One of the most elusive spring ephemerals to catch in flower here in Kentucky.  For only a day or two these plants push up single, large and white flowers that are about 1" across.  The petals stay on the flower for a very short time so if you miss a day or two in the woods you can miss the flowers but fortunately the foliage is very cool and lasts much longer.  At the same time the plant is pushing up flowers it is also sending up the foliage and each leaf opens up to resemble a pair of green butterfly wings which gives the plant its common name.  As the season progresses the leaves expand and form nice large clumps before dying back in the summer.