Hook Partridge Czech nymph, barbless, 12 (drop to 14-16 by splitting the yarn strand in half)
Thread Black Semperfli Nano Silk 12/0 (or 8/0 black)
Materials
Crystal flash Pearl flashabou (3-4 strands)
Dirty Bug Yarn Green olive dirty bug yarn (1 full strand (split in half for smaller sizes))
Whiting Brahma hen hackle Olive brahma hen fibers (1 feather)
Cobbler's wax n/a (A touch on the thread)
How to tie it
Rub a little cobbler's wax on the thread, Nano Silk is slippery on a slippery barbless hook, then start it behind the eye and lay a full base of touching wraps all the way to the bend. Hold the thread at an angle to the shank as you wrap and the turns will sit tight against each other with no gaps. The materials grip that base, so it is what makes the fly last.
Cut three or four strands of pearl crystal flash to length, lay them on top of the shank at the bend and bind them down so they trail about half a shank length past the bend as a shuck.
Tie in one strand of green olive Dirty Bug Yarn at the 80% point, then wrap the thread back over it all the way to the crystal flash and forward again to lock it in.
Wind the yarn forward up the shank, then take a second pass back over the middle third so the body is fattest at the mid-point and tapers at both ends. Leave a clear gap of about 15% of the shank behind the eye for the hackle. It is easy to crowd this.
Half hitch to hold, then scrub the whole body with a piece of Velcro or a stiff brush to pull the fibres out and make it shaggy.
Prepare the hen hackle: hold it against the front of the fly and check that the barbs reach back only to about the hook point. You do not want too many legs. Strip the barbs off the left side of the feather (viewed from above), then trim the tip into a small triangular anchor.
Wax the thread, tie the feather in by that trimmed tip with the shiny side facing up, attach hackle pliers and take two turns of hackle. Tie it off well before you clip the stem.
Sweep all the barbs rearward and build a distinct black head, then take two whip finishes. Resin or glue on the head is optional. Two whip finishes in Nano Silk hold fine.