This is Matt Grobert's extended body light cahill dry. It's easier to tie than it looks, quite durable and perhaps most importantly, really catches fish.
Matt begins by mashing the barb on a Dai-Riki #305 size 12 dry fly hook and then securing it in his vise. He starts wrapping olive 6/0 Danville at about the 1/3rd point on the hook shank and works rearward to the hook barb before breaking or snipping off the tag end.
Select a single wood duck flank feather. The off-color ones with shorter fibers, that are unsuitable for dry fly wings, work just great for this pattern. Strip the lower fuzzy fibers from the stem. Orient the feather so the concave dull side faces toward you. Pull all but the very tip fibers down toward the butt of the stem, don't strip them off. Wetting your fingertips will help you to do this. With the fibers pulled down, place the feather on the near side of the hook and pick up your bobbin with your left hand. Make two loose collecting wraps of tying thread then gently pull the feather rearward. The idea is to create a hook shank length long abdomen with the folded back fibers. Thread torque will help carry them to the top of the hook shank. When you're happy with the result, take a few good firm wraps to lock everything in place. You can then snip the butt ends of the feather off close.
Next, pull down one fiber from either side of the feather and then carefully snip out the tip. You should be left with an abdomen and two tails that look something like this. Take wraps forward to the 1/3rd point on the shank.
From the bottom of a snowshoe rabbit's foot snip a small clump of hair. Snip all the way down to the bases. Strip the longer guard hairs out of the clump then reorient it so you're holding the tips between the thumb and index finger of your right hand. Tie down the butts to leave a wing that's about a hook length long. With the clump completely secured, snip the butt ends off close and cover the area with a few wraps of tying thread.
For dubbing, Matt uses cream colored rabbit, disregard the cryptic writing on the box. Form about a 2 inch long dubbing noodle on your thread then begin wrapping it forward to form the rest of the body of the fly. You should end just behind the wing. Then go back to your dubbing to create a smaller noodle and start wrapping it just behind the eye to build a dam in front of the wing. Pull the wing forward and make one wrap with the noodle behind and then continue wrapping in front. This insures the wing will stay upright. Do a 5 or 6 turn whip finish and then snip or cut your tying thread free.
If there are any errant hairs carefully snip them away. And that's all there is to it. Believe it or not, these things fish even better than they look.