Swallowtail Caterpillar – Generations of Black Butterflies

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Do you know how to attract the friendly black swallowtail caterpillar to your garden? Plant lots of parsley or carrots and you might get lucky enough to enjoy many generations of pretty green and black caterpillars that transform into amazing butterflies!

The swallowtail caterpillar feeds extensively on parsley and its relatives, such as carrot greens. If you’ve seen a pretty green and black striped caterpillar munching on your garden herbs or carrot tops, you’ve likely found a swallowtail caterpillar!

These caterpillars are so pretty you almost just know they’re good guys!

What Does a Swallowtail Caterpillar Look Like?

The Eastern Black Swallowtail Caterpillar is generally a bright lime green and black striped caterpillar with yellow dots on the black stripes. When young, the swallowtail caterpillar is mostly black, sometimes with a thick white stripe near the center as it gets a little older.

Before they are full-grown, swallowtail caterpillars may have white stripes along with the black and green, but those fade to just green and black stripes as the caterpillars prepare to form a chrysalis.

Swallowtail Caterpillar and another one on parsley in a ceramic pot

What Are the Swallowtail Caterpillar Stages?

The swallowtail caterpillar goes through the butterfly lifecycle of egg, larva (caterpillar), pupa (chrysalis), and butterfly. During the caterpillar phase, the black swallowtail goes through five instars. It begins very small in the 1st instar (mostly dark in coloring), and progresses through 2nd and 3rd instar stages (dark coloring with a white center band), 4th instar (black, white, and green stripes), and finally the 5th instar (green and black stripes), after which it will pupate after about 10-14 days.

What’s the Most Common Swallowtail Caterpillar Food?

Eastern Black Swallowtail Caterpillars most commonly host on parsley and carrot tops. They also enjoy eating dill, Queen Anne’s Lace, fennel, parsnips, and turnips. I’ve also heard that swallowtail caterpillars will eat poison hemlock! (My husband told me it’s sometimes a host plant for the black swallowtail caterpillars.)

Who Are the Swallowtail Caterpillar Predators?

Swallowtail Caterpillars face a number of predators that may prevent them from reaching their butterfly stage.

Black Swallowtail Caterpillar predators include:

  • Birds
  • Spiders
  • Toads
  • Wasps and Parasitic Wasps
  • Other Insects

What Are Those Swallowtail Caterpillar Orange Horns?

When the black swallowtail caterpillar orange horns come out, it is usually when they feel threatened. The orange horns on the swallowtail caterpillar can stick out a little or a lot. The orange horns may be most noticeable after you touch an unsuspecting swallowtail caterpillar, startling it.

Swallowtail Caterpillar Orange Horns Sticking Out
Swallowtail Caterpillar Orange Horns Sticking Out

I’ve also seen the horns come out when watering the garden!

Finding a Swallowtail Caterpillar in Your Garden

For a fun and educational activity with the kids, try raising swallowtail caterpillars. The caterpillars show up almost as if by magic if you merely plant some parsley, carrot tops, or other crops in the carrot family or Apiaceae / Umbelliferae family.

Look closely among carrots, celery, parsley, and other plants for small, dark-colored caterpillars or larger, green and black striped caterpillars with yellow dots.

Black swallowtail caterpillars are wonderful garden friends, visiting your flowers and delighting your family as they turn into beautiful black butterflies.

I can’t be totally sure, but through my research, I once read that swallowtail butterflies will come back to lay their eggs where they hatched as long as the food supply remains sufficient!

We’ve been sure to plant lots of parsley this year to entice these magnificent creatures to enjoy our garden with us.

Caterpillars and Kids: Tips  

Kids love seeing butterflies all over the yard and in the garden. Try these tips to encourage butterflies to lay eggs and eastern swallowtail caterpillars to thrive.

  • Get a butterfly hatching enclosure. You can find numerous choices of caterpillar houses on Amazon and similar.
  • Keep some parsley or carrots in a small planter. Choose one that fits inside the enclosure so you can move the entire pot inside when the caterpillar is ready to make its chrysalis.
  • Replenish your swallowtail caterpillar crops regularly. You may be surprised at how quickly they can decimate a parsley patch! We planted parsley in four or five different places and they’ve enjoyed almost every bite so far.
  • Get to know the swallowtail caterpillar phases. Once you’re familiar with the different instars, that makes it easy to know when it’s almost time to move the caterpillar into the enclosure.
  • Check your enclosure every day. Make sure it is in a secure location so it won’t blow around in a thunderstorm or other weather event. Watch to see when the caterpillar pupates and makes its chrysalis. And when it hatches!
Two Swallowtail Caterpillars Holding onto Parsley Plant

Final Thoughts: Raising Swallowtail Caterpillars

In our experience, the black swallowtail butterflies continue to come back to lay more eggs as long as we keep replenishing our supply of parsley or carrot tops.

If you’d like to raise swallowtail butterfly caterpillars, you might enjoy our previous post. Also, know that it’s a fun and easy hobby that doesn’t cost much but time!

If you’d like, you can invest a few dollars in an inexpensive butterfly enclosure so you and your family can see the butterfly when it breaks out of the chrysalis. I highly recommend this!

(Using these affiliate links will result in a tiny commission that will go toward our girls’ future at *no* additional cost to you. TY!)

Do you have any experience raising swallowtail caterpillars or butterflies yet?

Please share in the comments below – we’d love to chat and share tips!

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    1. Hi Kathy,
      Thanks so much for your comment – I am so glad you found the info helpful. We’ve loved seeing black swallowtails in our yard and garden again this year. It always brightens our day seeing the butterflies and caterpillars. I hope some come to visit your garden! – Kate

  1. The weather is turning cold in PA and there are 2 swallow tail caterpillars in different in star stages on the parsley in my raised bed. How can I help them survive until they are ready to pupate?
    I put the plant in a pot and brought it in when the temperatures were in the 50s the last few days?

    1. Hi Wendi! So nice you are enjoying the swallowtails too! I’ve done some research on this just now and it seems your approach bringing the pot indoors is a great plan to help them mature and survive until they can pupate!

      I found this article very informative – https://www.gardenatoz.com/what's-up!/tip-cuttings/caterpillars-before-butterflies/. It suggests that a warm house, even grow lights, can help the swallowtail caterpillars thrive until they pupate.

      For the chrysalis, once they form, the best plan may be to find a semi-sheltered area outside, protected from predators if possible, and keep the pot there. I just saw if the butterflies are native to our area (I am in PA as well!) that they should overwinter in the chrysalis as nature intended. I believe the cooler temperatures will help them to maintain the right body temperatures for diapause, which I’ve just learned is suspended development, almost like being frozen in time and then continuing development again later when the time is right – spring!

      I will add that last year I thought we needed to bring our swallowtail chrysalis indoors for the winter and put it in my garage, but it never did hatch come spring. 🙁 I think helping to regulate the temperature until they pupate and then putting them in a sheltered outdoor setting would be a great plan!

      Wishing you good luck! Please let us know how it goes.


  2. We are housing 9 black swallow butterfly chrysalises in an aquarium we purchased, after rescuing them from our fennel bush in their catapillar stage. W
    We kept them fed w/ organic dill, parsley and fennel. Now, I have questions as to what I do with them over the winter. We live in northeast Texas. Do we keep them inside the house or move their aquarium into the garage for the winter?
    We really want to see them hatch out and allow them to fly away.
    Can you give some advice?
    Thank you.

    1. Hi Rochelle, That sounds amazing with your black swallowtails! That’s a great number of them you have and the perfect menu. 🙂 From my experience, the caterpillars will go into diapause if the temperatures are cold enough and they will then continue their lifecycle in the spring. If it isn’t cold enough yet, they may have time to hatch, release, and make a new batch of eggs that would then winter over and hatch in the spring. I believe the typical black swallowtail butterfly lifespan once hatched is 10-12 days. If you still have some zinnias or other nectar flowers in your garden, they may enjoy those once they hatch! Since you are in Texas, I am hopeful your temps are above ours so I think you are safe to release once they hatch. 🙂 I believe they prefer 60 degrees and above but I am still working through some of this myself. 🙂 Best of luck and feel free to come back and let us know how it goes!

  3. This is a lovely article. We got lucky last week to find 9 black swallowtail caterpillars in our herb garden. We certainly weren’t expecting them! Now, after feasting on dill and parsley, they are super fat! Lol! I find myself watching them for long periods of time as they move around and make decisions on what to chomp next. It’s really cute and fun. Thanks again!

    1. Hi Jennifer, oh that is so wonderful that you have so many black swallowtail caterpillars loving life in your garden! It makes me so happy to know others enjoy being a part of their survival and lifecycle. So glad you liked the article and thank you so much for taking the time to comment on your experiences – wishing you many more lovely garden friends!

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