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The Tale of the Black Swallowtail

By Paul James

I love parsley, especially the flat-leaf, Italian variety. I use it more often than any herb I grow. But lately, my parsley crop has suffered, not because of something I did or didn’t do, but because it’s being consumed by the larvae of numerous black swallowtail butterflies. And I couldn’t be happier about it. After all, I can replace the parsley, but I can’t replace the swallowtails.

The black swallowtail butterfly is Oklahoma’s state insect. Has been since 1996. It’s not the only swallowtail that calls Oklahoma home (eight different species have been recorded), but it is one of the largest and most beautiful, with a wingspan of three to four inches. Of course, it doesn’t get the attention that the monarch butterfly does, but then unlike the monarch, it isn’t threatened or endangered.

Papilio polyxenes (that’s its scientific name) has two generations a year. After overwintering in their chrysalises, the first group emerges between late April and June, at which point mating begins. The females then lay eggs on the leaves of various plants (my parsley included). The eggs hatch in three to five days, develop into a caterpillar with an enormous appetite, then pupate for nine or ten days. The second group then emerges in late summer, and their eggs become the first generation the following spring.

The caterpillar undergoes dramatic changes between hatching and pupating. It starts out mostly black with a white saddle. As it grows, it develops reddish orange spikes on its body. The white band soon disappears, and the caterpillar develops its familiar green and black bands with yellow spots. It also develops an osmeterium, which is a bright orange, two-pronged fork behind its head. When disturbed, the caterpillar pops out the osmeterium, through which it releases an unpleasant smell (think rotten cheese) to ward off predators.

The black swallowtail caterpillar feeds on many different plants, including Queen Anne’s lace (a pretty but rampant weed), carrots, celery, dill, fennel, parsley, and rue. The butterfly eats nectar from bee balms, coneflowers, clover, milkweed, thistles (also weedy), Pentas, Phlox, and Salvias, just to name a few.

Sadly, adult black swallowtails typically live only 10 to 14 days. That’s reason enough to enjoy them all the more.

Happy gardening, ya’ll.

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26 responses to “The Tale of the Black Swallowtail”

  1. Peter Hilger says:

    My fennel is covered with these caterpillars. I probably have 50 caterpillars on the patch, Well worth the time and effort for the butterflies.

  2. Judith Nole says:

    My fennel was covered with Swallowtail caterpillars last summer, too! This summer, rabbits ate my Southwood fennel about three days after I planted it. (At least SOMEONE was getting fed…)

  3. Janice S says:

    Just beautiful! Didn’t know they were our state insect! Thanks for all the info.

  4. Ken says:

    I had six caterpillars on my parsley. Watched them grow and then abruptly they vanished. Sadly I cannot find their chrysalis . We saw the Swallowtail butterfly deposit the eggs. Looking forward to seeing the butterflies in the spring.

    • Paul James says:

      They’re pretty good at hiding their chrysalises, so I wouldn’t be too concerned by the fact that you can’t find any.

  5. Bev Metcalf says:

    Happen to me last year.
    Happy to tell you once they were done feeding
    parsley came back stronger than before and grew
    into the fall. Made everyone Happy!

  6. shepperd says:

    I plant herbs for the butterflies. Just released 5 black swallowtails this morning and have about 30+ chrysalises in butterfly cages that should emerge within the next 5 days. Getting ready for the monarch’s journey south with 8 varieties of milkweed ready for them whenever they decide to visit!

  7. Virginia Koehler says:

    Hi Paul Always love to hear from you all the best Ginni from New Jersey

    • Paul James says:

      Thanks, Ginni. I always love hearing from folks in The Garden State! One of my sons went to Princeton, and we always enjoyed visiting and exploring the area.

  8. Janelle Young says:

    Planted dill along with my cucumbers so I would try
    my hand at making pickles. Well the caterpillars devoured the dill but was thrilled to watch them grow fat and happy. Thanks for your article, always enjoy your sense of humor.

  9. Roxanne Snider says:

    I have fennel, parsley, and rue. I have seen a female depositing eggs but no caterpillars!! I had tons last year. My question is, the fennel grows very tall and “flowers”. Should I cut it back or leave it be.
    Thank you
    Roxanne Snider

  10. Marilyn Ogletree says:

    I’ve been using dryer sheets after they’ve been used several times in the dryer to hold potting soil in flower pots. It lets water go through easily but holds the soil in. I’ve repotted flowers after several years and the fabric sheets are still working. Roots may grow through them in spots. I’ve also used the used dry-cleaning sheets in big pots with good results. I think the dryer sheets work better than squares of landscape fabric and easier to get.

  11. Charlene says:

    I use coffee filters in the bottom of flower pots. They hold the soil in then disintegrate.

  12. Sara says:

    Such a timely article. Just the day before I had enjoyed watching a black swallowtail feeding at my Southwoods hanging flower baskets. I did not realize it is the state insect either. And I did find a caterpillar on the parsley in my garden. Now I’m enjoying watching it grow and anticipating its transformation. Thank you for the great info!

  13. welda scott says:

    I have released 9 black swallowtail so far this year. Have 7 catapillows in one jar and 4 in another one. Am feeding them fennel and have parsley ready to go. Has been the best of the summer. They were only tiny little things when I put them in jars. The white band was barely visible.