Found on the leaves of cultivated Swamp Milkweed, Asclepias incarnata at night. It was captured and posed. Its behavior was odd. It alternated between spasming onto its back and standing up with elytra outstretched, clearly some sort of threat. It emitted quite a stink as well, surely chemical defenses.

Identification is based on key in Ciegler, Ground Beetles of South Carolina. (1) See other photos for details.