Dainty Sulphur

There were two tiny yellow butterflies flying around the parking lot when we left Cedar Bog State Nature Preserve (Urbana, Ohio) last week.  I wasn't able to identify them while I was traveling, but after looking closely at the two photos I took of them, I believe they are Dainty Sulphurs.  This is another "new" butterfly species for me, but it is not one that is found in Massachusetts.