I had a difficult time identifying this caterpillar. It looked a lot like an American Painted Lady (Vanessa virginiensis), but not exactly the same. I couldn't find anything else that it resembled any more, though.
It's been a big year, as far as spiny/bristly caterpillars go. On the driveway today I spotted a Yellow Bear. Also a tiny, tiny shrew or vole. And me without my camera.