Whirligig Beetle

• Its eyes are divided into two independent halves: the upper one looks into the air and the lower one into the water, so that it watches both at once.
• It detects obstacles and prey from the ripples it generates on the surface and that bounce back, a system comparable to sonar.
• Its middle and hind legs have become flattened paddles that beat up to sixty times a second, among the fastest movements of any animal limb.
• Its eyes are split in two: one pair looks upwards, into the air, and the other downwards, into the water. It sees above and below the surface at the same time.
• It swims in extremely fast circles on the surface film, hence its name. Its middle and hind legs are transformed into flattened paddles that beat up to sixty times per second.
• It navigates by ripples. With its antennae it detects the ripples it generates itself as they bounce off obstacles, a system comparable to a surface sonar that lets it wheel about in a swarm without colliding.
• Those groups are defensive: when they gather in dozens or hundreds, each individual is less likely to be the one a predator picks.
• It secretes a foul-smelling milky substance when handled.
• It can fly and colonise new ponds, and it can also dive, taking a bubble of air down with it beneath its elytra.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

The surface of ponds, lagoons and still backwaters

Size at birth

The larva is slender and cylindrical and reaches 30 mm; it breathes through several pairs of feathery abdominal gills

Sexual maturity

Copulation begins in spring and can go on until August; the male holds the female with suckers on the tarsi of his front legs

Gestation / incubation

The eggs incubate between 5 and 17 days depending on conditions; the larvae develop in summer on the bottom, among stones and vegetation, and the full cycle from egg to adult lasts several weeks

Litter / clutch size

20 to 50 eggs per female, laid in rows or groups on submerged vegetation shortly after copulation

Sources consulted: Buglife; Natural History Museum de Londres; Voise y Casas (2010), Journal of the Royal Society Interface; Pond Informer, ficha Whirligig beetle; Macalester College; ScienceDirect (Hughes 1989); Science Advances, How colonial animals evolve; Wikipedia, Zooid; Macalester College, ficha Whirligig beetle; Pond Informer; Ficha de especie de Gyrinus natator; Brickfields Park, ficha Gyrinus ssp; Brickfields Park

Best time: Visible from March to November on still or slow-flowing water, with two generations a year (April-June and July-August); the adults form rafts or floating swarms of many individuals