Pipevine swallowtail caterpillars (larvae) feed on Aristolochia, or pipevine, plants. There are about seven subspecies of pipevine swallowtails widely distributed throughout the United States. The Northern California subspecies (Battus philenor sp. hirsuta) is smaller and hairier than other pipevine swallowtails. The sole diet of its caterpillars is Dutchman’s pipevine (Aristolochia californica).
Adult pipevine swallowtails at first appear to be black butterflies. But look more closely. The hindwings are an iridescent metallic blue under the correct lighting and have white and orange submarginal spots and a scalloped margin. There is a single tail-like projection from each hindwing. Adult pipevine swallowtails have seven white submarginal spots. Adults feed on the nectar of a variety of plants.
Pipevine swallowtail caterpillars are black with rows of orange tubercules and fleshy projections along the body. Two horn-like projections protrude from behind the head when the caterpillar is disturbed. Scent glands in these “horns” produce a disagreeable odor.
The female lays from one to twenty reddish-orange spherical eggs in clusters on the host plant, Dutchman’s pipevine. The caterpillars rest on a silken nest in rolled pipevine leaves. When ready to pupate, the caterpillar fastens its hindmost feet securely to the place chosen for the chrysalis with silk. Then the caterpillar loops a tough silk thread behind its body, fastening the ends like a “safety belt”. Pipevine swallowtails overwinter as a chrysalis.
Pipevines species contain aristolochic acid, a powerful toxin and carcinogen. Because the caterpillars feed on pipevines, both caterpillars and adult pipevine swallowtails are poisonous to predators.
Because of other toxins they contain, some tropical pipevine species are poisonous to pipevine swallowtails. Butterfly enthusiasts must use care not to include certain tropical pipevines when developing “butterfly gardens”.
These pipevine swallowtails were photographed in McConnell Botanical Garden near the Sundial Bridge, Redding CA (Shasta County).
Look for information on Dutchman’s pipevine in my next post.