With their distinctive black and yellow markings, Eastern Tiger Swallowtails (Papilio glaucus) are among America’s most familiar butterflies.
They’re large and showy insects, with wings spanning 5 inches and long “tails” on their hind wings.
The species is closely related to several other swallowtails with tiger-like markings found in Canada and the western U.S.
Male Eastern Tiger Swallowtails are consistent in coloration, but females actually come in two color forms. Some resemble the yellow males, though with more blue on their hind wings, while others are black with blue markings.
Along with several other species of butterflies, these dark females are assumed to be mimics of the Pipevine Swallowtail, which they all resemble.
Pipevine larvae feed on native species of Dutchman’s pipe, or pipevine (Aristolochia spp.), and they sequester substances from this plant that make them distasteful, even toxic, to birds. This unpalatability persists into adulthood. And although Eastern Tiger Swallowtails are not toxic themselves, dark females may gain protection from predators by virtue of their unpalatable appearance.
Another defensive feature of swallowtail butterflies may be their tails. These projections may divert a predator’s attention away from the body proper and towards the outer part of the wings, which are more capable of sustaining damage.
Eastern Tiger Swallowtail caterpillars have their own defense mechanisms. Young larvae have the unappealing appearance of bird droppings. Older larvae bear prominent eyespots plus a brightly colored, forked organ called an osmeterium, which can be everted at will to emit an unpleasant odor.
Together, these features make the caterpillar resemble a miniature snake, presumably deterring predators.
The larvae eat the leaves of various shade trees, such as black cherry, ash, and tulip tree. Once fully grown, they shed their “skins” one more time, form a chrysalis, and in typical butterfly fashion, emerge some days later as winged adults.
In the Lowcountry, Eastern Tiger Swallowtails are common in woods, fields, parks, and gardens. Adults are familiar visitors to thistles, milkweed, and other nectar-rich flowers.
Five states have chosen this species as their state butterfly — including South Carolina.