Promotes colloidosmotic lysis by binding to the midgut epithelial cells of Lepidoptera larvae. Has a fairly broad spectrum of activity against members of the Pyralidae, Plutellidae, Sphingidae and Noctuidae families. It was the first insecticidal crystal protein characterized with activity against cutworms. No activity is observed against some beetles, such as the Colorado potato beetle. The crystal protein is produced during sporulation and is accumulated both as an inclusion and as part of the spore coat. Toxic segment of the protein is located in the N-terminus. Belongs to the delta endotoxin family.