I came across this fly for the first time on my trip to Montana last month. I picked up a few to bring home as tying samples thinking they would tear up the warm-water scene around here. On a whim I ended up tying one on the end of my tippet while fishing the Gardiner River instead of the hoppers everyone was using. The trout were all over it. I fished it a bunch of times during the rest of my trip and it always produced. This fly is PHAT!
It's relatively easy to tie. Thread body, contrasting colors of foam, centipede legs, and antron for the wing. I have a cutter that made perfect bodies without a lot of trimming so I am able to crank them out pretty quick.
Here's a few shots to explain the construction. I think its pretty self explanatory.