Hook 2X curved nymph hook, 13 Alec Jackson Covert Nymph, equivalent to a size 14 Daiichi 1760
Thread Fluorescent green UTC 70
Materials
Bead chain eyes, small Gold or black bead chain eyes small (1 pair, black preferred)
Marabou Fluorescent green marabou (about an inch off the stem, tail)
Ultra Wire, small Chartreuse ultra wire (counter rib)
Leech dub, Sunshine Collection sherbet Sherbet (body and head)
Crystal Flash Olive crinkle flash fine (4-5 strands, legs)
Superglue (on the eye wraps)
How to tie it
Start fluorescent green UTC 70 on the hook and figure-eight small bead chain eyes on top of the shank, gathering the wraps and then hitting them with a shot of superglue for durability. Tying the eyes on top rather than underneath means the fly hangs point-up more often and snags far less in the weeds, and the profile is virtually identical either way.
Tie in about an inch of fluorescent green marabou behind the eyes with snug wraps down the shank to the bend, take one wrap behind and pinch the tail to length. Keep it slim; you want just enough for movement.
Leave your thread at the back and capture small chartreuse Ultra Wire there rather than running the thread up and back, since every extra trip thickens a damsel body you are trying to keep thin. Note that the marabou tie-in already gives you a natural taper up front, so just extend it slightly.
Dub a slim tapered body forward with the sherbet leech dub, finishing just behind the eyes. This dubbing spins into a very tight rope, which is what lets you get a genuinely thin damsel body; Ice Dub is too much for this fly.
Counter the chartreuse wire forward, opposite the way you dubbed, for segmentation and durability.
Tie four or five strands of olive Crystal Flash in across the shank for legs, one side then the other, and trim them to about a quarter of the body length. Crystal Flash is not straight, and that gnarly kinked look is exactly what you want for legs.
Dub a head slightly bigger than the body, no wing case and no scud back, and whip finish. If the head looks too ropey, run a finger back and forth over it to blend it in. The fluorescent thread pops under UV as a hot spot at the front.