The black swallowtail butterfly, Papilio polyxenes, is a common insect across eastern North America. Its striking appearance, with black wings adorned with yellow spots and blue markings, often captures attention. Its dietary habits vary significantly between larval and adult stages. Understanding their diet helps appreciate their ecological role and how to support them.
The Caterpillar’s Menu
Black swallowtail caterpillars, sometimes called “parsley worms,” have a highly specialized diet. They are host-specific, feeding almost exclusively on plants belonging to the carrot family, Apiaceae. This family includes common herbs and wildflowers, essential for their growth. Female butterflies lay eggs individually on these host plants, ensuring an immediate food source for emerging caterpillars.
Common cultivated host plants include parsley, dill, fennel, and carrots. Wild species like Queen Anne’s Lace (wild carrot), wild parsnip, and golden alexander also serve as food sources. These plants contain specific chemical compounds that caterpillars metabolize, making them suitable for survival. Caterpillars are voracious eaters, consuming leaves rapidly to fuel their growth.
The Adult Butterfly’s Feast
In contrast to leaf-eating caterpillars, adult black swallowtail butterflies primarily sustain themselves on nectar. This sugary liquid, produced by flowering plants, provides the energy needed for flight, mating, and egg-laying. The butterflies possess a long, straw-like proboscis, a specialized mouthpart that allows them to reach deep into flowers to access the nectar. They are attracted to nectar-rich blooms, especially those with flat-top or clustered flower structures that offer a stable landing.
Several popular garden flowers and wildflowers serve as excellent nectar sources for adult black swallowtails. These include milkweed, thistles, purple coneflower, zinnias, phlox, and red clover. Butterflies also engage in “puddling,” sipping moisture and extracting mineral salts from damp soil or sand. This behavior supplements their diet, contributing to their health and reproduction.
Creating a Butterfly-Friendly Habitat
Attracting black swallowtail butterflies involves providing for their needs throughout their life cycle. Planting host plants for caterpillars and nectar sources for adult butterflies is an effective strategy. For caterpillars, ensure a generous supply of parsley, dill, fennel, or Queen Anne’s Lace, as they quickly consume entire plants. Planting these herbs in multiple locations or quantities helps sustain multiple generations.
For adult butterflies, select diverse nectar-producing flowers that bloom throughout the growing season for a continuous food supply. Incorporating plants like milkweed, coneflowers, zinnias, and phlox offers ample nectar for energy. Avoid pesticides, as these chemicals can harm both caterpillars and adult butterflies. Tolerating some plant damage from feeding caterpillars is a natural part of supporting these fascinating insects.