Created by Gary LaFontaine, it is one of the best caddis pupa patterns ever. I have done very well with this fly for over 40 years. The secret is the antron yarn which has tri-lobal fibers the reflect light the same way the insects air sac does. The pupa inflates the sac around its body with air to help it ascend to the surface then it pops out as an adult. This fly is to be fished just under the surface. This fly is to be nymphed deeper in the river near the bottom imitating the pupa as it is ascending to the surface.