I looked it up and she's a Promethea Silkmoth. After taking the picture I picked up the flashlight and she fluttered up into the darkness. Turns out she didn't go far.
Here she sat on the peak of the porch gable all night and all today. I was afraid some bird would come and pick her off but she was still there when we came in from evening chores. I hope tonight she goes on about her mothy life and is able to start another generation. Seeing these big lovelies is a real treat for me and certainly embodies a warm June night.