If you plan to fish out West in July and August you should have plenty of Gray drake patterns in both the dun and spinner stages. One of the best patterns I have found to imitate the Gray Drake dun is the Gray Drake Comparadun. The Western Gray Drakes are a large fly and should be tied on a size #10 hook. This pattern tied in smaller sizes #12 and #14 can be used to imitate our Light Hendricksons. A few years back I was using this fly in a #12 size and during a Hendrickson hatch on the Broadhead I got an 18″ brown.
Hook – Dry fly sizes #10 – #14
Thread – Gray 8/0Wing – Deer hair tied comparadun style
Body – Fly-rite dubbing #37 Gray Drake
Rib – Brown Thread
Fly tied by John Lazar