I'll bet you get a fair number of comments on this one. This is the kind of shot I might submit for kicks, so bravo to you for that. It's nice to see something different so I can take a break and write my sorry excuse of a comment. I admire the way you trained two flies to look one way, and two to look the other way, that must have taken a lot of time & patience. I'm assuming this shot was taken in England, as the flies are keeping left rather than right, except for that one fly which is obviously on his way home from the pub.
This is simply an amazing photo. By far the best one I've seen in this challenge. Very original. Not just a pic of animals but also suggest a certain mood and also has a very strong sense of place. Technically I think it's perfect. I really like the amount of detailed you've captured here, in the flies and the dirt on the window.