Family ALYDIDAE

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Family ALYDIDAE

Compiler and date details

15 February 2002

Introduction

The Alydidae or broad-headed bugs are a cosmopolitan family of coreoid bugs. About 45 genera and 254 species are known worldwide (Slater 1982; Schuh & Slater 1995; Zoological Record 1995–2001; Henry 2009), with most species occurring in the subtropical and tropical regions of the world. The Australian fauna comprises seven genera and 16 species.

The alydids were first recognised as a family by Amyot & Serville (1843), a ranking which has been followed by most subsequent authors (Schaefer 1965; Slater 1982; Schuh & Slater 1995). Stål (1867) regarded them as a subfamily of the Coreidae, and despite a close relationship, this classification has had little modern usage. Schaefer (1965) identified two subfamilies, the Alydinae and Micrelytrinae, with the latter divided into two tribes (Micrelytrinae and Leptocorisini). Ahmad (1965) raised the Leptocorisini to subfamily, thereby recognising three alydid subfamilies. Until recently, this arrangement had been followed by most authors (Schaefer 1979, 1980, 1996; Froeschner 1988). Li & Zheng (1993) provided a cladistic classification of the alydids, supporting Schaefer's (1965) division into two subfamilies. Schaefer (1999) reviewed the morphology and classification of the alydids and established the following classification: Alydinae (Alydini and Daclerini) and Micrelytrinae (Micrelytrini and Leptocorisini: Leptocorisina and Noliphina). This arrangement is followed in the Catalogue.

Lethierry & Severin (1894) is the most recent bibliographic treatment of the family on a worldwide basis. A number of regional catalogues exist, among them Oshanin (1912) and Dolling (2006 C; Palaearctic Region), Froeschner (1981; Ecuador) (1988; Nearctic Region)(2000; Panama). The Alydidae have received little modern monographic treatment. The most important revisionary works are: Stål (1859, 1867, 1873; world), Fracker (1918; Nearctic Region), Gross (1963; Micronesia), Schaffner (1964; world), Ahmad (1965; Leptocorisini of world), Linnavuori (1987; west and central Africa), Brailovsky (1991; Neotropical Region), and Moulet (1995; Mediterranean), Göllner-Sheiding (2000; Africa) and Schaefer (2004; Nearctic region).

The Australian alydids are not represented by a distinctive autochthonous element—only one genus and four species being restricted to Australia. A number of species are broadly distributed in Australia and also in Melanesia and/or the Oriental Region, e.g. Melanacanthus margineguttatus Distant, Riptortus abdominalis (Westwood), R. atricornis Stål, R. linearis (Fabricius), R. serripes (Fabricius), Leptocorisa acuta (Thunberg), L. oratorius (Fabricius), L. palawanenis Ahmad, Mutusca brevicornis (Dallas), M. prolixa (Stål), Noliphus annulipes Walker and N. erythrocephalus Stål.

The Alydinae are the most diverse alydid subfamily and are found in all major zoogeographic Regions (Schaffner 1964). In Australia, the Alydinae are represented by three genera (Hamedius Stål, Melanacanthus Stål and Riptortus Stål) and eight species. Species of the latter two genera are commonly found in the tropical and subtropical regions of Australia, often on the seeds of Acacia species. Both genera are in need of taxonomic revision and new species of Riptortus await description.

The Daclerini is a monogeneric tribe of alydids that are found in the Australian and Oriental Regions. In Australia, they are represented by the endemic species, Daclera rufescens Stål, which is only known from tropical coastal Queensland.

The Micrelytrinae are represented in Australia by both subtribes of the Leptocorisini. The Leptocorisina, best known by the paddy bugs (Leptocorisa Latreille), are serious pests of rice. Three species of Leptocorisa are known for Australia, two of which are ubiquitous in the north of the continent. The Noliphina are represented in Australia by two species of Noliphus Stål, both of which occur in the tropical regions of Queensland and the Northern Territory, and extralimitally.

Alydids are phytophagous on either vegetative material or ripe and unripe seeds. Schaefer (1980), Schaefer & Mitchell (1983) and Schuh & Slater (1995) summarised their feeding habits and host plant relationships. Alydinae feed predominantly on Fabaceae and Micrelytrinae feed mainly on grasses. Schaefer (1972) discussed the evolution of alydids in relation to feeding behaviour. He distinguished groups on the basis of 'primitive' (Noliphina) and 'advanced' (Leptocorisina) grass-feeders, and epigaeic (and perhaps arboreal) seed-predators (Alydinae). Panizzi et al. (2000) reviewed alydid biology and species of economic importance, including Leptocorisa acuta, Riptortus linearis and R. serripes.

The host associations of Australian alydids are poorly known and a number of hosts listed in the Catalogue are from collections and may represent merely 'sitting records'. The majority of alydine species in Australia are found on either legumes (e.g. Cassia spp.) or wattles. Riptortus linearis is a pest of legumes and is also known from several unrelated hosts. The pod-sucking bug, Riptortus serripes, feeds on Acacia species and is an occasional pest of soybeans.

The host associations of the Leptocorisina have been documented more fully. Sands (1977) provided a detailed account of the biology of Leptocorisa species in Papua New Guinea, outlining their life histories, host associations and crop damage. Leptocorisa acuta is a major pest of rice, and is also known from a wide range of other grasses. The larvae and adults of this species can cause complete crop loss by feeding on the developing rice grains in the milky stage (Siwi & van Doesburg 1984). Monteith (1982) reported that this species aggregates in large populations in monsoon forests of tropical Queensland in the dry season. There are no previously published host records for Mutusca species, but they are known to be abundant on a wide variety of grasses. Nothing is known of the host associations of Noliphus species in Australia.

Alydines are also characterised by ant-mimetic larvae. Oliveira (1985) and McIver & Stonedahl (1943) reported on the morphological and behavioural aspects of the mimicry.

Diagnosis

Most species of Alydidae are characterised by their elongate and slender form and often elongate appendages. They are often dull grey-brown in colour. Some species mimic ants (particularly the larvae) or wasps. The head width is greater than half the width of the posterior margin of the pronotum. The bucculae never exceed the antenniferous tubercles. The antennae are inserted dorsad of the midline of the eye. The metathoracic glands have a single small sac and the external efferent system has a distinct peritreme. The membrane of the hemelytra has numerous veins. The abdominal trichobothria are lateral and sublateral on sterna V–VII and submedial on sterna III and IV. The male and female genitalia are diagnostic. (Ahmad & Southwood 1964; Schaefer 1975; McIver & Stonedahl 1993; Schuh & Slater 1995)