"Great Brown
Drake"
Hexagenia
bilineata
mayfly nymph
Large, darkly mottled nymph. Widespread in America.
1". Hatches late June to mid July. Lakes & rivers.
Burrow into silt, detritus or soft bottoms.
Distinguishable by "hairy" gills. Shy, easily alarmed.
3 year life cycle.
Other
burrowing mayflies:
"Great Olive Winged
Drake" , Great
Dark Green Drake,
Green Drake