This merger pattern is from Bob Wyatt’s interesting read “What trout want”. It is a multi purpose emerger pattern that works equally well on caddis and mayfly hatches.
It’s simple design can be deceiving. The materials used ensures a buggy apperance that trout just love. For may fly hatches I have yet to fish a more effective merger pattern.
Be sure not to tie the deer hair to close to the eye of the hook. Put it a good 2-3 mm from the eye.