ARTHROPOD MUSEUM NOTES
Number 34 • June 1, 2005 • Jeffrey K. Barnes
Genus and species: Xylocopa virginica (Linnaeus)
Carpenter bees cause alarm because they are large insects – up to about an inch long – resembling bumble bees, the territorial males harass humans and other animals that enter their terrain, and they are often found boring holes in structural timbers, such as rafters and fascia boards. The males lack a stinger, but females have been known to deliver potent stings.
Carpenter bees are black, and they have yellow hairs on the thorax and first abdominal segment. Adults differ from bumble bees in that they are not social, the upper surface of the abdomen in mostly devoid of hairs, and the females have a brush of hairs on the hind leg instead of a pollen basket. Male carpenter bees have white faces, but females have dark faces. This species occurs from New England and nearby Canada south to Florida and west to Nebraska, Kansas, Oklahoma, and east Texas. It is common in Arkansas.
Carpenter bees nest in tunnels in sound wood of dead trees and in structural timbers. They use both soft and hard woods, but they seem to prefer pines. They rarely cause significant damage. Both sexes pass the winter in old nest tunnels. They emerge in spring and mate. Females either use old tunnels or build new ones in solid wood. They partition the tunnel into several cells. The nesting gallery can be excavated in either a vertical or horizontal plane. Galleries average less than half a foot in length, but they can extend for up to 10 feet. The female simply excavates the wood with her mandibles. She does not eat the wood. One bee can excavate a one inch tunnel in 6 days. Entry holes are circular and about half an inch in diameter.
Adult bees take pollen and nectar from a wide variety of native and introduced plant species. The female furnishes each cell in her nest with a mixture of pollen and regurgitated nectar and lays an egg on top of it. She then seals the cell with a partition made from chewed wood pulp. A new generation of adult bees emerges in late summer.
Although carpenter bees attack fence posts, utility poles, lawn furniture and structural timbers, they do not usually cause serious structural damage, unless large numbers of bees use and lengthen the same tunnels over a period of years. Carpenter bee infestations are often first detected by finding large amounts of sawdust in the area of the excavation. Control can be difficult. If only a few bees are present, it is probably best to simply swat or capture them, treat the tunnels with insecticide or insert a wire probe to kill the larvae or pupae, and plug the tunnel entrances so they cannot be used by other bees. Painting or treating wood can discourage attack by carpenter bees.