
I find it difficult to criticise this shot, because it's extremely good. However, I like the idea of a horizontal crop - just above the butterfly, and just below it's lowest foot. It somehow seems a bit nicer on the eye when cropped like that, and there is space on the left for the insect to 'look into'.
A polariser might have worked well here, to remove reflections from the wings - that way the transparent parts would have looked truly transparent, and would have appeared 'invisible'. I think this would have made the photo even more intriguing, as people might think the wings hade huge holes in them.