1. Larvae with 7 pairs of 4- to 5-segmented lateral filaments on abdomenal segments 1-7 and a single long caudal filament; 25 mm or less when full grown. . . . . . . Sialidae, Sialis Lateille
Larvae with 8 pairs of 2-segmented lateral filaments on abdomal segments 1-8, and a pair of 1- segmented filaments on abdominal segment 10; apex of abdomen with 2 anal prolegs, each bearing a pair of claws; 30-65 mm when full grown . . . . . . . . . . . . . . . . . . . . Corydalidae
Key to Megaloptera Nymphs Families