backswimmer, common name for water bugs of the cosmopolitan family Notonectidae, so named because they swim upside down, usually near the surface of the water. They have oval bodies and long, oarlike hind legs, with which they swim rapidly, but their backs are more convex than those of the water boatmen. The exposed belly is yellowish to black. Backswimmers, 1/8 to 1/2 in. (3–12 mm) long, feed on small crustaceans, insect larvae, snails, and sometimes on small fish and tadpoles from which they suck the body juices. They can inflict a painful bite on a human being. Most of the 50 North American species overwinter as adults. The eggs are usually laid on submerged plants or rocks and development to the adult stage takes 40 to 60 days. Backswimmers are classified in the phylum Arthropoda, class Insecta, order Hemiptera, family Notonectidae.
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