Re: Are these 'carpenter bees'?
- That is Megachile sculpturalis (first two pictures are both females), which we informally named Giant Resin Bee. (Years ago, I was the first one to find them in North America after their importation from Asia by some unknown route.)
GRBs are quite gentle, nothing like their appearance suggests. The males do not sting, and they may hover near the nest, waiting to mate with female nesters. The females do sting, but I have never seen them defend a nest (against a person), rather if disturbed they fly off, usually to return later, a behavior typical of solitary bees. I have worked with GRBs quite a lot, and the only time I have been stung is when I pick up the females. (There are no queens.)
The other responder is correct about them using old carpenter bees holes, a common nest site, but they are versatile nesters and finding other small cavities, using resin as their main nesting material. GRBs do not drill holes in wood - so GRBs are not damaging the wood.
You might get various methods of killing them (I have heard too many of them), even though GRBs are not hurting anyone. Here is my advice. Try to consider them as very small nesting birds, being active for only part of the summer. After the mother bee puts pollen and eggs in the tube, she plugs the nest hole with mouthfuls of tiny bits of trash, like leaves and bark bits, sometimes strung together on spider webs. Watching a female return to her nest loaded with a mouthful a nest material - she even reminds me of a nesting bird. And like a nesting bird, I think it is best to just leave them alone, after all they need a place to live in a crowded world. Hope this helps.
BTW, what is the general location of the nest?
Wyatt A. Mangum, PhD