This family (Perlodidae) has two subfamilies, the Springflies (Perlodinae) and the Stripetails (Isoperlinae). There are 5 genera and 13 species. The two subfamilies are not easy to distinguish without a microscope (use Family Key to Nymphs, top frame). As a family, they may be distinguished by the wingpads. The forewingpads are directed straight back while the hind wingpads are divergent, swept out at an angle (with the exception of one rare species, Cultus decisus decisus). The tail (cercus) is as long or longer than the length of the abdomen (Figure 1). To truely distinguish this family, break out your magnifying glass and look at the mouthparts. They should look like the Figure 2, not like Figure 3.
Fig. 2. mouthparts of Perlodid Stoneflies
Fig. 3. Mouthparts of Forestflies and Willowflies
Fig. 1. Tail
