This 2″ long, brightly colored caterpillar with a pair of orange horns, morphs into a large black and yellow swallowtail butterfly. It gets its name, because it is usually found on garden parsley. It feeds on carrots and related plants such as anise, celery, cilantro, dill, fennel, and queen anne’s lace. These worms eat leaves and stems, but produce only minor damage. No prevention is known. Hand pick the caterpillars and kill them or move them to an expendable host plant. Birds will pick off the caterpillars. Treat with Thuricide.