That is your basic BWO, approximately Catskill style. Whose recipe it is would entail going back fifty or eighty years and seeing who claimed to be the first to invent it.

The thing about mayflies is that once you have a basic pattern down, all you have to do to make a different mayfly is change the color of the materials and if needed, the size of the hook. So even though there are hundreds of species of mayflies out there, they can all be matched with one basic pattern (or another, there are lots of different approaches), with at most some minor tweaks.

Same with caddis, stones, midges... I have one mayfly pattern, one caddis pattern, one stonefly pattern, and one midge pattern, and they are all, with only minor differences, the SAME pattern. But I can match almost any bug out there with them.