Lead wire Gray lead wire (.020, several turns + side strips)
Goose biots Black/brown goose biots (2 (tails))
Wire Copper wire (short length (rib))
Dubbing Dark brown/black dubbing (abdomen + thorax)
Antron White poly yarn (small tuft (gills))
Barred rubber legs Black ostrich herl (2 pairs)
Flash / peacock Pearl peacock herl (1 strand (wingcase))
Feather stems Black ostrich herl (2 (antennae))
How to tie it
Slide the black bead to the eye, wrap 8-10 turns of lead behind it and shove them into the bead, then add a few lead wraps along each side and bind them flat. The side weight keeps the fly slim so it sinks fast without trapping air.
Tie in two splayed biot tails at the bend forming a V, and catch in a length of copper wire.
Dub a slim tapered abdomen forward to the 60% mark, then rib it with 5-6 open counter-wraps of wire and tie off.
Tie a short tuft of white Antron under the shank at the front of the abdomen for gills, the natural's prominent white gills are a key trigger.
Tie in a pair of black rubber legs at mid-thorax and a strand of flash for the wingcase.
Dub a fatter thorax up to the bead, then tie a second pair of legs at the front so the fly has legs fore and aft.
Pull the flash forward over the thorax as a wingcase and tie off, then add two short feather-stem antennae splayed forward over the bead.