SRI Caddis Pupa - Larva & Pupa. The SRI Caddis Pupa is a variation of the popular Caddis Pupa. Caddis Pupa are in there second stage of metamorphosis. You will have to be vigilant to spot this happening and get at our SRI Caddis Pupa imitation as this stage happens very quickly, most fly fishermen don't even notice it, but you can be assured the trout do. The Caddis quickly breaks open the cocoon and swims to the surface, it is at this point that they are most vulnerable to the trout feeding frenzy when they emerge through the surface film they are fully formed and ready to fly.