containing groups of two to five females, or solitary. Social nests are more common, despite the fact that brood productivity is actually lower when females choose to nest together. Because X. virginica builds its nests in wood structures, it is common for it to nest in constructed furniture or buildings. X. virginica is the most common large carpenter bee in eastern North America, and it nests in small groups, so nests are fairly commonly encountered. The nests are usually round and typically have one to four tunnels. They have multiple branches, with each adult female living and laying eggs in a separate branch but females sharing one common entrance. Because the nests are costly to build, it is common for females to reuse old nests. Life cycle In X. virginica, mating occurs only once a year, in the spring. Eggs are laid in July, starting farthest from the exit hole, and by about August and mid-September, larval development has completed and all the pupae have become adults. Researchers suggest that there is a mechanism that synchronizes the emergence time of young that are laid at different times by causing the younger eggs to develop faster. This mechanism prevents bees that would emerge sooner from removing their siblings and decreasing their potential competition. Bees that have newly emerged have a soft cuticle and white wings. The wings later transition to brown, then to a bluish black. They can fly 3–4 days after emergence, but they remain in their nest for at least two weeks, consuming nectar but not pollen. The juveniles begin the next mating cycle the following spring, so one generation develops in a year. Females begin to exhibit signs of senescence around July. The indicative behavior includes resting in flowers, remaining in the nest, or even just falling to the ground from flight. Older individuals also crawl, avoid taking flight, and do not struggle when handled by humans. The old bees die by early August, the same time that juveniles emerge from brood cells. Due to the simultaneous nature of expiration of old bees and emergence of new ones, there is little overlap between generations, except for some females that survive a second winter. Behavior X. virginica is not a solitary bee species, but it is not truly social either. The weak form of sociality they exhibit, with one female doing the majority of the work and caring for