Hans, I have been thinking about our caddis bubble discussion (but not too overly much!). I have some ideas: Let's consider only stream Trichoptera as emergence dynamics are probably much different than for stillwater types of caddisflies. Caddis are mostly found in more riffly portions of streams (or at least let us consider these types). In this area the surface tension of the water is less so that emergence from the pupal skin would be more difficult than stillwater in which the surface tension aids the insect in holding the pupal shuck so that it can escape. Therefore the caddis pupa probably needs some help in loosening the shuck prior to arriving at the water surface (possibly the bubble theory?!?). I did look up Gary's description of emergence in Caddisflies and he did say that the gas bubbles are beneath the pupal skin (so around the about to emerge adult but within the pupal skin). I could surmise that as the gas (possibly from bug farts (right Don??) but remember that some species of caddis have gills (to get oxygen from the water)) distends the thin pupal skin enough that the whole thing could look kind of like a mylar balloon. But.... remember not all caddis species are going to behave the same. As far as photographic evidence, I would guess that actual stream underwater pictures might be necessary because of the different conditions found in an aquarium, ie. dissolved oxygen, current, lighting, etc. Please chew on this for awhile and let me know. We may have to go scuba diving in Montana to find out for sure ;^)
Have a very Merry Christmas Bruce Whittle
