This is a pattern that some crafty fly tier on the Bighorn River? came up with. It works like hotcakes in the spring, especially on tailwaters like the Bighorn. Tie it with a pink, tan, or gray body. Wapsi Sow-Scud Dubbing is the preferred dubbing. Ice dubbing would also make a great version of this fly- try UV Tan, UV Gray, or UV Shrimp Pink.
This simple to tie nymph has held a spot in my fly box for the last 3 seasons. Purple flies work extremely well in certain situations. For me this purple nymph works well in the spring and fall, especially when fish are keying in on Baetis mayfly nymphs. Tie in sizes 16-20.