The foodies among us will note that sassafras, a local woodland tree, is the source of root beer. But its true gift to us is the gorgeous spicebush swallowtail. The caterpillars of this native butterfly are picky eaters. They feed on the leaves of sassafras, spicebush and closely related woody plants. This butterfly, which is also a pollinator, is not able to survive on cultivated plants like peaches and cherries.