Its not often I see a picture of two flies that I would almost describe as the perfect insect portrait!
This photograph is a winner a two levels. For a start there's the strong diagonal of this branch, which is always going to add to the strength of photograph's design, but then at angles to this you have not just one, but two flies. One fly on its own would have been boring, but the two provides for an interesting balance. I am almost reminded of the shadow drawings that you used to find in the Jane’s Fighter books, where there was typically an illustration of what an aircraft would look like from front on, from the side and from above. The exposure is also well handled, the tonal range is perfect and the balance of muted reds against the greens couldn’t be better.
So, why is this image not actually perfect?
If you look long enough, you keep getting into that open, boring space to the right of the frame, and that is what is really letting this picture down. But here is the good news; making a small crop to an image is about the easiest thing you can do to improve most photographs.
My advice? Rather than cropping this image with a 3:2 crop, use a 5:4 crop and in doing so, keep the tip of the stalk in the top-left corner, place the top fly in the top middle portion of the picture and bring in the right to lose some of that open space on the right. Do that and this image will be perfect. Well done.
Gotta go now; some of your models are being a pest!