adults feed exclusively on milkweeds, mostly swamp milkweed but also common milkweed and possibly others, and on the invasive vine black swallowwort. In southwestern United States they also feed on twinevine.
Adults are solitary. They are active during the day. They can fly but only for short distances. When feeding, they cut several veins on the leaf margin to “bleed out” the milky latex that would otherwise make feeding difficult.
After hatching, a larva may cannibalize nearby eggs and smaller larvae.
Like the monarch caterpillar, the beetle larva stores cardiac glycosides, present in all milkweeds, in its body. This makes the larva and the adult poisonous and unpalatable to potential predators.
Eggs are laid on the underside of host plant leaves. The larvae moult four times, drop to the ground, burrow into the soil, and pupate. The last generation of adults overwinter in leaf litter.