Butterflies displaying purple coloration are a captivating sight. While truly pure purple pigment is uncommon, many species exhibit striking iridescent purple hues. These apparent purple colors are typically not from pigments in the wings, but rather from the way light interacts with their intricate wing structures. This phenomenon creates a dynamic visual effect, making certain butterflies appear purple under specific conditions.
Butterflies with Purple Hues
Several butterfly species are known for their prominent purple or iridescent hues. One of the most recognized is the Purple Emperor (Apatura iris), found across broadleaved woodlands in Europe and parts of Asia. The male Purple Emperor possesses vivid iridescent blue-purple upper wings, which are particularly striking when caught in the right light, while females are typically brown with similar markings. This species is known for its elusive nature, often soaring high in tree canopies.
Another group featuring purple is found within the Morpho genus, primarily in Central and South America. While many Morpho butterflies are famous for their brilliant blue iridescence, some species, like the Menelaus blue morpho (Morpho menelaus) or certain blue morphos, can display purple tones or a mix of blue and purple depending on the viewing angle. The rare Morpho sulkowskyi, for instance, is fundamentally white but exhibits a pearlescent purple and teal iridescence. Additionally, the Purple Hairstreak (Favonius quercus) is a smaller butterfly common in areas with oak trees, where the males display purple on their upper wings, and females have a purple patch.
The Science Behind Purple Colors
The purple colors observed in many butterflies result from structural coloration, not pigments. Unlike pigments that absorb certain wavelengths of light and reflect others, structural coloration arises from the physical interaction of light with microscopic structures on the butterfly’s wings. Butterfly wings are covered in tiny, overlapping scales, and these scales possess intricate nanostructures, such as ridges and lamellae.
When light hits these structures, it is scattered and reflected in a way that produces iridescent colors, including purple. The precise arrangement and spacing of these nanostructures determine which wavelengths of light are strongly reflected, leading to the perception of specific colors. For example, in Morpho butterflies, the brilliant blue-to-purple iridescence is caused by the diffraction of light from millions of tiny scales on their wings. This optical phenomenon creates a shimmering, changing color that shifts with the angle of observation.
Variations in Perceived Purple
The perceived purple coloration in butterflies can vary significantly due to several factors, including lighting conditions, viewing angle, and even the observer’s perspective. The iridescent nature of these colors means that a butterfly that appears vividly purple from one angle might look blue, or even dull brown, from another. For instance, the male Purple Emperor’s wings only show their characteristic iridescence under the right conditions.
Many butterflies, such as some Morpho species, have undersides that are dull and camouflaged, contrasting sharply with their vibrant iridescent upper wings. This allows them to “turn off” their flashy colors by closing their wings, providing a defense mechanism against predators. The “purple” seen in these butterflies is often a dynamic and transient display, influenced by how light interacts with their unique wing architecture at any given moment.