Division of labor in insect societies has been studied from diverse perspectives, including some rooted in evolutionary biology, ecology, behavior, genetics, developmental biology, endocrinology, and neuroethology. This talk is based on an analysis of division of labor in honey bee colonies that is inspired by chronobiology. Studies of individually marked bees in observation hives revealed that age-related division of labor in honey bees is associated with changes in activity rhythms. Young adult bees perform hive tasks with no daily rhythms, while older bees forage with strong daily rhythms. These differences between young and old bees were found to be related to an ontogeny of behavioral circadian rhythm for locomotor behavior. Bees reared in social isolation under controlled conditions in the laboratory showed no circadian rhythms for locomotor behavior for about the first week of life and then developed robust rhythms. Hive bees and foragers also differ in brain mRNA levels of period, a gene well known for its role in circadian rhythms. The level of period mRNA in the brain oscillated in bees of all ages in circadian fashion but was significantly higher at all times in foragers. Results were obtained from colonies maintained under controlled conditions in the laboratory and under more natural conditions in the field. These results constitute the first report of the regulation of a “clock” gene in a social context and suggest that there are connections at the molecular level between division of labor and chronobiology in social insects.

Index terms: behavioral plasticity; period gene

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