I can't seem to find where in the guide this photo was placed. Can you let me know? Or did you want me to move it to toxomerini? (not quite sure if that's what you wanted me to do)

It is in the Toxomerini tribe, which includes all the Toxomerus, that is the best we can do with this images. You don't need to do anything.
On second thought, maybe I understand your confusion and apologize. I meant to move it to Syrphinae. I was moving a number of images that needed better placement and got tired. I should know when to quit.
Oh! About the tings on their faces, those are the antennae. These kind of flies have very short and funny looking antennae which helps to differentiate them from bees when you don't get a chance to count the number of wings.

Thank you so much for taking the time to explain. I'm just an "armchair naturalist" & find the comments fascinating. Didn't mean to keep you up so late!

The value of this picture is the behavior: Not many shots of mating flies. But as far as ID, as Ron said, without a dorsal view we may never know the species or even genus. So it is not terribly important where it is placed.

I notice this post is now in Toxomerini. Is there any other genus there than Toxomerus? If not, why not put these in Toxomerus? (I realize you believe placement of this particular post isn't important.)

Thanks so much for all the info! Unfortunately, I did not get a photo of the upper parts of the body. The body, though, appeared to be striped black/yellow, if I remember correctly. And the photo that you show sure looks like my pair. Thanks again!