An outbreak of Deidamia inscriptum (Lettered Sphinx Moth) caterpillars was noted in northeast Tennessee where Oxydendrum arboreum (Sourwood) trees were defoliated. Nearly all published literature and online resources list only plants in the grape family (Vitaceae) as larval food plants. Food-plant preference trials using fresh leaves of 3 woody plant species showed that Deidamia caterpillars from this region had a preference for Sourwood over Parthenocissus quinquefolia (Virginia Creeper), and rejected Acer rubrum (Red Maple), a non-host species. Ursus americanus (Black Bear) were feeding on the caterpillars as evidenced by bent and broken Sourwood saplings bearing claw marks and by abundant sphingid remains in bear scat.