Thorax Black dubbing (super fine, beaver, hare's mask or rabbit)
Hackle Blue dun hen cape feather
How to tie it
Start the black thread about an eye length back from the eye and lay a smooth thread base back to the bend.
Select a biot and trim the outside edge off the wide base of it to narrow it.
Tie the biot in by its tip end with the raised edge toward you, overlapping it all the way up to where the body will finish (never tie it in by the very tip, which will break).
Put a thin coat of Zap-A-Gap around the hook.
With hackle tweezers, start the first turn at the bend with the stand-up edge on the back of the turn and wrap the biot forward in fairly tight turns, building a slight taper; tie off with a couple of tight turns and trim.
Dub a small ball of black dubbing about an eye length and a half behind the eye, leaving room for the hackle.
Trim a few fibers off the butt of a blue dun hen cape feather, tie it in, and with wet fingers sweep the fibers back to one side.
Take one turn of hackle, then a second or at most about two and a half turns, tie it off behind the eye and trim the stem.
Push the hackle back, take a few turns over the butts to slope it back, whip finish over the stub, trim the thread and crush the stem so the fibers slope back.
Other versions
2 more in the app: As tied by InTheRiffle, As tied by Charlie's Fly Box (2).