This pattern is very similar to the Eastern March Brown, but with some minor, yet significant color variations to the body, wings, and hackle collar. You can certainly catch fish by using an Eastern March Brown in the Western streams,
This is one of the most productive flies I carry. In fact I'd be willing to bet that most fly fishers carry a few as a "just in case" fly. Translated, that means just in case nothing else works. The Wooly Bugger always seems to produce