Protandry in the parasitoid Cardiochiles nigriceps , as related to its mating system

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. The experiment also showed that 1‐ to 5‐day‐old males are more successful than 1‐hr‐old males in mating with 0‐ to 1‐hr‐old females. Thus, it is argued that males emerging on a given day have a disadvantage in competition for mates with males that emerged days earlier, and that this disadvantage may serve as a selection pressure toward diurnal protandry. A monogamous mating system for females of C. nigriceps is suggested because sexual selection would be expected to be strong in species exhibiting both seasonal and diurnal protandry. A possibility of a sibling mating system in C. nigriceps is questioned partly because newly emerged females are unreceptive to males that emerged 1 hr earlier and partly because this parasitoid is solitary in what is considered highly dispersed hosts in the field.