The Slim Shady Splitback PMD was designed to take advantage of the fish that are eating emerging PMD nymphs duding the summer. I've watched fish lined up and pick off every bug that drifted by in the top column of the water when they were emerging. This fly represents that exact stage when thy are splitting their wing case open to crawl out. The yellow simulates the lighter colored adult PMD as it emerges. I've also fished this pattern as an attractor and also as a Yellow Sally nymph.