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Carpenter bees (Xylocopa sp.) are very large, wood boring bees that become active in early spring. They range in size from 0.75 of an inch (1.9 cm) to 1 inch (2.5 cm) long and are about 0.5 inch (1.3 cm) in diameter. These bees have a yellow thorax and a black, shiny abdomen. They are often confused with their close relative the bumble bee; however, bumble bees have a fuzzy rather than a smooth abdomen.
In some areas, carpenter bees can become a problem, as they like to nest in houses or other domestic structures made of wood. Very adept drillers, the female bees quickly bore holes in wood siding, eaves and decks to lay their eggs. Nest sites are marked by very noticeable sawdust accumulation below their holes. The holes may appear to be superficial at about 1 to 2 inches (2.5 to 5 cm) deep, but from this point, female bees make a 90° turn and burrow downward up to 4 feet (1.2 m).
Once the nest has been excavated, the female deposits her eggs and stuffs the hole with pollen for her offspring to eat when they hatch. Laying only one egg per nest, female carpenter bees may bore many different holes in close proximity to one another, which may exacerbate problems for homeowners.
Unlike most bee species, carpenter bees only travel in mating pairs. While the female is drilling her nest, the male acts as a guard. Males hover around the potential nest site, buzzing loudly and aggressively chasing any insects or other animals that come near.
Due to their size, male bees may seem very threatening, but they are in fact quite harmless because they do not have a stinger. Females do have a stinger and the ability to sting, but they are by nature very docile; she will only sting if she is handled or abused. Male bees attempt to scare people away, but when left alone they simply resume hovering around their nest. Carpenter bees are mostly concerned with predatory insects and usually ignore people and pets.
Carpenter bees are profuse pollinators and are therefore an important part of the ecosystem. Unless they are damaging one's home, they are not a threat to people. While they prefer raw wood over painted or stained wood, painting or staining won't necessarily make a home immune from attack. Commercial pesticides labeled for wasps and hornets also work to kill these bees when necessary. Perhaps the best method for prevention is treating the problem at its source, the nest, if possible.