Eastern Black Swallowtail

Natural Habitat

Eastern Black Swallowtails are common in open areas like fields, meadows, gardens, parks, and disturbed areas. They prefer habitats with abundant flowering plants for adult nectar sources and host plants for their larvae. Their range extends across eastern North America, from southern Canada down to the Gulf Coast states and west to the Rocky Mountains.

Diet & Feeding

Adult Eastern Black Swallowtails primarily feed on nectar from a wide variety of flowers, including milkweed, clover, thistle, and phlox. The larvae (caterpillars) are herbivorous, feeding on the leaves of host plants, which are typically members of the carrot family (Apiaceae), such as dill, parsley, fennel, and carrot, as well as rue (Rutaceae).

Behavior Patterns

Adult Eastern Black Swallowtails are active during the day, frequently visiting gardens and open fields to nectar on a variety of flowers. Males often patrol areas to find females. Females lay single eggs on host plants. The larvae (caterpillars) progress through several instars, feeding on the host plant leaves. When disturbed, the caterpillar may evert an orange, Y-shaped osmeterium from behind its head, which emits a foul-smelling chemical to deter predators. They pupate in a chrysalis, which can be green or brown depending on the surroundings, camouflaging them from predators. They can have multiple broods per year depending on the climate.

Risks & Benefits

Eastern Black Swallowtails pose no risks to humans. As pollinators, they provide significant benefits to ecosystems by assisting in the reproduction of numerous flowering plants, including many agricultural crops. Their larvae can be considered minor pests in home gardens due to their feeding on cultivated plants like parsley and dill, but typically cause minimal damage. They serve as a food source for various insectivores.

Identified on: 8/16/2025