Phyciodes mylitta aka Mylitta Crescentspot

The specimen on the left has a distinct orange-yellow median band and would appear to be a female.
The individual on the right -- lighter, smaller, showing more wing-wear -- appears to be a male.

Caterpillars feed on Carduus and Cirsium thistles; these exotics are constantly expanding their range, which
might explain why this species is so common. Adults nectar on a wide variety of flowers, here on Black Mustard.