The Heptagenia Fuscogrisea is brown on top, but turned around you’ll see that the color the fish see is olive with brown undertones. The wings of are brown just after hatching, but really quick turn transparent with a pale yeallow tint. The Fuscogrisea has large backwings, and distinct black veins on both wing pairs. The two tails are barred and pale yellow. Legs are golden olive, with brown/cherry bands on each thigh.
The nymphs are clingers.
The Hetpagenia Fuscogrisea hatch start in early June and may last for three or four weeks into the summer. They thrive in slow running water, preferably where there is some vegetation on the riverbed. In a river with both strong and slow currents, you’ll find the Heptagenia Sulphur and the Heptagenia Dalecarlica where there is a strong currents and a rocky riverbed. The Heptagenia Fuscogrisea is in the slow and backwaters
The fly with the garters
The Fuscogrisea is one of the easy flies to identify. There are three distinct features to look for.
First look underneath the fly, and identify the elevated area between the second and third pair of legs. The two lines on the elevated area should converge at the front, forming an upside-down V. Compare this area with the Joernesis where these lines run in parallel.
Secondly look at the legs. The Heptagenia Fuscogrisea has two brown or cherry colored bands on each thigh. This is the most visual and easy identifiable characteristic of the fly. If you’re early in the season and stumble across a brown/olive colored mayfly about 12 mm, dressed up in cherry garters, you have found th Heptagenia Fuscogrisea!
Third. If you want to go scientific, look for the first joint on the back leg. It’s longer than all the others.
But really, in practical terms it is sufficient to look for the garters on the thighs.