This specimen appears to be of the same species as this one collected in the same spot two months earlier. The identification of both is tentative. This one suffered some physical damage before being photographed, too, so the colors aren't totally natural. I was mostly photographing it to test out some new camera setting idea, which worked really well for a couple of closeups.
Some species of spiders actually live underwater, but they seem less common than those which live on land near the water. From a fly angler's perspective, then, spiders are mostly important as terrestrials.
Because of their relatively stable life cycles, there don't seem to be any points at which spiders become available to trout en masse. But they're undoubtedly a part of the mixed bag of summer terrestrials.