A pair of Giant Silk Moths resided on our front porch by the
light for a week or so and then moved on to wherever Giant Silk Moths go. They are so pretty.
Their scientific name is Polyphemus. Bill Welch (the Bulb Baron at www.BilltheBulbBaron.com) identified it for me.
Wikpedia describes the moth as having a 6-inch wingspan and purple eyespots on hindwings. The caterpillar eats 86,000 times it's weight in less than two months.