Spicebush Swallowtail Caterpillar
Papilio troilus

f25 @ 1/160s, ISO:2000, Nikon D3S w 105mm macro

"Papilio troilus," Wikipedia, the free encyclopedia. At first, young larvae are brownish. The brown color of the larvae is independent of leaf color and will occur even on a green leaf. A folded leaf serves as the home for the young larvae. During the day, the larvae remain in the shelter so as to avoid predators and come out at night to feed. Additionally, if larvae are disturbed while rolled up in the leaf, they emit a foul-smelling substance. When these larvae reach later stages, they turn greenish yellow before pupating. Older larvae live in a leaf, rolled up and lined with silk and held together by a line of silk. In order to pupate, the larvae will leave the shelter and find the underside of a leaf near the ground to do so. Upon discovery of a suitable leaf, the larvae begin the pupating process by emitting silk from their salivary glands, which helps attach the larvae to the branch or leaf. Then the larvae turn around while still emitting silk, which creates a "safety harness" for the pupating process. At the end of the pupating process, the larvae have become pupae which are either brown (winter) or green (summer). The practice of turning either brown in winter or green in summer is called seasonal polyphenism. Because the color of the pupa reflects the color of the deciduous host plants, since the leaves will turn brown in winter and green in summer. Even in cases where the leaves are not yet brown, the pupa appear to turn that color in anticipation of the changing colors.
East Falmouth, Massachusetts