Tiger Swallowtail

Papilio glaucus — the eastern tiger swallowtail — is one of about 600 species in family Papilionidae, the swallowtails. The family contains some of the largest and most ornate butterflies on Earth, and is named for the characteristic tail-like extensions of the hindwings. P. glaucus is widespread across eastern North America, from southern Canada to northern Mexico. Females exhibit dramatic dimorphism: in the southern part of the range, many females develop entirely black wings (instead of the tiger-yellow male coloration), mimicking the toxic pipevine swallowtail (Battus philenor) for predator defense. Caterpillars employ a multi-layered defense strategy: early instars resemble bird droppings, later instars develop two huge fake 'eyespots' on the swollen front body that make them look like small snakes, and at all stages they can evert a bright orange Y-shaped gland behind the head (the osmeterium) that releases a foul terpenoid smell to repel birds and parasitoid wasps. Larvae feed on a range of trees including tulip poplar, wild cherry, and birch. The closely related giant swallowtails (P. cresphontes, P. homerus) and the birdwings (Ornithoptera) are among the largest butterflies in the world. Swallowtail caterpillars are important in toxicology research — many sequester plant alkaloids that make the adults bird-aversive.