The Umpqua Cripple Dun is a critically important dry fly pattern designed to imitate a mayfly that has failed to fully emerge from its nymphal shuck, known as a “cripple.” Trout frequently key in on these vulnerable, struggling insects, which are unable to fly away and sit partly submerged in the surface film. Fished as a surface pattern, the Cripple Dun is highly effective during prolific mayfly hatches like PMDs or Blue-Winged Olives when trout become notoriously selective.