Family HYGROBIIDAE

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Family HYGROBIIDAE

Compiler and date details

2001 - Updated by Andrew A. Calder, CSIRO Entomology, Canberra, Australia

1987 - J.F. Lawrence, T.A. Weir & J.E. Pyke

Introduction

This family contains the single genus Hygrobia with two Palaearctic species (from western China, Europe, North Africa and Israel) and four species in Australia. The family is unknown in the fossil record and its relationships to other groups of Adephaga are still open to question (Lawrence & Newton 1982).

Hygrobiids are relatively slow-moving, bottom-feeding predators occurring in lentic habitats, such as ponds, in which the bottom is covered with fine ooze and freshwater swamps where the bottom is covered in mud and rotten plant debris. Adults swim using alternative leg movements. They periodically come to the surface to replenish their air supply, which is stored beneath the elytra. They are capable of flight and occasionally come to lights at night. They also stridulate by rubbing the abdominal apex against the inner surfaces of the elytra (Britton 1970; Lawrence & Britton 1991). Larvae occur in the same habitat as adults, but remain on the bottom and breathe through gill filaments located under the thorax and abdomen. There are three instars, the last with functional spiracles and capable of leaving the water to pupate in sand or mud. Both larvae and adults are predaceous. The European species Hygrobia hermanni (Fabricius) is known to feed on insect larvae and tubificid worms (Balfour-Browne 1922; Cuppen 2000).

Larval Hygrobiidae are described and illustrated by Bertrand (1972), Böving & Craighead (1931) and Lawrence (1991). The family is included in the world catalogue of Zimmermann (1920) and the Australian species were reviewed by Britton (1981) while Hendrich (2001) added a new species from the peatland swamps of south west Western Australia.