I think this is a type of bumblebee, but I am unsure after looking at other photos of bumblebees on this site. As you can see, it doesn't have much in the way of yellow markings anywhere. It is larger than the honey bees in our area, but smaller than the carpenter bees. There are quite a number in our yard, buzzing around all day, though they do not seem to sit still on flowers for very long. I was lucky to get this picture at all. Sometimes the seem to be a little aggressive with each other, buzzing at and around others ones in the area.