Oh a butterfly

This image is superb and very impressive considering you say you're not used to photographing insects.

There are several aspects that, in my opinion, makes a good photograph. One of these is the point of focus, which I would say is spot on the butterfly in this image. Another aspect is the depth of field, which you have used in this very effectively with a short depth to put all the viewer's attention onto the butterfly. It also creates a nice blurred background, which I think always look good in images focusing on one element. I think perhaps the depth of field cuts a little short on the top left of the wings, as they are blurred.

I'll talk about just one more of my "makes a photo good" aspects - colour. There is a nice variety of colour in this image, but not so much that you lose the sense of unity or distract the viewer. The yellow through to red tones from the flower match the butterfly's reddy-brown, and there are also hints of yellow and brown to the colours in the background.