A laboratory study was conducted of the emergence times and mating success of Cardiochiles nigriceps Viereck (Hymenoptera: Braconidae), a larval parasitoid of the tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), and in view of this information, the parasitoid's mating system was explored. Observations on laboratory populations of C. nigriceps confirmed the occurrence of two types of protandry, i.e. seasonal and diurnal; males emerged 2 days before females in a generation, and emerged about 1 hr before females on a given day. An experiment on mating success showed that newly emerged females are not receptive to males that emerged 1 hr earlier, but that these males and females often mate successfully after 1 more hr.