Fortunately, Hypercompe Scribonia is one of the non-toxic ones. Lucky Me! He is fairly common in forested areas. As caterpillars go, the giant leopard moth isn't very picky in his diet, eating many broad-leafed plants...though non of those were growing under my deck. The deck is directly beneath a black walnut tree--but I've been unable to verify that giant leopard moth caterpillars eat black walnut leaves. Butterflies and Moths of North America says they eat violets, though, so I collected a few to put in a jar with this fellow while I learned a bit more about him.
The photo doesn't make it clear how shiny that punk hairdo is, but it is. Nor does it give you a sense of scale--he is nearly two inches (5 cm) long, and more than a half an inch (1.5 cm) in diameter. (If you include the spines.) And pitch black. Until he rolls up and you can see his red bands. A really excellent photo illustrating the bristles and bands is here at the Hilton Pond site.
The Giant Leopard Moth is so striking that I did think of keeping my caterpillar captive until spring...but I couldn't do it. In my last sighting of him (at right--click to enlarge), he was munching on my arrowwood viburnum. At maturity, he will resemble a snow leopard--white with black spots, some of which are hollow. On his head, some of these hollow spots have a metallic blue hue, looking like eyes. No doubt this is where he gets one of his other names, the Eyed Tiger Moth. (I don't like this name because obviously, tigers have stripes. Not spots.) Check out the photos at BugGuide to see the other part of him that is amazing--his iridescent abdomen!
Without better information, I can't say what exactly brought his parent to our yard. We are close to, but not in, forest. We have quite a diversity of plants. But which ones? The little stinker wouldn't tell me. But he did eat my violet leaves!