Dusty Moth
DB: This is Earth and Sky. Scott Hembree wants to know, “Why are moths so dusty?”
JB: Scott, what seem like dust particles on the wings of moths are really minute scales. Moth wings and butterfly wings are covered with these delicate pigmented or prismatic scales that rub off easily. Each scale is a flattened hollow bristle with fine ridges on the top. The scales cover the insect’s wings like overlapping shingles on a roof.
DB: The pigment in the scales produces the wide variety of coloration and markings that moths and butterflies use to advertise or camouflage themselves. The scales on the wings of some butterflies reflect ultraviolet light – invisible to our eyes – but clearly visible to other butterflies. And there are some butterflies and moths with almost no scales and virtually transparent wings.
JB: In some cases – generally in males – certain scales seem to be outlets for scent glands that produce an odor with a musky or flower-like fragrance. Some scientists hypothesize that the scales may also make the wings slippery so predators can’t hold on. When you catch a moth or butterfly, be gentle. Once an insect gains its wings it doesn’t grow any more – and those dusty scales that get rubbed off won’t grow back.
DB: Scott, thanks for your question. And special thanks today to the National Fish and Wildlife Foundation – and to the U.S. Forest Service. We’re Block and Byrd for Earth and Sky.
The following individuals were interviewed for today’s show. Our thanks to:
Robert Dudley
Section of Integrative Biology
The University of Texas at Austin
Lawrence E. Gilbert
Professor, Section of Integrative Biology Director, Brackenridge Field Laboratory
The University of Texas at Austin
Dr. C. Riley Nelson
Department of Zoology
Brigham Young University
Provo, UT
Additional Teacher Resources
San Diego Zoo, Animal Bytes, Butterfly: Insects: Butterfly
This site is a great resource that provides interactive information on all facets of the butterfly, including its wings scales and coloration. The site also provides photo images and video images of a variety of butterfly species along with links to more information.
Insects.org, BugBios: Learn About the Planets Most Diverse Organisms: Class: Insecta
Most butterfly and moth wings are covered with a dense mosaic of tiny individually colored scales forming a myriad of striking color patterns and designs. This site provides students with examples from several species and allows them to interact and zoom in and out on wing patterns while learning about wing structure, design, analysis, pattern formation and adaptational benefits.
