Legs Hungarian partridge fibers (two clumps of 10-15 fibers)
Bubble-back wing Natural dun cdc feather (1-2 feathers)
Thorax Tan Antron dubbing (pinch)
How to tie it
Start the thread behind the eye and run it to the bend of the curved hook. Dub a slender, slightly tapered abdomen of tan Antron over the rear 60% of the shank.
Tie in one natural dun CDC feather by its tip at the front of the abdomen with the tip pointing forward over the eye for now; it will be folded back later to form the air bubble.
On each side of the shank tie in a clump of 10-15 partridge fibers as swept-back legs reaching to about the hook point.
Dub a small tan Antron thorax just in front of the leg tie-in.
Pull the CDC feather back over the top of the thorax and abdomen to form a puffy 'bubble back' that traps air, tie it down at the eye, and trim the excess leaving a short stub as a stubby head.