Comparing and contrasting life history and development strategies in the pupal hyperparasitoids Lysibia nana and Gelis agilis (Hymenoptera: Ichneumonidae)

Abstract

Since the concept of the ‘niche’ was proposed by Hutchinson almost 50 years ago, many researchers have investigated factors that enable species within ‘guilds’ (i.e., species that exploit a common resource and are likely to compete with one another) to co-exist and to persist. Here, development, host utilization, and life-history characteristics are compared in two species of solitary secondary hyperparasitoids, Lysibia nana and Gelis agilis, attacking pre-pupae of their primary parasitoid host, Cotesia glomerata. More than 80% of the host cocoons presented to L. nana successfully produced adult hyperparasitoids compared with only about 20% for G. agilis. Adult hyperparasitoid body mass increased with host mass, but there was little difference in the mean overall body mass of either species. However, egg-to-adult development time for L. nana was significantly less than that for G. agilis. When provided with unlimited food (honey solution), G. agilis had a lifespan that was almost twice that of L. nana. However, dissections of the ovaries of adult wasps at death revealed that L. nana usually had accumulated more than 20 mature eggs, whereas G. agilis was effectively sterile. We suggest that several eco-physiological factors, as well as differing degrees of specialization amongst the guild of secondary hyperparasitoids attacking C. glomerata cocoons, enable them to successfully co-exist in nature.