Family Gyrinidae: Whirligig Beetles

Adults: Adults are round, shiny black or dark green and fast moving. They have two pairs of compound eyes, one located on top of head and one below. The front pair of legs is most prominent, and the antennae are short and clubbed. Whirligig beetles are often seen in large groups swimming in circles on the water’s surface.

Larvae: Whirligig beetles larvae are slender with large mandibles and feathery lateral gill filaments along both sides of the abdomen. They have two pairs of gills at the end of abdominal segment nine.

Habitat: Slack-water areas in streams and in calm water of swamps, ponds and lake margins.

Ecology: Large colonies of adult whirligig beetles are a common sight on the surface of small ponds in late summer. Adults feed on live or dead insects found on the water’s surface. They will swim undewater, occasionally fly to lights a night, and migrate to large rivers or lakes to overwinter. The larvae are aquatic predator of small aquatic animals. They swim by undulating their bodies or crawl among submerged logs and vegetation, breathing through the feathery gill filaments that extend from abdominal segments.

Life History: Whirligig beetles have a holometabolous (complete) life cycle. Mating occurs on the water surface and eggs are laid under water on stems of emergent vegetation. The larvae hatch from eggs in 1-2 weeks and undergoing three instars. Pupation occurs on shore out of the water.