Order:
Adults: With or without wings. If wings present, forewings typically leathery or hard basally and translucent and flexible apically. Nymphs: With or without wing pads. Segmented legs present. Mandibles hidden within needle-like beak in adults and nymphs.
Family:
Similar in appearence to Belostomatidae (giant water bugs) except that margins of eyes are contiguous with anterior margin of head and retractile breathing straps absent from end of abdomen. Beak cylindrical and 3- or 4-segmented. Antennae shorter than head and located beneath eyes, not readily visible dorsally. Middle and hind legs with fringe-like hairs, useful for swimming. Legs are raptorial (suitable for use in predation) with broad femora, and weakly convex dorsally.