May 31, 2012 —
In May, a friend had quite a few bees flying around his barn; they appeared like bumblebees and frequently could be seen chasing each other around, occasionally meeting in a mid-air grapple. I looked around the upper part of the structure and found a few round holes about the size that a .38 caliber bullet would make. These were not bullet holes; the bees chasing each other were male carpenter bees defending their territory.
Carpenter bees, Xylocopa virginica, resemble bumblebees, except that carpenter bees have shorter yellow hair on the thorax, and the abdomen of the carpenter is shiny and almost hairless. Like bumblebees, carpenter bees feed on nectar and pollen. Their diet does not include wood; the wood boring activity is part of this insect’s breeding cycle.
Female bees construct the chamber by boring into the wood a couple of inches and then making a perpendicular tunnel where they will eventually make six to eight brood chambers. Males are more easily noticed as they buzz around, defending their territory from other bees. Males cannot sting; the females can, but are not overly aggressive, and usually have to be handled before a sting is inflicted.
The damage to wood incurred by a single gallery initially is slight. However, as these bees enlarge galleries in subsequent years, damage can become significant. Insecticidal dust can be applied to the nest openings. Care should be taken when using any insecticide for both you and for any non-target species that may be affected by application of insecticide. A good method for control is outlined by the Penn State Extension Office here at ento.psu.edu/extension/factsheets/carpenter-bees.