This buggy looking conglomeration of fly tying goodness is a Rabbit's Foot Emerger originated by Tom Rosenbauer. This one's supposed to imitate an emerging blue-winged olive, but you can change colors and size to match a variety of hatches.
The pattern really benefits from a curved shank hook and I personally like the Dai-Riki #125. This one is a size 16. Begin by mashing the barb on the hook and then securing it in your vise.
For thread I'm going to use a brown olive 70 Denier Ultra Thread. Get your thread started on the hook shank, leaving about a two eye lengths space behind the eye.
Antron works just great for the trailing shuck, here a chocolate brown dubbing with nice long fibers. Pull out a thin wisp and then fold it to double it around your tying thread. You can then secure the Antron to the top of the hook shank and take wraps a good ways down the hook bend. Cut the fibers off so they're a bit more than a hook gap in length. Using just one blade of your scissors to cut, rather than snip them results in a more natural looking shuck.
Plain old rabbit fur is used for the abdomen of the fly, here a brown olive. Create a slender, tapered dubbing noodle on your thread and try to get the first turn to land right at the base of the shuck. Continue to wrap the dubbing noodle up the shank to the start of your tying thread.
Select a CDC feather and snip just the tip out so you end up with something about like this. Pull the lower, longer fibers down to expose the stem and then with two wraps of thread, secure it to the hook. This allows you to pull the feather forward until the CDC fibers reach just beyond the hook point. Do your best to get the fibers evenly distributed around the underside of the fly. With this done, you can snip the butts off close.
Hair from a snowshoe rabbit's foot is used for the emerging wing. This particular one has been dyed light dun. Now here's a little tip from Pennsylvania tier Eric Stroup. Carefully use a sharp knife to split each toe from the foot. This exposes the prime hair found in the toe area. I've already used the majority of the hair on this toe, but there is one little clump left right up here by the nail. Snip the hair from the foot and place the clump on top of the hook so the tips extend to the base of the shuck. With a pinch wrap, followed by two more tight wraps, secure the clump to the hook shank. With your thumb, try to distribute the hairs around the top of the hook. To really lock the hair in place, lift the butts and take two wraps around just the hook shank then release the butts and take two more wraps around both them and the shank. Next, snip the butt ends off at an angle.
Take a few more wraps to cover the butts and make a foundation for the head of the fly. Here I'm going to use a slightly darker olive dubbing to create a small noodle which then gets wound to build a nice bushy head.
Finish the fly with a 4 or 5 turn whip finish and snip or cut your tying thread free. Hats off to Mr. Rosenbauer for coming up with such a wonderful pattern. I hope I've done it justice here. You can just imagine it sitting in the surface film at about this angle, buoyed up by the snowshoe rabbit with the trailing shuck and newly emerged abdomen hanging below. Awesome.