Water Beetles

On this page, Gyrinidae, whirligig beetles - Gyrinus natator

Water beetles overview

Nearly all water beetle adults are air breathing, so they have to rise to the surface for air which they often store under their elytra. Some rise tail first and others head first. Links to other water beetle families can be found on the main beetle page.

Note the rear legs of all these beetles, they are fringed with hairs and bristles to aid in swimming, and are unsuitable for movement on land.

Gyrinidae, whirligig beetles

Gyrinidae, whirligig beetle

Above and below is the whirligig beetle, there are 12 species in Britain and 700 in the world. The adults range in length from 3 - 15 mm long.

True to its name, this is the beetle you will see gyrating around on the surface of the water utilising the bubble of air it stores under its elytra (wing case) for breathing underwater.

Below are the mouthparts of a whirligig beetle. The mandibles are for biting/chewing, and are the equivalent of our jaws. The maxillae are accessory jaws; the maxillary palps are sensory for testing food, and the labium and labial palps are also sensory. The labium is the equivalent of our lower lip.

whirligig beetle mouth parts

Its eyes are divided into two parts; the lower part is used for looking down and through water, and the upper for looking ahead and in the air, so it can see above and below the water simultaneously. It can escape from danger below by flying and from above by diving into the water.

Flight. In order to fly the adult climbs up some vegetation, opens its wing cases, unfurls its wings, then flies off. Quite often whirligigs will make a squeaky noise just as it is about to take off. And in flight the wing cases rub against the body making a humming or buzzing sound.

It uses its middle and hind legs like oars for swimming, and its fore legs for grabbing prey. The adults prey on small insects that fall on to the water surface.

Gyrinus natator

The most common whirligig in the UK is Gyrinus natator, and it should be a welcome resident in any garden pond as it feeds mainly on mosquito larvae.

Over wintering. In the U. K. Most adults do not survive the winter. However any adult whirligig seen in spring has managed to successfully overwinter by hibernating in the mud at the bottom of a pond.

The adults (above right) are 5 - 6 mm long, shiny black oval-shaped with yellow legs and short, clubbed antennae. They are found in slow-moving and stagnant water. The middle and hind pairs of legs are flattened and fringed with hairs. The abdomen extends a little beyond the elytra. The adults hibernate in mud at the bottom of ponds and streams.

The larvae (below) look like small centipedes and though highly predatory, tend to lurk in vegetation or detritus in shallow water. They have a small head, 3 pairs of legs, 1 pair of gills on each abdominal segment except the last which has 4 hooks. When fully grown they can reach 15 mm long. The larvae pupate out of water by climbing up vegetation and spinning a cocoon.

Gyrinidae larva, whirigig beetle larva

The female lays her eggs on submerged plants.

Related pages

Main insect page
Main beetle page
Beetle body shapes
www.bumblebee.org insect ebook
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