 1895, 1896, 1900, 1907) was the most productive of the early Australian workers and described 44 species. Fairmaire (1877a, 1877b, 1877c, 1879) described a number of new species of Cryptodus W.S. Macleay, although only six are now considered valid (Endrödi 1977). Lea (1917, 1919a, 1919b, 1920, 1926) described 21 species. Arrow (1900, 1908, 1911, 1914, 1937) described five new genera and nine new species.

Carne (1957) monographed the Australian fauna, described six new genera and 45 species, and provided a list and keys to all the taxa. A further eight new species were described by Carne (1985a, 1985b), Allsopp & Carne (1986), Carne & Allsopp (1987) and Allsopp (1990, 1993, 2000). Dechambre (1999) described a new genus and species of unusual Pentodontini from Western Australia.

New work by Barbero & Palestrini (2003) and Silvestre (2012) added a number of new species. The Australian fauna presently (September 2015) consists of 42 genera and 199 species.

BIOLOGY
The biology of most Australian species is not well known. Many species are thought to be univoltine. A few of the larger species in genera such as Xylotrupes Hope and Haploscapanes Arrow, however, require two to three years for development. Adults are generally nocturnal, are usually associated with the soil and are not leaf feeders. Adults of Xylotrupes gideon (Linnaeus) have been observed to feed on the bark of Poinciana trees and tunnel in ripe pineapples. They are also considered pests of coconuts, boring into the spathe of young palms (Szent-Ivany 1969). Members of the genus Cryptodus live in association with ants and termites. The larvae, in general, feed on roots or decaying vegetable matter in the soil or in rotten logs.

Carne (1957) detailed two distinctive types of life-cycles. The first is shown by Cyclocephala signaticollis, some Cryptodus species and probably genera such as Cavonus Sharp, Corynophyllus Hope, Cryptoryctes Carne, Pseudoryctes Sharp and Teinogenys (the Pseudoryctina of Carne 1957). This type lays eggs in mid to late summer, the larvae overwinter and pupate in the spring, and adults emerge in early summer. This is correlated, at least in the latter five genera, with quite marked sexual dimorphism, vestigial or non-functional mouthparts and sedentary females that are rarely collected. The second type of life-cycle is exhibited by the introduced Heteronyx arator, and species of Adoryphorus Blackburn, Semanopterus Hope and probably genera such as Pimelopus Erichson, Neodon Carne, Metanastes Arrow (the Metanastina of Carne 1957), Trissodon, Novapus Sharp, Cheiroplatys and Dasygnathus Macleay (the Cheiroplatina of Carne 1957). In this type, the eggs are laid in early summer, the larvae develop rapidly, and the adults either emerge in autumn or remain in their pupal cells until the following spring. These species have strongly developed functional mouthparts and a minimum of secondary sexual armature. Equal numbers of active females and males are collected.

The introduced species Heteronyx arator and Cyclocephala signaticollis are regarded as pests of pastures and lawns. The native species Neodon pecuarius (Reiche), N. intermedius (Blackburn), Metanastes vulgivagus, Adoryphorus couloni and Dasygnathus globosus Arrow have been implicated in pasture damage (Carne 1957). Elsewhere, Oryctes rhinoceros is regarded as a serious pest of coconuts.

Diagnosis

Members of the Dynastinae are black or brown, sometimes bicoloured beetles. They range in size from 9 mm for some species of Trissodon Burmeister and Neatocnemis Prell, to 60 mm for some specimens of Haploscapanes barbarossa. In the adult stage, dynastines can be distinguished from other subfamilies by a combination of the following character states: simple, tarsal claws equal; elytra without a narrow membranous margin and leaving pygidium at least partly exposed; spiracles diverging so that several lie on abdominal sternites and at least two pairs exposed beneath elytra; mid coxae transverse, not produced ventrally; mesothoracic epimera not visible from above; and mandibles at least partly visible from above (except in Cryptodus W.S. Macleay). Sexual dimorphism is often markedly developed with the head and/or pronotum of males usually bearing horns, tubercles, or complex excavations and elevations (Lawrence & Britton 1991).

The larvae are characterised by the following combination of character states: apical antennal segment as wide as penultimate; galea and lacinia fused to form a mala; anal cleft transverse; sternum 9 without raster of longitudinal row of spines; mandible with ventral stridulatory area; labrum symmetrical with deeply pigmented notch on right side of midline; legs long, with hind coxa larger than width of clypeus; stridulatory teeth on dorsal edge of maxilla bluntly rounded; and head usually strongly punctate. Cumpston (1940) described the morphology of the larvae of Heteronyx arator (Fabricius) and Metanastes vulgivagus (Olliff). McQuillan (1985) described and figured the larvae of Pimelopus nothus Burmeister, Cheirplatys latipes (Guérin-Méneville) and Adoryphorus couloni (Burmeister).