Backswimmers are ¾ to 1 inch long. Their backs is keeled, coming to a pointed ridge in the center. The hind legs are very long, and are flattened and equipped with hairs to make them into effective paddles. The do not use their front 4 legs for swimming, but keep them folded close to their bodies except when catching prey.

Backswimmer, Notonecta undulata. Dorsal View

Backswimmer Notonecta undulata Ventral View

While swimming underwater, backswimmers keep a bubble of air trapped under their wings to breathe

Backswimmers are often confused with water boatmen, which they resemble. Water boatmen have a flatter wider body, usually with horizontal bars on it. The water boatman's head is wider and its hind legs are shorter.

The backswimmer is a fierce predator whose beak can inflict a painful bite. It is sometimes called a water bee because it's bite feels like a bee sting.

At one time, these were very common in the park, particularly in the prairie pond. However specimens have been very rare in recent years, probably due to reduced rainfall.

Mouthparts of Notonecta undulata

Pigmy Backswimmer Plea striola

Its legs are not modified for swimming, but this does not keep it from moving quickly in the water.

The pigmy backswimmer, Plea striola, is very common in the park. It is usually only about 0.1 inches long. It swims on its back but often is found crawling on its stomach. It normally feeds on small crustaceans, but has been observed attacking larger prey.

Pigmy Backswimmer Plea striola

The pigmy backswimmer resembles a very small creeping water bug, but does not have the very powerful raptorial front legs of the creeping water bug. Also, the body of the pigmy backswimmer is much thicker proportionally than that of the creeping water bug.

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Coleoptera

Water Boatman

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