1. Mash down the barb and attach the hook to the vise. Secure the thread behind the eye and wrap a foundation to the bend of the hook.
2. Clip 4 strands of Mallard Flank and secure them at the tail tie-in position at the bend of the hook. The tail length should not exceed the shank length.
3. Wrap the butt end of the Mallard Flank up past the midpoint of the shank. Clip off any excess. Bring the thread back to the tail tie-in position. Clip a section of z-lon. If you are using z-lon strands, you might wish to divide the material in half. Attach the material to the tail tie-in position. The ends of the z-lon should be less in length than the Mallard Flank strands. Secure this material along the shank up to the midpoint of the shank.
4. Wrap the thread back to the tail tie-in position and select a Turkey Biot. Biots are the leading edge of the feather. It is generally sold as matching pairs. You need to select the biot that has the ridge on the left hand side when you bring the biot with the ‘V’ facing away from you. This will ensure that the ridge can be spaced uniformly. Place the tip at the tail tie-in position and secure with some thread wraps.
5. Wrap the biot forward with evenly spaced ridges. If you can’t do this, the ridge is probably on the right hand side of the biot and it’ll get spaced greater as you wrap. You’ll need to select the biot from the other matching feather. Wrap the biot up to the 3/4 position and secure with thread wraps.
6. Apply the Superfine dubbing and create a thorax that is significantly larger than the abdomen. Make sure to leave some space behind the eye.
7. Select 2 CDC feathers and match the tips. Place the base of the CDC feathers just in front of the thorax and secure with thread wraps.
8. Wet the CDC with moistened fingers and bring the fibers over themselves so that they extend beyond the eye of the hook. The bend of the material should just exceed the thorax. You can fine tune this by placing a bodkin within the loop and pull out the loop until it meets the desired length. Secure the material just behind the eye and add a couple of thread wraps under the tag end of the CDC to lock it in. Trim off the tag. It’s OK to have some CDC tag material extend beyond the wraps.
Rene and Bonnie Harrop are fly designers/fly fishing couple out of St. Anthony, Idaho . Living next to the Henry’s Fork, they have refined many fly patterns that relate to mayfly hatches. As the hatch progresses, the Harrop’s have developed patterns that meet specific periods of the mayfly’s development. The Captive Dun represents an emerging mayfly which is stuck in the surface film and has not quite opened it’s wings. Using CDC for the budding wings, this material allows the fly to float in the surface film with it’s shuck trailing below. The Harrop’s also like to use Turkey Biots for the abdomen which can be tied to form gill-like appendages or a smooth body, depending on how you wrap the material. The material is also easily dyed for a large number of colorations. These colorations can represent the Pale Morning Duns, Blue Wing Olives, and Callibaetis. The Captive Dun is one pattern of a series that the Harrop’s developed to mimic a specific development period of the mayfly. Utilizing both CDC and Biots, they have also developed the CDC Biot Thorax, CDC Biot Dun, CDC Biot Last Chance Cripple, CDC Biot Emerger, and CDC Para-spinner.