Nesting Biology of Xylocopa xinjiangensis (Hymenoptera: Apidae: Xylocopinae).

Xylocopa, an important genus in Hymenoptera: Apidae, is of great significance in research on the early stages of insect social evolution. Most species in this genus burrow into wooden structures. Only the Proxylocopa subgenus nests in the soil. Here, we report the nesting behavior of Xylocopa xinjiangensis (Hymenoptera: Apidae: Xylocopinae), which is distributed only in Western China. During July 2013 and August 2016, we observed the nest architecture and nest building process of X. xinjiangensis. X. xinjiangensis is solitary and nests in the soil walls of gullies, mounds, and cliffs in the Manas area, Xinjiang, multiplying at the rate of one generation a year. Newly emerged females eclose in the fall and build wintering nests first. The next spring, outbound wintering females build breeding nests, although a few wintering females may use the breeding nests built by their mothers. The location and structure of X. xinjiangensis wintering nests are different from those of the breeding nests. The wintering nest is simple in structure, consisting of a tunnel leading perpendicularly from the surface to the interior. The structure of the breeding nest may be either a branching tunnel or a straight-chain tunnel. The first cell that X. xinjiangensis builds in the breeding nest is closest to the entrance, which is a significant difference from the behavior of carpenter bees that construct nests in wood structures. The results of this study lay the foundation for the utilization and protection of X. xinjiangensis resources and facilitate a better understanding of the evolution of the Xylocopa population.