Well done, Stuart. Subject is in fine condition, good sharpness, the composition works quite well and is nicely balanced. If I could change one thing it would be to add a touch more space on the left so that leaf doesn't touch the edge of the frame.
Beautiful composition and pose, very clean image. Excellent detail. The butterfly looks good , for me the other yellows and blue components are a little too high, I attach an alternative for your consideration:
A bright and happy image. Wonderful photo of this Monarch on a Butterfly Weed--a native. Nice details on the Monarch! I'd like to see a version somewhere between the OP and Jonathan's version. The flowers in the OP are a bit too bright, but in Jonathan's version they aren't bright enough.