Adults are rarely noticed as they are relatively inactive, reluctant fliers, and blend into the background. They are largely nocturnal. They live for just 2 or 3 weeks, and they spend most of this time crawling around on stream side stones or nearby vegetation.
Many do not feed as adults, but those that do eat algae or pollen. They tend to fly only when disturbed.
The hind wings tend to be slightly broader than the fore wings, and the wings beat out of sync. Some males may be wingless, or have short, non-functional wings.
An adult stonefly can be recognised by the "double ladder" down its wings, this can be seen in the photograph on the right and below. This is formed by 3 almost parallel veins with a large number of cross-veins.
The cerci may be long and filamentous. The antennae can have up to 80 segments. Their compound eyes give them good vision, and they also have 3 ocelli.
The stoneflies on the right and below are in the Perlodidae family. The double ladder can be seen, but the antennae are blurred as they were in constant movement.