After feeding on Dogbane (Apocynum cannabinum) roots and overwintering underground, larval Dogbane Beetles pupate and emerge in early summer, shortly after the Dogbane plant for which they were named begins to flower. It’s hard to miss these iridescent beetles as they gather to feed on Dogbane leaves (which are poisonous to many creatures, including humans, and can cause cardiac arrest). Soon after the adult beetles emerge from the soil , they mate, usually about once a day, frequently early in the day. Males search for and choose females to mate with. Dogbane beetles often have more than one mate, so after breeding, males ride on the backs of the females to guard them from other suitors (see photo insert).
Dogbane beetles (Chrysochus auratus) appear suddenly, usually when the plant which they consume and for which they are named is flowering. Look on the leaves and blossoms of Dogbane, or Indian Hemp, (Apocynum cannabinum) for this blue-green beetle with a metallic copper and crimson shine to it.
The iridescence is a special type of color that shines and changes as the insect changes position or we change position looking at it. It is produced by special body structures and light. The surface of the body parts of this beetle is made up of stacks of tiny, slanting plates, under which is a pigment. Some light rays reflect from the surface of the plates, and other light rays reflect from the pigment underneath. At different angles, the light reflects at different speeds, causing interference and resulting in our seeing different colors that shine.
Although all parts of this plant are toxic to humans, Dogbane is tolerated by Dogbane Beetles, whose larvae reside underground where they eat the roots of Dogbane. When they mature into adult beetles, they climb up the plant to the leaves and flowers, which they then consume.