
Isonychia bicolor, Mahogany Dun, Slate Drakes, Leadwings, Leadwing Coachmen
All the species of Isonychia are similar in appearance and behavior
They may be abundant on one river, and be absent from a neighboring river.
In Pennsylvania mountain Freestones look for Isonychia in early to mid-June, the Catskills in mid-June through early July and the Midwest and Appalachians from late June through mid-July.
This is an evening hatch occurring in light numbers. It is important because of the hatches duration and the size of the flies.