Alder larva.
Good early season stillwater fly (haven't used it in ten years, maybe fifteen, but thought to myself, "Why, the alder larva! That's a good one"). It also happens to double up as a stonefly imitation and a free-swimming caddis. So you'll definitely be needing one of these.
Tying instructions:
size 10 long shank, heavily leaded, light and dark brown scruffy fluff and pheasant tails tied in fairly random places - hey look I'm trying to take this seriously, you know this whole fly-tying thing, but Christ, *it just doesn't matter*, you can stick any old bit of fluff out there and catch fish, so long as it's the right size and presented half way right *it catches*, not only that it catches more bloody fish than if you were to spend hours tying the thing "to look pretty". Sorry guys, that's the truth. Welcome to flytying enlightenment.