I have what seems like thousands of these in the backyard of the home we just rented. I am trying to get the yard back into shape and they are quite annoying. I don't believe they are wasps. They usually hang out where the yard meets the house and they never really fly higher that a few inches above the grass. I would like to get rid of them if I could. We have several dogs and don't like using chemicals. My apologies for the pic but they don't stand still and I took it with my iPhone. I was thinking a Hoverfly?
