This lockdown gave me the opportunity to spend time in my garden, I came across little colorful aviators- Butterflies. For millennia, mankind is fascinated by butterflies. Combined with beauty, grace and vibrant design – it is a brilliant work of nature. A butterfly has true art painted on it.
A whole parade of colors and shapes, these tiny creatures have added remarkable strategies to their biggest asset: wings. Their attractive wings draw our attention. Different species visit my garden each day. I’m fascinated with their beauty -What is the significance of the beautiful patterns? Why are some brightly colored? Why are some not?
(Photo Credits: Mr. Sandip Rajguru)
There are vital clues hidden in their wings-
The Wings of butterflies are made of colorless translucent membranes covered with tiny scales and hairs. The wing scales are made of cuticular proteins, chitin fibers, lipids, and pigments which overlap each other -like roof tiles - when viewed under the microscope (1). They are responsible for the magnificent colors. This is advantageous not only to camouflage themselves but also to communicate, these scales also protect and insulate them. Since butterflies are cold-blooded, the scales help them to absorb the heat required in flying (2).
Apart from quick flying, butterflies use these vast arrays of color patterns to evade off predators. It has been seen that many ground-dwelling butterflies have wing patterns like the fallen leaf or rock. They seamlessly blend, making it impossible to detect even at close quarters. Examples include the leaf butterfly Kallima inachus from India and Zaretis itys, a Peruvian species, convincingly disguised as a dead leaf.
Another popular technique used by butterflies is known as aposematism, which helps the butterflies to exhibit warning colors to alarm the predators. Studies showed that non-colored Heliconius models were significantly more attacked than colored models demonstrating the significance of aposematic signals to avoid predation (3).
Butterflies have eyespots marking on their wings, which effectively trick their predators. Some species are even found to change patterns with the season. For example, (Fig 1) Junonia almanac, found in tropical parts of Asia, show pronounced seasonal polyphenism. During the dry season, they form hidden undersides with reduced eyespots whereas in the wet season the eyespots become more prominent (4).
Some butterflies are found to be toxic and poisonous to their predators. Bright colors like red, yellow, orange are highly contrasting to the background and are commonly used by butterflies to advertise unpalatability (5). Even closely related non-toxic species are found to mimic the toxic ones to avoid being eaten. These butterflies either biosynthesize some noxious elements de novo or acquire them from the poisonous host plants as a defense (6). Danaus genutia (commonly called striped tiger Fig 2B, 2C) resembles Danaus chrysippus (plain tiger Fig 2A) but bears more prominent black stripes on its fore and hindwings (Fig 2). They feed on the sap of plants like Asclepias sp. from where they sequester toxin or alkaloid which makes them poisonous. Both these butterflies resemble the American monarch butterfly (Danaus plexippus).
Other butterflies use the colors or patterns as an identity badge for their potential mates. In many genera like Apatura, Doxocopa, and Morpho the wings of males have a highly reflective blue sheen that glint brilliantly in the sunshine and play a major role in mate location and recognition. The Japanese cabbage butterfly (Pieris rapae), fly over cabbage fields to find their pair. In these butterflies, only the females have UV colors on their wings which are strikingly attractive. Thus, eliciting a mating response (7).
These tiny creatures have observed to have English alphabets (A to Z) and numbers (0 to 9) printed on their wings (Fig 3).KjellBloch Sandved, in 1975, for the first time published his “Butterfly Alphabet” poster, with all 26 letters and 9 numerals, all represented in the varied hues on butterfly wings in Smithsonian Magazine (8).
The next time you spot a butterfly, examine closely the little details on their wings. You will find evidence of the exceptional creation of nature.
Refrences:
1. Moussian B. (2010). Recent advances in understanding mechanisms of insect cuticle differentiation. Insect Biochem, MolBiol, 40, 363-375.
2. Wade R. (1995).Wing scales may help beat the heat. Science, 269, 5232.
3. Finkbeiner S.D., Briscoe A.D., Reed R.D. (2014). Warning signals are seductive: relative contributions of color and pattern to predator avoidance and mate attraction in Heliconius butterflies. Evolution, 68, 3410-3420.
4. Kodandaramaiah U., Vallin A., Wiklund C. (2009). Fixed eyespot display in a butterfly thwarts attacking birds. Animal Behaviour 77, 1415-1419.
5. Arenas L.M., Troscianko J., Stevens M. (2014). Color contrast and stability as key elements for effective warning signals. Frontiers in Ecology and Evolution, 2, 1-12.
6. Nishida R. (2017). Chemical Ecology of Poisonous Butterflies: Model or Mimic? A Paradox of Sexual Dimorphisms in Müllerian Mimicry. In: Sekimura T., Nijhout H. (eds) Diversity and Evolution of Butterfly Wing Patterns. Springer, Singapore. https://doi.org/10.1007/978-981-10-4956-9_11
7. Obara Y., Hidaka T. (1968). Recognition of the female by the male, on the basis of ultra-violet reflection, in the white cabbage butterfly, Pierisrapaecrucivora. BoisduvalProc Japan Acad, 44, 829-832.
8. Kirkus Reviews. (1996)The Butterfly Alphabet.
Date: Aug 28, 2020
Author: Kiron Bhakat
Kiron was fascinated towards science from childhood, as the subject is so interesting- it raises the question itself and also answers it. Later, when she grew up her interest lead her to take Microbiology as the course study to know more about the world of invisible life. Kiron says "Without full support from my parents, I would never able to pursue the career of my dreams." Now She is working as a Research Scholar, under the guidance of Dr. Ekramul Islam, Assistant Professor, in the Department of Microbiology, University of Kalyani, Nadia, West Bengal.