These rare moths are quite a sight. This one flew into my friends at the end of summer last year, and it is the Atlas Moth, or Snake Head moth, Attacus atlas, which is a large Saturniid moth.
They can have a total wing surface area of more than 400 cm2 (62 sq in), and about 26cm wingspan, which is the biggest surface area of any insect as far as I know.
They are so big and heavy that they do not fly much and the adults only live for a couple weeks, and a fascinating fact is that adult Atlas Moths don't eat. They basically do not have any developed mouthparts so they must subsist on what they built up as a gluttonous caterpillar. But, in case you are interested, they can still poop.