Carpenter bees don't endear themselves to people. They excavate nests in wood decks, porches, and homes, and the males exhibit an unsettling aggressiveness. Despite their bad behavior, carpenter bees are quite harmless, and are actually excellent pollinators. Large carpenter bees belong to the genus Xylocopa.
Carpenter bees get their name from their woodworking skills. These solitary bees excavate nest tunnels in wood, especially in lumber that is bare and weathered. Over several years, the damage to wood can become quite extensive, as the bees expand old tunnels and excavate new ones. Carpenter bees often nest in decks, porches, and eaves, putting them in close proximity to people.
Xylocopa bees look quite similar to bumblebees, so it's easy to misidentify them. Look at the upper side of the bee's abdomen to differentiate the two kinds of bees. While bumblebee abdomens are hairy, the top of a carpenter bee's abdomen will be hairless, black, and shiny.
Male carpenter bees will hover around nest entrances, chasing away intruders. They lack a sting, though, so just ignore their buzzing and aggressive flights around your head. Females do sting, but only if seriously provoked. Refrain from swatting at them, and you shouldn't have to worry about carpenter bees causing you harm.
Like honey bees, carpenter bees feed on pollen and nectar. Female bees provision their larvae with food by placing a ball of pollen and regurgitated nectar in the brood cell. Carpenter bees do not feed on wood at any time during their life cycle.
Carpenter bees overwinter as adults, usually within vacant nest tunnels. As the weather warms in spring, the adults emerge and mate. Males die after mating. Females begin excavating new tunnels or expanding tunnels from previous years. She constructs brood cells for her offspring, provisions them with food, and then lays an egg in each chamber.
Eggs hatch within a few days, and the young larvae feed on the cache left by the mother. Within a period of 5-7 weeks, depending on environmental conditions, the bee pupates and reaches adulthood. The new adult generation emerges in late summer to feed on nectar before settling in for the winter.
Special Adaptations and Defenses:
Though they are good pollinators of open-faced flowers, deeper flowers present a challenge for the large carpenter bees. To get to the sweet nectar, they will slit open the side of the flower, breaking into the nectary and robbing the flower of its juices without providing any pollination services in exchange.
Carpenter bees practice buzz pollination, an active method of collecting pollen grains. When it lands on a flower, the bee uses its thoracic muscles to produce sound waves that shake the pollen loose.