THE XERCES SOCIETY FOR INVERTEBRATE CONSERVATION

Aquatic Invertebrates in Pacific Northwest Freshwater Wetlands
An Identification Guide and Educational Resource

Anyone who has spent much time around ponds or wetlands will probably recognize adult whirligigs. These beetles congregate on the surface of still waters, spinning in circles or zigzagging back and forth. Their flattened, oar-like middle and hind legs allow them to swim at speeds up to 1 meter per second! Another unique feature of adult whirligig beetles is their eyes, which are divided to allow them to see simultaneously in the water and in the air.

Whirligig beetle larvae live under water. Their elongated abdomens have stout, pointed filaments, which can cause confusion with Megaloptera at first glance. Unlike larvae of Megaloptera or of other beetles with lateral abdominal filaments (some Dytiscidae, Haliplidae, and Hydrophilidae), gyrinid larvae also have two small pairs of hooks at the tip of the abdomen. These four hooks help larvae crawl on available subvstrates while hunting small organisms. The filaments can undulate to help larvae obtain dissolved oxygen from the water, escape predators or move to new feeding substrates.