We discovered this moth on our way in from the park today. It's really impressive, about 5 1/2 inches across. The girl wanted to pet it, but we decided that it would probably prefer to be left alone. I thought the daytime photo was washing out some of the details, so I just ran out and took the second pic. The Antheraea polyphemus doesn't eat after becoming a moth, and doesn't even have a mouth. Apparently she's going to be hanging out on our porch until a lucky male finds her there, then they'll mate.
The caterpillar is pretty cute, and reminds me of a certain Very Hungry one that's pretty popular around here.