Pearl Crescent", but then I stared at the photo, and something just didn't seem right. I looked around at the likely alternatives, and determined it was a Silvery Checkerspot (Chlosyne nicteis). I'll send it to BOMA to be sure, but it looks pretty solid to me.
I got a few other pretty good pictures today too:
Zebra Swallowtails have been pretty reliable this year. Whatever affect the others didn't seem to make much of a dent on them
Eastern Tiger Swallowtails are becoming more common again. There are usually one or two hanging around the bushes during the day. On the left is a female yellow morph, and below a female black morph.
Spicebush Swallowtail (left and below) fairly often, which is pretty similar to the black morph of the tiger, although both sexes are black, and the males have a greener wash on the hindwings than the females, which are blue. They are also somewhat smaller than the tiger, which is the biggest North American butterfly.
Just for fun, I took a short video of the one on the right visiting flowers (Verbena):