stoneflies, Plecoptera, Isocapnia, North America, Holarctic


This paper presents descriptions, diagnoses, figures, and keys for 12 western North American species of the Holoarctic genus Isocapnia Banks. Complete known distributional records and a cladistic analysis are included for the Nearctic species. Isocapnia fraseri and I. missourii are synonymized with I. integra, and 3 new species are described: I. eichlini n. sp., I. palousa n. sp., and I. rickeri n. sp. Representatives of 5 of the 7 known Palearctic species of Isocapnia were examined and are compared with the Nearctic species. Type localities and distributional data are listed for all 7 Palearctic species.