I'm too tired to go into the behavior of caddisflies, but here's what you need to do to catch trout right now consistantly. Late afternoon and into the evening, fish a subsurface caddis imitation. Not just any though, it should be size #16-18, dark gray, and have a bright green/chartreuse egg sac on the end of its abdomen.
Yes, all those caddis (the females) you see flitting about come back to lay their eggs by flying to rocks and logs that are partially submerged. They crawl down under the water and affix their eggs onto the downstream side of the object. Many of these flies get dislodged and washed into the water column, becoming easy prey for the trout. If you fish in the evening right now, check your waders after you are done, you will see a cluster of tiny, green balls on the downstream side of the legs. These are from the caddis that used your legs for ovipositing. Gross!
The trout will line up below submerged objects to feed on the egg-laden caddis that lose their grip. For the trout, this is one easy meal.
A simple, gray soft hackle fly is all you need to take advantage of this. Tie a small, bright green ball of dubbing on the end of the hook right at the top of the bend. Then dub a tapered body using a gray fur or other dubbing of your choice - I like to use Haretron because it has some sparkle in it. Finally, make two wraps with a gray hen body feather at the thorax, and tie off. I also like to tie a sparse wing on some using snowshoe rabbit foot hair or gray antron. Cast it alongside of and just below partially submerged logs and rocks letting it dead-drift like a nymph into the feeding lane below. I like to position myself so I am casting upstream and across. Be sure to fish it through the drift letting the current grab it as it swings below you so it rises to the surface from the line tension and current. Sometimes the trout will follow it and then grab it as it ascends to the surface.
It's a deadly technique and speaks of the importance of knowing the behavior of the insects the fish feed on as well as the trout that eat them.
Hope that's clear, I'm off to bed.
Life is good. Don't let anyone tell you different.