I observed this specimen today stopping occasionally on my Cassia marilandica and Lupinus perennis plants. It seemed considerably larger and more yellow (almost greenish) than the other Sulphurs I see here locally. Later when I checked the leaves for eggs I observed what appear to be several little translucent objects. Overnight they turned white.

I will be watching these for the next few days and will report back.

As I suspected, this is Phoebis sennae according to a local butterfly watcher I consulted.