The Gray CDC Emerging Dun is a biot-bodied CDC and synthetic-winged mayfly emerger originally developed as a spring creek fly to imitate Blue-winged Olives. Parks’ Fly Shop ordered it in much larger sizes than standard as an emerger for the various species of Green Drakes present in the Lamar drainage. It is most useful in this purpose in sizes 12-16.
Hook: #12-20 1xl or standard-length dry fly or light nymph hook (nymph hook used here).
Thread: 8/0 olive-dun.
Shuck: Gray crinkled synthetic yarn (Sparkle Emerger Yarn, Zelon, etc.).
Abdomen: Gray-olive turkey biot wrapped over a thread underbody.
Wing: Natural gray CDC (medium dun if natural unavailable) and same material as tail.
Head: Gray dubbing.