Patch exploitation behaviour by a parasitoid of a forest pest: The influence of host cues and intra- and interspecific interactions

Abstract

1. For parasitoids, host foraging is the most significant activity for their reproductivesuccess, as it directly translates into offspring production. Therefore, foragingbehaviour and patch-use decisions by parasitoids still attract research interest,especially when the studied species are biological control agents.2. In laboratory conditions, we studied the patch exploitation behaviour of Megarhyssanortoni (Hymenoptera: Ichneumonidae), a larval–pupal parasitoid of several wood-wasps (Hymenoptera: Siricidae), exposed to intra- and interspecific interactions.3. It is known that M. nortoni females are attracted to the symbiotic fungus carried byits hosts, which support host larval development inside the wood. Additionally, inthe introduced range where the species has been released in biocontrol programsaimed at managing invasive Sirex noctilio populations, Megarhyssa nortoni coexistswith the egg–larval parasitoid Ibalia leucospoides.4. First, we investigated whether host–fungal symbiont cues and direct presence ofconspecific females affected patch time allocation and oviposition behaviour ofM. nortoni, as both stimuli could provide information on concealed hosts. Second,we studied the influence of prior parasitism by I. leucospoides on patch time alloca-tion decisions and oviposition behaviour.5. The main results showed that females modulated their responses to the fungal cueswhen foraging simultaneously with conspecifics. Also, patch-leaving tendencies andpatch residence times were not affected when females foraged patches previouslyexploited by I. leucospoides; indeed, they probed these patches more frequently.6. Our study contributes to the understanding of patch-use decisions made by parasit-oids and their impact on the biological control of damaging insect populations, par-ticularly in a context of two parasitoid species and one host.