Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
Some say caddisflies are even more important than mayflies, and they are probably right. The angling world has taken a while to come to terms with this blasphemy. Caddis imitations are close to receiving their fare share of time on the end of the tippet, but too many anglers still assume all caddisflies are pretty much the same.
Caddis species actually provide as much incentive to learn their specifics as the mayflies do. There is just as much variety in their emergence and egg-laying behaviors, and as many patterns and techniques are needed to match them. Anglers are hampered only by the relative lack of information about caddisfly behavior and identification.
Troutnut on Oct 29, 2006October 29th, 2006, 12:06 pm EST
Some do. It depends on their egg-laying behavior. Also, even the species which do fall spent usually won't do it every time you see them egg-laying or mating; unlike mayflies, many caddisflies can go at it again a few times.
The species which dive underwater to lay their eggs are probably less likely to fall spent, although I've read that they can make multiple dives, so maybe they can expire in the air, too.
Sorry I don't have a really definitive answer to your question. I also don't have a picture of one that's actually spent, but they spread out their wings kind of like a mayfly spinner and I have a live one in a similar pose to give you a bit of an idea: