Pipevine Swallowtail

Pipevine Swallowtail, Battus philenor 

Pipevine Swallowtails are a species of butterfly found within the southern states and into southern Mexico. They prefer open woodlands and meadows, flying primarily in late spring into summer, but may be found in fall or year round in its far southern range. The adults feed solely on nectar including thistles, azaleas, buckeye, lantana, and lupines.

Eggs of a Pipevine Swallowtail on White-veined Dutchman's Pipe.

The common name comes from the host plant for the caterpillar: pipevines of the Aristolochia family which include wooly pipevine, white veined Dutchman's Pipe, Virginia snakeroot, and California pipevine. The toxic aristolochic acids within the plant are sequestered resulting in both caterpillars and adults to be poisonous. Up to 20 red, circular eggs may be laid on the young, tender shoots of pipevine.

Black phenotype caterpillar of Pipevine Swallowtail in 28°C (82°F).

While the caterpillars may initially feed in groups, they scatter as they grow to feed on the more mature leaves of the pipevine. When they are ready to pupate, they find somewhere a ways away from their host plant. The caterpillars are black with red projections and spots along the back, but they are affected by temperatures resulting in shading from black to red as it warms.

Red phenotype caterpillar of Pipevine Swallowtail in 40°C (104°F) weather.

Typically, black caterpillars are found in the southeast and California while red caterpillars are more common in western Texas and Arizona. The presence of the red phenotype increases in other areas as the growing season progress and daily temperatures increase, especially at temperatures above 30°C (86°F). Caterpillar found in Texas were specifically found to be more tolerant of higher temperatures than those found in other regions, specifically California.