Honeybee colony integration: worker-worker interactions mediate hormonally regulated plasticity in division of labor.

Adult workers in honeybee (Apis mellifera) colonies exhibit plasticity in hormonally regulated, age-based division of labor by altering their pattern of behavioral development in response to changes in colony conditions. One form of this plasticity is precocious development: levels of juvenile hormone increase prematurely and bees begin foraging as much as 2 weeks earlier than average. We used two experimental paradigms inspired by developmental biology to study how bees obtain information on changing colony needs that results in precocious foraging. An analog of "cell culture," with bees reared outside of colonies in different sized groups, revealed that worker-worker interactions exert quantitative effects on endocrine and behavioral development. "Transplants" of older bees to colonies otherwise lacking foragers demonstrated that worker-worker interactions also affect behavioral development in whole colonies. These results provide insights to a long-standing problem in the biology of social insects and further highlight similarities in the integration of activity that exist between individuals in insect colonies and cells in metazoans.