Family NAUCORIDAE

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Family NAUCORIDAE

Compiler and date details

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

Introduction

The Naucoridae, or creeping waters bugs, are a cosmopolitan group of nepomorphan bugs presently comprising 39 genera and 391 species , including Aphelocheirinae and Potamocorinae (Polhemus 1979; Polhemus & Polhemus 1988a; Zoological Record 1980–1994; Pollhemus, J.T., pers. comm.).

Naucorids are medium sized, usually over 5 mm in length, dorsoventrally flattened, ovoid-elliptical to broadly oval. They are blackish brown to yellowish brown and sometimes mottled. The head is transverse and opisthognathous. The eyes are large and contiguous with the anterior margin of the pronotum. Ocelli are absent. The antennae are 4-segmented and are not visible from above in most naucorids, except in Aphelocheirinae. The labium is 3 or 4-segmented, and short in all naucorid subfamilies, except for the aphelocheirines. The pronotum is large, subtrapezoidal, and the lateral margins are mostly divergent caudally. The scutellum is large and triangular. The forewings have no membrane veins. Wing polymorphism occurs and brachyptery is common in aphelocheirines. The forelegs are enlarged, flattened and raptorial, except in the aphelocheirines. The hind legs are usually modified for swimming. The tarsi are 2-segmented and the mid and hind pretarsi have elongate claws. The aphelocheirines lack metathoracic scent glands, but all other naucorids have glands with an accessory gland. All naucorids have larval dorsal abdominal glands between terga III and IV. The male abdomen and genitalia are often asymmetrical (Polhemus 1979; Slater 1982).

Naucorids are predaceous, feeding on a wide variety of invertebrates, including corixids, dragonfly larvae, molluscs, and midge and mosquito larvae (Polhemus 1979). Most naucorids live in lentic freshwater, typically ponds and lakes, or sluggish streams. Polhemus & Polhemus (1988b) report that naucorids occur in subsurface habitats in both lentic and lotic waters, crawling amongst vegetation and debris. Polhemus & Polhemus (1988a) reviewed the biology of aphelocheirines and reported that they are benthos dwelling bugs. Naucorids lay their eggs on submerged plant material or pebbles. Respiration is specialised in aphelocheirines and Cryphocricos Signoret (neotropical Region), which have a unique plastron connected to rosette-shaped spiracular openings (Thorpe 1950). In the remainder of naucorids, adult spiracles open into a subalar airstore (Polhemus 1979).

The suprageneric classification of the Naucoridae is based largely on Usinger (1941) who recognised eight subfamilies: Cheirochelinae, Aphelocheirinae, Potamocorinae, Laccocorinae, Cryphocricinae, Limnocorinae, Ambrysinae and Naucorinae. This classification was largely followed by China & Miller (1959) and La Rivers (1971). Stys & Jansson (1988) claimed that the naucorid suprageneric classification was unsatisfactory and regarded the aphelocheirines and potamocorines as separate families. We do not follow this arrangement in the Catalogue and have adopted the more conservative classification given in Carver et al. (1991).

The Aphelocheirinae are monogeneric (58 species) and are restricted to the Eastern Hemisphere, with the greatest diversity in SE Asia (Polhemus & Polhemus 1988a). The Potamocorinae are monogeneric (Coleopterocoris Hungerford) and are found in the Neotropical Region. The Cheirochelinae contains three tribes: Cheirochelini (three genera from the Oriental Region), Sagocorini (eight genera from the Oriental Region and Melanesia) and Tanycricini (three genera from Melanesia). The Cryphocricinae are a Western Hemisphere subfamily with two monogeneric tribes (Cataractocorini and Cryphocricini) and the Ambrysini (two genera). The Laccocorinae are primarily a palaeotropical subfamily, with species also known from the Palaearctic and Neotropical regions.

The Australian naucorid fauna is represented by three subfamilies, four genera and nine species. The Aphelocheirinae are represented by one species, Aphelocheirus australicus Usinger, which is known from tropical Queensland (Lansbury 1985; Polhemus & Polhemus 1988a). Laccocorinae have been listed from Christmas Island. There is some doubt that Laccocoris montandoni Izzard occurs on Christmas Island, but it is retained in the Catalogue following Izzard (1936). The Naucorinae are represented in Australia by six species of Naucoris Geoffroy. Polhemus (1984) reviewed the genus in Australia, describing a new species from the Northern Territory, also known from Malaysia. Lansbury (1985, 1991) described two new species from the tropical parts of the Northern Territory and Western Australia. Most naucorids are known from few localities. N. congrex Stål, however, is broadly distributed in eastern Australia, Tasmania, South Australia and the Northern Territory.