Body/grub Green beaver or caddis dubbing (1 pinch)
Legs/gills Black hen or CDC fibers (small clump)
How to tie it
Slide the black bead to the eye and wrap a lead-free wire underbody, shoving it into the bead to seat it.
Tie in the copper rib and a bunch of turkey tail fibers at the bend, cement the shank, then wrap the turkey forward to build the rough stick-and-gravel case over the back two-thirds.
Counter-wrap the copper rib forward through the case for segmentation and durability. Why: counter-wrapping locks the fragile turkey fibers so the case survives repeated eats.
Dub a small, thin green grub section in front of the case (keep it slimmer than the case, like the larva poking out).
Tie in black hen or CDC fibers at the back of the bead as legs/gills on both sides, then whip finish behind the bead.