Nature Notes: Swallowtail Caterpillars

Black Swallowtails are common in our garden from spring to late fall. Several times during the season we find caterpillars munching on parsley or fennel which we plant specifically for them.

As soon as we see butterflies fluttering around the garden we start checking the host plants. In late March we found two early instar caterpillars on the bronze fennel.

March 30th

My children love to watch them grow and check on them daily. They molt often and grow quickly (the caterpillars not the children...although the children do grow like weeds).

April 5th

April 11th
These two caterpillars have eaten one entire plant, stems and all. One caterpillar has already gone to pupate. The second caterpillar has moved to the neighboring fennel plant and is still munching away.

Swallowtails tend to wander pretty far from their host plants to pupate. Before they depart they will empty their digestive track. If you observe the frass you will see that it looks different than the normal poop (I will spare you the photograph). This is the sign that your missing caterpillar has gone to find a good spot to make its chrysalis.

In about two weeks we should see a few more of these beautiful butterflies gracing our garden.

Black Swallowtail on Black & Blue Salvia
Linking to Rambling Woods for Nature Notes Wednesday. Please stop by to see observations of nature from all parts of the world.


  1. Wonderful photos. You show great clarity in them.
    Cher Sunray Gardens

  2. Oh how lucky to be able to follow the development of these caterpillars to butterfly. Here all my monarch cats get grabbed by paper wasps unless I bring them in to pupate.. Thank you so much for participating in Nature Notes, I am very happy to have you...Michelle

  3. I loved the whole story with photos!! Your kids are so lucky to be doing this with you. I like how you plant the caterpillars their own plants.

    Do you think that they look like the caterpillar in Alice and Wonderland in the photo where the 2 of them are sort of making a V shape - LOL! That just sort of struck me :)

    Really nice post!

  4. Haven't seen any yet here in Kansas. But looking forward to it.

  5. Lovely post, the caterpillars and the butterflies are gorgeous. Thanks for sharing.

  6. Those are beautiful swallowtails, but i dont think we have them here. Yet we also have very beautiful swallowtails. I am not familiar yet with your description about the poo being different when they are about to pupate! I think you should have put that photo, haha!

  7. You last image is so pretty and so is the one with the two caterpillars forming a V.

  8. How beautiful! I've planted fennel this year, hoping to attract some of these lovelies!

  9. Karin, I saw my first butterfly of the season yesterday. It is always such a treat to see them isn't it? I love parsley and always plant lots, but have never noticed any butterfly caterpillars.Maybe I should give fennel a go.

  10. Can't wait to see the first Swallowtails. We have lots of Yellow, but I love the Black ones.

  11. What anticipation your children must enjoy! Ha, actually, I'm just as giddy about them as the kids! Ironically, not one parsley, dill or milkweed plant has been touched so far. Keeping my hopes up though that they will be found and eaten!

  12. You inspire me to try harder to identify the caterpillars I see in my garden... I've already seen a few black swallowtails fluttering around, as well as tiger swallowtails.

  13. I am always amazed at how tiny the caterpillars start off and how quickly they grow. I used to watch them a lot in Virginia.....haven't seen too many here. I have offered a lot of parsley up to the elements, no takers.

  14. From such scrubby little black things to large elegant and colourful caterpillars - they certainly change a lot even before they emerge as a butterfly. great photography - thank you


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One of my favorite things about blogging is the conversation with readers. Leave a comment and let's get talking. ~Karin

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