Start the yellow Sumo thread on the curved N111 and add a few turns of tungsten wire at the thorax only. The tyer avoids lead on two counts: it is toxic, and it is bulky. Tungsten wire is thin and twice as heavy, so the fly stays slim.
Run the thread to the bend, tie in a sparse tail of natural pheasant barbs as the trailing shuck, and catch in the copper wire.
Tie in Mojo yarn in A21 and wind it forward to the 60% mark. The mottled yarn gives a broken, natural colouring that flat single-colour dubbing cannot match. Real insects are never one shade.
Rib with four or five open turns of copper wire, tie off and trim.
Tie in a bunch of creamy brown CDC by the butts, fold it forward and back to form a standing loop wing over the thorax, and secure. The loop traps air, which gives the fly both its buoyancy and its lifelike motion in the surface film.
Add partridge barbs each side as legs sweeping back, whip finish, and keep the head small. Fished peche a vue you place it just in front of a cruising trout and let it hang in the film. A tiny fly, but the take is usually immediate when fish are on struggling emergers.