A report on a very hungry caterpillar Gypsy moths are non-native. They’re considered invasive. The caterpillars feast on oak and many other hardwood leaves, and can defoliate whole trees. By leaving them alone, Andrew wonders if he’s endangering his backyard oak and even the local biome. “Do I leave them alone, try to get rid of them, somewhere in between? Is there an in between?” he asks. Reassuringly, there probably is, says Michigan State University entomologist Deb McCullough. She’s studied gypsy moths for years, and says, though the voracious caterpillars can be a nuisance, there’s no need to panic over them.