The Tiger Swallowtail (Papilio glaucus) is a familiar sight across North America, recognized for its striking yellow and black striped wings. The nutritional demands of this insect undergo one of nature’s most dramatic changes as it transitions from larva to adult. The diet is entirely different between the two primary life stages: the caterpillar focuses on consuming leaves, while the adult relies on liquid energy sources. Understanding these specific dietary requirements is necessary to appreciate the full life cycle of this large butterfly.
The Diet of the Tiger Swallowtail Caterpillar
The larval stage of the Tiger Swallowtail is characterized by specialized, voracious feeding, focused solely on leaf tissue from specific woody plants. Caterpillars are obligate herbivores, meaning they can only survive on a narrow range of “host plants” selected by the female butterfly for egg-laying. These plants must possess the correct chemical compounds and nutritional profile for the caterpillar to successfully digest and grow.
The caterpillar’s primary purpose is to accumulate the significant biomass of energy and protein needed to fuel metamorphosis. This intense feeding stage involves five distinct growth periods called instars. Acceptable host plants include the leaves of:
- Tulip tree (Liriodendron tulipifera)
- Wild black cherry (Prunus serotina)
- Sweet bay magnolia (Magnolia virginiana)
- Various species of birch (Betula)
- Ash (Fraxinus)
- Willow (Salix)
The leaves provide the necessary energy and building blocks required for the transformation inside the chrysalis. The caterpillar spends its life resting on a silk pad on a leaf, chewing the foliage of its host plant. Gardeners who host the caterpillars must accept the resulting leaf damage as a sign of a healthy habitat. The caterpillar will eventually reach a length of over two inches before it turns dark brown and seeks a secure location to pupate.
The Nectar and Nutritional Needs of the Adult Butterfly
Upon emerging from the chrysalis, the adult Tiger Swallowtail shifts its diet completely to liquid sustenance, primarily consuming nectar from flowers. Nectar is a sugar-rich fluid that provides the immediate energy necessary for powered flight and reproduction. The butterfly uses its long, straw-like proboscis to sip this fluid from the base of the flower.
Adults are generalist feeders, preferring flowers with bright colors and a relatively flat surface that allows for easy landing. The search for nectar is continuous, as the energy expenditure of flight requires frequent refueling. Common nectar sources include:
- Joe-Pye Weed (Eutrochium purpureum)
- Milkweed (Asclepias)
- Purple coneflower (Echinacea)
- Phlox (Phlox)
- Ironweed (Vernonia)
The adult diet also includes supplementary sources to acquire essential salts and minerals. Butterflies may occasionally feed on tree sap flows, the juice of rotting fruit, or animal scat. A behavior known as “puddling” is particularly important, especially for males, who congregate on damp soil, mud, or wet sand to ingest water containing dissolved sodium ions and amino acids. These minerals are thought to be transferred to the female during mating, aiding in reproductive success and egg viability.
Cultivating a Habitat to Support Both Life Stages
Creating an environment that supports the Tiger Swallowtail requires a dual-pronged approach, providing resources for both the caterpillar and the adult butterfly. Successful habitat cultivation involves planting a selection of preferred host trees and shrubs, such as wild cherry or sweet bay magnolia, to ensure a food supply for the next generation. These plants serve as the nursery for the butterfly’s future.
Gardeners should simultaneously establish a continuous source of nectar-rich flowers that bloom from spring through fall, ensuring the adults can maintain the energy for flight and reproduction throughout their lifespan. Planting these nectar sources in large, dense clusters makes them more visible and accessible to foraging butterflies. The overall strategy should prioritize native plant species, as they are naturally adapted to the local ecosystem and attract regional wildlife.
It is necessary to completely avoid the use of broad-spectrum pesticides, as these chemicals can harm both the leaf-eating caterpillars and the nectar-sipping adults. Providing a designated puddling area, such as a shallow dish filled with moist sand or mud, also meets the mineral needs of the adult butterflies. By integrating both the larval host plants and the adult nectar sources, a garden can effectively support the Tiger Swallowtail across its entire life cycle.