The biggest problem I had with taking this photo of a pearl crescent, Phyciodes theros, was the wind. The wind moved the subject into and out of focus. So I held the flower by the stem, and focused by moving the camera in and out. I used a little bit of fill flash to get this shot.
But the wind helped a little bit, also. Pearl crescents have a tendency to rest with their wings out horizontally, and the underside is more difficult to photograph.