Length: 8-11 mm
As the common name says, this beetle is found on species of Dogbane, genus Apocynum. The beetle is bright metallic green with red and gold luster. The legs are green to dark greenish black. The antennae dark greenish black to black. The head and pronotum are coarsely and sparsely punctate, while the elytra are finely punctate. No other eastern beetle on Dogbane looks like this one.
Dogbanes are central to the life history of Chrysochus auratus, with the adults’ entire life history played out there. Adults feed and mate on the leaves of Dogbane; the larvae feed on the roots.
Charles E. Williams (1991) observed populations of the Dogbane Leaf Beetle near Blacksburg, Virginia and Oxford, Ohio. He was interested in how this species copes with the milky latex sap of Dogbane, which is noxious and has the potential to gum up the beetle’s mouthparts. The beetles fed at the margins of the Dogbane leaves. They made a 5-7 mm cut for the purpose of allowing the sap to flow out; they then moved "downstream" of the cut to do their feeding. Very little sap flowed out at their feeding sites. The typical beetle did get some of the sap on its mouthparts, but had a behavior for clearing this sap. Williams described how the beetle "pressed its mouthparts to the surface of the leaf on which it had fed, and walked backward, dragging the ventral portion of the mouthparts across the leaf." By walking backwards instead of forward, the beetle avoided getting sap on its legs.
Mate choice seems to be almost entirely up to the males. Matings of each adult beetle average one per day and perhaps fifty over the season. After mating, males engage in mate-guarding by riding on the backs of the females. Thus as Peterson et al. (2005) note, copulation occupies only about twenty minutes, while the two beetles remain together for an average of 1.7 hours.
Insects of West Virginia