What Bug Is That? The guide to Australian insect families.

Logo: What Bug Is That? Logo: Taxonomy Research & Information Network



The giant water bugs contain the largest true bugs in the world, some extending in size to over 100 mm long.

Though they bear a superficial appearance to the some of the Nepidae, the Belostomatidae lack the extend breathing siphon and many have legs modified for swimming. They usually inhabit quiet pools and ponds. They remain concealed in the vegetation and detritus floating near the surface of the water with the tip of their abdomen exposed above the surface of the water to take in oxygen.

Belostomatids have been recorded as feeding on a wide range of invertebrate and vertebrate organisms including insects, crustaceans, tadpoles, frogs and fish. Fish farms sometimes have problems with Belostomatids preying upon the fish fry.

The females of the subfamily Belostomatinae lay their eggs upon the back of the males (left), who cares for them by alternatively wetting them and exposing them to air. This is thought to enhance the survival of the eggs to the hatching stage.


Only 4 species are recorded from Australia. The genus Diplonychus in the subfamily Belostomatinae contains 1 species, Diplonychus eques, that is found in most states except Tasmania and South Australia and 1 species, Diplonychus planus, restricted to the northern gulf region. The subfamily Lethocerinae contains two species of the genus Lethocerus distributed across the eastern, central and northern areas of the mainland.

  • Belostomatidae (Heteroptera)

  • Lethocerus sp.