Eastern Black Swallowtail Caterpillar
These early instar caterpillars are bird-dropping mimics. They are mostly black, spiky, and have a white saddle around their middle. The white saddle is caused by uric acid deposits that may function as an antioxidant, protecting the larvae from phototoxic chemicals in their host plants. There are usually two broods in the summer, but occasionally a partial third brood will emerge later in the season, which seems to be the case with this caterpillar. It was only 41 degrees Fahrenheit (5 degrees Celsius) when I spotted it.
The Black Swallowtail is a butterfly found throughout much of North America. It is the state butterfly of Oklahoma. An extremely similar-appearing species, "Papilio joanae", occurs in the Ozark Mountains region, but it appears to be closely related to "Papilio machaon", rather than "P. polyxenes".
