What Do Caterpillars Eat?

“What can caterpillars eat?”

Have you ever read The Very Hungry Caterpillar by Eric Carle? In that book, the hungry caterpillar eats through apples, oranges, and strawberries before moving on to sausages and cupcakes! At the end, he eats “one nice green leaf” before settling into his chrysalis. But do caterpillars really eat those kinds of foods?

A caterpillar looks like a worm, but it’s not actually a worm. It’s the larvae (the “baby” stage) of a moth or a butterfly. It has a voracious appetite—that means it eats a lot (like a lot!). Caterpillars eat and eat and eat before wrapping themselves in a cocoon (for a moth) or a chrysalis (for a butterfly).

A caterpillar that wraps itself in a chrysalis emerges as a butterfly!
Photo by Suzanne D. Williams on Unsplash

But what do they eat and eat and eat?

Most caterpillars chow down on plant material, such as leaves or grasses. If you see a leaf with holes, it was probably chewed on by a caterpillar. But caterpillars can’t just eat any nice, green leaf because most caterpillars are specialists.

This leaf is being eaten by a caterpillar.
Photo by Joyful on Unsplash

A specialist is an animal that eats only one type of food (like a koala—they only eat eucalyptus leaves). Most caterpillars are like this. They have just one group of plants they can eat.

Specialists exist because plants don’t want their leaves to be eaten! In our fallen world, many plants create toxins or chemicals that taste bad and pump them into their leaves. Certain caterpillars are designed to be able to get around the defense of certain plants, but not every plant. This is a wise design by our Creator that limits caterpillars from being able to eat and eat and eat every single plant (you don’t want a world with no plants, right?).

Monarch butterfly caterpillars are a great example. They can only eat leaves from milkweed plants. Fun fact: In this case, being a specialist protects the caterpillar and the butterfly. The toxic chemicals in the milkweed end up in the caterpillar’s body, making them taste nasty to birds!

Monarch caterpillar on a milkweed leaf
Photo by Lasclay on Unsplash

Eastern black swallowtail butterfly caterpillars can only eat plants in the carrot kind. This includes parsley, dill, fennel, and other plants related to carrots. But their relative, zebra swallowtails, mostly eat leaves from pawpaw trees.

Eastern black swallowtail caterpillar on a parsley plant
“Eastern Black Swallowtail Caterpillar” by Paul-W, CC BY-NC-SA 2.0

Some caterpillars, like woolly bears (also known as woolly worms), are generalists. Generalists can eat a much wider variety of plants. There are even some caterpillars that eat other insects, or things like wool or grain.

Woolly bear caterpillars are generalists.
“Woolly Bear Caterpillar” by Juanita Demchak, CC BY-NC-ND 2.0

There’s so much variety in God’s creation! That’s what makes it such a joy to study what he’s made—you never know what you might discover.

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