Critter GlitterBy Ellen Lambeth
There’s a wild light show going on right outside your door. Go look for it!
Where do colors come from? They appear when light bounces off things and enters your eyes. Most colors are caused by chemicals called pigments. In people, pigments give color to hair, skin, and eyes. In animals, they give color to fur, feathers, skin, and scales. And don’t forget plants. You may know about a pigment called chlorophyll, which makes leaves green. Now take a close look at the sparkly colors on this resplendent quetzal. Those aren’t from pigments. They’re from iridescence (eer-uh-DEH-sns).
Iridescence is created by surfaces that have tiny ridges or very thin layers on them. When light hits the ridges or layers, it scatters different colors in different directions. And when the scattered light reaches your eyes just right, you see shifting colors that shimmer and shine.
These two birds look alike—except for their color. Both are common grackles, which normally appear to be black. But when they turn this way and that in bright sunlight, you might catch a sheen of purple, green, bronze, or blue.
This six-legged gem is a dogbane beetle. It’s named that because it’s usually feeding on a toxic plant called dogbane. The beetle isn’t harmed. But the toxins it takes in can poison other animals that try eating the insect. So, this critter’s glitter is a bright warning: “If you bite, you won’t feel right!”
The creature with the gleam in its eyes is a horsefly. Each huge eye is made up of hundreds of tiny layered lenses. (The better to see you with, my dear!) All those lenses scatter light in different directions, with dazzling effect.
“I’m the king of the world!” this male peacock spider seems to be shouting. It’s part of a dance he does to attract a mate. Some of the flashy colors come from ridged scale-like hairs on his backside. There are different species of peacock spiders, each with its own pattern of dazzling colors.
Snakes are supposed to slither, not shimmer! But this tropical rainbow boa does both. Look where light strikes the top scales, and you’ll see how the snake got its name.
This bigfin reef squid has some skin cells that contain pigments. The squid can control those cells to make shifting colors and patterns. But other skin cells scatter light. It all adds razzle-dazzle to the underwater world!
The animal that once lived in this shell—called an abalone (AB-uh-loh-nee)—wasn’t iridescent. But the inside of its shell is. Check out its natural sparkle in the closeup photo.
Dancing colors aren’t found only in living things. Certain minerals are iridescent, too. Some, such as opals, make beautiful gemstones. You can even find little rainbows in a streak of motor oil floating on a rain puddle. As you can see on these pages, iridescence is nearly everywhere!