First Impression: Critiquing a top 20 shot can be difficult and if its the submitters highest scoring image its even harder! That said, this is a nice bright image and a very unusual situation, I've never seen 3 butterflies on a single flower before (thats worth at least 1 point)
Composition: A square crop was the way to go here, the butterflies fill the frame well.
Subject: Yup, its from above and meets the challenge well, flowers and butterflies might be seen as cliche at dpc but are most often well received. Kudos for an 'of the moment' shot.
Technical: The backgound is a little noisy (ISO 1600 would cause that) and I'd prefer a little more definition on the butterflies (esp the right one)
Final thoughts: A great shot for the challenge and might well have ribboned in a 'three' challenge. Thanks for showing this to us!
Fabulous capture. I hope you used sugar water and didn't wait for this naturally. *grin* An 8 from me... The noise and lost details in the dark areas took off a point. The composition is perfect. (voted earlier, back to comment)