Whirligig Beetle
Gyrinus substriatus
Print fact sheet (PDF)
Spins in frantic circles on the surface — with each eye split in two, half above water and half below.
A small, shining blue-black oval beetle that lives on the surface film of ponds, canals and slow water, usually in groups that whirl and circle at speed. Whirligigs are common on still and slow waters around Dumfries. Their most remarkable feature is invisible at a glance: each compound eye is divided in two, giving simultaneous vision above and below the waterline.
Behaviour
The middle and hind legs are flattened into short, fast paddles, and a group can spin at speed without collisions — they detect one another through surface ripples picked up by their antennae, a form of natural echolocation on water. They scavenge and hunt small insects trapped in the surface film, and dive carrying an air bubble when alarmed.
When to see it
Quick facts
- Family
- Whirligig beetles (Gyrinidae)
- Size
- 5–7 mm
- Status
- Native; common on still and slow waters
Photo by Christian Fischer, CC BY-SA 3.0, via Wikimedia Commons