Part of the rescue flies program, I tied these long ago with brown rug yarn and a semblance of a peeking pupa (or is it larva) protruding from the casing (rug yarn). The hook shank could have been longer to form a slightly longer casing. Not sure it matters much. The pattern is not weighted…probably should be with a couple turns of weight beneath the casing. The flies are on a size 12 hook.