Distalless expression in larval wing imaginal discs in both the Junonia and Bicyclus genus is correlated with the eyespots in adult wings in this Java video sequence. Use the blue Play button to initiate playback of the sequence.

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Butterfly Larval Wing Imaginal Disc: Second Instar Specimen: Butterfly Imaginal Disc Authors: Julie Gates, Eric Hazen, and Stephen Paddock

A network of scales covers most of the butterfly wing, giving it a beautiful array of colors produced either by pigmentation or through optical interference. The iridescent colors usually associated with butterfly wings arise from the small ridges on the scales, which interact with light causing constructive and destructive interference, much like that produced by a soap bubble. Other coloration in the wing is caused by clusters of dehydrated blood cells, leading to a wide spectrum of colors that we see as distinct patterns in the wings.

Over 160,000 species of butterflies and moths together comprise a large order of insects named Lepidoptera, which is Greek for wing scale. There are a number of similarities and differences between butterflies and moths. Most butterflies are brightly colored and fly during the day while a majority of moths have a dull and drab appearance and usually fly by night. Butterflies tend to hold their wings upright over their backs when resting, but most moths spread their wings flat near the surface when not flying. These insects also differ in the construction of their antennae. Butterfly antennae are usually long and thin and knobbed at the tip whereas moth antennae can be much more complex and often resemble feathers.

The first moths appeared about 150 million years ago during the Cretaceous period when the world was largely inhabited by dinosaurs. Butterflies evolved much later, about 40 million years ago, and many of the species alive today have evolved during the last five million years.