Characters for Identifying Common Families of Plecoptera1

For Capniidae: Of the 3 tarsal segments, segment 1 (-most ) and 3 (apical-most) are long and about the same length, and segment 2 is much shorter; none of the tarsal segments with any conspicuous membranous pads. No long series of cross veins on the wings.

Capniidae - Slender Winter Stoneflies. This is a common and widespread of “winter stoneflies.” Adults are usually small and black and emerge from streams in late winter and early spring. They crawl around on the snow, especially on sunny days, seeking refuge from the cold at night in little crevices in the snow and ice. They feed on algae. Some have winged, brachypterous, or micropterous adults.

For the other 3 families: Of the 3 tarsal segments, segment 1 (basal-most ) is much shorter than 3 (apical-most); segments 1 an 2 with conspicuous membranous pads.

For Pteronarcyidae: Adults with conspicuous remnants of the larval gills on the thorax between the coxae and on the basal abdominal sterna.

Pteronarcyidae - Giant Stoneflies. These are the largest stoneflies in MN and North America. They are dark brown or black, with red or orange markings on the thorax, and with many cross veins in the wings. In the West, where they are knows a Salmonflies, they often emerge, mate, and oviposit in large numbers from rivers. Our local species are Pteronarcys dorsata (NE part of state) and P. picteti (central to SE).

1 Illustrations from Merritt, Cummins, & Berg (2008); photographs from BugGuide.net. 1 For Perlidae and Perlodidae: On some species there may be remnants of gills on the thoracic sterna behind the coxae, but gills are absent on the basal abdominal sterna.

Perlidae - Common Stoneflies. HIGHLY TECHNICAL: Metathoracic sternacostal sutures along posterior margin of basisternum not reaching furcal pits. IF gill remnants present on thorax, they are branched or ragged stubs.

A widespread and common family of stoneflies. Adults emerge in spring and summer. Some species are large, but not as large as the giant stoneflies, and most are brown in color. The large bodied species may spend 2-3 years in the nymphal stage. Adults probably do not feed. Acroneuria and Paragnetina are common MN genera.

Perlodidae - Perlodid Stoneflies. HIGHLY TECHNICAL: Metathoracic sternacostal sutures extend laterad from anterior corners of furcal pits to margins of basisternum. IF gill remnants present on thorax, they are finger-like (or a single fork).

Adults are similar to perlids, with similar habits and habitats. A very common MN species, Isoperla bilineata, is yellow.

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