There were actually two of them on the underside of this leaf. At first they did not move much at all, but after only a few moments, they each started moving around with some vigor. I suspect they were warmed by exposure to the sun. I wonder if they can survive freezing. It seems at least somewhat likely that they can survive somewhat below freezing, as it has been colder here lately and they were not well insulated under snow or many leaves.
Location: Sawmill Creek Road, Sitka, Alaska