Caterpillars on the Parsley

Black swallowtail larvae on parsley

This evening I found eight little caterpillars on one parsley plant that I am growing in a mixed container out on the patio, and fifteen more on another plant out in the veggie garden. They are fascinating-looking little guys, mostly black with white stripes. Even though I hate to lose the parsley, I'm leaving them alone to enjoy their meal. I hope that at least some of them make it to adulthood, as they are the larval stage of a really lovely butterfly, the black swallowtail.


I'd mentioned caterpillars on parsley to some folks at work, and they immediately called them monarchs.  But monarch caterpillars don't eat parsley; you'll find them on milkweed plants.

The swallowtail larvae so often feed on parsley, that they are sometimes known as the parsley worm.  They also like carrots, dill, parsnips and fennel. If you want to attract black swallowtails to your garden, just plant lots of things in the carrot family. I had made a point this year of planting about twice as many parsley plants as I wanted for myself, so I'd have enough to share with them.

Photos I've found at several websites show the swallowtail caterpillars at various stages of their lives, and the changes they undergo.  They have five stages, or instars, during the larval stage, each time molting their exoskeleton, and growing larger; until they build a chrysalis (the pupal stage), and then the adult butterfly.

When they first hatch from the egg, they are tiny, mostly black but for a light stripe around the middle, with black spiky hairs. As they progress from the first to the fifth instar, they lose the hairs, and develop a pattern of stripes and dots.

Based on that information, those in the first photo look like fairly young caterpillars, while the larger one in the second photo is much nearer the pupal stage.  They have lots of natural enemies, so their chances of making it to become adult butterflies is pretty slim.  I sure hope some of these reach maturity, as they are truly beautiful butterflies.

The adults feed on nectar from flowers such as phlox, zinnias, red clover, milkweed, and thistle.

Update (8/10/13):  The parsley plant where there had been eight is down to three caterpillars, and the one with 15 is down to one.  There must be some well-fed birds around here!