Sexual Competitiveness of 60Co-Irradiated Tobacco Budworm1,2

Abstract

When single male, Heliothis virescens (F.) were irradiated with 15, 22.5, or 30 krad of gamma irradiation and placed with one unirradiated male and one unirradiated female, the irradiated moths were fully competitive based on the percentage egg hatch. Similarly irradiated males exposed to a normal-type population (equal numbers of males and females) or to a population with more unirradiated females than unirradiated males were not fully competitive. These differences in measurements of competitiveness may be influenced by artifacts caused by the test of competitiveness employed. Males irradiated with a dose of 22.5 krad as adults were more competitive than males irradiated with the same dose as pupae when they were exposed to a normal-type population. However, reduction in competitiveness was not more than 32%, even when the pupae and adults were irradiated with 30 krad. Moths irradiated at 15 krad as pupae were more competitive than those similarly irradiated as adults.