Hook standard/fine dry-fly hook (e.g. TMC 100 or 101), 18-24
Thread Black 8/0 or 10/0
Materials
Tail Split microfibetts, white (4-6 fibers)
Abdomen Black thread or black biot (1)
Thorax Black Superfine dubbing (trace)
Wing Sparse white CDC + sparkle poly, spent (small clump)
Hackle (optional) Grizzly, light turn for support (1)
How to tie it
Split a few white microfibetts into a widely spread tail at the bend to float the tiny fly flat.
Build a slim black abdomen with thread (or a black biot) to the 60% mark; keep it very thin for the delicate Trico silhouette.
Tie in a very sparse clump of white CDC and a strand of sparkle poly two eye-widths behind the eye. Why: Trico wings must be sparse to keep the light silhouette, and buoyant poly/CDC keeps the tiny fly floating.
Figure-eight the wing flat and spent to each side (add one light turn of grizzly hackle for support if desired).
Dub a tiny black thorax and whip finish behind the eye.