Family CORIXIDAE

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Family CORIXIDAE

Compiler and date details

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

Introduction

The Corixidae, or waterboatmen, are an aquatic family of nepomorphan insects. They are a cosmopolitan group of 35 genera and 607 species (Stonedahl & Lattin 1986; Henry 2009; Polhemus, J.T. pers. comm.).

Corixids are small to medium sized, ranging in length from 1.5 to 16 mm. They often have characteristic transverse stripes on the pronotum and the hemelytra. The body is usually elongate, subparallel, and compressed. The head is broad, short, triangular, and overlaps the anterior margin of the pronotum. The eyes are large, and ocelli are usually absent. The labium is triangular, unsegmented, and broadly fused to the head. The antennae are shorter than the head. The pronotum is large and often covers the scutellum. The metathoracic scent glands open near the mesocoxae. The larvae have dorsal abdominal scent gland openings between terga III–IV, IV–V and V–VI. The foretarsi (= palae) are short, unsegmented and scoop-like and usually have a single claw with a row of long hairs. The midlegs are long and slender, with the tarsi usually 1-segmented, and the pretarsi with two elongate claws. The hind legs are modified for swimming, being flattened and fringed with long hairs, and the tarsi are 2-segmented. The abdomen is concave dorsally, forming an air-reservoir between the wings. The genital segments are asymmetrical. The male tergum VI is modified into a strigil. The spermatheca is characterised by a long tube and bulb (Slater 1982; Stonedahl & Lattin 1986).

Štys & Jansson (1988) provided a modern suprageneric classification of the Corixidae, which is largely derived from Hungerford (1948). They recognised six subfamilies: Corixinae (26 genera within four tribes—Agraptocorixini, Corixini, Glaeonocorisini and Graptocorixini); the Cymatiainae (Cnethocymatia Jansson and Cymatia Flor, the former as a subgenus of Cymatia in the Catalogue); the monogeneric Diaprepocorinae; the monogeneric Neotropical Heterocorixinae; the Micronectinae (containing three genera, the Old World Micronecta Kirkaldy and Synaptonecta Lundblad, and the Neotropical Tenagobia Bergroth); and the monogeneric Afrotropical Stenocorixinae.

Corixids are detritus feeders, predators, or algal and diatom feeders. Polhemus et al. (1988) reported that corixids forage predominantly on bottom ooze, consuming algae, Protozoa, mosquito larvae, brine shrimps and other aquatic animals. Corixids are found in lentic and lotic waters. They are often found at the bottom of water bodies holding fast to various objects. Most species are known from freshwater, although some species are known from saline waters (Scudder 1976). Some Micronecta species live in freshwater sponges and among water weeds. Corixids lay eggs in groups or singly, usually attached to the substrate by a pedicel. Dispersal flights are common and adults are often attracted to lights. Stridulation is often used as a mating signal in many genera, with the songs either species or sex specific (Jansson 1976).

Hutchinson (1929) reviewed the fauna of equatorial Africa. Hungerford (1948) revised the corixids of the Western Hemisphere. Brooks & Kelton (1967) and Stonedahl & Lattin (1986) provided useful reviews of the Nearctic fauna. Backman (1981) reviewed the Argentinian corixid fauna, including keys, and biological and distributional information. Jansson (1986) revised the European corixid fauna, giving detailed descriptions, keys, and notes on distribution. Tinerella (2008) revised the micronectids of Papua New Guinea and Oceania, including two genera Papuanecta Tinerella and Micronecta Kirkaldy and provided keys for species of those two genera; he treated the micronectids as a family, which we do not follow in the Catalogue .

The Australian corixid fauna is represented by four subfamilies, five genera and 31 species. The Corixinae are represented by two tribes (Agraptocorixini and Corixini), two genera and 13 species. Knowles (1974) revised Agraptocorixa Kirkaldy and recognised six species, most of which are widely distributed in mainland Australia. The Corixini were revised by Lansbury (1970) and comprises seven species of Sigara Fabricius. The Diaprepocorinae, known from the Jurassic of Europe and Central Asia, are now restricted to the southern half of Australia and New Zealand. Knowles (1974) revised the genus Diaprepocoris Kirkaldy and recognised three species, with endemic species known from Tasmania and south-western Australia. The Micronectinae, represented by 14 species of Micronecta, were revised by Chen (1965) and Wróblewski (1970, 1972, 1977). Lansbury (1995) listed the species of Corixidae of southern Western Australia. Andersen & Weir (2004b) provided a key to the Australian corixids.