Rib - fine black wire; Body - pearl flashabou over tapered built-up thread body; Hackle - Partridge kept sparse by stripping all the barbs off one side of the feather before wrapping.
This is a modification of a fly I saw in a book called "Guides Flies." The original didn't have the wire rib, but I found that the flashabou would not stay put without it. I sometimes tie this with a few turns of lead wire under the thorax if I want to fish it deeper in the water column. I commonly fish this as an emerger trailing behind a dry fly.
Sorry about the crappy shot of this beauty. I had everything pre-positioned and pre-focused but this one got away from me. By the time I finally saw the blurry shot, I had already put everything away and had shift gears to get ready to go to a Superbowl party :-(