her sisters, may be a transitional step in the evolution of sociality. Dominance hierarchy Female X. virginica can have solitary nests, but they usually nest in social groups. The social order of X. virginica is broken into three groups: primary, secondary, and tertiary. Primary females act as the dominant within a nest and are in charge of reproduction, providing food for the larvae, and laying all the eggs. This is different from many bee species in which there is a queen that focuses her energy solely on laying eggs while relying on provisions provide by subordinate bees. Secondary females may sometimes participate in oviposition, and they reinforce this potential role by helping provide for the larvae or performing nest maintenance. Tertiary females rely on the provisions provided by primary females and quietly await overwintering while remaining inactive. Studies have shown that primary females are usually the bees that have overwintered twice, while tertiary bees have only overwintered once. Tertiary bees will most likely survive a second overwintering and develop further to become primary female the following year. Secondary bees may survive a second winter, but that is unlikely if they actively forage after their first overwintering. Division of labor among the sexes Not all females do the same work in a social nest. This is evident based on the varying levels of wear on the wings and mandibles of females of various social standing. Although many nests have more than one female, there is a division of labor between the older and younger females. During nesting time, only the older females are responsible for nesting duties such as digging, excavating the cells, lining the cells, collecting food, and ovipositing. Evidence of this activity can be found in their worn mandibles. Young females rarely leave the nest and guard the entrance while the older females work, resulting in unworn wings and mandibles in the younger females. Additionally, X. virginica is the only known species in which one-year-old females cohabit the nest with two-year-old females that do all the labor. Males often spend long periods of time hovering, flying, or in fast pursuit of intruders, while female flight activity is usually very directed, such as flights to flowers and food sites. Larger females have an advantage because they can carry larger amounts of pollen or nectar back to the nest and can fly longer distances. Diet X. virginica survive mostly on nectar