Carpenter bees bore tunnels into wood to construct a
nest, which they provision with a mixture of pollen and nectar
sculptured into an elongate shape. This acts as a food source for their
developing larvae. A number of partitions (each containing a single
larva) may be constructed within the tunnel, the partitions are made out
of chewed wood.
Reference
Michener, C.D. 2000. The Bees of the World. Johns Hopkins
University Press. 953 pp.