Raising Black Swallowtails

I am really excited to share something a bit different today…a post about how to raise black swallowtail butterflies! Our focus this year has been largely on adding butterfly-friendly plants to the garden, so we’re swimming in caterpillars.

Identification

The black swallowtail—otherwise known as the eastern black swallowtail, American swallowtail, parsnip swallowtail, and papilio polyxenes—is found throughout much of North America. Females are generally larger than males, and the upper wings are black with two rows of yellow spots. The spots are larger and more vivid on males—smaller and lighter on females.

Females also have a striking blue area between the two yellow rows, while the male black swallowtail’s blue area is much more understated. The lower area of the wings (the ventral side) look pretty much the same on each sex. They have two rows of pale yellow dots and rows of orange spots with powdery blue. Males and females also both have a red spot on the inner margin of the hindwings (the two back wings).

Host plants

There are quite a few host plant options listed on the black swallowtail Wikipedia page. However, the main ones are dill, rue, fennel, parsnip, parsley, and golden alexanders. We planted a ton of dill this year, and that’s what attracted the females to our yard.

Next year, I’ll plant dill again for sure. I like using it for pickles—and I like letting it flower to help attract beneficial bugs. However, dill doesn’t last super long into the season where we are. Around the end of July, it’s struggling.

So next year, I’ll probably plant some additional black swallowtail host plants to help provide food for the entire season (usually through late August, sometimes longer).

Swallowtail timing

The first round of black swallowtail butterflies will emerge from hibernation between late April and June. These are the butterflies that entered their pupal (chrysalis) stage late in the year and remained in the chrysalis all winter long.

The second round of butterflies will lay eggs more toward the middle of summer. We found our baby caterpillars in July in Maryland.

Finding eggs can be tough. I actually didn’t find any of my multiple black swallowtails until they were teeny tiny caterpillars. If I found an egg, I’d take the exact same steps as I took with my tiny caterpillars, though. Here’s what I did.

Step 1: Setting up an outdoor enclosure

I purchased a mesh and plastic butterfly cage online. This is what our local library used, so it’s what I decided to use. Whatever you use, make sure you can set it up in a somewhat protected area outdoors.

There is some disagreement (mostly when it comes to raising monarchs) about whether or not you need to raise your caterpillars outdoors. Some findings have shown that raising monarchs indoors may inhibit their ability to migrate.

Because caterpillars and butterflies live outdoors, I figured it just made the most sense to keep our enclosure outdoors under our covered patio. To keep it from blowing away, I put a cheap concrete paver in the bottom of it.

I also added in several sticks and a few paper towels on the bottom of the cage. (Caterpillars grow quickly and poop a lot!)

Step 2: Adding food, eggs, & caterpillars

When I found a caterpillar, I’d simply snip the stem off of the plant and put it in the enclosure. I also used a small plastic cup with water in it and refreshed the dill every day or two to make sure everyone had plenty to eat.

You don’t have to use dill. You can use any of the other host plants. I just found my caterpillars on my dill, so I kept feeding them dill.

My friend also told me that the caterpillars will drown themselves, so I used a bit of aluminum foil to cover the top of the plastic cup.

Like this? See my post with 17 Plants That Attract Beneficial Insects, my tips for How to Grow Sunflowers, and my guide for How to Grow Beautiful Zinnias!

Step 3: Refreshing food & keeping cage clean

If you have an egg, know that the egg stage will last about a week, maybe a little less or a little more depending on the conditions. Once the egg hatches, it’s time for the larval stage. This is the caterpillar stage, and it lasts about 3 weeks—again, give or take depending on conditions.

While a caterpillar, the black swallowtail grows quickly and eats a lot. It will shed its skin 5 times as it grows. Especially when the caterpillar is nearing its pupal stage (entering the chrysalis), check the food daily.

Your little baby is going to be chowing down, and you don’t want to leave it without food. At this point I was also cleaning out the paper towels on the bottom of the cage every day or so. Lots of poop.

Step 4: Waiting for butterflies

The caterpillar stage generally lasts about 3 weeks or so. However, we had a few caterpillars, and all had slightly different timelines. Once the caterpillar gets fairly large, you’ll know it’s about time.

We also noticed what my daughter called “the zoomies” when they are about to pupate (enter the pupal, or chrysalis, stage). They crawled all around the cage, up and down the sticks, along the top of the mesh. I’m assuming that this is just them looking for a nice place to set up shop.

Below are a few pictures of some black swallowtail caterpillars close to forming a chrysalis. When it’s time, they will form kind of a “hook-like” shape and spin a silk girdle. This silk girdle will hang them in place to whatever surface they’ve chosen.

One cool thing—their chrysalis can be green or different shades of brown depending on what they are attached to. This helps to keep them hidden while they are pupating.

You can see the first chrysalis below is green to match the green edging on the cage. Another caterpillar chose a stick for its spot, so its chrysalis is brown instead. Nature it pretty metal.

At this point you can remove everything else from the cage. You don’t need anymore food, paper towels for poop, or extra sticks. It’s time to hunker down.

Step 5: Releasing the butterflies

After it’s been about a week and a half, start checking your chrysalis. They can remain in this stage for 10-20 days depending on the temperature and conditions. Mine were all about 10-12 days.

They all also emerged in the morning. But if you’re getting close, I’d check a few times a day just to make sure! When the butterfly does emerge, the wings will be all crumpled up. The butterfly will latch onto something nearby and hang upside down to dry its wings.

This can take an hour or so. When the butterfly begins fluttering around in the cage, open it up and let it fly out. If you want to hold the butterfly, make sure you hold it by all four wings at once so you don’t accidentally injure it. And that’s that!

When everyone had flown the coop, I emptied the cage and washed it on a gentle cycle in our washing machine, letting it air dry. I like the cage because you can collapse it when you aren’t using it, too.

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