Body/abdomen Olive, tan or pink scud/shrimp dubbing (as needed)
Rib Clear mono or fine wire (1 strand)
Shellback Thin latex or Scud Back (tan/olive) (1 strip)
Hot spot Fluorescent pink/orange dubbing or thread (optional) (small pinch)
Coating UV resin over shellback (as needed)
How to tie it
Fit the oversized slotted tungsten bead and add a lead-free wire under-wrap, the deliberately heavy bead 'bombs' the fly straight to the bottom, so it fishes as the point/anchor of a Czech-nymph rig.
Start thread and tie in the shellback strip and the mono/wire rib at the rear.
Dub a fat, tapered caddis-larva/scud body forward over the shank, adding a hot-spot of bright dubbing in the middle if desired.
Pull the shellback over the top, then counter-rib with the mono/wire in 5-6 even turns to lock it down and segment the body; tie off and break the rib.
Coat the shellback with UV resin and cure for a shiny, tough back.
Build a small thread collar behind the bead, whip finish and pick out the belly dubbing to suggest legs.