This clean-looking little fly is Pat Dorsey's Mercury Midge. If you're a fly tier who's just beginning to tie small flies, this is a great place to start.
For a hook, I like the Dai-Riki #125 and here I'm using a size 22. Start by mashing the barb. This not only makes it easier on the fish, but also helps when you're threading the bead onto the hook.
The bead is really what distinguishes the Mercury Midge from other similar patterns, I prefer Killer Caddis Glass Beads. The midge-sized grey glass with a silver core look great and really do resemble a small air bubble, especially underwater. A little dubbing wax on the end of a popsicle stick makes it easy to separate a single bead from the herd. It's also a very good way to hold the bead steady while you're threading it on the hook. E-Z hackle pliers, of course, make it easier to perform all these tasks, including securing the hook in your vise.
Cream colored 70 Denier Ultra thread is a good choice for the Mercury Midge, it both flattens and cords well. Start your thread on the hook shank just behind the bead and then snap or snip the tag end off close.
For the wire rib, I prefer extra-small copper Ultra wire, but small will work just fine. Cut or break about a 4-inch piece free from the spool.
Tie in the wire behind the bead and secure it to the top of the shank, well down into the hook bend and then wind your tying thread back to behind the bead. I like to build up a tapered body by first taking wraps down the hook shank about a 1/4 of the way then back up, then going a little further and back up. When you have a nice little taper going, get the thread back to behind the bead and give your bobbin a counter-clockwise spin to untwist and flatten the thread. Then take 4 or 5 wraps down the hook shank before giving the bobbin another counter-clockwise spin. You'll find the flattened thread allows you to make a nice thin and even top coat over the tapered body.
With that done, leave your thread at the hook bend, and make open spiral wraps with the copper wire to segment the fly. When you reach the bead, take a few wraps and snip, helicopter or break the wire off close.
Pick up your bobbin and take wraps up the hook shank between the wire wraps and then cover and secure the wire behind the bead.
Do one 4 or 5 turn whip finish to secure your thread and then do another to build up the thorax a bit. You can then snip or cut your tying thread free.
This video was shot very close up so you may be surprised just how small a size 22 hook looks in your vise. But with a little practice you'll find the Mercury Midge is a fairly simple pattern to tie. I know some people use them year round, but for me, Pat Dorsey's creation is kind of the quintessential winter midge pattern.