Monarch caterpillars: How to satisfy their ravenous hunger

Consistency and cleanliness are key

Jun 11, 2025

Once the caterpillar enters the fourth and fifth instars, about three weeks after hatching, proper nourishment is critical. These efficient eating machines grow exponentially in a matter of days. Milkweed is their only food source. The best course of action is to have enough on hand well before the ravenous eating starts.

As soon as the caterpillar exits the egg, it eats the shell. They’re so small that the only way I know they’re alive is when I see a small arc eaten out of the leaf after the egg disappears. At this size, they don’t eat much, so a single leaf for the first instar is adequate for a few days.

As larvae grow, the speed and quantity of their intake will increase, and will be evident by the multiple holes left in the milkweed. I usually transfer them to a milkweed stalk picked from my garden when they enter the third instar.

I planted my first milkweed crop a few years ago. The first year it grew, I noticed a Monarch laying eggs on it. I had to supplement milkweed from other sources as mine wasn’t growing fast enough to meet the demands of three hungry caterpillars.

This May, I raised two caterpillars that ate through approximately five stalks of milkweed in a day or so. The stalks contained about 8-10 leaves each. My established milkweed crop was just under a foot high. Luckily, there was enough food this time to keep them fed.

A caterpillar’s hearty appetite. Time to get more milkweed.

After you find your first egg, make no mistake, the growing process will keep you on your toes. Here’s how to feed your hungry caterpillars while creating an environment that will keep them safe, healthy, and happy.

Establish a steady and stable source of milkweed.

I’ve read many social media posts from frantic people running out of plants after their cats decimated the ones in the enclosure. Once your crop is established, you’ll be able to harvest enough food to keep them satisfied.

Planting milkweed in your yard is best, unless you can ensure you’re getting it from a source that doesn’t use any pesticides, as it will be a death sentence for the caterpillar. Believe me, it’s not pretty.

In the Midwest, milkweed seeds can be sown in the fall before the first frost, or seedlings can be planted in early spring. Purchase milkweed that isn’t sprayed with pesticides. Look for local native plant sales in your area instead of the big-box stores. Most of these organizations sell plants strictly for the preservation of pollinators and use more natural means to grow their plants.

When Monarchs begin migrating further south, I remove all the pods in September and October and then donate them to a volunteer butterfly organization that maintains a sizable Monarch Waystation habitat. It’s satisfying to extend my reach of conservation in this manner. It also prevents the seed from blowing into unsuspecting neighbors’ yards, who might not want to see milkweed popping up in their lawn.

Just make sure the pods are removed before they open, allowing the seeds to escape. Pods are ready when they’re no longer bright green and are turning brown. If you press on the seam of one and it makes a small popping noise, that’s another sign they’re ready to be picked.

Stay one step behind the feeding frenzy.

Replace milkweed before it’s gone with fresh plants. Fifth instar caterpillars will be ready to pupate in a matter of days and need to take in an enormous amount of energy. Most of the feeding happens when you're not around to observe it. My recent two were introverted and would become motionless as soon as I got near the enclosure. They mostly ate overnight. In the morning, I’d wake up to empty stems with caterpillars that doubled in size, clinging to them upside down. Immediately, I’d go out and retrieve more food to keep them both going. This occurred a couple of times before they pupated. They climbed to the top of the enclosure, which was the first time they had crawled off the milkweed. Somehow, they ended up together side by side and transformed only hours apart. Now I await their emergence.

Two Monarch caterpillars are ready to transform

Create a caterpillar-friendly habitat that keeps them safe and healthy

As a newbie, I used a disposable coffee cup with a plastic lid to hold milkweed stalks. To stabilize it, I placed gravel at the bottom before adding water, then I pushed the stems through the hole on the lid. After a while, I realized I needed a more permanent solution.

Before the eggs hatch, a shallow plastic food container with a lid and a moistened paper towel will suffice, but they will soon outgrow it. Transfer them to a fresh milkweed stalk as soon as you can. Take the original leaf with the tiny caterpillar on it and place it on a fresh leaf. It will find the new leaf and abandon the old one.

A screened enclosure with tubing for milkweed stalks is a worthwhile investment if money is no object. They are reusable and, after a few years’ use, will prove to be money well spent. But there are many ways to accomplish this without purchasing additional equipment. A homemade screened enclosure, a system of disposable water bottles, plastic food containers, and paper towels will work just as well if they:

Allow caterpillars to access fresh air
Allow room for milkweed stalks and adequate movement of caterpillars within the enclosure
Clean up easily, can be disinfected or discarded to prevent harmful bacteria
Keep frass away from larvae
Have easy access to swap in fresh milkweed, and for frass removal

Midwest Butterfly Garden enclosure with tubing and stand

Become a top-notch housekeeper for your temporary guests

A well-maintained screen enclosure, along with careful inspection of new milkweed, will keep your caterpillar safe and happy until metamorphosis. At the very least, it will keep out other insects that will harm them.

Frass, the scientific name for caterpillar poop, will become familiar as your larvae increase in size. The little black pellets build up fast and are very messy. They contain bacteria that can be harmful to caterpillars and should be cleaned up regularly, at least once a day, and more as necessary.

I use a small brush dedicated to sweeping frass off the tube racks onto a reusable flexible liner at the bottom of my enclosure. Then I lift it out and dispose of the poop easily. You can also use paper towels or disposable liners that fold up and can be discarded.

Over 450 species of insects feed and live on common milkweed. After harvesting, inspect the leaves for stowaways. I always run the leaves under cool water, then dab them with paper towels to remove unwanted critters before inserting them into the plant tubes. Remember to refill the tubes with fresh water. Each stalk absorbs water quickly within a day or so and will wilt if not replenished regularly. Extra tubes make it easy to swap devoured plants with fresh ones.

Wash your hands regularly to prevent the spread of bacteria and to remove milkweed milk from your skin. It is toxic to humans and pets.

After releasing your butterflies, clean and disinfect all equipment. I use warm soap and water and discard disposable items.

Over the years, my meticulous housekeeping has led to many successful and beautiful Monarch releases that were bittersweet.

On a personal note,

I’m not one for raising any more than a few Monarchs at a time. I don’t want it to become a chore that becomes overwhelming. Overcrowding any species, not just butterflies, increases the likelihood of disease that affects not just one or two members but the whole group.

I refuse to crowd caterpillars into small enclosures or treat them like specimens rather than living creatures. I strive to do what benefits the species, not my social media feed. My photo documentation is taken when opportunities present themselves, not by manipulating them or the environment. I’m not in a race to see how many Monarchs I can raise in a season. If Mother Nature blesses my milkweed with butterfly eggs, she is my guide, and I will do what is best for the species.

From egg to butterfly, with enough food and shelter, these tips will ensure that your caterpillars turn into happy and healthy butterflies that will carry on the next generation heading in the direction the migration takes them.