Raising Monarch Caterpillars: Week One

Monarch egg
A close-up of a monarch egg, circled with a pen, on a milkweed leaf.

On my local neighborhood Facebook group, the discussion of milkweed came up. A butterfly garden is being built in the local cemetery and I mentioned I needed to thin out my milkweeds, if anyone wanted to try and transplant.  No one took me up on that offer, but a neighbor did offer to come check my plants for monarch butterfly eggs.

She found several. Taking a few back for her daycare pupils and leaving a couple with me, the eggs helpfully circled so I could find them. Monarch eggs are very, very small. A little white dot about the size of the head of a pin.

Milkweed leaves in a plastic container
Baby spinach box repurposed for a monarch hatchery. They don’t need much oxygen in the egg stage, so don’t worry about air vents.

Knowing what to look for, I found several more in a different section of my yard later that day. Why collect monarch eggs and raise them inside instead of leaving them where they were laid? Because they have a low survival rate outdoors. By collecting the eggs and raising them indoors (about a month-long process) the monarch doesn’t have to deal with predators until they are released as butterflies. Monarch eggs usually take about 4 days to hatch. The best place to keep them is a plastic container with a damp paper towel. Any sort of container will work, I used an empty baby spinach box.

Two days after collecting the eggs, one of them has hatched. They are very small, so look for chew marks in the leaf.

I checked the leaves every day, and two days after I had collected the eggs, my first caterpillar hatched. Considering the size of he egg, it is probably not a surprise that the baby caterpillar is almost too small to see. It is just a little grey line and can easily be overlooked. The best way to look for them is to look for the part of the leaf they have eaten. DO NOT TOUCH the caterpillar. They are very delicate at this stage and you could kill it.

Monarch caterpillar just hatched
This is a zoomed in so you can see how tiny they are when they first hatch.

Here is a digitally zoomed in version of the last photo. The caterpillar is less than a quarter inch long and the stripes can’t bee seen with the naked eye. But you can see it is already pooping a great deal! If you decide to try this, be prepared to deal with a lot of caterpillar poo.

caterpillar mesh enclosure
The caterpillar habitat with a sprig of milkweed.

Once the caterpillars started to hatch, I realized I needed a different sort of container to keep them in. After some research, I settled on this zippered, mesh habitat. Its footprint is about a foot square and it stands about 2 feet tall. One panel is clear plastic (they call it a viewing panel, but the wrinkles in the plastic do obscure the view a bit) and the rest are white mesh. One side panel has a zipper opening so moving things around inside is pretty easy.

monarch caterpillar 2 days old
Two days old and the stripes are starting to show.

At this point, it was four days into my monarch experiment and I had three caterpillars. I placed a spring of milkweed in the enclosure with them with a wet paper towel wrapped at its base to keep it fresh. The first caterpillar to hatch was just beginning to have stripes visible without a digital zoom.

Monarch caterpillar on milkweed
Three days old and growing!

At three days old, they start to look like caterpillars. Their days consist of eating milkweed, pooping, and resting.

butterfly habitat in window
With the caterpillars getting bigger, I added a bottle with a tall milkweed cutting to the habitat.

One week after first collecting the eggs, I have six caterpillars and they have eaten through most of the original milkweed sprig. I decide to upgrade and, using an old bourbon bottle as a vase, I cut a medium sized – aphid free – milkweed plant from my side garden and set that up as their food source. I tucked the original twig in at the base so the caterpillars could climb over as they needed. Since the leaves are now pretty far off the ground, I left a couple leaves on the base of the habitat in case any of the caterpillars fell.

Milkweed with small caterpillars
With the zipper of the habitat open, you can see several of the caterpillars.

Here is a view inside the habitat. If you look closely, you can see several of the caterpillars. The base of the habitat will start getting covered in poop at this point (officially it is called “frass”). It can be cleaned up with a small vacuum, as long as you are sure all the caterpillars are safely up in the leaves.

Monarch butterfly caterpillar, 5 days old
One week from egg collection and 6 days from hatching, this one is getting big!

This is the biggest of the caterpillars. I assume it was the first to hatch, but since they all look the same, I can’t be sure. If it is the first to hatch, it is 6 days old and looking like a traditional monarch caterpillar.

Monarchs generally take about a month from egg to butterfly, so I’ll be updating once a week on progress.

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