Carpenter bees resemble bumblebees in both size and appearance, but are not social insects. They construct their nests in trees or in frame buildings. Most of the top of the abdomen of carpenter bees is without hairs and is shiny black in color. By contrast, the abdomen of bumblebees is fully clothed with hairs, many of them yellow in color.
The male bee is unable to sting. It is the male carpenter bee, which is most often noticed. They hover in the vicinity of the nest and will dart after any other flying insect that ventures into their territory. A common behavior of the males is to approach people if they move quickly or wave a hand in the air. The males may even hover a short distance from people causing unnecessary panic. The female however, is capable of stinging but seldom does. She must be extremely provoked (i.e. handled) before she will sting.
Carpenter bees do not eat wood. They excavate the tunnels for shelter and as chambers in which to rear their young.
They usually attack unpainted objects such as doors, windowsills, roof eaves, shingles, railings, telephone poles, and sometimes wooden lawn furniture.
A carpenter bee begins her nest by drilling a nearly perfectly round entrance hole (about 1/2 inch diameter) into the wood. This hole is usually against the grain of the wood. When the tunnel is about 1 inch deep, the bee turns at right angles to the initial hole and tunnels with the grain of the wood. Bees prefer to attack wood that is greater than two inches thick.
Young adult male and female bees hibernate in the tunnels during the winter. They mate in the spring and set about to clean out and enlarge the old tunnels or to excavate new ones as brood chambers for their young. Each chamber is provisioned with a portion of "bee bread", a mixture of pollen and regurgitated nectar, which serves as food for the larvae. An egg is deposited on the food supply and each chamber is sealed off. There are typically 6 to 8 chambers created by the female. The larvae that hatch from the eggs complete their development and pupate. Newly developed adult carpenter bees emerge in August, feed on nectar and return to the tunnels to over-winter.
Carpenter bees are relatively easy to treat. Locate the wood in which the bees are active and apply an insecticidal dust directly into nest openings. Do not plug the holes immediately! The bees should be able to pass freely through the nest entrance where they will contact the dust and distribute it inside the tunnels.