Development of hyperparasitoid wasp Lysibia nana (Hymenoptera: Ichneumonidae) in a multitrophic framework

Abstract

Lysibia nana Gravenhorst (Hymenoptera: Ichneumonidae) is a solitary hyperparasitoid that attacks newly cocooned prepupae and pupae of braconid wasps in the subfamily Microgastrinae. One of its preferred hosts is Cotesia glomerata L. (Hymenoptera: Braconidae), a gregarious endoparasitoid of white butterfly caterpillars that feed exclusively on plants producing partly inducible glycoside toxins known as glucosinolates. Here, adult body size, egg-to-adult developmental time, and developmental mortality were compared in L. nana reared from prepupae of C. glomerata (the "primary host") emerging from larvae of Pieris rapae (L.) and Pieris brassicae (L.) (Lepidoptera: Pieridae) that were in turn maintained on two related crucifers, Brassica oleracea L. and Brassica nigra L. (Brassicaceae). Moreover, offspring sex ratio of L. nana reared in the laboratory was compared with that of field populations of C. glomerata reared on P. brassicae. Hyperparasitoids attained larger mass when "originating" from P. brassicae than P. rapae, a pattern that closely reflected host quality for C. glomerata. However, for a given host cocoon mass at parasitism, hyperparasitoid mass was greater on P. brassicae reared from B. oleracea than from B. nigra. Developmental time was more uniform across the different species combinations. Sex ratios in L. nana were higher than in C. glomerata, irrespective of the secondary (herbivore) host. Our results suggest that plant and herbivore quality are important factors affecting the development of L. nana as mediated through the primary parasitoid host. Consequently, both qualitative and quantitative constraints characterize interactions among L. nana and lower trophic levels.