Maize (=corn), Zea mays L., in the central United States is annually attacked by several species of Lepidoptera. Common species that feed on maize silks and kernels are the European corn borer, Ostrinia nubilalis Hübner (Crambidae), corn earworm, Helicoverpa zea Boddie (Noctuidae), and western bean cutworm, Striacosta albicosta (Smith) (Noctuidae). Larvae of each species can cause economic yield losses but rarely does more than one species occur in a maize ear. European corn borers and corn earworms occur throughout the Corn Belt, while the western bean cutworm has only recently expanded it’s range into the eastern Corn Belt. Transgenic maize for control of Lepidopteran pests has been widely planted throughout the central United States, substantially reducing European corn borer populations and possibly the corn earworm. However, the western bean cutworm has substantially increased in numbers and geographical range. In 2000, large western bean cutworm populations (six per ear) were found for the first time in western Iowa, damaging up to 95 percent of maize ears in some fields. By 2006, the western bean cutworm had expanded its range over 1,000 km eastward into Indiana and Ohio. A partial explanation for this species expansion may be a change in intraguild competition between the corn earworms and western bean cutworms resulting from increased transgenic maize plantings. The objective of our study was the measure the potential intraguild competition between corn earworms, European corn borers and western bean cutworms in transgenic and non-transgenic corn hybrids.