Butterflies and moths are unique insects partly because their entire bodies are covered by microscopic scales that aid in flight, waterproofing, and coloring. The digital image below, captured with the MIC-D microscope, is a relatively high magnification view of a butterfly wing revealing the intricate structure of the wing scale network.

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 Earth 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.

Butterflies and moths have a complex life cycle that consists of four separate stages. The first stage is the egg, which is fertilized during a typical insect mating ritual. Male butterflies and female moths secrete airborne pheromones that act as sexual stimulants to members of the opposite sex. In many instances, courtship is highly complicated and involves the coloration of the partners, a prenuptial courtship flight, and specialized "dances" that lead to mating. The sex attractant pheromones are complex biochemicals that probably determine most aspects of this mating behavior.