Black Swallowtails are pretty butterflies with rows of double spots on their backs and one of the prettiest caterpillars, or larvae, especially right before they begin to grow into a chrysalis.
Females have more blue on their wings and fewer yellow spots, while males are more yellow. (There is not a photo of a female in this post~ I have yet to get a photo of one.) They like open fields and the edges of marsh and forest. Sometimes they annoy gardeners, because the caterpillars gnaw on parsley, fennel, dill, and carrots. Others, like our friends at Wild Birds Unlimited Mount Pleasant, use it as an opportunity to teach their kids about caterpillars and butterflies. They took the video of the caterpillars above.
Identifying Black Swallowtails
We see several swallowtail butterflies regularly out here on the island, and it can be hard to tell them apart. Here is a good website with ways to distinguish all of the swallowtails. One of the most common similar swallowtail on the island is the Palamedes Swallowtail, which is a little larger and browner.
Without carrying a field guide with me, the easiest ways for me to tell them apart is the body: Palamedes has a striped body and the Black Swallowtail has a spotted body. Both can be found nectaring on the same plants, but the Palamedes uses Red Bay for laying eggs, and the Black Swallowtail uses plants in the carrot family.
Palamedes is larger, browner, and spots are fused into a stripe
Giant Swallowtails are much larger with big stripes on back and yellow underneath
Another swallowtail we have on the island is the Giant Swallowtail. Unless you’re really in a hurry and don’t get a good look, these are harder to confuse with a Black or even a Palamedes. First of all, they are much larger. The Black Swallowtail is 3.5″, the Palamedes 4-4.5″ and the Giant is 4.5-5.5″! In addition, the giant has a yellow body, and distinctive stripes on the top, with mostly yellow on the underside of the wings.
While researching this, I learned a bunch about how black swallowtails develop. Like many other butterflies, the young caterpillars are called larvae, and they develop in stages called instars. I found a photographer named Dori Wagner Eldridge (instagram @dorwageld) who had a great photo showing all the instars. I reached out to her, and she sent me to her youtube channel to see some video of the chrysalis/hatching process. Check out this one of a butterfly eclosing, or emerging from the cocoon. You can see how he unfurls and sort of inflates his wings, “zips” his probiscis, and begins to fly around. This is some seriously cool stuff here!!!