Multiple inseminations occurred among Culex tarsalis females simultaneously exposed to irradiated males and to unirradiated males that carried the black-eye genetic marker. Two of 38 egg rafts deposited by females simultaneously exposed to the irradiated males and unirradiated males produced individuals with normal-eyes and black-eyes indicating multiple insemination. No mixed hatch egg rafts were obtained when females were exposed 1st to irradiated males and after 3 days to unirradiated males.