is a foundress, which is a gyne that is always mated and starts her own colony after hibernation each cycle. She is considered the foundress queen if she is the one that established the nest, and recruits her daughters to act as workers. A gyne is any female that enters diapause, with the potential to become a nest foundress the following season. Below that is a non-gyne, which is a female who stays in an existing colony and may or may not reproduce. Within these non-gynes, there are some that are considered replacement queens, if they take the place of a dead foundress queen in the colony, but the majority are workers, who forage and maintain the colony. Replacement queens and workers appear to produce mostly male eggs, when they reproduce. Neither replacement queens nor workers enter hibernation, and die at the end of the season. Division of labor In eusocial colonies, there is a division of labor similar to that in other eusocial bees. In these colonies in New York, the first brood is primarily worker females, which in turn help the foundress rear her second brood, and a number of gynes and males. The second brood in New York yields only gynes and males, which breed to repeat the cycle. In Kansas, the first brood is exclusively worker females, and it is not until the second brood that gynes and males begin to appear, while the third brood is exclusively gynes and males. However, in non-eusocial nests within the New York populations, or at high elevation in Colorado, the brood contains only males and gynes. The cooperative breeding behavior of worker bees in eusocial colonies benefits the fitness of the foundress queen. However, in solitary nests, the offspring do not serve as workers and do not help the mother establish a second brood, but rather go off to try to establish nests of their own the following season. There is no evidence for predetermined morphological or physiological differences in caste for H. rubicundus. The differentiation into different castes is based on behavior. Females that do not mate immediately after emergence become workers or replacement queens while the others become gynes. The factor that may dictate whether a female mates is the relative abundance of males to newly emerged females; there is a higher percentage of gynes relative to non-gynes when males are relatively more abundant. This has population-level