(Hayvan Bilim, Zooloji) Any of numerous weak-flying insects of the order Plecoptera, whose flat, elongated nymphs live under stones along the banks of streams. Adult and larval stoneflies are used as fishing bait. Also called plecopteran
25-2.5 in. (6-60 mm) long, that are generally gray, black, or brown. They have long antennae; weak, chewing mouthparts; and two pairs of membranous wings that, at rest, fold like a fan. The hind wings are generally broader but shorter than the forewings. Despite their well-developed wings, stoneflies are poor fliers. The female drops a mass of up to 6,000 eggs into a stream. Nymphs resemble adults but are wingless and may have external gills; they feed on plants, decaying organic matter, and insects. The nymphal stage lasts one to four years; adults live several weeks