"Creeps and idiots cannot conceal themselves for long on a fishing trip."
A very true statement by Gierach... Irrelevant to the topic at hand but thoughtful insight and partially the reason most of my fishing pursuits are spent alone. My fly fishing idiot-ness is best left without an audience.
My last trip to the upper reaches of the Guadalupe River tailwater were spent doing more casting than catching but improved to some degree after some entomological research (fancy terms for flipping over submerged rocks to see what bugs reside there). I didn't make any startling discoveries or insights into the meaning of "matching the hatch". It was pretty obvious by the fluttering caddis flies dancing on the water and the occasional swell from a fish eating said flies that caddis were staple of this river's trout.
During a pause in the "action" (while beer drinking tubers floated by pissing on themselves), I decided to checkout the nymph version of the caddis for color, size, etc. Flipping a few rocks in the riffle upstream did the trick. This is what I found (and creepier yet what I took pictures of); followed by a picture of the best performing fly pattern:
Guadalupe River Caddis Larva
Caddis Larva Fly Pattern
Caddis Fly Pattern (Elk Hair Caddis)
...Real quick entomology lesson: Baby Caddis = Nymph/Larva that live under rocks in a river. Adult Caddis = Flies that flutter around dancing on the water. This is a very dumbed-down version of the whole story, but all you need to know to catch fish with a fly rod.