Small worker bumble bees (Bombus impatiens) are hardier against starvation than their larger sisters
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In bumble bees (Bombus spp.), where workers within the same colony exhibit up to a tenfold difference in mass, labor is divided by body size. Current adaptive explanations for this important life history feature are unsatisfactory. Within the colony, what is the function of the smaller workers? Here, we report on the differential robustness to starvation of small and large worker bumble bees (Bombus impatiens); when nectar is scarce, small workers remain alive significantly longer than larger workers. The presence of small workers, and size variation in general, might act as insurance against times of nectar shortage. These data may provide a novel, adaptive explanation, independent of division of labor, for size polymorphism within the worker caste.
KeywordsPolymorphism Robustness Social insects Bumble bees Bombus impatiens
We thank Jennifer Bonds for her help with data collection and Duncan Jackson and Dan Papaj for comments on the manuscript. This work was funded by a NIH PERT fellowship to MJC through the Center for Insect Science.
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