I have seen this pattern tied several times at tying shows. It is the standard Elk Hair Caddis, but the CDC is tied in and wrapped forward instead of a dubbed body and palmered hackle. This causes the fly to float flush in the film and the wing still allows for visibility. The wrapped CDC causes tentacles of CDC fibers to undulate in the water suggesting life.  A dab of floatant only to the wing or some false casting should keep the fly floating fine…but should it sink…that would be ok also. Impart some action to it as it is retrieved.   Hans Weilenmann has written several times re this fly and the picture is from a recent article in Flyfiserman.