Eastern Tiger Swallowtail

Papilio glaucus — the eastern tiger swallowtail — is one of the most familiar and most-recognized butterflies in eastern North America and one of the largest swallowtail butterflies on the continent. The species is widespread across all of eastern North America from southern Canada south through the eastern US to northern Florida and west to the Great Plains. Adults are 8-14 cm wingspan with bright yellow wing color and bold black 'tiger-stripe' markings on the forewings; black border around the wing margins; the species' classic SWALLOWTAIL TAIL EXTENSIONS on the hindwings, with blue and orange spots near the tail bases. The species is the OFFICIAL STATE BUTTERFLY of Alabama, Delaware, Georgia, North Carolina, South Carolina, and Virginia, and has been recognized as one of the cultural icons of southeastern US natural history. The species' most-cited biological feature is FEMALE COLOR DIMORPHISM. Males come in only one color form (the standard yellow-and-black tiger pattern), but FEMALES come in TWO COLOR MORPHS: a 'yellow' form that resembles the male, and a 'BLACK' form in which the entire wing surface is dark brown-to-black with the tiger stripes barely visible. The black female form is a BATESIAN MIMIC of the toxic pipevine swallowtail (Battus philenor) — the black females gain protection from bird predators by resembling the unpalatable pipevine, which contains aristolochic acids from its larval host plant. The frequency of the black-female morph is highest in the southeastern US (where pipevine swallowtails are most common) and lowest in the northeastern US (where pipevines are rare). Larvae are equally dramatic — early instars are bird-dropping mimics (white-and-black blotchy patterns), but later instars are bright green with two large EYESPOTS on the thorax that make the caterpillar resemble a small snake (a striking example of mimicry that has been documented to deter bird predation in laboratory studies). Larvae feed on a wide range of host trees including tulip tree, wild cherry, sweet bay magnolia, and ash. The species is widespread, harmless to humans, and one of the most-photographed butterflies in eastern US macro nature photography.