Hook: Fresh or saltwater hook
Thread: White 3/0 or Monocord
Tail: Very sparse bucktail or marabou plumes overlaid with five or six strands of pearl Glimmer or Krystal Flash
Body: White closed-cell foam, with five evenly-spaced segments. Foam should be 1/2"-5/8" wide for most flies. Use foam at least 1/8" thick.
Rib: White or Grizzly saddle hackle palmered between segments
Carapace or Shell: Closed-cell foam pulled over body and secured just behind eye. Trim foam leaving an excess of about 1/2" protruding beyond eye.
Reference: Jack Gartside Gurgler