Subfamily Melolonthinae

<I>Sericesthis geminata</I> Boisduval, 1835

Sericesthis geminata Boisduval, 1835

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Subfamily Melolonthinae

Compiler and date details

1 December 2002 - W.W. Keith Houston & Tom A. Weir; updated by Andrew A. Calder, CSIRO Entomology, Canberra, Australia

Introduction

The cosmopolitan Melolonthinae comprise some 750 genera and 10,500 species. They form the largest of the scarabaeid subfamilies containing more than one third of the total number of genera and species. The adults, commonly called chafers, range in length from 3 to 32 mm and are usually a reddish brown in colour, but may be black, metallic or even bicoloured.

Gemminger & Harold (1869) provided the first complete catalogue of the world fauna and Masters (1871) listed the Australian fauna known at that time. The last world catalogue of the subfamily is that of Dalla Torre (1912, 1913). The tribal classification used in this Catalogue follows Britton (1978, 1990).

The described Australian fauna currently comprises some 117 genera and almost 1,300 species, distributed in 14 tribes. The degree of endemicity is high. Only seven genera have extralimital representatives: Chariochilus Brenske occurs also in New Guinea; Dermolepida Arrow in New Guinea; Gnaphalopoda Reiche in New Caledonia and New Zealand; Heteronyx Guérin-Méneville in New Guinea, New Caledonia, Moluccas, Brazil, Paraguay and Bolivia; Lepidiota Kirby in New Guinea, Indonesia, South-East Asia and India; Maechidius Macleay in New Guinea and the Moluccas; and the introduced Plectris Lepeletier and Serville. Plectris aliena Chapin, introduced from the Neotropical Region, is the only member of the Macrodactylini in Australia. The largest Australia genera are Liparetrus Guérin-Méneville with 240 species, Heteronyx with 207 species, and Colpochila Erichson with 133 species.

In the Scitalini, the genera Telura Erichson, Protelura Britton and Hadrops Britton form a southern group separate from the other genera and related to the Chilean genus Sericoides Guérin-Méneville (Britton 1987). The Xylonychini also show southern affinities, having four genera in New Zealand, two in South America (Britton 1957) and six in Australia. The Melolonthini as a whole, on the other hand, indicate northern affinities with the Palaearctic and Oriental Regions (Britton 1978).

Melolonthines are generally distributed throughout Australia but there are few species in Tasmania. Britton (1957) gives combined figures for the distribution of the genera of Sericini, Phyllotocidiini, Xylonychini, Automoliini and Maechidiini. The Melolonthini are mainly tropical with 86 of the 111 species occurring in northern Australia and only the genera Antitrogus Burmeister and Rhopaea Erichsoin being predominantly southern (Britton 1978). The majority of species of Scitalini are found in moderate to high rainfall areas of eastern Australia but most species of the genus Gnaphalopoda are restricted to the Northern Territory and Western Australia (Britton 1987). Protelura and Homolotropus Macleay are restricted to rainforest, as are 12 species of Sericesthis Boisduval. In the Liparetrini, the numerically large genera Colpochila Erichson and Liparetrus Guérin-Méneville occur mainly in drier areas of the continent, including open woodland, mallee, grassland and semi-desert (Britton 1986). There are 73 species of Colpochila in Western Australia, 31 in South Australia, 23 in Northern Territory and 32 in eastern Australia. Liparetrus has 101 species in Western Australia, six species of which are common and widely distributed in eastern Australia, one species which appears to be restricted to high mountains in Victoria and New South Wales, and other species which are widely distributed across northern Australia.

The profusion of species of Melolonthinae may be explained by temporal isolation resulting from local rainfall in semi-desert areas (Britton 1986, Lawrence & Britton 1991).

The order of tribes proposed by Britton (1978) and the number of genera and species currently listed in the Australian fauna is:

Sericini: 10 genera, 55 species
Xylonychini: 6 genera, 13 species
Phyllotocidiini: 1 genus, 4 species
Automoliini: 5 genera, 56 species
Maechidiini: 6 genera, 80 species
Scitalini: 17 genera, 128 species
Comophorini: 1 genus, 1 species
Systellopinini: 7 genera, 23 species
Liparetrini: 32 genera, 428 species
Heteronycini: 11 genera, 236 species
Diphucephalini: 3 genera, 79 species
Macrodactylini: 1 genus, 1 species (introduced)
Pachytrichini: 1 genus, 7 species
Melolonthini: 16 genera, 119 species

In this Catalogue, however, we use a non-committal and self-indexing system where tribes, genera within tribes and species within genera are given in alphabetical order. For subgenera or subspecies that are present in Australia, however, the nominate subgenus or subspecies of the genus or species is given first.

Fabricius (1775) described the first Australian melolonthine species, Melolontha sylvicola, from specimens collected at Endeavour River during Captain Cook's enforced sojourn there in 1770. During the next century, the richness of the fauna became apparent as material collected during exploration voyages was described by European workers such as W.S. Macleay (1826), Guérin-Méneville (1831, 1838), Boisduval (1835), White (1841), Hope (1842) and Blanchard (1846, 1853). Burmeister (1855) revised the world fauna known to him, providing keys to genera and species. He described many new species, including 40 from Australia, as well as providing redescriptions of most previously described species.

It was not until the latter half of the 19th century, however, that workers in Australia began to document the fauna. The first major contributor was Macleay (1864–1888) who described 153 species. He was followed by Blackburn (1888–1912), who described a massive 545 new species. Lea (1895–1930) contributed descriptions of 180 new species. Little further attention was paid to the Australian species until Britton (1957) produced a key to tribes and revised the Automoliini, Maechidiini, Phyllotocidiini, Sericini and Xylonychini. Further comprehensive papers on the Melolonthinae by Britton followed: Melolonthini (Britton 1978); Liparetrus (Liparetrini) (Britton 1980); Colpochila (Liparetrini) (Britton 1986); Scitalini and Comophorinini (Britton 1987); and synopses of the genera of Heteronycini (Britton 1988, 1990, 2000). Britton (1995a) described a new genus of Sericini, Adossa, from Tasmania. The Systellopini were revised by Allsopp (1990a) and the Pachytrichini by Allsopp (1990b). Allsopp (1989, 1990c, 1993c, 1993d, 1999) described a further 12 new species while Allsopp & Watkins (1995) described a new species of Lepidiota, the southernmost representative of the genus that reaches central New South Wales. Szito (1993, 1994a, 1994b, 1995) described another eight new species and two new genera of Liparetrini from south-western Western Australia. A synopsis of the tribe Diphucephalini was provided by Britton (1995b) and all described species of the large genus Heteronyx (Heteronycini) were revised by Britton (2000). Only the species of the genus Diphucephala Dejean remain to be revised, although Hawkeswood (1992) described a new species of Diphucephala from New South Wales. McQuillan & Michaels (1997) described a new Pseudoheteronyx from sand dunes in Tasmania.

The most recent key to tribes can be found in Britton (1990), while keys to genera and species can be found in the appropriate papers by Britton and Allsopp, as listed above.

BIOLOGY
The biology of the majority of species of Melolonthinae is poorly known. The information available indicates a very brief period of adult life, lasting only a few days or weeks. This is in contrast to the long larval life, which may last up to two years (Britton 1957). Most adults are crepuscular or nocturnal, but there are some conspicuous diurnal species. The latter include the metallic species of Diphucephala and the bicoloured species of Phyllotocus (Lawrence & Britton 1991). The males of Colpochila species are attracted to light, as are many species of Melolonthini (Britton 1978, 1986). Many adults, including species of Automolius, Diphucephala, Heteronyx, Liparetrus, Phyllotocus and Sericesthis feed on leaves of eucalypts and other trees and can be serious defoliators (Lawrence & Britton 1991). On the other hand, in the Melolonthini, members of some genera, such as Antitrogus and Rhopaea, do not feed at all in the adult stage (Britton 1978).

After mating, the eggs are laid in the ground and the larvae feed on roots and humus. Pupation occurs in a cell in the soil and adult emergence may be delayed until the soil is softened by rain (Britton 1957). Britton (1978) speculated that because of their size, abundance and mainly root-feeding habits, the larvae of many species must be of economic importance. He stated that it is not difficult to show that the weight of sheep per acre grazing on Australian pastures is commonly exceeded by the weight of scarab larvae feeding beneath the surface. Roberts et al. (1982a) point out that there are two types of scarabs that feed in pasture as larvae. Firstly, those whose adults fly to eucalypts and feed on foliage, e.g. Sericesthis geminata Boisduval and Sericesthis nigrolineata Boisduval, both considered serious pasture pests in eastern Australia. Secondly, there are those whose adults do not feed, e.g. species of Antitrogus and Rhopaea (Soo Hoo & Roberts 1965). For species that feed, the concentration of adults on the trees facilitates mating, whereas the males of the non-feeding species locate females by means of a sex pheromone emitted by the virgin females.

Pest species of Sericesthis were studied by Ridsdill Smith & Roberts (1976), Wensler (1974) and Roberts et al. (1982a, 1982b). They found that the larvae feed upon young roots of grasses and clover as well as organic matter in the soil. Apart from the defoliators mentioned above, other noted pest species occur among the Melolonthini, e.g. the larvae of Dermolepida albohirtum (Waterhouse), are the most serious pest of sugar cane in northern Queensland (Mungomery 1949). Species of Antitrogus and Lepidiota are also pests in the larval stage, especially of sugar cane (Britton 1978; Jarvis 1929).

The information that is available on the ecology and distribution of most species is minimal. This is reflected in this Catalogue by the very limited amount of data included in the Ecology and Distribution sections for each species. As more information becomes available, it is hoped that further descriptors will be included in the database.

Diagnosis

As adults, Melolonthinae can be distinguished from other scarabaeid subfamilies by a combination of: tarsal claws equal; abdominal spiracles diverging which have one pair exposed beneath edge of elytra; mid coxae transverse or only slightly oblique; fore coxae transverse, mesothoracic epimera not visible from above; mandibles completely concealed from above; and head and pronotum of males unarmed (Lawrence & Britton 1991). The larval stages can be distinguished from those of other scarabaeid subfamilies by a combination of: apical antennal segment about as wide as penultimate segment; galea and lacinia either partly fused proximally or fitting tightly together; anal cleft usually Y-shaped or angulate; and mandibles without transverse granular ridges forming stridulatory areas (Ritcher 1966). McQuillan (1985) gave detailed descriptions and a key to the larvae of 14 species of melolonthine larvae found in pastures in Tasmania.

Australian Biological Resources Study

Australian Faunal Directory