Hendrickson Mayfly Mating Biology

The last few evenings, depending on where you are along the Grand River Tailwater, a natural spectacle has occurred. It’s the mating ritual of the Hendrickson mayfly, whereby males and females flutter over a riffle in the river and mate at dusk. The females then lay their eggs and after all the reproductive work is done, the spent insects fall to the water as spinners, where they are frequently consumed by hungry trout. Here’s a video of this spectacular event from Wednesday evening, just downstream of Fergus.