Hook curved emerger/pupa hook (e.g. TMC 2487 or 2488), 18-22
Thread Black, olive, or red 8/0 or 10/0
Materials
Abdomen Tying thread or fine wire, black/olive/red (1)
Rib (optional) Fine silver wire or Krystal Flash (1 strand)
Thorax Peacock herl or dark dubbing (1-2 strands)
Wing/gills White or dun CDC, tied over the thorax (1 tuft)
Head Thread or tiny black bead (1)
How to tie it
Build a slim, smooth abdomen with thread (rib with fine wire or a strand of flash if desired) up to the 70% mark, keeping it thread-thin for the midge pupa silhouette.
Tie in a short white or dun CDC tuft standing up/forward at the 70% mark as the emerging wing and trapped-air gills.
Add one or two turns of peacock herl or a touch of dark dubbing behind the CDC for a thorax bulge.
Post a couple of thread wraps to stand the CDC upright so the fly hangs vertically in the film. Why: the buoyant CDC head keeps the fly suspended nose-up under the surface like a hatching midge.