Order:
Wings developing in wing pads. Mouthparts suitable for chewing. Gills present on tops and sides of abdomen. Segmented legs present. One tarsal claw per leg. Usually with 3 tails (sometimes 2).
Family:
Femora and tibiae of forelegs with double rows of long setae along inner margins. Abdominal segment 1 with dorsolateral gills, similar in appearance other gills, each consisting of longer dorsal lamella and shorter fibrilliform portion. Nymphs with streamlined, minnow-like body shape. Isonychia is the only genus in the family. Widespread and common.