Last week I wrote about the larvae of swamp milkweed leaf beetles (Coleoptera: Chrysomelidae: Labidomera clivicollis), and I posted a video of one nibbling on some flower buds. A few days later I revisited the southeast Michigan floodplain forest where they were found, and I came across some adult beetles.
Sticky milkweed sap can gum up mouthparts, but these beetles use a unique approach to get around that problem. They bite into the leaves in several locations, causing the sap to gush out. They then feed in different locations, where the sap then flows out with less force. Their bold coloration also suggests they may acquire toxicity from the plant’s toxins, helping to protect them from predators.