Peggy Cummings, age 13, of Shreveport, Louisiana for her question:

What is the powdery stuff on a butterfly's wins?

A butterfly's wings, flitting and fluttering in the sunlight, seem to be made from durable velvet. But when you hold the lovely creature in your hand, you know that this is far from true. Those beautiful wings are very fragile and delicately dusted with loose powder. '

When you hold a butterfly, the dusty powder from his wings comes off on your hands. You will be surprised to notice that the powder seems to be White, even though the handsome wings are patterned with jewel toned colors. Biologists classify the moths and butterflies in the insect order Lepidoptera, a scientific term meaning scaly wings. The powder shed on your hands is actually tiny scales from the butterfly's papery wings. Some members of Lepidoptera also have similar flaky scales on their heads and feelers and furry bodies.

If you examine one of these scaly winged insects with a hand lens or a good magnifying glass, you can see the tiny ridged scales overlapping each other and arranged in neat rows. If you could probe deeper, you would find that each tiny scale is propped on a tiny stem. The stem fits into a cup shaped socket on the gauzy wing. Neither the scale nor the stem is fitted very tightly to the wing. The slightest touch tends to shake them loose. This explains why some of the powdery flakes brush off when a butterfly is handled, even by the most gentle fingers.

With the help of a good microscope, you get a better view of the scaly wings and the surprising beauty of their structure. No, they do not reveal the jewel colors of a butterfly on the wing. Neither they nor the powdery dust on your hands shows any colors at all. In fact, the microscope reveals that the tiny scales themselves are as clear as glass. A group of them packed close together looks for all the world like a city of houses and tall buildings. The walls and roofs of the miniature city seem to be made from sheets of shiny glass. Even the microscope does not help us to find the painted colors that our eyes see on a butterfly fluttering in the garden.

However, those shiny walls and roofs give us a clue. We know that glass plays tricks with the sunbeams. A plain sheet of glass lets through the light and itself becomes invisible, or almost so. But a glass prism bends the different colored rays in white light and fans them out at different angles. The glassy scales on a butterfly's wings also play tricks with light, and by a process of refraction, we are presented with a pattern of colorful rays on its velvety wings.

Most butterflies live only during one season, just long enough to lay eggs and hand on life to a new generation. They shelter from pelting raindrops and try to avoid brushing against obstacles in flight. Their wings, as a rule, stay freshly powdered as long as they need them. But the monarch, the mourning cloak and several other butterflies live from one summer to the next. They lose many of their powdery scales. The monarch migrates hundreds of miles and when he returns in the spring, his velvety wings are worn thin and blotched with colorless bare patches