There are dozens of these caterpillars in my back alley. I presume they have fallen or been blown out of the largish tree. We find them crawling around in the concrete road, with no food source within miles (for them, at least). We try to rescue as many as we can (which reminds me of the story about the baby turtles washed up on shore and one lone person is walking along the beach picking them up one at a time throwing them back into the sea. Someone says, "There's no way you can save all of them; why bother?" To which the rescuer replies, "It makes a difference to this one.")
We did some serious investigative research (Internet search engine) and think they're going to turn into a giant leopard moth. Which makes me laugh. For now they're all cute and fuzzy and I feel quite charitable trying to rescue as many as I can.
But come July I'll be beating them off me as I try to race them into the house.