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.
SwittersB & Exploring 
Amazing fly! Love it! Thanks for posting it!
LikeLike
How would I fish this fly?
Guillermo
Puerta del Cielo
LikeLike
Hello Memo,
Fish these flies along the bottom like a nymph or in this case, a cased Caddis, drifting right above the rocks. Study up on ‘behavioral drift’ and picture the little critter has let go of its hold and is drifting downstream before reclaiming its hold on the substrate.
SB
LikeLike