Elm sphinx moth caterpillar, nearly the size of my index finger, crawling along our roof below mature elm trees (yes we still have elms on our property). My son kept it during the day. It showed no interest in eating elm leaves but kept moving around. I concluded that it had reached its "wandering stage" at which point it digs down into the ground to pupate and overwinter, before emerging as a ~4 inch moth. So in the evening, we left it on the ground by the elms. Enjoy the long slumber!