These characteristics make endocrine systems good candidates for accounting for extensive evolutionary novelties such as those associated with the evolution of animal societies. Consistent with this premise, there is evidence implicating hormones in the regulation of processes such as caste differentiation and division of labor that are pivotal for the organization of insect societies. Bees provide an excellent model system for studying hormonal aspects of the evolution of sociality because phylogenetically related species show diverse forms of social living and the endocrine system of bees is better studied than that of other social insects. While most bee species are solitary, there are also many social species that exhibit diverse levels of social complexity, from small groups consisting of only a handful of individuals, to the perennial societies of honey bees and stingless bees with their complex communication systems, morphological caste system, and intricate division of labor among workers. The best-studied endocrine signal in the context of social organization is juvenile hormone. JH regulates important functions in diverse developmental and physiological processes in insects. In adult insects it typically functions as a gonadotropin that in females is best manifested in the regulation of oocyte development. One of the pivotal roles of JH is regulating the production of the yolk protein Vitellogenin in the fat body and its accumulation in the developing oocyte. This JH-Vg-oogenesis model has been supported by studies on many, but not all, insect species studied to date. One of the well-studied exceptions for this model is the honey bee Apis mellifera in which both the highly fecund queen and egg-laying workers have low levels of JH and high levels of Vg. Queens in which the corpora allata glands, the only known source of JH in insects, were surgically removed still lay eggs at a rate comparable to control queens. In contrast to the positive correlation in most insects, in the honey bee JH and Vg levels are negatively correlated and there is evidence for a dual repressor model in which JH downregulates Vg expression and Vg suppresses JH levels. In worker honey bees JH and Vg have important non-reproductive functions, including a pivotal role in the regulation of age-related division of labor. Young worker bees that carry out in-nest tasks such as brood care have low levels of JH and high levels of Vg, whereas older workers typically perform foraging activities with high levels of JH and low levels of Vg. Manipulations of JH levels by allatectomy or treatments with JH or its analogs delayed or HhAntag691 customer reviews accelerated the time of transition from in-nest to foraging activities, respectively. Taken together the studies with honey bees are consistent with the premise that in this species JH has lost its gonadotrophic function during the adult stage and instead is involved in the regulation of age-related division of labor. These striking differences in JH function between solitary insects and the highly social honey, and the influence of JH on the division of labor lead to the hypothesis that modifications in JH signaling.