Fly's head

I have included two extra photos today.

One is the rear end of this fly.

The second is a bit baffling. I found these two insects locked in some embrace. At first I thought it was just two insects mating but on closer inspection, they appear to me to be of different species. I wonder if one is being parasitic and laying eggs into a host. Your interpretation would be most welcome.

STOP PRESS. I am having difficulty uploading the extra photos.