Blue Winged Olives (BWO) are often seen just about everywhere on rivers around the world. This important mayfly hatch is a member of the Baetis genus. The Dun BWO is imitating the stage of the mayfly between a nymph and an adult mayfly. Technically this is the subimago stage. This is an easy time for fish, but a vulnerable phase for the mayfly since the wings are formed, but have a dull opaque color. Trout are often actively feeding on the water surface at this Dun stage. These nymphs, dry flies, cripples, and emergers can provide anglers with some incredible fishing.