There are at least 106 species of this genus in North America. Adults and larvae inhabit both fast and slow streams and littoral zones of lentic habitats. They are piercing predators. Adults are climbers on rooted plants and efficient swimmers.
Mid-Atlantic: 8 and higher
Piercer / Predator
Widespread (east of the Rocky Mtns.)
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Order: Adults with hardened forewings (elytra) covering the hind wings.
Family: Ventrally, pronotum with conspicuous curved lines near each lateral margin (notopleural sutures). Metasternum without transverse sutures. Elytra covering entire abdomen or exposing only part of 1 tergite. Hind coxae each with median portion extending in posterior direction, dividing abdominal segment 1 into lateral sclerites, but not expanding into broad plates. Without large spur on end of each front tibia. Dyticidae without broad wedge-like hind coxal plate. Scutellum usually visible; if hidden, then front and middle tarsi apparently 4-segmented and hind tarsi each with 1 claw. Hind tarsi and usually tibiae flattened, streamlined, and bearing long, stiff swimming bristles. Body usually 3–25 mm long.
Genus: Moderate-sized, 5 to 14 mm long, and black or brown, with elytra appearing leathery with small cracks or net-like. Pronotum margined. Males with tarsi of front legs swollen and bearing dense setae tipped with minute discs. Hind claws of equal length. Metacoxal lines not strongly convergent anterior of metacoxal lobes; elytra without longitudinal striae; metafemora with or without setae on posteroapical angles.