The moth Hypena opulenta (Christoph, 1877) (Lepidoptera: Erebidae) was approved for release in eastern Canada and is pending approval in the United States of America as a biological control agent of the invasive European swallow-worts (Vincetoxicum spp.). Descriptions of the adult in Noctuidae Europeae do not accurately represent the color morph of the rearing colony so a new description is provided. Also for the first time the larva is described and illustrated and a simple key is provided that separates H. opulenta from most of the Hypena spp. in the Northeastern U.S.