Unlike other bees that live in colonies, carpenter bees are mainly solitary. They are pollinators, foraging for pollen to feed to their young. While some species prefer to build their nests in natural structures such as trees, others will target man-made structures such as decking, fencing, and siding, which can become an issue for home and business owners.
Female carpenter bees make their nests by boring holes into wood. A nest entrance will exhibit a perfectly round hole and a small pile of sawdust. Valley carpenter bees prefer partly deceased oak, eucalyptus, and other hardwoods. California carpenter bees favor more aromatic dwellings, including incense cedars and redwood trees. Mountain carpenter bees have been known to nest in wood decks, eaves, fascia boards, doors, railings, window trim, and other wooden surfaces—even painted and sealed woods. They are persistent and don’t seem to mind either way.
In the spring, females will search for nests left by earlier generations or excavate new ones, preferably in soft, untreated wood. The tunnels they excavate provide shelter for their eggs, and larvae and may include several brood chambers. A new generation of adults will emerge in late summer.