If you’ve found a caterpillar and want to help it grow, knowing what to feed a caterpillar is the first and most important step. Getting their diet right is simple when you know a few key rules, and it’s essential for their health and development into a butterfly or moth.
Caterpillars are eating machines, but they are also very picky. Most species will only eat the leaves from one specific type of plant, known as their host plant. Offering the wrong food means they will starve, even with other greens all around them. This guide will walk you through the simple, nutritious choices that will give your caterpillar the best chance.
What To Feed A Caterpillar
The absolute best food for any caterpillar is the fresh leaves from its host plant. Your first task is always to identify both the caterpillar and the plant you found it on. Here’s how to get started.
Start with the Plant You Found It On
This is your biggest clue. Caterpillars don’t wander far from their food source. If you found it on a plant, that plant is almost certainly its food.
- Carefully cut a small branch with several leaves, not just a single leaf.
- Place the stem in a small container of water to keep the leaves fresh. Make sure the caterpillar cannot fall into the water.
- Observe if the caterpillar is eating. Fresh droppings (called frass) are a good sign.
Common Caterpillars and Their Host Plants
Here are some frequent garden visitors and their preferred foods:
Monarch Caterpillars
These iconic caterpillars only eat plants in the milkweed family. This is non-negotiable.
- Common Milkweed
- Swamp Milkweed
- Butterfly Weed (Asclepias tuberosa)
Black Swallowtail Caterpillars
They feast on plants in the carrot family (Apiaceae).
- Dill
- Fennel
- Parsley
- Queen Anne’s Lace
Cabbage White Butterflies
Their caterpillars eat plants in the brassica family.
- Cabbage leaves
- Broccoli
- Kale
- Nasturtium flowers (a great garden alternative)
What If You Don’t Know the Species?
Don’t panic. You can try a process of safe elimination.
- Keep it on the original plant material you found it with.
- Offer a few fresh leaves from common host plants like milkweed, parsley, or oak.
- Watch closely for a few hours. A hungry caterpillar will usualy start eating the right food quickly.
- Remove any uneaten leaves before they wilt and mold.
How to Serve Caterpillar Food Correctly
Presentation matters. Freshness and cleanliness are crucial for your caterpillar’s health.
1. Always Provide Fresh Leaves
Caterpillars need fresh, not old or dried, leaves. Replace the leaves every day or every other day. Wilted leaves lose nutritional value and can make the caterpillar sick.
2. Keep the Food Plant Fresh
Stems in water last much longer. Use a narrow jar or bottle and plug the top with cotton or paper towel so the caterpillar can’t get in. This prevents drowning accidents, which are sadly common.
3. Clean the Habitat Daily
Remove the old, uneaten leaves and all the frass (droppings) from the bottom of the container. A dirty enviroment promotes mold and bacterial growth, which can kill a caterpillar fast.
4. Don’t Use Pesticide-Treated Leaves
This is critical. Only use leaves from plants you are sure have not been sprayed with any insecticide, herbicide, or other chemical. Even organic sprays like neem oil can be harmful. When in doubt, find a new source or buy organic plants from a nursery.
Special Nutritional Considerations
Caterpillars get all their nutrients and water from the leaves they eat. You don’t need to give them extra water droplets or other fruits and vegetables. In fact, doing so can cause mold.
- Moisture: Fresh leaves provide all the hydration they need.
- Nutrition: A varied diet from their specific host plant provides everything required.
- Molting: They may stop eating just before they shed their skin (molt). This is normal; just keep fresh food available.
What Not to Feed a Caterpillar
Avoid these common mistakes to keep your caterpillar healthy.
- Lettuce or Spinach: These are not nutritious for most species and will not support proper development.
- Fruit: It will rot and attract fruit flies and mold.
- Meat or Dairy: Caterpillars are strict herbivores.
- Generic “greens”: Unless it’s the specific host plant, it’s not food.
Feeding Caterpillars in Different Stages
A caterpillar’s appetite changes as it grows.
Very Small Caterpillars (Instars 1-2)
They need tender, young leaves. Older, tough leaves might be to hard for them to eat. Sometimes, gently scoring the leaf surface with your nail can make it easier for them to start feeding.
Large Caterpillars (Instars 3-5)
These are the serious eaters. They can consume large amounts of leaf material daily. You’ll need to provide bigger branches and clean the habitat more often due to the large amount of frass produced. It’s a good sign they are getting ready to pupate.
Troubleshooting Feeding Problems
What if your caterpillar refuses to eat?
- Check the Food: Is it the correct host plant? Is it fresh and clean?
- Check for Molting: Is the caterpillar still and possibly preparing to shed its skin? It will not eat during this time.
- Check for Illness: Is it discolored, leaking fluid, or very limp? Unfortunately, caterpillars can get sick from viruses or parasites.
- Give it Space: Constant handling or disturbance can stress it out. Observe quietly from a distance.
From Caterpillar to Chrysalis: The Final Meal
When a caterpillar is ready to pupate, it will stop eating. It may wander away from the food source to find a suitable spot. This is completely normal behavior. At this stage, you should:
- Stop offering new food.
- Ensure the habitat has sturdy sticks or a paper towel for it to attach to.
- Keep the environment humid but not wet.
FAQ: Your Caterpillar Feeding Questions Answered
How often do caterpillars eat?
They eat almost constantly when they are not resting or molting. You should have fresh food available to them at all times.
Can I feed a caterpillar grass?
Almost never. Very few butterfly or moth species eat grass. Stick to the host plant rule.
What do you feed a caterpillar if you don’t know what it is?
Start with the plant it was found on. You can also try offering a leaf from a common tree like oak, willow, or cherry, as these host many species. Offer one type at a time and observe.
Do caterpillars drink water?
No, they get all the moisture they need from the fresh leaves. Do not place water dishes in the container, as they can drown.
How can I tell if my caterpillar is eating?
Look for bite marks on the leaves and for small, round droppings (frass) at the bottom of the container. These are the best signs.
What do you feed a monarch caterpillar?
Only milkweed. Several types are acceptable, but it must be a plant from the Asclepias genus or closely related milkweed vines.
Raising a caterpillar is a rewarding project that teaches you about nature’s specific connections. By providing the simple, nutritious choice of the correct fresh leaves, you are giving it the fuel it needs to complete its amazing transformation. Remember, patience and attention to detail are your best tools. Always prioritize cleanliness and fresh food, and you’ll have a great chance of success.