Thread Blue dun (body), black (rib), copper (thorax) 8/0 blue dun, 6/0 black, 8/0 copper
Materials
Bead Matte black tungsten bead (3/32 in, one)
Thread (body) Blue dun thread (8/0, two thin layers)
Thread (rib) Black thread (6/0, one length)
Thread (thorax) Copper thread (8/0)
Paint marker (gills) White uni stretch (One dab on top of the bead)
Loctite / thin cement Clear head cement (Thin coat over the whole fly)
How to tie it
Slide a 3/32 in matte black bead onto a size 16 2XL curved hook with the small diameter toward the eye, and start 8/0 blue dun thread behind it.
Lay the black 6/0 thread along the shank and wrap the blue dun over it all the way down to the bend in a single layer, then clip the excess black tag and leave the black thread hanging off the back for the rib.
Wrap the blue dun thread forward again, two thin layers total, no more. Spin the bobbin to untwist and flatten the thread so the body stays as slim as possible.
Rib the body with the black thread, six or seven evenly spaced turns, plus one more close to the head, then lock it with a couple of wraps of blue dun and cut the black away.
Whip finish the blue dun thread and cut it off.
Start 8/0 copper thread as tight to the body as you can and wrap a small tapered thorax up to the bead, a few turns only.
Whip finish three or four turns in the copper, cut close, and pass a small flame over the stub to burn off any leftover thread and keep the fly thin.
Shake the white paint marker and dab a small white dot on top of the bead to stand in for the gills.
Coat the whole body and the paint dot with a thin film of Loctite or similar thin cement to protect the fly.