Spicebush swallowtails excel in deception and camouflage throughout their lifecycle. As adults, they employ Batesian mimicry by imitating the pipevine swallowtail (Battus philenor) . Pipevine swallowtail larvae consume plants with aristolochic acids, which are retained through their life stages, making them unpalatable to predators. By adopting a similar color pattern, spicebush swallowtails confuse potential predators, gaining some protection from being eaten.
But the deception doesn’t end there!
Egg
Females use both visual and chemical cues when finding host plants on which to oviposit her eggs. After landing on a plant, a female confirms the plant as a host plant by drumming the surface of a leaf with her forelegs. She then will lay a single egg on the undersides of leaves of host plants to keep them hidden from wasps and other predators. Eggs are spherical and greenish-white or white in color and transparent.
Caterpillar
All five instars of the spicebush swallowtail caterpillar is marked by visual deception and hiding from detection. The earlier stages of the caterpillar are camouflaged to look like bird droppings. In later stages caterpillars develop two pairs of false eyespots on their body, which are believed to be a mimicry of either green snakes or tree frogs.
Spicebush Swallowtail larvae are leaf-rollers. They create shelters for by first cutting and pulling small sections of leaves around themselves to hide from predators. As they grow larger, they wrap up in entire leaves, and fifth-instar caterpillars may even stitch several leaves together. The caterpillar then hides in the shelter during the day and emerges at night to eat. This simple way of rolling a leaf as a shelter is one of the amazing ways that they’ve adapted for survival.
If their clever camouflage and sheltering tactics fail, they have another defense mechanism. At each larval stage, they possess bright orange, horn-like organs called osmeteria. When disturbed, these organs emerge behind the caterpillar’s head and release an unpleasant odor, helping to repel potential predators.
As the final instar larva prepares for pupation, it dons another cryptic disguise. The caterpillar turns a muted orange-yellow color. It is believed they do this to more closely resemble the leaf litter that it crawls around on when looking for a suitable site in which to anchor itself before forming the chrysalis.
Chrysalis
When the caterpillar is ready to form a chrysalis and pupate, it engages in one final act of mimicry. The chrysalis resembles a curled-up leaf. Caterpillars that pupate early in the season create a green chrysalis to blend in with the predominantly green leaves. However, if they pupate later in the season and will overwinter as pupae, the chrysalis turns brown, mimicking a dead leaf.
Adult
This species displays sexual dimorphism which means that males and females have different coloration. Males have hind wings with a pale green to yellow coloration. Females display a blue iridescent coloration.
