That certainly looks like a Buckeye! They don't get too big but I would think you'd have a few more days before he makes his chrysalis. But caterpillars have a mind of their own and since they don't exactly have large brains - who knows? It seems to me that the ones I've raised at the museum got to at least an inch long, though. I'm not very good at guessing measurements but it seems like they were at least an inch. Still think that it's weird that it's eating Butterfly Bush.
