When I first saw this fly, I thought it was mating. I guess that's still my first guess but I'm not really confident about it now. I wonder if it could have been eating something. . By just looking without the camera, I couldn't be certain either. After I took several photos, the fly suddenly flew away. It happened so quickly that it seemed like only one fly took off but I guess there might have been two. I do know that no fly or food of any kind was left behind. It was around supper time and the temperature was 16⁰C. The fly was on a stone wall in our back yard. I'm guessing that it may be Calyptratae but I don't really know.