Caddis Pupa Husk
When mature, caddis larvae seal themselves in a pupal chamber and metamorphose into the pupa. The mature pupa is rightly called the “Pharate Adult.” It is the adult inside the pupal husk. There has been much discussion of the appearance of the Pharate Adult as it rises to the surface to hatch out. Some say it is a shining ball of movement that rockets to the surface and emerges in a heartbeat. And that is what I thought for years–it’s what many of the books say. But after much onstream observations, reading much scientific literature, and going back and reading the accounts in angling texts, I am convinced otherwise.
The insects seen with a shining bubble appearance that pop to the surface and “hatch” in an instant are caddis females returning from egg laying. They dive or crawl to the bottom and lay eggs directly on the bottom (see Caddisflies in the archives). They carry an air bubble with them so they don’t drown, and when done, they swim to the top (assisted by the buoyancy of the air bubble; the air bubble bursts, and the adult flies off.
The Pharate Adult is dressed in a loose cuticle (the pupal skin) which is separated from the adult inside by molting fluid. This gives the Pharate Adult a bit of a glistening appearance; the cuticle hangs on the adult like a filmy negligee. My friend Will Koukkari and his colleague Tracy Anderson have provided some excellent photos of the Pharate Adult showing the filmy cuticle and its pale, almost pearlescent glow. He has graciously allowed me to post these for all to see. Thanks Will.