The holes are almost perfectly circular and it is remarkable how the bees are able to cut them out of wood with their jaws. The tunnels enter and then turn at right angles to parallel the edges of planks and can be a potential problem to the strength of the wood if there are enough of them. Although Wikipedia says that the burrows do not pose a threat to wood structures, you may judge for yourself from the photo of some siding with multiple burrows. It seems to be similar in some ways to the threat posed by teredo ship worms (actually a mollusk) to wooden-hulled ships in salt water; one or two is a minimal problem but a large number can indeed threaten the integrity of the wood.
Male carpenter bees have a whitish face, tend to hover close in front of you, but lack a stinger and are harmless. Females do have a stinger but are docile unless bothered. Males have larger eyes than females because of their mating behavior.
So do we tolerate these bees that can be a nuisance or exterminate them? This is an interesting conundrum that can often arise in dealing with animals that like to live around human habitation. Since many of our rather primitive sheds and barns are not really threatened by carpenter bees, I can afford to take a "live and let live attitude" and enjoy observing their antics.
For comparison I am attaching a photo of a bumblebee nectaring and obtaining pollen from a false indigo flower spike in our yard. The flowers have been unusually prolific this year perhaps due to heavy rainfall and the lack of killing frosts when the buds were forming. Note the hairy abdomen of the bumblebee (not always so easy to see beneath the folded wings), the huge amount of orange pollen stored on the hind legs, and the abundant grains of pollen scattered all over the legs, wings and body. Clearly this bumblebee is a pollinating machine! Indeed the entire story of how bumblebees operate in cool climates to forage, collect and store food is fascinating. For more information see a book by B. Heinrich entitled "Bumblebee Economics."
Bill Dunson, Galax,
VA & Englewood, FL