Mayfly Genus Tricorythodes = Tricos
Trico Duns are pale gray/olive in color with light gray wings and hatch either in late evening or early morning.
Male Tricos emerge throughout the night. The little olive females emerge in the morning. In the summer this happens at first light, but it occurs later in the day as the weather cools down.
Tricos return as spinners soon after emerging, sometimes within a few minutes and sometimes a few hours. The mating spinners gather in very tight swarms rather than roaming the full width of the river.
After mating, the males fall "spent" and the females fly to shore to rest while pushing their little eggs from their abdomens. They return in about half an hour and fall on the water to drop the eggs. They can fall "spent" or take off again