This is the venerable Yellow Humpy. It floats like a cork, can represent a variety of mayfly species and, if nothing else, makes one heck of a strike indicator. Here author, tier and blogger Matt Grobert's going to tie one on a size 12 TMC 100 dry fly hook.
For thread Matt's going to use 3/0 yellow Danville. Start the thread at about the midpoint on the hook shank and take wraps rearward just to the point.
Snip a small clump of moose body hair free from the hide. Strip the fuzzies and shorts from the butt ends and remove any errant hairs. Snip the butts off to facilitate stacking. Once you've stacked the hair, remove it from the stacker, being careful to keep the tips aligned. Measure to form a tail about a hook shank in length and then transfer that measurement to your other hand. Bind down the moose hair real well with wraps of tying thread and then snip the butt ends off just past the halfway point on the hook shank. You can then finish binding the butts down.
Now, snip a clump of elk body hair free from the hide and, again, strip out the shorts and fuzzies. Stack the hair and, while keeping the tips aligned, measure it so it equals the length between the hook eye and the tip of the tail. Transfer that measurement to your other hand and then snip the butts off square.
Place the butts over top of your last wrap and make turns of tying thread to compress and anchor them. With the butts covered, make open spiral wraps rearward, pulling up on the elk hair as you go. This keeps it roughly on top of the hook. When you reach the base of the tail, start back in the other direction and build a layer of thread which will become the underside of the abdomen.
Now fold the elk hair over to create the top side of the abdomen. Use nice tight wraps to form a short little band of tying thread. Pull the tips of the hair up and make a ramp of tying thread to hold them back. Split the hair tips into two equal bundles then carry your tying thread across and back. Bring the thread behind the far wing and cross over your previous wrap to the backside of the near wing. Bring your thread around the bottom of the near wing and cross over between the wings once again. Take a single wrap around the hook shank to lock your work in place. Cross from front to back again and then begin taking wraps to post the far wing. Once you're satisfied with the result, repeat the posting process on the near side wing and take a wrap around the hook shank to save your work. Finish the wings with a figure 8 wrap between them. You should end up with your tying thread behind the wings.
Select one each of appropriately sized grizzly and brown hackles. Orient them so the back or dull sides are facing each other and the tips are roughly aligned. Snip off the stems to get rid of the webby fibers and then strip off about 1/8th of an inch of fibers from both stems. Secure these stripped segments to the near side of the hook, first behind the wing and then with a few wraps in front. End with your thread a hook-eye length behind the eye.
With hackle pliers, get hold of the brown hackle and take 2 or 3 wraps, first behind, then in front of the wings. Anchor the hackle with a few tight wraps of tying thread and then snip the tip off close. Repeat this process with the grizzly hackle.
To finish the fly, do a 5 or 6 turn whip finish being careful not to trap fibers as you go. You can then snip or cut your tying thread free.
And there's the Humpy. There's a reason it has been around so long, it works.