The WD-40 is another simple pattern meant to imitate midge pupae and Baetis nymphs. I believe it originated somewhere in Southern Colorado and was popularized on the San Juan River in New Mexico. This pattern is a quick, easy tie that uses just two materials besides thread. This is a great fly to fish with no lead on the leader, just under the surface as well as with more traditional nymphing techniques. Color variations include chocolate brown, grey and black.