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.
plethora of Plecoptera!
Mature nymphs normally find a large rock protruding above the water upon which to climb out of the water for emergence into the adult, or they crawl out of the water onto shoreline vegetation for adult emergence. There are some interesting exceptions to this normal emergence behavior however. Several species have been observed emerging directly in the surface film similar to a mayfly nymph. One species, Isoperla longiseta, has actually been seen walking on the underside of the surface film in some Alberta streams, apparently looking for floating debris to crawl out on for emergence. Because of such varying emergence behavior, you should study both the insect behavior and fish feeding behavior carefully before selecting your fly and fishing technique during a hatch of little yellow stones.