Biologically active substances mediating caste differentiation and social organization of bumble bee societies

Insects such as bees provide excellent model systems with which to study the organization and evolution of complex societies. We propose to study annual bumble bees in which larvae with close contact to a queen differentiate into workers, pupate at an earlier age, and are commonly smaller than siblings that do not contact a queen. We propose to test the hypothesis that the queen can affect larval growth and development by feeding her female offspring substances she produces in her head glands. To thoroughly test this hypothesis, we will use state of the art methodologies to identify chemicals, proteins, and small RNA molecules that differ in abundance in the regurgitates and head glands of queens and workers. We will next test the influence of queens without (surgically removed) or with supplementation of focal head glands (by adding gland extracts) on larval development. Based on the findings of these experiments and the known functions of key substances we identified, we will synthesize and feed the most promising candidate substances to larvae and test their influence on development. We expect to identify substances mediating two key organization principles of insect societies: caste determination, and division of labor, which in bumble bees relates to body size. This project will be important for basic research by providing new insights into the evolution of sociality, insect development, and communication, and for applied research given bumble bees are key pollinators in agricultural and natural ecosystems.