Limnology

Stoneflies (Plecoptera)

The order Plecoptera, or stoneflies, is a small group within Iowa's aquatic insect fauna, but is very important in determining water quality. This is because most of a stonefly's life (usually one to three years) is spent as a nymph in aquatic environments. Adults, on the other hand, are terrestrial and live for only a few days or weeks. Stoneflies in Iowa are most often found in flowing water habitats with rocky substrates and cool water. However, there are some species that can be found in slow, warm water creeks and streams as well. Stonefly nymphs are distinguished from other aquatic insects by their two long antennae, two stout tail filaments and segmented legs terminating with two claws. Adults have a similar body shape as nymphs, but there is usually two pair of membranous wings folded flat over the abdomen. The word Plecoptera, the Latin "plecto" meaning folded and "ptera" meaning wing, comes from this morphologic feature. There are a little over 2,000 stonefly species worldwide and almost 670 species within North America. Currently, there are 44 species reported from Iowa (Heimdal et al. 2004, Heimdal and Birmingham 2008).