Look closely at the Atlas moth above and you’ll see that one of these wings is not like the other. We don’t usually notice, but in many butterflies and moths, the top and the underside of the wing are visually quite different.

That’s because they serve different purposes. “It’s really quite shocking,” says National Geographic photographer Robert Clark. “On the bottom side, one of them looks like a brown, deadish leaf, and then on the top side it’s blue and orange. It’s the perfect example of camouflage.” The butterfly he’s describing is the Sumatran Indian leafwing, seen here.

Lepidoptera (the order of insects that moths and butterflies belong to) have long intrigued Clark, drawing him to visit various insectariums and entomological collections