You can often see them walking on the snow in early spring.
Black stoneflies begin to emerge in early spring, and I don't think they can be seen much until April.

When they emerge on land, they ride the current and climb onto rocks on the shore to emerge, but like a mayfly, they stay still with their wings upright. When the wind blows them around, they fall into the current and are eaten by fish.

It seems that the fish that are learning are positioning themselves near the rocks and waiting for the black stoneflies to swing at them. Perhaps this is why I have often caught fish by dropping my fly right on the edge of a rock right after the fishing season opened.

Also, during the time of emergence, there seem to be quite a number of nymphs floating in the water, and when I see a fluffy dimple rise, I mistake it for a rise for midges and use a fly of size 20 or smaller, but it doesn't react at all. Sometimes.

Black stonefly flies may only be used for a short period of time, but we will introduce adults and nymphs as matchthehatch flies in early spring.