Okay, so today I found this caterpillar that, at first, I thought was a swallowtail caterpillar. I looked up the common swallowtails in our part of Ohio (Columbus) and it didn't look like any, so I looked up a link to Geometrids. The only really complete site I found was Wikipedia, and I couldn't find anything that looked like the caterpillar I found.

It is a little over an inch long and looks like a pale twig, light grey with darker grey markings. I can't identify the plant it's on, but I'm wondering what kind of moth it will turn into.