The adults are rather large, between a 1/2 – 1 inch in length. They are robust and resemble a bumblebee. The difference is that the carpenter bee has a shiny black abdomen, while the bumblebee has a hairy abdomen with yellow markings. The male carpenter bee can be distinguished from the female by a bright yellow spot on his head.
These big black bees get their name because they excavate galleries in wood for their nesting sites. They do not eat or consume wood. But rather, feed on pollen and nectar. Carpenter bees do not live in colonies and are not considered social insects. Females will nest in a wide variety of woods, but prefer wood that is either weathered or unpainted. The male often act aggressive towards humans and even buzz around us, but since the male does not have a stinger… it is all just for show. The female however, does have a stinger, but rarely uses it.
Carpenter bees will attack structural timbers as well as other wood products such as fence posts, utility poles, firewood, and even lawn furniture. In buildings, carpenter bees nest in bare wood such as in eaves and gables, fascia boards, decks, porch ceilings, wood siding, railings, shutters, shingles, and other weathered wood products. Carpenter bees avoid wood that is well painted or covered with bark.
Their main diet consists of pollen and nectar.
Life Cycle & Reproduction
Carpenter bees are solitary insects that do not form colonies. The life cycle (egg, larva, pupa, adult) is completed in approximately seven weeks, although developmental time may vary depending on the temperature. The new adults typically remain in their gallery for several weeks then chew through the cell partitions and venture outside in August. They collect and store pollen in the existing galleries, but also spend much of their time just huddled together inside a gallery. These new adults hibernate in galleries because they require shelter during the winter.
After overwintering, adults emerge in the spring to mate. The females bore holes into wood to create tunnels to lay their eggs and raise their young. Each year they will either create new tunnels or expand on an old one. After the tunnels are prepared, the female lays an egg on a mass of pollen mixed with nectar. She produces 6 – 8 eggs. The development from egg to adult takes about 36 days. There is one generation per year.
Carpenter bee damage to wood initially is minor, and carpenter bees seldom cause serious structural damage. However, their repeated colonization of the same wood can eventually cause considerable wood damage. Carpenter bees preferentially refurbish and enlarge existing tunnels instead of boring new ones, and a gallery can extend for up to 10 feet if used by many carpenter bees over the years.