I know I have carpenter bees, as they are doing a number on my barn eaves.
However, I have a large New England aster blooming now, which is covered with bees. A couple are the large bees that I am used to seeing as carpenter bees. Most others are small, maybe 1/2" long, but they look like miniature versions of the carpenter bee.
Stupid question: Do carpenter bees come in different sizes? Or do they emerge full size? (Never heard of a bee moulting.) If these are carpenters, I would be wise to knock down the population now. But if they are bumble bees, I definitely do not want to do them any harm, but according to my insect ID book, bumbles have yellow on the abdomen. These are all black. Perhaps a Mining Bee?