Foraging behaviour at the fourth trophic level: a comparative study of host location in aphid hyperparasitoids

Authors

  • R. Buitenhuis,

    Corresponding author
    1. Centre de Recherche en Horticulture, Université Laval, Québec, QC, Canada, G1K 7P4;
      *Correspondence: Rosemarije Buitenhuis, Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, 2585 County Road 20, Harrow, ON, Canada, NOR 1G0. Tel.: +1 519 738 2251 x534; Fax: +1 519 738 2929; E-mail: BuitenhuisR@agr.gc.ca
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  • L.E.M. Vet,

    1. Laboratory of Entomology, Wageningen University, PO Box 8031, 6700 EH Wageningen, The Netherlands;
    2. Netherlands Institute of Ecology (NIOO-KNAW), PO Box 1299, 3600 BG Maarssen, The Netherlands;
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  • G. Boivin,

    1. Centre de Recherche et de Développement en Horticulture, Agriculture et Agri-Food Canada, 430 Blvd Gouin, St-Jean-sur-Richelieu, QC, Canada, J3B 3E6
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  • J. Brodeur

    1. Centre de Recherche en Horticulture, Université Laval, Québec, QC, Canada, G1K 7P4;
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*Correspondence: Rosemarije Buitenhuis, Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada, 2585 County Road 20, Harrow, ON, Canada, NOR 1G0. Tel.: +1 519 738 2251 x534; Fax: +1 519 738 2929; E-mail: BuitenhuisR@agr.gc.ca

Abstract

In studies of foraging behaviour in a multitrophic context, the fourth trophic level has generally been ignored. We used four aphid hyperparasitoid species: Dendrocerus carpenteri (Curtis) (Hymenoptera: Megaspilidae), Asaphes suspensus Walker (Hymenoptera: Pteromalidae), Alloxysta victrix (Westwood) (Hymenoptera: Alloxystidae) and Syrphophagus aphidivorus (Mayr) (Hymenoptera: Encyrtidae), to correlate their response to different cues with their ecological attributes such as host range and host stage. In addition, we compared our results with studies of primary parasitoids on the same plant–herbivore system. First, the olfactory response of females was tested in a Y-tube olfactometer (single choice: plant, aphid, honeydew, parasitised aphid, aphid mummy, or virgin female parasitoid; dual choice: clean plant, plant with aphids, or plant–host complex). Second, their foraging behaviour was described on plants with different stimuli (honeydew, aphids, parasitised aphids, and aphid mummies). The results indicated that olfactory cues are probably not essential cues for hyperparasitoid females. In foraging behaviour on the plant, all species prolonged their total visit time and search time as compared to the control treatment (clean plant). Only A. victrix did not react to the honeydew. Oviposition in mummies prolonged the total visit time because of the long handling time, but the effect of this behaviour on search time could not be determined. No clear correlation between foraging behaviour and host stage or host range was found. In contrast to specialised primary aphid parasitoids that have strong fixed responses to specific kairomones and herbivore-induced synomones, more generalist aphid hyperparasitoids seem to depend less on volatile olfactory stimuli, but show similarities with primary parasitoids in their use of contact cues while searching on a plant.

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