Twenty populations of Heliothis zea (Boddie) larvae collected from 7 hosts and 11 populations of Heliothis virescens (F.) collected from 6 hosts were treated topically with DDT to determine if host specific strains of these insects exist. DDT was selected as an indicator insecticide because of the known resistance to it as a result of its extensive use in cotton insect control. Larvae for both species in all cases were found to be highly resistant to DDT, indicating that a free exchange of hosts occurs between cotton, the only treated host, and other common host plants in the area.