Behavioral ontogeny of maternal care in an annually eusocial insect

Understanding how parents balance their time and energy under changing social conditions is a major goal in biological research. Bumble bees are annually eusocial insects in which queens undergo a stark transition from living a solitary, to subsocial, to eusocial lifestyle over the course of several weeks. We examined how performance of five brood care-related tasks differs for bumble bee (Bombus impatiens) queens living either subsocially (with no adult workers) or eusocially (with three or five workers). With three workers in the nest, queens exhibited an approximately 60% reduction in brood feeding and 30% reduction in incubation frequency, relative to subsocial queens. The addition of just two additional workers resulted in a nearly complete cessation of pollen and nectar collection behaviors. Thus, for bumble bee queens, maternal care behavior appears to be tightly regulated by the number of helpers in the nest during the incipient stage of nest development.