Mating flights of the mayfly Ephoron album (Say) were observed on the Sturgeon River in Houghton County, Michigan, on five evenings between 16 and 22 August, 1977. Peak emergence occurred about 30 minutes befqre sunset on 19 August and the flight period lasted about two hours. Many more adult males than females were collected on three evenings, but on one evening females greatly outnumbered males collected.
Kraft, Kenneth J.; Johnson, D. Kent; and Sypniewski, Richard H.
"Mating Flights of Ephoron Album (Ephemeroptera: Polymitarcidae) in Michigan,"
The Great Lakes Entomologist, vol 11
Available at: https://scholar.valpo.edu/tgle/vol11/iss2/2