Mystery

Our friend, Stan, took a picture of this strange critter that possesed a "forked tongue". I knew it had to be a larval stage of a butterfly (prolegs were present), but I could not remember which species. The "forked tongue" had to a horn, because all caterpillars have chewing mouth parts.) It turned out to be the larva of the Spicebush butterfly. The Spicebush Swallowtail butterfly is a large, dark swallowtail. It is one of our most beautiful and interesting swallowtails. All developmental stages are great examples of adaptive coloration.

Swallowtail caterpillars vary in color and shape, depending on the species, but most have smooth skin, and some have long, tentactle-like projections. Swallowtail caterpillars are able to extend a brightly-colored, Y-shaped horn (called an "osmeterium") from behind their heads when they are disturbed. These horns are able to secrete foul-smelling defensive chemicals.

Eggs are laid singly on the undersides of leaves of the host plants. Young trees are usually selected and eggs are typically laid from two to five meters above the ground. First instar larvae bend a leaf edge over and silk it down to make a leaf next. Older larvae spin a silk mat on a leaf that contracts to curl the two lateral leaf edges upward and together to form a leaf nest. Larvae usually hide in the leaf nest during the daytime and to molt when birds and other predators are unlikely to see them. They come out to feed at night.

Young larvae are bird-dropping mimics, and mature larvae with their swollen thorax and eyespots are believed to mimic either green snakes or tree frogs. Larvae pupate on slender stems among vegetation, and pupae of the late summer or fall generation hibernate. Pupae may be either green or brown during the summer, but over-wintering pupae are brown. Both are leaf mimics. Adults are believed to be Batesian (palatable) mimics of the poisonous blue swallowtail.