I looked at the pictures, and the mason bees don't look like what I'm seeing. I think we've got carpenter bees--they look more like this, and they do leave small, perfectly round holes. I can actually hear them munching away in the windowsills, and they're what flies out when disturbed. All the wood in our trim is already painted, but they don't seem to care much! I don't really want to spray insecticides all over the house to discourage them, and I wondered if anyone had any other ideas. I don't care if they're in my garden (in fact, they very well may be beneficial there), but I don't want them damaging my house.