Water Striders, Backswimmers, and other Water Bugs of Columbia County, Oregon

Water Bugs (infraorder Nepomorpha) are a diverse group containing the aquatic members of the True Bugs. They include Giant Water Bugs (family Belostomatidae) and Water Scorpions (family Nepidae) that crawl on the bottom, Backswimmers (family Notonectidae) and Water Boatmen (family Corixidae) that swim just under the surface, and Toad Bugs (family Gelastocoridae) that crawl on the muddy shores.

Kirby's Backswimmer Notonecta kirbyi columbia county northwest oregon — **Kirby’s Backswimmer** **(*Notonecta kirbyi*)** – 0.4-0.6″. Back is a mix of blacks, browns, and whites, but since it swims on its back it will usually show its brownish belly. Rear legs especially long for swimming. Found in water bodies. (photo © Thomas J. Bright)

Grouse-winged Backswimmer Notonecta undulata columbia county northwest oregon — **Grouse-winged Backswimmer** (*Notonecta undulata*) – to 0.45″. Body is predominantly white with black markings including all-black pronotum. Found mostly in ponds/pools but will use lakes, streams, and rivers. Feed on mosquito larva and other small arthropods. (photo © Kurt Steinbach)

V-marked Backswimmer Notonecta unifasciata columbia county northwest oregon — **V-marked Backswimmer (*Notonecta unifasciata*)** – 0.4-0.5″. White with black markings and brownish “V” on black pronotum. Like other backswimmers, uses surface tension to cling to water’s surface upside-down. Backswimmers have painful bite. (photo © Chris Evers)

Water Boatmen Corixidae — **Water Boatmen** (*Corixidae*) – to 0.45″. Similar to backswimmers but legs of uniform length and swims right-side up. Numerous very similar-looking species in our region. Feed on algae, small invertebrates, and debris. Found in ponds (photo © Eric Carlson)

**Big-eyed Toad Bug (*Gelastocoris oculatus*)** – 0.4″. Rough round body with distinct eye stalks. Mottled in grays, browns, rust-brown, and blacks. Found on shores of lakes and streams, spending most time on land unlike other water bugs. Eats small insects. (photo © Howard Bruner)

**American Giant Water Bug (*Lethocerus americanus*)** – 2.0-2.4″. Huge brown bug with front pair of legs held forward as substantial pinchers. Found in ponds and shallow parts of lakes and slow streams. Eat insects, crayfish, tadpoles, and small fish. (photo © Jim Johnson)

**Brown Waterscorpion (*Ranatra fusca*)** – 1.3-1.7″. A long slender brown insect that walks on four legs while using the front two as pinchers. A thin breathing tube protrudes from the back. Feeds on insects, tadpoles and small fish in ponds and slow streams. (photo © Andrew Cope Emlen)

Water Striders (family Gerridae of infraorder Gerromorpha) are thin-bodied insects with long legs that use surface tension to “walk” on the water. They are predatory, grabbing aquatic insects that move near the water’s surface as well as terrestrial insects that fall in the water. Included in this section are the closely related Water Treaders (family Mesoveliidae) and Riffle Bugs/Small Water Striders (family Veliidae), which have similar habits but more robust bodies and shorter legs.