You did an excellent job of getting good detail throughout the butterfly's wings and head but, at f16, you also got quite a bit of the background as well. Next time, try a lower ISO (seems to be bright daylight - you should be able to make the image at 100 or 200 ISO instead of 800) and a wider aperture (4.0 or 5.6 maybe?) and see if that doesn't give you a softer BG so the butterfly can take center stage without competing against all that grass and straw.
Also, I noticed you have clipped highlights on the histogram. Make sure you check that each time you make an image - anything that rides up on the right edge of the histogram means the whites in the image will have no detail left in them (notice the white patches on the butterfly's wings that seem to almost glow?). If you lower your exposure you can avoid that and then your whites will keep their detail.
Hey Paolone, This is a very touch shot as you have to deal with a really messy background. Jules and Robert have given you good advice. Keep em coming.