Stoneflies vary in size from very small to gigantic, depending on species. Habitat can vary widely, too.
Nymphs of the larger species live in fast, riffly water with lots of oxygen. Because of their environment, they are often knocked loose into the current and are eaten eagerly by trout. Many small species burrow into the river bottom or are otherwise rarely available until their emergence season.
In general, mature stoneflies migrate to shore, climb out of the water, and emerge in the open air. They are vulnerable when they migrate, and again as adults, but they are not available to trout at the time of emergence. There is a species of yellow stonefly, however, that emerges in the river just like a mayfly.
For details on individual genera and fly fishing tactics, use the pull-down menu below.