Wood Boring Wasps (Carpenter Bees)

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Carpenter bees do not consume wood, but they excavate galleries in wood to create nest sites. Homeowners often complain about the round holes in wood. Carpenter bees sometimes become a nuisance outdoors when they hover or fly erratically around people. In actuality, these are male bees, which are territorial but harmless because they lack a stinger. Only females have a stinger. However, females are docile and rarely sting, except if handled. Carpenter bees sometime are bothersome because they are noisy. Nonetheless, carpenter bees are beneficial insects because they are important pollinators of flowers and trees.

How to Identify a Carpenter Bee: Carpenter bees are large, 3/4 to 1 inch long, heavy-bodied, black with a metallic sheen. The thorax is covered with bright yellow, orange or white hairs and the upper side of the abdomen is black, shiny, and bare. The female has a black head, and the male has white markings on the head. Carpenter bees have a dense brush of hairs on the hind legs. Carpenter bees somewhat resemble bumble bees, except bumble bees have dense yellow hairs on the abdomen and large pollen baskets on the hind legs.

What is the Carpenter Bees Life Cycle Unlike carpenter ants, which are social insects, carpenter bees are solitary insects that do not form colonies. The males are not long lived, and the female carpenter bee prepares the nest during springtime. The female uses her strong jaws (mandibles) to excavate a clean-cut, round nest entrance hole that is ~1/2 inch wide, approximately the diameter of her body. She then excavates a gallery (tunnel) that continues inward from the entrance hole for one to two inches then turns sharply at a 90� angle and runs in the same direction as the wood grain for four to six inches. She excavates the gallery at the rate of about one inch in six days. The female then places a mixture of pollen and regurgitated nectar at the far end of an excavated gallery, forms this larval food into a ball and lays an egg on top of the mass, then walls off the cell with a plug of chewed wood pulp. Each female may have six to ten partitioned brood cells in a linear row in one gallery. Larvae feed on the pollen/nectar food mass, which is sufficient food for them to develop to the adult stage. The life cycle (egg, larva, pupa, to adult) is completed in approximately 7 weeks. The new adults chew through the cell partitions and emerge in late August. They collect and store pollen in the existing galleries, return to the tunnels to hibernate, then emerge and mate the following spring (April and early May). The previous year's adults die. There is one generation per year.

What are the Signs of Infestation: Typical indicators of carpenter bee activity in wood include the round entrance hole in wood and the coarse sawdust from their borings. Carpenter bees deposit excrement and pollen on surfaces below their entrance holes, leaving unsightly stains. The entrance hole may not necessarily be in an exposed area. Carpenter bees can nest in all species of dried, seasoned wood, but they prefer softwoods such as cedar, redwood, cypress, pine, and fir. Woods that are soft and that have a straight grain are easy for the bees to tunnel through. Nail holes, exposed saw cuts, and unpainted wood are attractive sites for the bees to start their excavations. These bees may nest in wood trim near roof eaves and gables, fascia boards, porch ceilings, outdoor wooden furniture, decks, railings, arbors, fence posts, telephone poles, siding, shingles, dead tree limbs, and other weathered wood.

Carpenter bee damage to wood initially is minor. However, old galleries may be enlarged by the bees, eventually resulting in considerable wood damage. A gallery can extend for 10 feet if used by many carpenter bees over the years. Carpenter bees may refurbish an existing tunnel instead of boring a new one or they may construct new tunnels near old ones, with infestations persisting for several years. Sometimes several carpenter bees use the same piece of wood. If more than one bee uses the same entrance hole, their tunnels extend in opposite directions or run parallel to each other.