I have raised stone garden beds. We have a dwarf alberta spruce in one of the beds and there have been tiny bees flying into the alberta spruce. I was finally able to get close enough to see where they are going and there is a tiny quarter sized hole in the ground under the alberta spruce. They must be in the ground. They are little yellowish brown bees about 3/8" long. What are they? What should I do about them?