Note: Contested against a published dressing: OUR ABDOMEN AND THORAX COLOURS LOOK REVERSED. John Barr's BWO Emerger has an OLIVE-BROWN abdomen and a GREY muskrat/beaver thorax; our record has an 'Olive/gray' abdomen and a 'Dark olive-brown' thorax. Source: Charlie Craven — "Barr Emerger BWO" step-by-step, Charlie's Fly Box — https://charliesflybox.com/blogs/step-by-step-tutorials/barr-emerger
Reference Recipe
Hook Standard dry/emerger hook, 16-22
Thread Olive 8/0
Materials
Tail Blue dun material (hackle fibers)
Abdomen Olive/gray material (fine dubbing)
Thorax Dark olive-brown material (fine dubbing)
Legs Blue dun rubber legs (a few hackle fibers)
How to tie it
Mount the hook and start olive thread, running it back to the bend.
Bind a short, splayed tail of blue dun hackle fibers about half a shank long.
Dub a slim, tapered olive-gray abdomen forward to the 60% mark with sparse dubbing.
Tie a few blue dun fibers along each side of the thorax as legs, reaching the hook point.
Dub a darker olive-brown thorax over the leg butts up to the eye.
Whip finish and cement lightly; leave it ungreased so it rides low in the film.