Build the body first. Take about two feet of 15LB Green Amnesia Running Line, make a big overhand loop, and pass the end through it 14 times as one long overhand knot.
Rub the line on a bar of soap to lubricate it, then pull the knot tight so it collapses into a segmented body. Peel off the soap shavings and snip one tag end.
With the black tungsten bead on the hook, start the thread and run it back to the bend. Bind the amnesia body onto the shank by its remaining tag, curving slightly upward, bind it tight, and snip the excess.
Coat the body all around with Loon Fly Finish in Thick or Thin, building a glassy layer, and cure with the UV light.
Bind a Natural or Olive Brown CDC feather in by its tip behind the body and snip the excess. Trim out the longest fibers if you want a cleaner look; leave them for a shaggy pupa.
Stroke the CDC fibers rearward, then palmer the feather forward with hackle pliers, brushing back any strays, and capture the stem behind the bead. This collar is the pupa's air bubble.
Dub Hareline Natural Hare's Ear Dubbing, spiky fibers and all, a little at a time to build a collar right behind the bead.
Whip finish behind the bead, then brush the collar out with a brush or velcro so the fibers lay back as legs and antennae.