The Green Rock Worm is a long standing Montana Tradition.
Franz Pott tied a rock worm as far back as the 1920s in Montana.
Bob Jacklin caught a ten pound brown on a Green Rock Worm just a few years ago, while demonstrating nymphing in front of a video crew.

I'm working on a new take. This fly does need some work yet. But I think it has promise. It goes quickly enough, once you get the hang of it. The modular bodies do lend themselves to mass production (which means three or four at a time for me). If you capture the naturals in a net and then throw them back (after photographing) they curl up in tight arc until they hit bottom again. So the curved body here is as much intentional as it is a side effect of the material. Combining match-the-bug realism (to the extent it's practical and possible) with extra-natural sparkle is theme for me now, thanks to inspiration from my fly tying and fishing buddy Willy Self. Al Troth often said (in his seminal fly tying seminars) "if you want to learn how to tie a pattern you have to spend at least three days working on that pattern, and nothing else." I'm starting to get there with this one. This particular dressing is new for me. But the Green Rock Worm in the general case has been a goto fly for me for years. I'm looking forward to wetting this one soon.

hook: #16 DaiRiki 125
bead: Copper
thread: 14/0 tan
body: Green UV Chewey Skin tied around a temporary beading needle mandrel, with a bit of flashy yellow dubbing on the abdomen underside.
hackle: Tan

The real deal (one of several not-case making Caddis common in the Northern Rockies. This one is not a net-spinner):


The fly: