Family HEBRIDAE

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Family HEBRIDAE

Compiler and date details

October 2010 - Dr G. Cassis, University of New South Wales, Sydney, NSW

Introduction

The Hebridae, commonly called velvet water bugs or sphagnum bugs, are a cosmopolitan gerromorphan family. Nine genera and 221 species are recognised worldwide (Andersen 1981; 1982, Slater 1982; Zoological Record 1980–1994; Andersen & Weir 2004a; Henry 2009; Polhemus, J.T. pers. comm.).

Hebrids are small and stout, usually dull brown, grey or green and range in length from 1 to 3 mm. The body is covered with a velvety hydrofuge pile. The head is distinctly extended in front of the eyes, with prominent ventral lobes. The bucculae form a groove that houses the labium. The eyes are small, globular and coarsely faceted and two ocelli are present. The antennae appear 5-segmented and segments III and IV are slender. The labium is 4-segmented, long, and usually reaches the metacoxae. The pronotum has a narrow collar and raised humeral angles. The metathoracic glands open onto the posterior half of the metasternum and are without evaporative areas. The legs are short and the coxal cavities are widely separated. The tarsi are 2-segmented, with the first segment very short and the second segment much longer. The pretarsus is inserted apically, the claws are very long, and dorsal and ventral arolia are present. Wing polymorphism is common. The venation of the forewings is greatly reduced, the apical half lacks distinct veins and the basal half has one or two closed cells. The abdomen is relatively long. Abdominal scent orifices are present in larvae and adults. The female ovipositor is reduced. The male genital segments are reduced, the claspers are almost symmetrical, and the endosoma is bilaterally symmetrical (Andersen 1981, 1982; Slater 1982; Dolling 1991).

Hebridae are found in semiaquatic habitats, particularly in moist detritus or amongst floating plants (Polhemus & Polhemus 1988). Unlike other gerromorphans which favour the water surface, hebrids prefer marginal aquatic habitats. Dolling (1991) reports that British species live in wet moss and on the margins of still waters. Lansbury (1990) reports that Hebrus monteithii Lansbury is found in rainforest litter in Queensland. Merragata hackeri Hungerford is quite common on the surface of stagnant pools in Victoria, New South Wales, Queensland and Northern Territory. Hebrus axillaris Horváth is found in marginal vegetation alongside ponds, lakes and streams (Carver et al. 1991). Hebrids are predators and scavengers, and are known to feed on springtails and other small arthropods (Bennett & Cook 1981). They lay their eggs on moss or algae (Hungerford 1920; Polhemus & Chapman 1979). Cobben (1968) described hebrid egg morphology, embryology and eclosion.

Reuter (1912) included the Hebridae and the Mesoveliidae within the superfamily Reduvioidea (= series Anonychia). Lundblad (1933) and Drake & Chapman (1958) recognised that hebrids have gerromorphan affinities. Andersen (1981) gave a cladistic classification of the family, recognising two subfamilies, the cosmopolitan Hebrinae and the monogeneric Hyrcaninae (Oriental Region). In the same study, and subsequently, Andersen (1982) demonstrated that the Hebridae are monophyletic, based on apomorphies of the head, mesoscutellum, pretarsus, and genitalia. He suggested that the Hebridae are the sister group of all the gerromorphans except the Mesoveliidae (Andersen 1979, 1982).

A number of regional taxonomic works are available on the Hebridae. Drake & Harris (1943) and Drake & Chapman (1958) reviewed the Western Hemisphere hebrids. Polhemus & Chapman (1979) described the Californian hebrids including the diverse Hebrus Curtis fauna. Polhemus (1984) gave a key to the North American species and Polhemus & Polhemus (1988) catalogued the North American fauna of three genera and 17 species. Froeschner (1981) catalogued the hebrids from Ecuador. Polhemus & McKinnon (1983) described new species of Hebridae from the Americas. Cobben (1982) gave an account of some of the Afrotropical hebrids. Linnavuori (1980, 1981) described numerous new species of Hebrus from the Afrotropical Region. Polhemus & Polhemus (1989) described two new species from mangrove swamps in Singapore. Zettel (1998) revised the genus Hyrcanus Distant from Southeastern Asia.

Lansbury (1990) revised the Australian Hebridae, recognising two genera (Hebrus and Merragata White) and five species. He gave detailed descriptions of all species, including three new Hebrus species. Most Australian species are known from tropical Queensland and the Northern Territory, although H. axillaris is also known from temperate south-eastern Australia, South Australia and Tasmania. Andersen's (1981) subgeneric classification of Hebrus is used in the Catalogue, although both Cobben (1982) and Lansbury (1990) indicated that it is difficult to assign the Australian Hebrus species to subgenera. Andersen & Weir (2004a, 2004b) revised the Australian Hebridae, including their placement within the Gerromorpha and a key to genera and species of this family.Three genera and six species are now recognised.