Wonder Nymph
This fly, designed by Brad Downey, of Ft. Smith, Montana, is unusual in its use of the base of a hackle to form the emergent wings and legs of the mayfly. (See below.) The thorax is always dark dun. It is best fished with weight on the leader, bouncing on the bottom, but permitted to swing and rise at the end of the drift. Most takes will occur as the fly comes off the bottom.
To tie the wings/legs, measure the bottom of a grizzly hackle to twice the length of the thorax, and trim to that length. Holding the quill, butt to the top, trim the bottom half of the hackles on each side of the quill closely. You should now have a short feather that looks like a chevron with a tail.
After completing the tail and abdomen of the fly, tie the wing in, on top of the fly, by the "tail", concave side up, and the full portion of the feather pointed to the bend. Dub the abdomen in the normal fashion, and pull the wing over the top. If you've correctly measured everything, the butt of the quill should be in position right above and behind the eye of the hook. Trap it and tie it down firmly. Trim any excess, and whip finish.
The wings/legs should now be streaming out to the sides and sweeping back from the head of the fly, with the quill running down the center of the back of the thorax. (Tough to articulate, easy to tie.)