Environmental writer Elizabeth Kolbert had an interesting article in the New Yorker about the little-known world of caterpillars and other insects. I have to admit, caterpillars had not figured much in my consciousness but was impressed to learn that they undergo a dizzying array of transformations in their very short lives.
From a caterpillar’s perspective, humans are boring. The young they squeeze out of their bodies are just miniature versions of themselves, with all the limbs and appendages they’ll ever have. As they mature, babies get bigger and stronger and hairier, but that’s about it.
Caterpillars, for their part, are continually reinventing themselves. They emerge from tiny, jewel-like eggs and for their first meal often eat their own egg cases. Once they reach a certain size, they sprout a second head, just behind the first. They then wriggle free of their old skin, the way a diver might wriggle out of a wetsuit. (In the process, the old head drops off.) In the course of their development, they will complete this exercise three, four, in some species sixteen times, often trying out a new look along the way. The spicebush swallowtail, for example, which is found throughout the eastern U.S., emerges from its egg mottled in black and white. This color scheme allows it to pass itself off as a bird dropping. After its third molt, as a so-called fourth instar, it turns green (or brown), with two yellow-and-black spots on its head. The spots, which look uncannily like a pair of eyes, enable the swallowtail to pretend it’s a snake.