Family ACANTHOSOMATIDAE

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Family ACANTHOSOMATIDAE

Compiler and date details

15 February 2002

Introduction

The Acanthosomatidae are a cosmopolitan family of pentatomoid bugs, most commonly encountered in the temperate and subtropical parts of the world (Thomas 1991). The family comprises 46 genera and over 184 species (Kumar 1974; Slater 1982; Schuh & Slater 1995; Henry 2009). Seventeen genera and 45 species are recorded for Australia.

Signoret (1863) was the first to recognise the group at family level. Stål (1876) maintained the family status, primarily on the basis of characters of the female abdomen. Breddin (1897) disputed this arrangement and relegated the group to a subfamily of Pentatomidae. Kirkaldy (1909) further revised their status to a tribe in Pentatominae. Dupuis (1948) suggested that the group is distinct because of 'primitive' characters. Leston (1953) re-established the Acanthosomatidae, an arrangement that has been followed by most subsequent authors (e.g. Kumar 1974, Carver et al. 1991, Schuh & Slater 1995). Gapud (1991) in a cladistic analysis of pentatomoid families, established relationships of the Acanthosomatidae with the Dinidoridae + Tessaratomidae and the Scutelleridae.

Kumar (1974) monographed the Acanthosomatidae of the world, providing a generic reclassification, including keys and a tribal and subfamilial classification. The Acanthosomatidae are divided into three subfamilies and four tribes, the Acanthosomatinae, Blaudusinae (Blaudusini and Lanopini) and Ditomotarsinae (Ditomotarsini and Laccophorellini). All these suprageneric groups, aside from the Ditomotarsini, are present in Australia. This arrangement was followed by Cassis & Gross (2002).

Lethierry & Severin (1893) and Kirkaldy (1909) catalogued the world fauna. Froeschner (1988) catalogued the North American fauna, updating previous treatments by Van Duzee (1916, 1917) and Torre-Bueno (1939). McPherson (1982) and Thomas (1991) revised the north-eastern North American fauna. Froeschner (1981, 1988, 2000) catalogued the acanthosomatids of North America, Ecuador and Panama. Rolston & Kumar (1974) gave a key to the acanthosomatid genera of the Western Hemisphere. Leston (1953) referred to the Afrotropical fauna and Jacobs (1985) reported the presence of seven genera and 12 species from southern Africa. Cachan (1952) described three genera and five species from Madagascar. Kment (2005) revised the genus Mahea and provided a key to the Acanthosomatidae of Madagascar and Seychelles. Ahmad & Moizuddin (1990) revised the Indo-Pakistan acanthosomatids and provided a cladistic analysis of the genera. Larivière (1995) described the New Zealand fauna.

Australian acanthosomatids are highly endemic with 12 of the 17 genera and 43 of 45 species restricted to Australia. The family is found primarily in temperate Australia, across all the southern States. The Australian fauna was described mainly by Dallas (1851), Walker (1867), Stål (1866, 1876), Reuter (1881) and Distant (1909, 1910). Jensen-Haarup (1928, 1930) and Kumar (1974) provided the most recent descriptions of new Australian species.

The Acanthosomatinae are found in the Palaearctic, Oriental and Australian Regions. The subfamily is represented in Australia by six genera and 25 species. The well-known genera Elasmucha Stål and Elasmostethus Fieber, are found in the Nearctic Region and the Eastern Hemisphere. In Australia, Amphaces Dallas (6 species), Elasmostethus (6 species) and Eupolemus Distant (10 species) are the most speciose genera. Rhopalimorpha Dallas occurs in Australia and New Zealand (Pendergrast 1950, 1952; Woodward 1953) and is represented in Australia by a single species.

The Blaudusinae are restricted to the Southern Hemisphere and the two known tribes, the Blaudusini and the Lanopini, are known from South Africa, Madagascar, Australia and South America. The Blaudusini is represented in Australia by seven genera and 19 species, all of which are endemic. The most diverse genera are Andriscus Stål (4 species) and Hiarchas Distant (4 species). The Lanopini is represented in Australia by two endemic genera (Anischys Dallas and Galgacus Distant) and three endemic species.

The Ditomotarsinae are known from Africa, Australia and South America. The subfamily is represented in Australia by two genera and two species belonging to the tribe Laccophorellini. The Australian record of Aesepus signoretii Stål is doubtful. Kumar (1974) synonymised this species with the South African species, Dregea capensis Distant, and suggested that the type locality information of A. signoretii is erroroneus. He suggested that the specimen label 'Austral' of the type could be interpreted as southern and could equally be applied to southern Africa. Although no specimens of this species are known in Australian collections, the species is tentatively retained in the Australian fauna pending further investigation.

Knowledge of the biology of acanthosomatids is limited. They are thought to be chiefly phytophagous and most species are associated with trees and shrubs (Froeschner 1988). They are known from a wide variety of angiosperms but there is no pattern to their associations (Schaefer & Ahmad 1987). The Madagascan species, Catadispon imernensis Cachan, is known from a Ficus species (Moraceae). The Australian species, Sangarius paradoxus Stål has been taken on a Hakea species (Proteaceae). The New Zealand species, Rhopalimorpha lineolaris Pendergrast is known from a variety of monocot plants belonging to the genera Carex Linnaeus (Cyperaceae), Juncus Linnaeus (Juncaceae), Cladium P.Br. (Cyperaceae) and Dactylis Linnaeus (Poaceae). There is incidental information that Anischys lundbecki Jensen-Haarup feeds on chrysomelid beetles. A few extralimital species have been recorded as being cannibalistic as well as feeding on carrion (Miller 1956).

Acanthosomatids exhibit maternal care of eggs and early instars (Southwood 1956; Slater 1982; Kudo et al. 1989, Tallamy & Schaefer 1997, Thomas 1991). Aldrich (1988) reported that acanthosomatids are semiochemically adapted to this behaviour with larvae depositing trail pheromones and emitting alarm pheromones. Both sexes have exocrine glands and the females are thought to guard the eggs. Cobben (1968) provided information on the egg morphology and embryology of acanthosomatids. Jones & McPherson (1980) described in detail the biology of a few North American species. There are no such studies for any Australian species.

Diagnosis

Acanthosomatids are small to medium-sized bugs. The head is keeled laterally. The antennae are 5-segmented. The mesosternum has a strongly projecting keel. The tarsi are 2-segmented. The second visible abdominal sternum has an elongate spine, projecting anteriorly. Abdominal segment II has the spiracles concealed by the metapleura. Paired trichobothria are present on abdominal sterna III. The genital capsule of the male is specialised. The posterior margin of sternum VII of the female is emarginate. Females have one or two pairs of Pendergrast's organs (abdominal sternal glands). The spermatheca is simple. Sternite VIII is exposed in males. (Leston 1953; Kumar 1974; Slater 1982; Schuh & Slater 1995)