Development of a hyperparasitoid wasp in different stages of its primary parasitoid and secondary herbivore hosts

Parasitoid wasps are model organisms for exploring constraints on life history and development strategies in arthropods. Koinobiont parasitoids attack hosts that may vary considerably in size at parasitation. Thus far, studies exploring koinobiont development in hosts of different size have been exclusively done with primary parasitoids attacking insect herbivores. However, the larvae of primary koinobiont parasitoids may in turn be attacked by koinobiont hyperparasitoids. We examined development of the gregarious hyperparasitoid Baryscapus galactopus in different stages of its primary parasitoid host, Cotesia glomerata, itself developing in different stages of caterpillars of the cabbage butterfly, Pieris brassicae. This is the first study exploring hyperparasitoid development in different stages of a primary and secondary host. Second instar (L2) larvae of P. brassicae were parasitized by C. glomerata, and separate cohorts of L3 to L5 P. brassicae containing different stages of C. glomerata were then presented to B. galactopus females. B. galactopus was able to parasitize tiny larvae of C. glomerata in L3 caterpillars of P. brassicae, but hyperparasitism efficiency increased in later instars of both C. glomerata and P. brassicae. Development time of B. galactopus was extended in younger C. glomerata/P. brassicae hosts, whereas adult mass was largest when C. glomerata was attacked in L3 through early L5 P. brassicae. Our results show that B. galactopus adjusts its development rate in accordance with the size of both its primary and secondary hosts, in order to ensure survival. Adaptive responses to phylogenetic constraints on the development of primary hyperparasitoids are discussed.

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► Studies development of a hyperparasitoid wasp in differently sized hosts.
► Hyperparasitoid brood sizes did not vary with the different stages of the hosts.
► Hyperparasitoid development time was extended in younger hosts.
► Smallest adult hyperparasitoids emerged from oldest hosts.
► Results contradict most models of host-parasitoid development.