Eastern Tiger Swallowtail

The eastern tiger swallowtail is a large member of the swallowtail family (Papilionidae) and is among the most familiar and widely admired butterflies in eastern North America, often serving as a state symbol in several states. Its bold yellow-and-black "tiger stripe" pattern and graceful tailed hindwings make it easy to recognize even for people with little interest in insects.

The species exhibits notable sexual and regional variation: females occur in two color forms, a yellow form resembling the male and a dark form that is almost entirely black with only faint stripe traces, an adaptation believed to mimic the toxic pipevine swallowtail and thereby gain some protection from predators. This dark female form is more common in the southern part of the range, where the model species it mimics is also more abundant.

Ecologically, the eastern tiger swallowtail is an important pollinator across a wide range of flowering trees, shrubs, and garden plants, and its caterpillars have an equally distinctive appearance, including a resemblance to a small snake in later stages, an example of a defensive mimicry strategy in the larval stage.

• Wingspan roughly 7.9–14 cm; wings are bright yellow with four to five bold black tiger-stripe bands running across the forewing.
• Hindwings have elongated black "tails" and often show a band of blue scaling along the trailing edge, with orange spots near the tail base.
• Females occur in two forms: a yellow form similar to males, and a dark form that is mostly black with shadowy stripe outlines still faintly visible.
• Body is stout with a fuzzy thorax typical of large swallowtails.
• Lookalikes: the Canadian tiger swallowtail is very similar but generally smaller with a slightly different stripe pattern and a more northern range; the pipevine swallowtail, mimicked by dark-form females, lacks yellow stripes and shows iridescent blue-green hindwings instead.

Common throughout deciduous forests, forest edges, river and stream corridors, parks, and gardens across eastern North America, from southern Canada down through the eastern and central United States into parts of the Gulf region. Adults are active from spring through late summer, with multiple generations in the southern part of the range and typically a single generation further north. Caterpillars are found on the leaves of preferred host trees along woodland edges and riparian areas.

Adults are strong, graceful fliers that visit a wide variety of flowering plants for nectar, including native wildflowers, flowering trees, and garden plants, making them significant pollinators. Males frequently patrol along stream corridors, roads, or forest edges searching for mates and can sometimes be seen gathering at damp mud or puddles, a behavior called puddling that supplies them with minerals. Caterpillars rest on silk pads on leaves during the day, and early instars mimic bird droppings while later instars are green with large false eyespots that give them a snake-like appearance, both serving as defenses against predators; when disturbed, larvae can also extend a forked, odorous organ called an osmeterium from behind the head.

Complete metamorphosis, with two to three generations per year in warmer parts of the range and typically one generation in the north. Eggs are laid singly on the leaves of host trees such as tulip tree and wild cherry, among various other deciduous species; caterpillars pass through several instars, changing from a bird-dropping mimic to a green, eyespotted form as they grow, and construct a silk-lined leaf shelter for resting. Pupation occurs in a mottled brown or green chrysalis attached to a twig or nearby structure, with the final generation of the year overwintering as a chrysalis through the winter before adults emerge in spring.