In bumblebees (Bombus spp.), a diploid egg is bipotent: it can develop into either a worker or a gyne (new queen) depending on the environment experienced during larval growth. Environmental factors affecting caste determination in some species of bumblebees include larval nutrition and queen dominance, either through direct contact with developing larvae or through antagonistic behavior towards workers attending those larvae. However, factors affecting caste determination in Bombus impatiens, a common North American species, have not been examined. Therefore, we studied the effects of worker to larva ratio (high or low), queen dominance (high or low), and queen contact with developing larvae (with or without contact) on caste determination in this species. Using a complete factorial design, we tested three replicates of each of the eight treatment combinations. We measured the effect of each treatment by recording the proportion of gynes that emerged from four focal brood clusters in each of the 24 colonies. We discuss the relative influence of each factor in relation to colony development, caste determination, and the evolution of sociality.
Species 1: Hymenoptera Apidae Bombus impatiens
Keywords: caste determination, social insects
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