Two species of Xylocopa, carpenter bee or wood-nesting be, can be found in the eastern United States. Xylocopa virginica is found from Maine to Wisconsin and south to Florida and Texas. Xylocopa micans Lepeleter occurs in the southeastern states. Carpenter bees are widespread in their distribution, but are seldom abundant in any given locality.

The adult carpenter bee resembles the common bumble bee. Carpenter bees are large (20 to 30mm), robust, and have a shiny, bluish-black abdomen. Bumble bees, on the other hand, have a hairy abdomen that is mostly yellow.

Adults excavate nests in wood. Softwoods (pine, redwood, fir, cedar, and spruce) are preferred, but they have been seen nesting in hardwoods such as willow and oak. A "nest" consists of a round entrance hole (0.5 inch diameter by 1.5 to 2 inches deep) and a system of tunnels oriented along the wood's grain. Tunnels range in length from a half foot to several feet. The bees cut one half inch per day to open the entrance hole and then move at a faster pace as they cut the tunnels with the grain.

Nests are located in porches, eaves, fascia boards, garages, sheds, carports, fences, window trim, lamp posts, and other wood objects. Nests are most likely to be southern or eastern in aspect and tend to avoid wood that is painted, whitewashed, or covered with bark. The bees continuously clean and enlarge the next. They seem to prefer this to establishing new nests. Therefore, nests ma be used by many generations of bees. Some nests have been known to have been in use for 14 years.

Juvenile (unmated) adults of both sexes overwinter in the tunnels. They become active when temperatures reach the 70s in the spring. Mating, accompanied by a strange "bobbing dance" by the male, occurs in April.

The females prepare a series of brood cells in the tunnels, providing each with food ("bee bread," a mixture of pollen and nectar), an egg, and a partition of chewed wood. Most females produce six to eight young. The larvae develop from May to August, emerging in September. The oldest bee emerges first and must cut through all the partitions and crawl over the other developing bees. There is only one generation per year.

There are two principle concerns about the activities of carpenter bees. One is the possibility of stings. However, this is actually of minor consequence since the females (males can't sting) are very hesitant to sting, and in fact must be held to provoke a sting. In addition, the stings are mild.

The second concern is for wood damage. It is generally more of a cosmetic problem since carpenter bees rarely nest in structural timbers. Damage is most severe in trim and decorative wood on the exterior of a building. Other concerns include stains of excreta, the buzzing flight of the adults, the noise of nest construction, and the attraction of hungry woodpeckers. Carpenter bees are not particularly important as pollinators.

In addition to woodpeckers, there are two species of bee fly (Diptera and Bombyliidae) that are natural enemies of the carpenter bee. The flies deposit their eggs in the entrance of the tunnel and the maggots parasitize the bee larvae.

Carpenter bees are best controlled by injecting carbaryl 5%, ready-to-use diazinon, or contact sprays of pyrethroids in the tunnels. After thoroughly treating, plug the entrance with a dowel of the appropriate size or with wood putty.

It may be helpful to treat the sites used, or most likely to be used, with an insecticide. This should be done in the spring prior to the time when the bees begin nest construction.

Courtesy MSU Extension