Moths force you to look at patterns. This next series of four images may be the same species of moth. You probably won't have any trouble believing that when comparing the first two pictures. It's the third and fourth pictures that are more challenging. But if you look very carefully, there are enough overlapping elements (spots and stripes) that I'm leaning towards thinking all four are the same species, even though they look quite different at first!
And here's one more example showing what I think is a different species than the first one documented above (although I'll admit, frustratingly, that I'm not 100% certain yet!). Note that in the two individuals below, the dominant colors are different, but the striping patterns are similar enough that I believe they're the same species.
I haven't had a chance to work on the identifications of these moths yet. If you know what they are, feel free to write. I'll update this post if I hear back from anyone or work out the identifications myself.
ADDENDUM (22 January 2014): Well, my first guess is that these are Oak Winter Highflier Moths (Hydriomena nubilofasciata). I actually wrote about them last winter, but these individuals look quite different than the ones I photographed in January 2013 (see those pictures here). If I'm right, this is one of the most variable species I've seen!