I was just in West Yellowstone but was only able to fish in the Park for a couple of hours Sunday morning. I was on the Madison just inside the west entrance and not catching anything. An older gentleman and his grown daughter came down and parked and were catching fish after fish within minutes. He was kind enough to show me how he was rigged and the fly he was using. It basically consisted of gold glass beads and a wing of what looked like antron. He gave me one and I re rigged and caught 2 whitefish and a rainbow before I had to leave about 30 minutes later. He said he was a local and that fly and a big ugly hopper chernobyl ant were the only two flies he used all summer long. My real question is about the antron. When it got wet or was in the water it seemed to turn blue and had a little iridescence. The antron I have doesn't do this as far as I know, so what do I need to get to replicate this fly, which he told me was fine as long as I didn't give it to any guides.