Monarch Butterfly Eggs and Raising Them

Monarch butterflies are among the biggest, brightest fliers in North America. If you’re lucky, monarch butterfly eggs might be developing in your neighborhood right now!

With lots of care and attention, you can raise these tiny butterfly eggs into brilliant, orange, and black butterflies.

The Lifestyle of a Monarch

Monarchs are unusual among butterflies for their amazing migration from central Mexico to Canada and back. Even more impressive is that the migration cycle involves four generations of butterflies. This means that no single butterfly has ever done the entire journey, but somehow they find their way back and forth every year.

During the winter, monarchs huddle in a select few patches of pine trees in Mexico. They cling to each other to keep warm. As a result, they create huge hanging masses of butterflies.

It’s a spectacular sight to see them in the winter because there are tens of millions of butterflies in these small areas of forest. Scientists estimate a density of 5,000 butterflies per square meter of ground area during the winter season!

An adult monarch feeds on milkweed nectar. Photo by Chesna via Pixabay

In the spring, they leave Mexico for the North, stretching from Texas to Maine to Saskatchewan. In the U.S. and Canada, they lay eggs and continue on their journeys.

How Are Monarch Populations Doing?

Monarch butterflies are in steep decline for a variety of reasons. A major issue is that milkweed, the only plant their caterpillars can live on, is sensitive to pollution. Wild populations of milkweed have declined across North America, leading to fewer places for monarchs to lay their eggs.

Widespread use of pesticides and herbicides, intensification of agriculture, and human development of wild places are all huge factors in milkweed decline.

As a side note, I live in California where there is a much, much smaller population of monarchs. Instead of hundreds of millions, this population is critically endangered in the tens of thousands. California monarchs overwinter in California and spend the rest of their lives on the west coast.

Milkweed flowers are gorgeous and geometric. Photo by Jan Haerer via Pixabay.

What Is Milkweed? Why Do Monarchs Lay Butterfly Eggs on Them?

If you’re hoping to raise monarchs, you must first learn about milkweed. While there are a bunch of different species, they all look similar. They are herbaceous, perennial plants that usually grow in moderately wet places.

Milkweed will always create a white, sticky sap when you break the leaves or stems. In fact, this sap is toxic to many animals, which is why the monarchs eat it!

Monarch caterpillars aren’t affected by the toxins, so they can munch milkweed and accumulate the toxins in their bodies. This prevents predation from birds and other potential predators.

To attract monarchs to your garden, plant lots of milkweed! It is a tough plant to start from seed, so most people buy milkweed from the nursery. In fact, urban and suburban areas present some of the greatest opportunities for milkweed restoration, and therefore monarch butterfly conservation.

Please don’t buy the tropical milkweed! It has lovely orange and red flowers, but it doesn’t die back in the winter like all the native milkweeds. As a result, the butterflies are tempted to stick around in the U.S. too long and miss their migration. Check with staff at your nursery to ensure what you buy is native milkweed.

An example of how to sterilize your milkweed. The pyrex dish is full of a 10% bleach solution. Photo by the author.

Harvesting Milkweed for Your Hungry Caterpillars

If you have more than a couple of caterpillars you will need regular access to a good source of milkweed. It’s amazing how much plant matter these tiny insects can digest! Before you try to raise monarchs, you must figure out how to feed them.

Once you find your source, only harvest healthy-looking milkweed. Aphids will often take over a patch of milkweed. Milkweed covered in aphids is not as good for your precious caterpillars as healthy, green milkweed.

A variety of diseases and parasites infect monarch caterpillars. As a responsible butterfly parent, you should disinfect any milkweed you bring into your house. But before you disinfect, inspect the plants for any monarch butterfly eggs! If you find any, take them off and put them in with your other eggs.

An easy way to disinfect milkweed is to make a 10% bleach solution (1 part bleach to 9 parts water). Soak the milkweed in the bleach for 5 minutes. Thoroughly rinse the milkweed off after soaking until you can’t smell any bleach.

Then, pat down the plants with a paper towel. If you are in a really humid environment, try your best to really dry off the milkweed. Too much humidity can be bad for the caterpillars.

Close-up of monarch butterfly eggs on small pieces of milkweed. Photo by the author.

Collecting Butterfly Eggs Thoughtfully

Since monarchs are a very special species of butterfly that is critically endangered in California and in decline elsewhere, you want to be thoughtful when collecting their butterfly eggs. Don’t collect more than you can handle! Start out with five or fewer and see how that works for you.

Monarchs typically lay their eggs on the underside of milkweed leaves. They are barely larger than the periods on this page. The eggs are white in color and can be very hard to spot!

When you find an egg, cut the entire leaf with the egg on it off the plant. Then, once inside, cut out a small square of around the egg. Tweezers are helpful to hold the square as you cut around it.

If you leave too much plant matter around the egg it could curl up as it dries. If it curls up too much, it could hinder the caterpillar from finding its way out.

Hatching Butterfly Eggs

Place your egg squares on a removable surface inside a Tupperware (which you have sterilized like the milkweed). Put the Tupperware in a place that doesn’t receive direct sunlight in your home because direct sunlight can cook the eggs.

The caterpillars emerge from their eggs around five days after being laid. Fortunately, it is easy to tell when they get close to emerging. The tip of the egg will darken to a dark grey color about 12 hours before the caterpillar emerges.

If you check your eggs in the morning and the evening, you will be able to catch the butterfly eggs before they hatch.

Now, you must prepare another caterpillar chamber. I prefer to use a second Tupperware (again, sterilized) with a slightly damp paper towel in the bottom.

Take a few of your sterilized milkweed leaves and wrap the bases of the leaves in a damp paper towel. This will keep the leaves fresh for about three days. Place your newly darkened butterfly egg on top of one of these fresh leaves. Soon, you will have a baby caterpillar munching away!

Butterfly eggshells are full of great nutrients, so the caterpillars will usually eat their shells first. However, naughty caterpillars may eat another, unhatched egg if they stumble across it. In their first few days they can’t move much, so placing the butterfly eggs an inch apart is sufficient to prevent cannabilism.

A caterpillar within hours of emerging from the monarch egg. Photo by the author.

Caring For Your Teeny Tiny Caterpillars

It’s best to always wash your hands before opening your butterfly cage or tending to the Tupperwares. Also, it is best to never touch the caterpillars with your hands.

I find it’s best to always have tweezers around as I can do just about everything I need to with the tweezers. And just like everything else, sterilize your tweezers frequently.

You will be surprised by how tiny the caterpillars are when they emerge. During their first few days, you don’t need to do much. Just let them eat their milkweed in peace. If you notice frass (caterpillar poop) building up on the paper towel, you can carefully change it by picking up the milkweed leaves by the end that is wrapped in paper towels.

One you feel like the caterpillars are big enough that you won’t lose them in the butterfly cage, it’s time to move them!

Three medium-sized caterpillars eating milkweed. I transplanted these from the Tupperware when they were about 1/3 to 1/2 this size. Photo by the author.

Transitioning to a Butterfly Cage

Instead of using individual leaves, you should use entire milkweed branches in your butterfly cage. I wrap the milkweed stems in paper towels until they fit snugly into a flower vase, which I fill with water. You want to make sure no unfortunate caterpillar can fall into the water.

Again, choose a spot in your house that gets indirect sunlight for your cage. A north-facing window works best.

Caterpillars prefer temperatures from 70-85°F. Fortunately, this is the temperature of most homes in the summer.

Put some paper towels at the bottom of the cage. I change these paper towels every day to prevent the buildup of caterpillar frass. You can usually take the vase out of the cage while changing the paper towel. Keeping a clean butterfly cage ensures the healthiest butterflies!

To transfer your caterpillars from their second Tupperware to their cage, pick up the leaves with caterpillars on them, and find a sturdy place to balance them on the milkweed stem in the vase. They will find their way onto the new milkweed, but it may take a day. It’s best not to disturb them.

An example of a full butterfly cage. Believe it or not, seven large caterpillars ate all of this milkweed within three days! Photo by the author.

Hungry, Hungry Caterpillars

At this point, the caterpillars start to eat a lot. Never let them run out of food. This will stress them out (like it would stress you out!) and make them more prone to disease. When I notice their food getting low, I will introduce a second vase full of milkweed and make sure that they can wander from one to another.

Don’t worry if sometimes your caterpillars don’t move for a while. They shed their skin about five times throughout the two weeks they are in the caterpillar phase. This process can take many hours. When they shed their skin they are very still.

However, if you do notice a caterpillar looking strange or sickly, isolate it immediately. It may be infected with some disease and could infect your other caterpillars. The best way to get rid of these poor guys is to freeze them and throw them away. It’s the saddest thing, I know.

A caterpillar in the ‘J-hook.’ The chrysalis is already forming inside this caterpillar! Photo by the author.

J-Hooking and the Cocoon

When you can’t imagine your caterpillars getting any fatter, they will spontaneously stop eating. This means they are getting ready to make their cocoon. Make sure they have a clear route to the top of the butterfly cage. If a few leaves of milkweed touch the side of the cage, that is good enough.

The caterpillars will meander to the top of the cage and search for their favorite chrysalis spot. Once they find this spot they will spend a while weaving a silk pad that they connect to in order to hang upside down.

They will hang upside down in a ‘J’ shape. This is called J-hooking. Once the caterpillar is in its J-hook, it has already begun to transform. Caterpillars will remain in their J-hooks for about a day.

It is critical that you do not interrupt the caterpillar from the moment it begins the J-hook to 2 days after it forms the chrysalis. They are super sensitive at this stage!

In a matter of minutes, the J-shaped caterpillar will shed its skin and turn into a bright green chrysalis. It is very easy to miss this! If you want to catch it, start paying very close attention once you notice their antennae begin to look deformed in their J-hook. That means they are very close to transforming.

Several caterpillars prepare to go into J-hooks. There are also three chrysalises in the picture. Photo by the author.

The Chrysalis Waiting Game

Monarchs will spend 9-14 days in their chrysalis. There isn’t much to do during this stage except wait. Always keep the door to your cage closed, because nasty wasps can lay parasitic eggs inside the chrysalises. However, these wasps can’t make it through the fine mesh of a butterfly cage.

You will notice the chrysalis become translucent a few days before the butterfly emerges. Once the chrysalis is completely see-through, you can be sure the butterfly will emergy that day.

Important! Don’t have any caterpillars in the cage where an adult will emerge from their chrysalis. The strange slime that comes out of the chrysalis may be heavily infested with an Ophryocystis elektroscirrha (OE) parasite.

If young caterpillars eat the slime, they will become sick. Also, clean your cage very well with bleach before raising another generation of butterflies.

A butterfly will emerge from this chrysalis within 24 hours. Photo by Lorry M via Pixabay.

The Emergence of the Monarch

The butterfly will look misshapen when it comes out of the chrysalis. Within a few hours, its wings should dry out and it will look like a normal butterfly. It is best to release the butterfly within 24 hours of it emerging.

The only exceptions to this should be if it is under 60°F outside. Monarchs can’t fly very well in these cooler temperatures, so if you release it below 60°F, it might not make it.

Monarchs don’t feed on their first day, and usually don’t eat much on their second day, either. This means you won’t have to feed them once they emerge.

To let them free, take the entire cage outside and open the door all the way. Let the butterfly come out on its own accord. As long as the other chrysalises are more than two days old, this gentle movement shouldn’t disturb them.

Good work! You’ve introduced more butterflies into the world. That should feel great!

I hope you’ve learned a little bit more about raising monarch butterflies here! Please remember that it is very important to keep their cages, their milkweed, and your hands, and tweezers clean at every point in the process.

[Featured Image by PublicDomainPictures via Pixabay.]

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