125I-Cry1Ac binding to E. insulana BBMV at increasing concentrations of the following unlabeled competitors: Cry1Ab (▪), Cry1Ac (•), Cry1Ba (⧫), Cry1Ia (○), and Cry9C (▾). Data for the competing toxins represent the means of three experiments, and error bars are the standard errors of the means. Data for the noncompeting toxins were replicated twice, and error bars are not shown for clarity.