I can’t help but smile whenever I see a spicebush swallowtail caterpillar. This caterpillar is in its fifth stage of life, called the fifth instar.
Its cartoonish look has a bigger purpose than amusing me. The eyespots have false “pupils” that bulge and even have white in them that gives the impression of light reflecting from them. The “mouth” is also false. This adaptive coloration mimics the head of a green snake and is meant to discourage birds and other predators from trying to eat it. Should a bird still pick it up, the caterpillar emits a type of chemical repellent to dissuade it from making it a meal.
One other line of defense during the fifth instar is that the caterpillar will lay down a silk mat on the top of a leaf, which causes the leaf to fold over on itself, leaving the caterpillar in-between the two halves. The caterpillar will usually stay there during the day and emerge from its leaf protection to feed at night.
The spicebush swallowtail is found throughout the eastern U.S. Its host plants in our area include the spicebush and sassafras.