What Do Caterpillars Eat

If you’ve ever watched a caterpillar munching away, you’ve probably wondered, what do caterpillars eat? The answer is more specific than you might think. Most caterpillars are picky eaters, sticking to one type of plant, which we call their host plant. Getting to know their diet is key for any gardener who wants to support these amazing insects.

Understanding caterpillar food helps you garden smarter. You can choose plants that attract beautiful butterflies or protect your prized veggies from hungry leaf-munchers. Let’s look at the fascinating world of caterpillar diets.

At their core, nearly all caterpillars are designed to eat plant material. But they aren’t random grazers. Their survival is tightly linked to specific plants. Here’s the basic menu.

Leaves are the Main Course

The vast majority of caterpillar species feast on leaves. They use their strong mandibles to chew and consume huge amounts relative to their size. This is why you’ll often find holes in foliage.

Tree Leaves: Many caterpillars prefer trees. For example, Monarch caterpillars eat only milkweed leaves.
Shrub and Bush Leaves: Plants like spicebush host the spicebush swallowtail caterpillar.
Herbaceous Plant Leaves: This includes garden plants and weeds, like the nettles loved by Red Admiral caterpillars.

Flowers, Stems, and Fruits

Some species have more varied tastes or target different parts of the plant.

Flowers and Buds: Certain caterpillars, like some cutworms, will eat flower buds and petals.
Stems and Roots: A few types bore into stems or feed on roots underground, though this is less common for butterfly caterpillars.
Fruits and Seeds: The codling moth caterpillar is a famous fruit-eater, tunneling into apples. Some also eat seeds.

The Rare Exceptions

A tiny number of caterpillars break the plant-only rule. A few are predatory, eating insects like aphids or even other caterpillars. Some clothes moth larvae eat animal fibers like wool, but these are the exception, not the rule for garden caterpillars.

Why Are Caterpillars So Picky?

It’s all about chemistry. Plants have evolved defenses, like toxins, to deter insects. Caterpillars, in turn, have evolved to handle the specific chemicals in their host plant. A Monarch caterpillar can safely digest toxic milkweed sap, storing it to make itself poisonous to birds. A caterpillar on the wrong plant often can’t overcome these defenses and will starve, even if surrounded by other green food.

How to Identify What a Caterpillar is Eating

Found a caterpillar and want to know its food? Follow these steps.

Observe Its Location: Look closely at the plant you found it on. It’s likely eating that plant or one very nearby.
Check for Damage: Look for signs of recent chewing on leaves, flowers, or fruits on that plant.
Note the Plant Type: Identify the plant. Is it a tree, a vegetable, a specific flower? This is your biggest clue.
Use a Guide: Look up common caterpillars in your area and their associated host plants online or in a field guide.

Common Garden Caterpillars and Their Diets

Here’s a quick guide to some caterpillars you might see and what they’re eating in your garden.

Monarch Caterpillar

Their diet is exclusive: Milkweed leaves (and only milkweed). No milkweed means no Monarchs. They are a great reason to plant common or swamp milkweed.

Cabbage White Butterfly Caterpillar

These are common veggie pests. They eat leaves of plants in the brassica family. That includes cabbage, kale, broccoli, and cauliflower. You’ll often see them in vegetable patches.

Black Swallowtail Caterpillar

Often found on herbs, they eat plants in the carrot family (Apiaceae). This includes parsley, dill, fennel, and carrot tops. If you see one on your parsley, it’s best to let it be if you can.

Tomato Hornworm

A large, green caterpillar that can defoliate plants quickly. It primarily eats leaves of tomatoes, peppers, eggplants, and potatoes (all in the nightshade family).

Tent Caterpillar

These social caterpillars build web-like tents in trees. They prefer deciduous trees like cherry, apple, and crabapple. While they can look alarming, they rarely kill healthy trees.

What to Feed a Caterpillar You’re Raising

If you’re caring for a caterpillar, providing the right food is critical. Here’s how to do it.

Never Assume: Don’t guess its food. An incorrect leaf can lead to starvation.
Start with the Source: Collect fresh leaves from the exact plant you found the caterpillar on. This is almost always safe.
Keep it Fresh: Provide new, clean leaves every day. Place stems in a small jar of water in the habitat (cover the jar opening so the caterpillar can’t fall in).
Research the Species: Once you identify it, you can confirm its diet and maybe even offer alternative host plants.
No Lettuce or Spinach: These are not suitable for most wild caterpillars and lack the nutrients they need to pupate successfully.

Gardening with Caterpillars in Mind

A healthy garden has insects, including caterpillars. Here’s how to balance their needs with yours.

Planting a Butterfly Garden

To attract butterflies, you must feed their caterpillars. Plant native host plants alongside nectar flowers.

Plant milkweed for Monarchs.
Plant parsley, dill, or fennel for Black Swallowtails.
Plant pawpaw trees for Zebra Swallowtails.
Plant violets for Fritillary butterflies.
Accept that host plants will get eaten—that’s the point!

Protecting Vegetable Crops

For caterpillars you don’t want on your veggies, try these methods.

Hand-Picking: Check undersides of leaves and remove caterpillars by hand. It’s very effective for larger ones like hornworms.
Floating Row Covers: Place lightweight fabric over crops like cabbage to prevent butterflies from laying eggs.
Organic Sprays: Use Bacillus thuringiensis (Bt), a natural bacteria that affects only caterpillars when they eat treated leaves. It’s safe for other wildlife.
Encourage Predators: Birds, wasps, and predatory insects eat caterpillars. Provide birdhouses and plant diverse flowers to attract beneficial insects.

Fascinating Facts About Caterpillar Eating Habits

A caterpillar’s first meal is often its own eggshell, which provides vital nutrients.
They have around 4,000 muscles (humans have about 600) to help them move and eat.
A Monarch caterpillar can grow up to 2,700 times its original hatching weight in just two weeks—all from eating milkweed leaves.
Some caterpillars, like the Oak Leafroller, use silk to pull leaves together, creating a sheltered spot to eat.
Caterpillars produce a lot of frass (droppings). This frass can even enrich the soil below their host plant.

FAQ About Caterpillar Diets

Do all caterpillars turn into butterflies?

No. Caterpillars are the larval stage of both butterflies and moths. The vast majority of caterpillars you see will become moths.

Can I feed a caterpillar fruit?

Only if it’s a species known to eat fruit, like some moth caterpillars. Most butterfly caterpillars only eat leaves of their specific host plants. It’s always best to match the natural diet.

How much do caterpillars eat?

An incredible amount. They spend almost all their time eating to store energy for metamorphosis. A single caterpillar can eat many times its weight in leaves each day.

What if a caterpillar stops eating?

It might be preparing to molt its skin (which it does several times) or to pupate. Ensure it has fresh food available, but don’t disturb it. If it’s on a plant and seems inactive, it’s likely a natural process.

Why are there caterpillars on my plants but no holes?

Some caterpillars, like leafminers, eat the internal layers of the leaf between the surfaces, leaving trails or blotches instead of holes. Others might be eating only at night.

Knowing what caterpillars eat gives you a window into one of natures most incredible transformations. By providing the right host plants, you can support these amazing creatures right in your own backyard. Watching a caterpillar munch away is the first step to seeing the beautiful butterfly it will become.