Superparasitism and its effects on the fitness of the larval parasitoid, Coccygidium luteum (Hymenoptera: Braconidae)

The tendency of parasitoid wasps to oviposit in a previously parasitised host (superparasitism) has long been considered detrimental to their fitness, until recent evidence showed that it may be an adaptive strategy. The solitary koinobiont parasitoid, Coccygidium luteum, was observed to superparasitise the fall armyworm, Spodoptera frugiperda, under laboratory conditions. This study was conducted to elucidate the oviposition choice between unparasitised and previously parasitised hosts by C. luteum and to determine the effect of superparasitism on progeny development and adult fitness, using fall armyworm larvae as hosts. In a choice assay, previously parasitised and unparasitised hosts were simultaneously exposed to C. luteum for oviposition. Oviposition duration and preference were observed and the influence of superparasitism on the development of immature parasitoids and adult fitness were investigated by exposing host larvae to single, double and triple parasitism at 1 h intervals. Coccygidium luteum readily attacked both unparasitised and previously parasitised hosts without discrimination. However, the time spent ovipositing on the unparasitised host was significantly longer than that on a previously parasitised host. Superparasitism did not significantly affect progeny development and the fitness of adult C. luteum. Offspring development time and size of adult parasitoids were similar in superparasitised hosts compared to hosts that were parasitised once. We conclude that superparasitism in C. luteum will have no effect on its mass rearing for the biological control of S. frugiperda.