Also known as the slate drake, the Isonychia mayfly is a very important food source for trout in both the eastern and western U.S. Isonychia may emerge on the surface or by crawling into the stream bank.
Matt Grobert ties an Isonychia Emerger here on a size 12 Dia-Riki #125 emerger hook and uses 6/0 olive Danville for thread.
More Isonychia tying videos:
Tying Vinnie’s Isonychia Nymph by Matt Grobert
Tying a Slate Drake Nymph by Rich Strolis