Carpenter bees can attack virtually any wood, including treated lumber, they prefer bare, unpainted softwood. Although they buzz, hover and look like bumble bees, carpenter bees are very much different in appearance and habit. Unlike bumble bees, which have hairy (usually yellow and black) abdomens, carpenter bees have hairless, shiny blue-black abdomens. Also, carpenter bees lack pollen baskets on their hind legs.
Carpenter bees are solitary bees, and although capable of delivering a
sting, female carpenter bees will only sting if prodded and provoked.
Male carpenter bees (which have a menacing habit of buzzing about a person's
head) do not have a stinger and, therefore, are harmless.
Female carpenter bees have strong jaws which they use to bore into, primarily, unfinished wood. Although the damage may appear minimal (all one sees is the 3/8-inch circular opening), the tunnels in the wood may be 6 inches in length.
Damage attributable to the excavating activities of a single carpenter bee is slight. However, the cumulative efforts of several to many carpenter bees can be structurally damaging.
Carpenter bees overwinter as adults. They emerge in the spring (usually April or May) and mate. Fertilized females lay their eggs within newly excavated tunnels or old ones that they have enlarged and reused. An individual egg is deposited in each of 6 to 8 cells off of a main tunnel.. Developing larvae feed off of "bee bread" (pollen and nectar) regurgitated by the female bee. Larvae become adults by late August and September, but do not emerge until the following spring.
Wood can be somewhat protected by preserving it with a solid coat of paint. Wood stains do not afford protection. Also, consider using wood pressure-treated with a preservative for constructing outdoor projects.