This is a simple and effective fly that I have found to be one of my top 3 subsurface flies for lakes in Oregon and BC. Its’ origins are Welsh and I read it was a river fly that has evolved into a popular reservoir fly with many variations. As you see the fly here, it is the standard pattern. I often see it with a medium silver tinsel rib and red thread head. I primarily use a thinner silver or copper wire ribbing for reinforcement of the fragile peacock. Also, if I opt away from the traditional medium brown hackle fibers for the tail and beard, I substitute mallard, teal or partridge. I like the barred appearance. I would not tie this fly on a curved caddis/scud/Cz hook. I think it is best served on a straight shank hook and with a thin body. Use only one or two strands of peacock to avoid an overly plump body. Think slender and a swimmer. Sizes 12-16 have been most beneficial.  Keep this fly simple and unadorned. Spend more time with the presentation and this simple fly will not disappoint.