Painted Lady & American Lady
This American Lady is more faded than the fresh individual above. I have found American Ladies from March through October, especially in spring and early summer. (Painted Ladies, by contrast, are usually scarce before July.)
This is a Painted Lady on a zinnia. Notice that the forewing tips are round instead of square, there is no white dot in the rectangular forewing cell, and the four dots on the bottom of the hindwing are about the same size.
At first glance, there is nothing special about this photo ... until you know the date when it was taken: December 2, 2017. This Painted Lady is one of only four butterfly species that I have seen in the month of December. (The others are Orange and Clouded Sulphurs and Eastern Commas).
This is an American Lady nectaring on a flower. American Ladies are very similar to Painted Ladies, but they can be distinguished in several ways. American Ladies have square-shaped forewing tips, a white dot inside the rectangular forewing cell, and blue centers inside the first and fourth dots on the bottom of the hindwing.
This is a ventral view of an American Lady on echinacea. Notice that it has two large eyespots on the hindwing (and a white dot in the rectangular cell).
For contrast, here is a ventral view of a Painted Lady. It has four small eyespots on the hindwing rather than two large ones.
Painted Ladies are migratory, and their numbers fluctuate widely from year to year. My personal early date is May 19th, but they are much more common in late summer and fall.
Painted Ladies are avid nectarers. This individual was photographed on a zinnia at Cox Arboretum.