Build a segmented body of green dubbing or wrapped latex strip around the curve, distinct segments, grub-like and slightly plump.
Dub a small black thorax behind the bead.
Add 1-2 turns of black hen hackle, sparse, for legs.
Whip finish behind the bead.
Substitutions
Body instead of Green dubbing or latex: Chartreuse Superfine — Bright green larva; Green latex strip — Translucent, segmented body; Cream dubbing — Cream caddis larva variant
Thorax instead of Black dubbing: Peacock herl — Iridescent dark thorax; Black Ice Dub — Dark with sparkle
Bead instead of Black tungsten: Gold tungsten — Brighter head; Copper tungsten — Warm tone