Spicebush Swallowtail

Papilio troilus — the spicebush swallowtail — is one of the most striking dark butterflies in eastern North America and a flagship example of both adult and larval mimicry in lepidopteran biology. The species is widespread across all of eastern North America from southern Canada south through the eastern US to northern Florida. Adults are 8-11 cm wingspan with predominantly BLACK WING COLORATION marked by green-or-cream spot row along the wing edges; the hindwings have brilliant BLUE-GREEN IRIDESCENT DUSTING (more prominent in females) or distinct blue-black coloration with green spots (males). The dark coloration is a flagship case of BATESIAN MIMICRY in North American butterflies — the species mimics the toxic pipevine swallowtail (Battus philenor), which contains aristolochic acids from its larval host plant and is unpalatable to bird predators. The mimicry is one of several pipevine-mimic species in eastern North America (along with black-form female tiger swallowtails, female Diana fritillaries, female red-spotted purples, and female Eastern black swallowtails — all converging on the same toxic-pipevine model). Adult swallowtails feed on nectar from a wide range of flowers (especially bee balm, milkweed, and Joe-pye weed) using a long extended proboscis. The species' MOST FAMOUS biological feature is the SNAKE-MIMIC LARVA. Spicebush swallowtail caterpillars are bright green with TWO LARGE BLACK-AND-CREAM EYESPOTS on the metathorax (the rearmost thoracic segment, just behind the head). When the caterpillar rears up the front of the body, the eyespots are exposed as the prominent visual feature — the caterpillar looks dramatically like a small GREEN SNAKE viewed from the front, with the head tucked under and the eyespots prominently visible. The mimicry is so convincing that small forest birds (especially warblers, vireos, and titmice) are documented to recoil and abandon predation attempts when the caterpillar performs the snake display. Late-instar caterpillars also CHANGE COLOR before pupation — turning from bright green to a 'jaundice yellow' or 'orange-pink' that signals the pupal preparation phase. Larvae feed exclusively on spicebush (Lindera benzoin) and sassafras (Sassafras albidum) — woody host plants in family Lauraceae. The species is harmless to humans and a major beneficial pollinator of eastern US wildflowers.