Pipevine Swallowtail – Battus philenor

Pipevine Swallowtail butterflies lay burgundy eggs on their host plants. On occasion they will lay eggs on the wrong species of pipevine. If young caterpillars aren’t moved to the proper host plant quickly, they will die.

A similar butterfly species, Gold Rim Swallowtail (also called Polydamas Swallowtail) butterflies use pipevine plants as host plants also. Burgundy eggs are from Pipevine Swallowtail butterflies and gold eggs are from Gold Rim Swallowtail butterflies.

Young caterpillars tend to be gregarious, staying together as they eat and molt. They are often on the underside of a leaf, not visible as we walk by their plant. The pattern of eating clues us in to the fact that there are caterpillars hidden under the leaf.

Caterpillars exposed to more light tend to lighten in color. Instead of a mid to deep burgundy, almost black color, they become lighter in color.

As they grow larger, they tend to separate a bit more, often becoming solitary by the time they are late instar caterpillars.

Pipevine Swallowtail osmeterium is yellow/orange. The caterpillars often extend these glands when they are disturbed. The osmeterium are coated with a bad smelling liquid.

Some species of pipevine, such as the Virginia Snakeroot, may be so small that one caterpillar will need to eat several plants before it grows large enough to pupate.

Before pupating, the caterpillar will empty its digestive system in a messy blob. This is known as a ‘frass dump’. It is wet and stains rearing habitats and containers.

When preparing to pupate, they create a silk pad and silk button. Attaching their anal prolegs to the silk button, they create a silken girdle, made of many loops of silk. Ducking their heads into their girdles, they work the girdle to the middle of their bodies. A day later, they pupate.

Freshly pupated, the new chrysalis is often bright yellow. It often changes color as it dries.

Male Pipevine Swallowtail butterflies are metallic blue on their hindwings. Females have metallic black in their hindwings.

Several species of swallowtails have orange spots underneath their hindwings. Pipevine Swallowtail’s orange spots are arranged in a tight J. Other species are arranged in more of a relaxed C.

Pipevine Swallowtail butterflies spend the winter in diapause in chrysalis stage. The last generation of the year will overwinter in chrysalis and emerge in the spring, when pipevine plants put on new leaves.