Forager Load Size Correlations with Colony Size in a Neotropical Wasp, Polybia occidentalis
Moon, Miranda J.
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Polybia occidentalis has proven to be an excellent wasp species to work with in developing a deeper understanding of sociality. A good example of emergent behavior in wasps is nest construction, and today much is known about roles and specialization of workers and how they regulate themselves to meet the changing demands of the colony. As P. occidentalis is a swarm founder, colonies can be observed as they build a new nest. Species-specific colony sizes vary significantly among the Hymenoptera and we ultimately want to know the reason for this variation. It has been found that per capita productivity (eggs, larvae, and pupae per adult female) increases with colony size in P. occidentalis. Various hypotheses have been offered for this phenomenon and are in the process of being investigated. One of these hypotheses was tested in the present study: individual foragers from large colonies bring larger loads back to the nest than do foragers from small colonies. Pulp loads were collected and weighed and nectar loads were measured from colonies of P. occidentalis with sizes ranging from 60 wasps to 2,294 wasps. No correlation was found between pulp load size and colony size, but nectar load size did seem to increase with colony size. Foragers were also collected, dried, and weighed, and a negative relationship was discovered when comparing load size with forager weight for both pulp and nectar. Additional investigations on work rates of nest construction workers and studies of related topics are currently underway and will be valuable in developing a deeper understanding of sociality in wasps and the evolution of sociality in other organisms .