The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
Wax on, wax off... :)
We are slaves to our senses...:)
A while back, when I posted the above question, I also posed it to Gary Borger on his site. Apparently he'd responded:
Gary Borger says:
Hi Paul, No one that I know of in the scientific literature has seen caddis pupa pumped full of gasses. They have seen and clearly showed that there is molting fluid between the pupal husk and the enclosed adult and that it makes the pupa glisten.