Some people consider the caterpillars of this butterfly to be a pest, since they eat parsley, carrots, and other garden plants. Many people enjoy butterfly-watching and collecting, and the Eastern Black Swallowtail is considered by most to be a handsome specimen.he Eastern Black Swallowtail is a common swallowtail butterfly, often confused with the Pipevine Swallowtail or female Tiger Swallowtail. Both male and female Eastern Black Swallowtails are bluish-black with yellow spots on the wings.