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

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Gyrinidae

Overview

Commonly called Whirlygig beetles. Gyrinidae inhabit both still and moving water. Adults are gregarious, usually active in daylight, and known for the way in which they gyrate, or swim in tight circles on the surface, with the aid of surfactants secreted by the pygidial glands (Vulinec 1987). They feed mainly on insects which have fallen into the water, and they locate prey using the Johnston's organ (located in the antennal pedicel), which is sensitive to surface waves. Larvae are bottom-feeding predators, which remain submerged and obtain oxygen through the abdominal gills; the final instar leaves the water to pupate within a cocoon.

Description

Adult gyrinids have the general streamlined appearance of Dytiscidae, but they are easily recognised by the fact that the eyes are completely divided into an upper and lower portion by a strip of cuticle and by their habit of swimming mainly on water surfaces. Antennae very short and compact; mid and hind legs short, flattened and paddle-like, with fringes of swimming hairs; fore legs long and slender, with expanded tarsi in males. Larvae elongate and slender, with falcate, perforated mandibles, 1 pair of lateral, feathery gills on each of first 8 abdominal segments, 2 pairs of gills on 9th segment, and 2 pairs of hooks at apex of 10th segment; functional spiracles absent except in last instar.

Distribution

The family is widely distributed throughout the world and is represented in Australia by the genera Gyrinus , Aulonogyrus , Dineutus , and Macrogyrus , the last of which includes our largest species. [Ochs 1949.]

  • Dineutus australis

  • Macrogyrus sp.

  • Dineutus australis

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