Sulfur CDC Biot Emerger

Welcome to the fly of the month! This month we’re going to tackle a style of fly that many anglers swear by, the emerger.   There are many types of emerger patterns, but my own personal favorite is this CDC biot emerger. The CDC wing case helps suspend the fly just right in the surface film, and the biot body adds a nice color and texture to the abdomen. By changing the colors of the materials used, you can easily create a fly box full of patterns that represent a whole host of mayfly species. We’re tying a sulfur pattern here, but by changing the biot and thorax colors to shades of olive and the CDC to light dun, you can make a blue winged olive emerger. And so on for other mayfly species. Let’s get tying…





HOOK: curved shank hook, size 14 to 16

           THREAD: yellow

TAIL: Hungarian partridge hackle fibers

           ABDOMEN: sulfur yellow turkey biot

          THORAX: sulfur orange dubbing

           WING CASE: white CDC feathers

           THROAT: Hungarian partridge hackle fibers





  1. Start the thread on the hook just behind the eye and wrap a base of thread to a point about halfway down the bend of the hook.
  2. Peel off a few fibers of a nicely mottled Hungarian partridge feather and tie them in as a tail. The length of the tail should be about half the length of the hook.
  3. Tie in the turkey biot at the point where you tied in the tail. There are a few things to keep in mind here. If you examine the biot, you’ll notice that each edge is different. One edge has small hairs protruding from it, while the other is more thin and transparent, almost like cellophane.  You will want to tie the biot in on the side of the hook with the cellophane edge facing toward the eye of the hook. Secure the tag end of the biot along the hook shank, ending at a point about one third of the length of the hook back from the eye to allow room for the thorax and CDC wing case. Clip off the excess.
  4. Now wrap the biot in slightly overlapping turns to create the abdomen. If done correctly, the hair follicles on the biot should be protruding from the abdomen like ribbing.
  5. At the point where the abdomen ends, tie in two or three CDC feathers by the tips, with the butt ends of the feathers hanging toward the bend of the hook. Trim off the excess tips and secure the loose ends.
  6. Dub a small, plump thorax.
  7. Peel off a few more Hungarian partridge hackle fibers and tie them in as a throat. These should also be about half the length of the hook.
  8. Pull the CDC feathers forward over the thorax, leaving enough material to form a bubble. Secure the feathers with a few wraps and clip off the excess. Some of the CDC fibers will remain loose – this is OK, even desired. It will give the fly more realistic movement on the water. Form a solid thread head, tie off, and add a drop of cement.


Tie a few of these up in different color combinations to mimic whatever happens to be hatching, fill your box, and hit the streams! As always, feel free to contact me with any questions at or 610-730-7928.