Burrowing mayflies (Hexagenia bilineata) were collected in 1991 in the vicinity of the DePere dam on the Fox River, Brown County, Wisconsin. Because Hexagenia mayflies are indicators of good water quality, their emergence from the Fox River is evidence of improvement in conditions at the sediment-water interface.
Cochran, Phillip A.
"The Return of Hexagenia (Ephemeroptera: Ephemeridae) to the Lower Fox River, Wisconsin,"
The Great Lakes Entomologist, vol 25
Available at: https://scholar.valpo.edu/tgle/vol25/iss2/4