Apanteles congregatus (Say) is a common and widely distributed parasite of Sphingidae. In North Carolina it is the most important enemy of the catalpa sphinx, Ceratomia catalpae (Bdv.) and the tomato worm, Protoparce sexta (Johan.), which in this region is usually called the tobacco horn worm. The hornworms increase in numbers rapidly in the late summer in fields where the tobacco stalks are left standing after harvest, and if the foliage is not completely destroyed they will usually remain in the fields until the first killing frost. Hornworm eggs can often be found in the field as late as October 1. The percentage of hornworms parasitized by Apanteles also increases steadily but there is considerable variation between different fields.