The Trick That Keeps From Treating

No matter how much work you put into your Ghostbusters get-up, giant swallowtail caterpillars have got you beat. They’re champions when it comes to mimicking…bird poop. Yup, their guano guise is one of the best forms of mimicry seen in the animal kingdom. From the brown-and-white patterning, to the shiny skin, they’ve got all the right accessories to pass as a fresh, wet piece of bird poop.

The swallowtail’s charade allows it to keep large predators—including birds—at bay. The above photo, taken by Stan Malcolm, a photographer and naturalist in Malborough, Connecticut, shows how a predator would see the caterpillar, standing motionless on the surface of a leaf.

Capturing that photo took a lot of time and work. Though the species is concentrated in the southern part of the States, Malcolm heard that a few had been sighted in Connecticut. He planted rue in his yard, in hopes of attracting a caterpillar or two. A year later he was rewarded with a voracious guano-like creature, measuring 3-centimeters long.  He set up his camera and started documenting the swallowtail’s journey as it went from larva to chrysalis.

Malcolm outlines the transformation on his blog. “Many swallowtails are bird-poop mimics early on, but the giant swallowtail sticks to it throughout all of its larval stages,” he says. Once the caterpillar had grown to its full size of 5 centimeters, the pace of metamorphosis quickened. Within the space of a few days, the insect emptied its gut, split open its back, retracted its legs, and wriggled out of its old skin. “Someone (I wish I could remember who—it was a long time ago) compared the process of shedding the skin to a woman removing her pantyhose without using her hands,” Malcolm writes on his blog.

For now the chrysalis will be kept in a cage in Malcolm’s office. As it ages it changes color. The body arches backward and the abdomen molds itself into the stem of the plant, causing the chrysalis to resemble a twig.

Mimicry is essential to swallowtails—they don’t just dress to be festive. They dress to survive.

h/t Stan Malcolm Photos. Read Malcolm's full post.