Foraging behaviour and resource utilization of the aphid parasitoid, Pauesia pini (Hymenoptera: Aphidiidae) on spruce: Influence of host species and ant attendance

We examined the foraging behaviour of the aphid parasitoid Pauesia pini (Haliday) (Hymenoptera: Aphidiidae) when foraging for Cinara piceicola (Cholodkovsky) or Cinara pilicornis (Hartig) (Hemiptera: Aphididae) on spruce. The foraging success of P. pini females differed for the two host species but depended also on the hosts' morph as well as on the presence of honeydew-collecting workers of Formica polyctena (Hymenoptera: Formicidae). Females found most hosts and laid most eggs when searching for C. picieicola-VI morphs feeding on the stem. There, they succeeded in laying more eggs into ant-attended hosts than into those unattended. C. piceicola sexuparae feeding on two-year-old shoots were less often discovered, and P. pini females did not oviposit into these small morphs, independent of the presence of ants. C. pilicornis, which is not attended by ants, was least often attacked but P. pini females occasionally parasitized this host species.