Whirligig Beetle

Gyrinus substriatus

Statistics

Taxonomic family: Gyrinidae

Length: 0.3 to 1 cm

Average life span: 1 to 2 years

Juvenile stage (in water): 4 to 12 weeks

Adult stage (out of water): upwards of 1 year

When To See

Most active on warm, sunny days. Larvae present from May onwards. The adults are present all year round, in winter when ponds freeze over, they head to the rivers and burns. They return to ponds in the spring.

Photo credit: Jim Rathert (Missouri Dept. of Conservation), Iain Reid

Habitat

They are very common on ponds, lakes and canals. This is due to them preferring still water surfaces. You may find them in rivers over the winters, especially where there are artificial structures such as weirs that create a pond like area above them. The young are predators feeding on small invertebrates, like springtails, that live or fall into the water. While the adults are scavengers, eating bits of plants and dead things that they find on the water’s surface and just below it.

How To Identify

They are oval-shaped, with shiny black bodies. Legs are orange, and the back legs are flattened like a paddle. Adults have two sets of compound eyes that allow them to see both in the water and the air above simultaneously. They move around in circles on the surface of the water looking for prey.

Seen It?

Been kicking about in your local river and come across one of these invertebrates? Not sure? Share it with us at trust@forthriverstrust.org, we enjoy chatting about inverts with you.

Gyrinidae dorsal