Whirligig beetle  (Gyrinus substriatus)

Widespread and common in Britain (3).

This small aquatic beetle is a metallic black colour with orange legs (4). They earn their common name from their habit of swimming in circles on the surface of the water, often very quickly (2). The name of this family of beetles, Gyrinidae, derives from the Latin for 'circle' (5). The middle and hind legs are modified for swimming; they are broad, flattened and oar-like, with a fringe of hairs (6). The compound eyes are unusual as they are divided into two, one pair is above the surface of the water, and one pair is below; this allows them to see above and below the waterline at the same time (3). The larvae have an elongated body shape, a narrow head and filamentous appendages on each segment (4).

Found throughout central Europe and Britain (1).

You can view distribution information for this species at the National Biodiversity Network Gateway.

Inhabits most forms of water bodies, including ponds, ditches and rivers (3).

This whirligig beetle is active during the day, and is often found in large numbers, whirling around on the surface of the water; when disturbed they are able to dive to safety. They carry an air bubble around with them on the tip of the abdomen, which is periodically replenished, and enables them to stay submerged for long periods.

During autumn, the adults fly at night in search of new ponds. In July and August the larvae undergo pupation on land, protected by a cocoon of plant matter and sand grains; the adults emerge 10 days later. Both the larvae and adults are predatory, taking prey such as mosquito larvae and other aquatic invertebrates (4).

Not threatened at present.

Conservation action has not been targeted at this species.

There may be further information about this species available via the National Biodiversity Network Gateway.

For more on invertebrates and their conservation see Buglife, the Invertebrate Conservation Trust at:
http://www.buglife.org.uk/