Ciprian found this fly to work for wild trout and grayling between 10 am and 6 pm on various trout streams in several European countries. So we called it the Daytime Emerger. It is very likely that it works in the evenings, too :) Easy to tie and versatile! Vary the hook size and the color of the body to cover a variety of mayfly emergers and midges.
Here is a simple and very effective CDC pattern. Ciprian got inspired by last summer's visit to the Crowsnest Pass area where we experienced some of the best dry fly fishing in our lives. This is intended to imitate a pale morning dun emerger but would work for a variety of light-coloured mayflies. It has no tail and the body is not ribbed, but the fish do not seem to care at all. Keep it simple!