Reversal of apparent feeding preferences of bumble bees by aggression from Vespula wasps

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Abstract
In field experiments, the nectar and pollen levels of Aralia hispida inflorescences were independently manipulated. In the absence of Vespula spp., Bombus spp. workers (the primary pollinators) appeared to prefer nectar-enriched inflorescences, learning their locations and visiting them at a higher rate, but did not respond to variation in pollen. In the presence of Vespula, however, Bombus appeared to prefer inflorescences with more pollen, showing no response to nectar variation. Vespula responded strongly to nectar level, aggressively patrolling the nectar-enriched plants and preventing Bombus from feeding.