Carpenter bees resemble large bumblebees, but the top of their abdomen is hairless, causing their abdomens to shine, unlike bumblebees. The females make large (13-mm- (1/2-in.-) diameter) tunnels into unfinished soft wood for nests. They partition the hole into cells; each cell is provided with pollen and nectar for a single egg. Because carpenter bees reuse nesting sites for many years, a nesting tunnel into a structural timber may be extended several feet and have multiple branches. In thin wood, such as siding, the holes may extend the full thickness of the wood. They nest in wood that has been finished with a stain or thin paint film, or light preservative salt treatments, as well as in bare wood.