Black Swallowtail (Papilio polyxenes)
Detailing the identifying qualities of the Black Swallowtail, including physical features and territorial reach.
Updated: 2/5/2018; Authored By Staff Writer; Content ©www.InsectIdentification.org
Adult and larval Black Swallowtails may be so abundant because they have great defensive strategies: excellent mimicry and an acrid discharge.
The Black Swallowtail looks almost identical to the pungent-tasting Pipevine Swallowtail. This mimicry is a good defense against predators. The caterpillar of the Black Swallowtail also has a defensive organ called an osmeterium. This "Y" shaped, fleshy organ is normally hidden, but will protrude if the caterpillar is threatened. It can then emit terpenes, an organic chemical that smells quite foul and discourages would-be predators from eating the caterpillar.
The body of the Black Swallowtail is black with rows of small white dots running down the length of it. The dorsal (back) view displays black forewings edged in two rows of white dots. Two larger spots are close to the edge. The smaller, black hindwings also have two rows of white dots, but an iridescent blue is sandwiched between them. Each hindwing sports a bright orange and black eyespot at the bottom near the body. The edges of the hindwings are scalloped with white inside the curves. A long extension forms a 'tail' on each wing. Most of the desert populations are more yellow in color, while other populations have less color.
Black Swallowtails can be found in gardens, meadows, forests and other habitats. Adults drink flower nectar and are attracted to fennel plants and flowering herbs like dill. Females lay eggs in spring and caterpillars emerge. Caterpillars eat the leaves of pipevines, Dutchman's pipe, and snakeroot as well as dill, carrots and parsley plants. They form a chrysalis on a stem or branch and tie it to that stem with a single strand of silk. It overwinters in the chrysalis, which turns from green to brown as it ages. Adult butterflies emerge in the spring.