A dye-job if I’ve ever seen one. In larger sizes, it’d make a passable golden drake; I’ve only seen that fly once, on a river in western MD where there aren’t supposed to be any (don’t think it lasted 2 seconds when it hit the water). Smaller, with a toned-down wing, maybe for sulphurs (orange thread underbody makes for a neat effect) or PMDs.
Part 1
hook - Mustad 94840 #12
thread - UTC 140 hopper yellow
tail - hackle fibers yellow
abdomen - stripped hackle quill dyed yellow
thorax/pfd - butts from wing
wing - deer hair dyed yellow
mash barb, tie in thread at point a bit more than one hook eye width back from front
clean and stack a real good-sized clump of deer hair; measure for length (hook shank)
trim butts, 2 soft loops (adjust position if needed to keep it from creeping too far forward); pull firmly, flare it, spin it
wrap thread to point above barb; make a little thread bump
measure a clump of hackle fibers (hook shank); tie in tight against the bump to set the flare and angle
