Advanced social systems are characterized by a division of labor between members of a social group. The evolution and current regulation of these systems are important questions in biology. By examining the molecular and physiological mechanisms that influence complex behaviors in the highly derived eusocial honey bee, this dissertation gives new insight into the pathways on which selection has acted to produce social phenotypes. A novel approach to the study of social behavior in honey bees that combined gene knockdown and behavioral assays demonstrated that vitellogenin (vg), a gene encoding a yolk precursor protein, influences the social foraging behavior of functionally sterile honey bee workers. Specifically, experimentally decreased vg titers from adult-emergence result in a knockdown phenotype that initiates foraging early and shifts foraging loading to larger nectar loads. Furthermore, this relationship is conditional on the sensitivity of a feedback relationship between vg and a systemic hormone, juvenile hormone (JH). In genotypes with decreased physiological sensitivity to vg titer, vg gene knockdown does not affect worker foraging behavior. The mechanisms by which vg/JH signaling affects behavior appear to be tied to the insulin/insulin-like signaling (IIS) pathway. Honey bees have two insulin-like peptides (ilps). The first, ilp1, is correlated with JH titer in bees with normal vg titers, while the second, ilp2, is correlated with vg levels. Combined with differential spatial expression of the ilps, these results suggest that JH and ilp1 signaling may influence somatic resource allocation, while vg and ilp2 may be signals of nutritional status.

This demonstrates that a gene which likely functioned solely in reproduction in the solitary ancestors of honey bees has evolved novel functions in the regulation of worker social foraging behavior. The combination of functional genomics tools and behavioral assays used in this dissertation promises to unlock new insights into the mechanistic regulation of complex behaviors, deepening our understanding on how selection may have produced social phenotypes.