Carpenter bees: Females 'boring' in real sense

Shiloh Church, behind which a trench was dug for a mass grave of rebel soldiers, was the local landmark for which the battle was named. The rough-hewn log structure still stands.

I stood silently near the lectern of the weathered backwoods church, but there was a buzz about the place. A carpenter bee flew by my face and entered a round hole it was boring in one of the beams of the rustic structure. Bits of oak cuttings trickled out of the hole, dusting the crude floor.

History be damned, there was nesting to be done.

I have no hallowed ground nor structures listed on any historic register, but I have trouble enough just keeping carpenter bees from chewing down my garage. The fat buzzing bugs don’t terrorize me like they do some folks who misunderstand them, but their ability to weaken wood framing with incessant boring is a concern.

Carpenter bees are solitary nesting bees that resemble bumble bees. The latter differ in that they are social insects, nesting in colonies. Dozens, even hundreds of bumble bees may abide together in a nest colony, usually in a hole in the ground.

On the other hand, a female carpenter bee staffs her nest all by herself. She does so in a tunnel bored into wood, the behavior that earns the bugs their common name.

A black and yellow carpenter bee is about one inch long, although most people, especially those intimidated by them, swear they are larger.

The bumble bee is about the same size, perhaps a tiny bit smaller, and has black and yellow coloration in common. Especially when one of the two species is in flight, it is easy to confuse one for the other.

There is a key to identification, however. It is easiest seen in the insect’s abdomen, what appears to be its rotund rump. The carpenter bee’s fat backsides are black and shiny; the bumble bee’s abdomen appears fuzzy and yellow to cream-colored because of hairy growth on it.

Nowadays, carpenter bees are nesting, boring into wood, making round, half-inch diameter tunnels that serve as nest chambers. They prefer bare wood in which to bore, which is why they are drawn to unpainted studs or siding inside garages, sheds, barns and such.

A nest tunnel or two isn’t a big deal, but repeated boring over time can weaken wood frame buildings. This proves troublesome and makes enemies of human property owners.

Creating a typical nest, a female bores six to 10 inches into the wood, often adding side branches of tunnels. In each branch, the lady carpenter bee deposits a small food ball of eaten and regurgitated plant nectar and pollen upon which she lays a single egg.

Each food/egg deposit is made in a cell that the bee forms by closing off a section of tunnel with a wall made of chewed wood — typically shavings that were created when she bored the tunnel in the first place. She creates a line of a few egg-housing cells in each tunnel branch.

While a female is tunneling, laying eggs and building cells, often a male carpenter bee will hover nearby the tunnel entrance to fend off other insects, you or me.

Male carpenter bees are aggressive and will get right in your face and menace you. But it is all a show because males don’t have venom nor the stingers to deliver it. They cannot hurt you.

It’s difficult to tell males and females apart, but any carpenter bee that seems to get after you almost certainly is a male. A threatening male bees usually has a patch of white or yellow on its face. The female has a solid black face, but the girl bees are docile and spend no time guarding the nest, so you seldom see those.

Female carpenter bees do have stingers and potentially can inflict a painful sting. However, people who have been stung by them seem few. A female typically won’t sting unless she is taken in hand.

Females die shortly after their tunneling and nesting in spring and early summer. Through mid-summer, the males are most of the bee presence seen. New carpenter bees hatch about August, cut their way out of cell chambers and emerge to feed on plant nectar and pollen.

At summer’s end, young bees hibernate in the woody tunnels. When they become active next spring, one or more females typically return to the same hole to nest.

To eliminate females in their tunnels, the experts recommend puffing an insecticide powder into the hole. Allow a couple of days for the bee to track the insecticide deep into the chamber, where it will kill the new bees, too.

After the insecticide has had a chance to work on the bees inside, seal the tunnel with caulking or wood putty or drive in a wooden dowel.

The best way to discourage further boring is to paint the bare wood surfaces.