I like the mostly head-on angle of view, the sharpness, DOF, and comp, Nicolas. Those eyes are really colorful! I'm not so sure about the dark band in the background as the fly's wings start to blend in with it. I'll be interested to hear some other opinions on this. :)
Very nice, Nicolas! I agree that the darker BG does hide the wings a bit - perhaps a small tweak with a levels adjustment or a screen blend mode could bring that up a bit and help bring out the wings a bit more.
I also see that you have the fly close to the ROT's position horizontally but he's really close to being in the middle vertically. I'd shave a little off the bottom of the frame to get him more in an overall ROT's position.
Love the details and clarity of the fly. Those eyes make the image really special!
I like the detail in this image. It helps me appreciate flies--those beautiful long legs and orange/green eyes are spectacular. I wish the wing didn't vanish into the dark BG. Otherwise, lovely.