Hackle Hen, partridge or hen pheasant soft hackle (1)
Body Working thread (or fine dubbing/silk) (1)
Thorax (optional) Peacock herl (1-2)
How to tie it
Start the thread one eye-length behind the eye and build a small thread bump; leave the tag end long if you want a slim body later.
Tie in a soft hen or partridge hackle by the stem with the shiny side facing the eye, so the fibers will cant forward when wound.
Wind 2-3 turns of hackle just behind the eye, stroking the fibers forward over the eye after each turn. This reversed ('sakasa') hackle pulses open and shut when you pulse the rod, the fly's whole trigger.
Wrap the thread back in touching turns to the hook bend and forward again, building a slim, slightly tapered thread body.
Optionally wind 1-2 turns of peacock herl as a small thorax right behind the hackle for flash and bulk.
Finish with a whip finish behind the hackle (not at the eye) and a drop of cement.