Among the most mysterious and beautiful of all moths are the Catocalas or Under-wings. These moths rarely come to light, but can be trapped by putting out a sweet bait of mashed bananas, stale beer and molasses on logs and trunks of trees in a forest or woods. This bait should be put out just before dusk. Then, when you come with a flashlight to the bait, you will often be rewarded by seeing underwings sipping daintily around the border of the bait. Some even become half-drunk with the delicious mixture and stagger about when they try to fly!
Watch an underwing flying in to the bait through your light and it may disappear before your eyes! The brilliant-colored under or hind wings are meant to catch your gaze, gleaning in the night like two great rubies, but suddenly the moth lights on a tree trunk and closes its forewings over its hind wings. The brilliant color disappears and in its place is a drab creature whose colors so closely look like the dark gray bark of the tree trunk that the insect is now invisible.
You might ask: “Why didn’t the underwing have both its wings look like the tree trunk?” And the answer is that in the ages long, slow, story of evolution, these moths developed a combination of a perfect defense against enemies with a way to recognize each other in the dark. The brilliant colors also help to confuse an enemy by first dazzling him and then giving him nothing to see.