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.
This peculiar midge lived in a case tightly fixed to a rock, with several others of its kind. The case seems to be made of tiny grains of sand. I'm not sure what the function is for the little lines sticking out the front, because they aren't legs.