I discovered this gal on my patio one morning. In this position with her wings folded back, she was about 2.5 inches (6 centimeters) long. Sadly, she took off after I snapped this photo, so I never did capture a better picture of her. Still, her wonderfully unique coloration is evident even in this sub-par presentation.
[Update]: This large moth is called a leopard moth (also giant leopard moth or great leopard moth) and is scientifically known as Hypercompe scribonia.