Carpenter bees are large, solitary insects belonging to the genus Xylocopa. They are among the largest native bees in many regions, typically found near wooden structures during the spring and summer months. Their common name is highly descriptive of their unique activity.
The Reason They Are Called Carpenter Bees
The common name “carpenter bee” is a direct reference to their nesting behavior: excavating tunnels in wood to create a secure nursery for their young. The scientific genus name, Xylocopa, literally translates to “wood-cutter.” Female carpenter bees use their mandibles to chew through wood fibers, creating a tunnel system that functions as a gallery.
Unlike termites, carpenter bees do not consume the wood; they discard the shavings, which appear as coarse sawdust, known as frass, below the entrance hole. The tunnels are provisioned with “bee bread” (a mixture of pollen and nectar) which serves as the food source for the developing larvae. The female then seals each brood cell with a partition made from chewed wood pulp and saliva before laying a single egg.
Visual Identification of Carpenter Bees
Distinguishing a carpenter bee from other large, fuzzy bees, especially the similar-looking bumblebee, relies on the abdomen. Carpenter bees have a large, smooth, and shiny black abdomen that appears almost polished or metallic, with very few hairs. The thorax is typically covered in yellow or golden fuzz, but the bare abdomen is the most reliable visual cue.
Bumblebees, by contrast, are covered in dense, fuzzy hair from head to tail, including their abdomens, giving them a rounder appearance. Adult carpenter bees typically measure between 0.5 to 1 inch in length. Males often have a distinctive white or yellow patch on the face, while the female’s face is entirely black. Only the female possesses a stinger, but she rarely stings unless handled.
Nesting Behavior and Structural Effects
The nesting process begins when a female chews a perfectly circular entrance hole, roughly the diameter of a finger, into a wooden surface. This hole extends one to two inches deep before turning at a right angle, following the wood grain to create the long gallery. Galleries may extend six to twelve inches initially, and are often lengthened and reused year after year.
Carpenter bees strongly prefer unpainted, untreated, or weathered wood, often choosing softer varieties such as pine, cedar, or redwood. Common targets include fascia boards, eaves, deck railings, and siding. While a single tunnel usually does not compromise a structure, repeated infestations or the expansion of tunnels over several years can weaken the wood.
The damage is compounded by secondary issues. The presence of larvae attracts woodpeckers, which drill into the wood to feed on the developing bees. Homeowners may also notice yellowish-brown waste stains near the entrance hole, which are excretions from the female bee during excavation. The most serious consequence of the holes is the potential for moisture intrusion, leading to wood rot and decay.