Lepidoptera have many ways of being transparent – sciencedaily
Butterflies and moths have beautiful wings: the luminous glow of an orange monarch, the vivid stripes of a swallowtail, the luminous green of a Luna butterfly. But some butterflies flutter on even more spectacular wings: parts of their wing, or sometimes the entire wing itself, are in fact transparent.
Many aquatic organisms, including jellies and fish, are transparent. But the transparent butterfly and moth wings are so striking that the mere sight of one usually causes a human to rush to a camera or at least point it out to friends. These enigmatic and transparent butterfly wings have not been studied extensively.
Doris Gomez and Marianne Elias (National Center for Scientific Research) decided to change that. Last week, together with a multidisciplinary team of ecologists, biologists and physicists, they published a massive study on the optics and ecological implications of moths and transparent-winged butterflies in the journal of the Ecological Society. of America. Ecological monographs. They found that transparency has evolved more than once in Lepidoptera and that there are many ways to be transparent.
Gomez, an environmentalist who has studied the physics and ecological aspects of the iridescence of hummingbird wings and other bird colourations, was intrigued by these so-called “glass-winged” moths and butterflies when she encountered Elias, an evolutionary biologist who has worked on the ecology and evolution of tropical Ithomiini butterflies, which have transparent wings. Gomez was surprised to find that almost nothing had been written about transparency in Lepidoptera, or any other land animal.
“This article is a breakthrough because everything that has been known about transparency so far has been about aquatic organisms,” Gomez said. “Transparency is so rare in terrestrial organisms that people have never bothered to study it in depth.”
She and her team analyzed 123 species of Lepidoptera from samples from the collection of the French Museum of Natural History. They found transparent, or “light-winged” species in 31 of 124 families. But not all species achieve transparency in the same way. They examined the extent to which transparency affects thermoregulation and provides protection against ultraviolet rays.
Many insects, including wasps, flies, and dragonflies, have clear wings. Their wings are made of a transparent chitin membrane. The wings of butterflies and moths are made of the same type of transparent membrane, but in most cases, moths and moths have opaque scales obscuring the membrane. The scales are responsible for their fascinating patterns and coloring.
Gomez and his team discovered that clearwing species have a number of ways of making their wings transparent. Some butterflies and transparent moths have no scales on their wings at all, letting the chitin membrane show through. Many other species have scales, which can be transparent, erect, narrow, or hair-like, allowing light to pass through the wing.
Physicists have studied cases of transparency in individual species or genera, hoping to understand the physics of how to adapt biological concepts to make people, vehicles, and even structures invisible or transparent. But until now, no one had appreciated the wealth of approaches Lepidoptera can take to achieve transparency, or the fact that it has evolved multiple times in different groups.
“This is the first comparative analysis of transparent butterfly wings,” Elias said. “What is remarkable is that transparency has evolved several times independently. But the way the wings become transparent can be drastically different, from heavily wrapped transparent scales, to simply having no scales, to reducing the size and density of the scale. There are many ways to be transparent. We don’t know why this diversity exists.
In some cases, different strategies lead to the same level of transparency, leaving researchers to wonder why such diversity exists. They theorize that transparency can be beneficial in different ways for different species, including as camouflage or to mimic wasps and bees. Transparency also appears to help moths and butterflies regulate their body temperature, but does not protect them from UV rays.
Gomez, who has a passion for working with scientists from other disciplines, included physicists in the study to explore the optical properties of wings, including discerning what birds, their potential predators, see when they look at a transparent butterfly. They found that the more light a wing can pass through, i.e. the more transparent it is, the less visible the butterfly is to predators. Transparency acts as the ultimate camouflage.
Like the butterflies themselves, the results are compelling. However, scientists point out that the study raised more questions and avenues for exploration to continue to uncover the evolutionary role and ecological implications of transparency.
“Butterflies are such iconic organisms,” Gomez said. “They are so wonderful to study. I love studying complex concepts, like iridescence and transparency, because there is so much to explore – and it’s so easy to get everyone excited about them.”