The key for Plecoptera can be found in Chapter 6 of the Guide to Aquatic Invertebrates of the Upper Midwest, pages 77-86. Once you have keyed out your insect, you can use the photographs on this website to verify your identification. If you click on the link to each family on the right, you will be directed to a page that has photographs of that family along with close-up photos of their identifying character. The character featured matches the character used in the identification key.
Plecoptera larvae are almost exclusively found in running waters and they reach their greatest diversity in small cold streams. Plecoptera are the most sensitive order of aquatic insects and many species are restricted to habitats with high levels of dissolved oxygen.
Stonefly adult - Allocapnia