It appears to be one of the genus, Eumorpha, probably either E. pandorus (Pandora sphinx) or E. achemon (Achemon sphinx). It is ready to pupate and is wandering until it settles on a good spot to burrow in the ground. You can put it in a container with about 4" of potting soil, or shredded paper towels and it will form a bare pupae if you want to observe the process. This late in the year, it will overwinter its cocoon and emerge next spring. It would be necessary to sprinkle the soil or paper towels with some water so that it does not dry out. I keep mine in the veggie compartment in the fridge in a Glad container, and once a month I give the cocoon a cold water bath and return it to the container, sprinkling a bit of water on the towels. But, a lot of people don't like to "house" cocoons in their fridge. It has to be kept at these lower temps in order to main "diapause", or the moth will emerge when there is no food available for it and temps are too cold for it to survive.

These moths lay their eggs on and their larvae eat the foliage of vines in the grape family. I find mine on Virginia Creeper. If I could see a side view of the caterpillar, I could tell you which species it is. Pandorus have round, white spots with a black dot inside, and Achemons have white slashes. I can tell it is this genus, though, from the spot that remains where a "horn" used to be. Eumorphas lose their horn about halfway thru the caterpillar's growth cycle.

Hope this helps! They are gorgeous, large sphinx moths, that have pink underwings.

Susan

Here is a link that might be useful: Eumorpha achemon