The Hickory Horned Devil is one of the largest caterpillars in North America. Fully mature (last instar) caterpillars, like this one, are hotdog-sized. Finding one is a Holy Grail moment for caterpillar hunters. They feed primarily on hickory and walnut, but will consume a variety of other woody plant foliage. The next stop for this caterpillar is pupation, which is how it will get through the winter. The caterpillar digs a subterranean chamber in soft soil to pupate within. The moth it will become as known as the Royal Walnut Moth, and is a huge bat-sized animal.