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.
These are sometimes called Little Yellows and Little Greens.
These stoneflies, the "little yellows" and "little greens," are quite common Summer fauna. They are spread out in a mix between the different genera. The common name for them is Sallfly.
These stoneflies--abundant during midday--seemed at first to be flying around with plain yellow bodies, but on closer inspection turn out to have striking, fiery red abdomens.