If I were you, I'd just put the caterpillar back where you found it. (Not on the tire of course, but in that area.) Caterpillars need to eat A LOT as they're growing and getting reading to make their crysalis, and I'm not sure how you'd know what that species of caterpilar usually eats. It might just die, and then you'd probably be disapointed.

If you REALLY want a caterpilar, you can actually buy a butterfly kit. They usually have them at nature/discovery stores or you can order them online. It comes with eggs, and the eggs hatch caterpilars, and it comes with food for them to eat. They grow, make crysalises, and come out as butterflies. Then you can set them free! It's awesome.

But if you do keep it, don't keep it with your ball python.