| - | Two claws at the end of each leg |
| - | Gills often absent, when present usually on thorax |
| - | Two stout tails of varying length |
| - | Growth instars: 10-30 |
| - | Two tails |
| - | Long antennae |
| - | Four wings of equal length, held flat over abdomen when at rest |
Stonefly larvae (nymphs) are easily recognized by their two stout tails, which are more widely separated at the base than those of mayfly nymphs.
Stonefly adults, which also have two tails, are easily recognized by their four equal length wings, which are held flat over the abdomen when at rest.