This is the caterpillar of the royal moth or royal walnut moth (Citheronia regalis) often referred to as the hickory horned devil.If you think it looks big,you are right,they reach about 6 inches in length. They feed on hickories and walnut,though in the south they prefer sweet gum or persimmon.They do not spin cocoons,instead they burrow into the ground to pupate.I was successful in rearing several from eggs to the pupae stage,but unfortunately none successfully overwintered,which seems to be a common problem amongst those trying to raise the moths.