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).
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).
In arthropods (crustaceans, insects and arachnids) the abdomen is the hind region of the body, which is usually segmented to a degree. In crustacea (e.g. crabs) the limbs attach to the abdomen; in insects the limbs are attached to the thorax (the part of the body nearest to the head) and not the abdomen. In vertebrates the abdomen is the part of the body that contains the internal organs (except the heart and lungs).
Stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
The process of becoming a pupa, the stage of an insect's development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
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