I thought the bee was attacking me. As I dashed out of our garage it suddenly hovered before my face seemingly challenging me. It looked like a bumblebee and what caught my eye was the white face. It soon moved away, but after a few trips I realized that every time I walked from the garage to the house, he was there to greet me.
I quickly found out that this is common behavior of male carpenter bees as they protect and patrol their small territories looking for intruders or mates. There’s no reason to be alarmed; males don’t sting. Only the dark-faced females can muster a sting and usually only if handled, something only an entomologist would do. Male territories usually encompass about 60 feet around the nest site or food-plant area. Despite having larger eyes than females, they will chase any interloper that comes near – birds, flying insects, people, and even towards the occasional airplane high in the sky.
There are hundreds of species of native bees in eastern North America, but there are only two species of carpenter bees – Southern Carpenter Bee (Xylocopa micans) found in the Southeast and the Eastern Carpenter Bee (Xylocopa virginica) from New England southward.
They’re fairly easy to identify. At first blush they look like large bumblebees, but if you look more closely you’ll notice that they have shiny, black and mostly hairless abdomens. Peer even closer and you’ll see their massive and sharp galea hanging down from their mouth. These are used to chew their way through wood, giving them their namesake.
Carpenter bees don’t eat wood. They just chew through it to create tunnels for nesting and resting in dead trees or branches, log, or unfinished wood on structures. They prefer softwoods like pine, fir or cedar, which are easier to excavate and have straighter grain. With their sharp galea, females chew a round entrance hole about a half-inch in diameter. It can take up to two days to chew across the wood grain. Once the tunnel is about the length of their body, they turn ninety degrees and excavate more quickly with the grain. If they come to a knot, the tunnel may go around it. Some nests have two or more tunnels that parallel the main hall, each over a foot long. They can use the same nest site year after year perhaps by just adding a new tunnel or lengthening one. One colony was used for 14 years.
Carpenter bees are solitary bees. Unlike bumble bees there are no queens or workers, just individual males and females. Newly hatched females may live together in their nest with their mother during their first year. But each female will have its own nest and brood.
At the end of a tunnel the female lays a huge egg on a loaf of pollen the size of a kidney bean. At just over a half inch it’s one of the largest insect eggs in the world. When it hatches the grub will feed on the pollen as it grows. The female chews the surrounding wood into a pulp to create a cardboard like partition that seals the egg within its own cell. Each tunnel can have up to eight cells.
Here’s what gets them in trouble. Carpenter bees can create nests in fences, outdoor furniture, and buildings. They select bare wood on roof eaves, fascia boards, porch ceilings, decks, railings, siding, shutters and other weathered and bare wood. They will seldom if ever bore into painted or varnished wood. Which makes their often minor damage both avoidable and solvable.
It takes years for carpenter bees to cause significant structural damage. You can minimize their damage by filling and sealing nest holes in the fall or winter with a small dowel or caulk. Filling them in the spring or summer will just cause them to make a new entrance hole. You can also provide alternative nesting sites in untreated cedar boards, their favorite wood.
Why not just eradicate them? From spring lupines to late summer goldenrods, carpenter bees are pollinators of plants representing 19 different families. Like most bees, they enter the opening of a flower and reach in with their glossa, like a long tubular tongue, to suck nectar. They also gather pollen to carry away on their bristled-covered rear legs.
Carpenter bees are also cheaters. If the flower is too small or too long for them to reach with their relatively short glossa, they simply rob them. After crawling up the flower they stab the base of the flower with their galea and gain access to the nectar. Sometimes other bees will feed at these holes later too. The flower loses the nectar it uses to entice insects to visit without being pollinated as the stamen and anthers are bypassed by the thieves.
Over the last decade carpenter bees have been moving farther and farther northward. Keep watch for the hovering male signaling his territory around you.