Eastern Carpenter Bee - Nesting

Nesting

Female carpenter bees make nests by tunneling into wood. They make an initial hole in an overhang, eaves trough, or similar structure, tunneling upward if the grain is horizontal and sideways if the grain is vertical. Then, they make one or more tunnels at a right angle. The final nest usually resembles a T and can have up to three T-shaped layers. Unlike termites, carpenter bees (also called woodcutters) do not eat wood. They discard the bits of wood, or use them to make partitions (walls) inside the tunnels of their nests. The tunnel functions as a nursery for brood and the pollen/nectar upon which the brood subsists.

Males will visit flowers only to feed themselves, spending the rest of the time hovering in their territory and investigating any movement, or guarding flowers where they might encounter females. Females spend the majority of their time gathering nectar and pollen to provision their nests. They also regurgitate some of the food to male relatives during the mating season, in the males' roosting sites.

Because of their value as pollinators some people allow carpenter bees to stay around the home in the early spring, living with the cosmetic damage caused. In some fruit growing areas carpenter bee populations are encouraged by supplying them with suitable blocks or boards of soft wood.

In the eastern U.S., Xylocopa virginica overwinter as adults inside the same tunnels where they hatched that summer. (Occasionally, when the nest is taken over by a dominant daughter the older female will start a new nest in the late summer and take her son or sons with her.) In spring, they awaken. The males hover around looking for mates. The female enlarges the existing tunnel, or moves nearby and bores a new tunnel. She creates separate partitions in the tunnel out of woven bits of wood fiber. She provisions each section with a paste-like wad of pollen and nectar, lays one egg on it, and seals it off. She makes many of these partitioned cells, as few as 1, often 4 to 6, but sometimes up to 13. The egg hatches into a grub-like larva which eats the pollen mass. It then turns into a pupa, which hatches into an adult bee in mid- to late summer. The newly hatched adults break through the partitions and crawl over each other to escape to the outside world. Usually, they do not then disperse, but continue to live in the tunnel, preparing to hibernate. Thus, the piece of wood is inhabited by bees year-round.

Rarely, active nests in a home can involve considerable damage, but woodpeckers normally are the primary cause of it, as they search out larval bees.

Carpenter bee nests are rather easy to spot. They bore a highly polished hole about 1 cm (about 3/8 in.) in diameter directly up into the bottom a nesting substrate (usually an eave, picnic bench or similar wood structure). The tunnels become larger -- about 1/2 in. -- inside. When the female is boring tunnels, there is a collection of fresh sawdust below the hole. The sound of boring can occasionally be heard, and the sound of a warmth-generating vibration inside the nest can often be heard. One can often see yellowish splashes of fecal material below the entrance.