This is the Speckled Wing Quill dun. It imitates the newly emerged insects as it floats on the surface during the hatch. The Speckled Winged Quills are often called "Callibaetis", which is the scientific name of the genus these mayflies belong too. They are found in slow moving water of streams and still water of lakes and ponds. Trout eat them in all stages of their life. A must for still water anglers.