One of the most popular dry flies during the off season. The great aspect to Blue Wing Olive’s or “BWO” as they are often referred to, is that they show up early in the season in the spring and are some of the first mayflies to hatch offering excellent early season dry fly fishing. Found across the entire west, these small green mayflies will take up a lot of a trout’s diet when not much else is sitting on top of the water in Spring.