Update information. Using the honey bee (Apis mellifera) as a model, we confirmed that honey bee queens actively adjust egg size in response to the number of workers: Queens lay smaller eggs in colonies with more worker bees than when in colonies with few workers. Reduced colony size also causes decreasing ovary weight but upregulation of energy production and protein processing in the ovaries. Complementary metabolomic and proteomic analyses of the produced eggs indicate that amino acid metabolism, cell development, and cell maturation processes are elevated in bigger eggs. Our study thus provides the first mechanistic insights into the adjustment of egg size in the honey bee, a model for complex social systems that demand integration of individual and collective life-history optimization.