Dr Irengbam Mohendra Singh
Butterflies and humans have been having a longloving relationship. Butterflies are dubbed “little soul” in Greek and Russian languages. One of the exciting recollections of my childhood was chasing beautiful butterflies in the height of summer.
It was culminated by visiting the Butterfly Museum at Chowringhee (JN Road) in Calcutta, as part of an educational excursion as an undergraduate in zoology. I was quite animated to find a Manipuri researcher on butterflies on the net, Jatishwor Irungbam. We need young science researchers like him and investment in them by our government, so that future generations will carry their genes for scientific research.We need to live today for a better tomorrow. Whatever has happened in the past is history, and best forgotten.
Equally delightful is the photograph of a very rare butterfly in India, Slate owletfrom Yaingangpokpi wildlife sanctuary, near Kwatha village in Manipur (Northeast Today,2015).
The species was photographed by Basabjit Chakraborty, a wild life photographer from Assam.It’s recorded that the species was first collected from Manipur 100 years ago by Lt Col HC Tytlet. Such aesthetic beauty of some butterflies has been the cause for their near extinction, because of the human hobby of ‘butterfly collection’.
There are about 20,000 butterfly species in the world, about 1,500 in India, and about 80, (identified so far) in Manipur. 50% of butterflies in India are found in Assam.
I’ve written in the past how moths guide themselves at night, using the light of the moon, and how they accidentallykill themselves when guided by a candle flame on the surface of the Earth as if they’re committing suicide. Likewise, the highly evolved butterfly known as monarch butterfly (Danaus plexippus)migrate themselves using the sun and their own body clock (unusually located in their antennae instead of the brain, identified in 2009)for direction.
The information from the two sources isprocessed by their tiny brains to maintain a southerly bearing all the way to Mexico, a distance of up to 4,000 km (twice the distance from Kolkata to Mumbai). Moth is a cousin of butterfly,separated 60 million years ago, from a moth-like insect ancestor.
Moth has the same blood venules running in their wings like in butterflies, and the same gene that controls the patterns in theirs and butterflies’ wings.
Theories of evolution are based on its systematic similarities to other closely related species, as well as genetic similarities to those species.
There are reasons for butterflies’ aesthetic beauty,form and function, as well as their biochemistry. Their beauty is related to their evolution for survival by their ability to mimic, camouflage and recognise mates in the same species.
Butterflies also have scientific beauty. They do a lot for our existence by pollinating and helping to keep control over a number of plants and even insects by eating them. They are also food to other species like birds. Because they are very sensitive to changes in the ecosystems, scientists use their population and behaviour shifts as gold standard in local environments.
About one third of the food people of the world eat depends on pollinators, such as butterflies and bees. The wingsof butterflies are made of a hardened transparent and translucent cuticle protein called chitin, like our nails.
On top of these chitin, are laid layers of thousands of flat tiny scales (like fish scales), arranged like roofing tiles, in rows that run anterior to posterior, to streamline during their flight.
These scales also insulate and protect them, by helping to soak up the heat for energy.They are cold-blooded animals and have to store heat for body function. Their wings are powered by blood called haemolymph (without red colour) that runs through a vein in the forewing and a system of microscopic venules.
The beautiful colours of butterfly wings are produced by two factors: (1) through the production of pigments in the scales, and (2) the structure of the scales to create photonic devices like LED, by manipulating photons of light.
The pigments in the scales produce white, yellow, orange, red, purple, and brown coloursby selectively absorbing and reflecting light, as flowers do.
The structural colours ie green, yellow, orange and purple that are brighter and more brilliant are produced through the reflection of light from the scale’s surface and internal structure.
These scales are easily rubbed off on your fingers when you handle them, and you can see them as dust on your fingers.
This is to allow the butterfly to escape from predators in a life-saving situation. Scientists thought the butterflies are deaf until the first butterfly ears were identified in 1912.
Most butterflies fly at 8-19 km per hour and for 8-20 km. The smallest is 12.7 mm, and the largest species may reach 30.5 cm across.
The evolution of these immensely diverse species, almost all of which differ in their wing patterns, shows the depth in the intricacies of biology. Besides, over the millennia, some of them like the Monarch butterflies have developed high skills for migration for their survival.Scientists think there is a particular association between butterflies and flowering plants in the evolution (145-65 MYA) during the Cretaceous Period, also called “Age of Flowering Plants”.
Modern humans evolved at the end of the Last glacial period (2.6 MYA). Monarch butterflies owe their name to their marathon flying capabilities. They are bright orange with beautiful markings. There has been a long disagreement as to where they first evolved, and about their evolution and coevolution.
They have been classified and reclassified so many times as in the case of Meiteilon (Manipuri) but with no final solution.
They are characterised by theirreduced first pair of legs.They have evolved to feed on poisonous blooms of milkweed plant to deter predators as they are distasteful to eat. So they are also known as milkweed butterflies.
The monarchs thatinhabit northern America, and Canada have been thoroughly studied. Each year, as autumn approaches across Canada and northern US, young monarchs prepare for a very long and tedious journey to a warmer climate.
By early September, they begin to gorge on nectar to fatten up themselves, conserving energy for their migration. By September/October, when they can’t stand the cold weather anymore, they migrate south, to centralMexico. This massive exodus has been called “one of the most spectacular natural phenomena in the world”.
Because of their annual migration they can live up to 8 months ie 10 times longer than their parents and grandparents, though some species do not migrate at all. An average lifespan of an adult monarch is just over 4 weeks. Half a million monarchs migrate en masse, covering upto 100km a day.
They know where they are going, all planned out. Though none of them has travelled the route before, their destination is the same every year for thousands of years. How they do it is still unsolved.
Scientists believethey have developed a special gene for navigation, using their circadian rhythm and the sun to guide them.
Their inner timepiecemay dictate when their migration has to begin, by keeping track of day-length.
Circadian rhythm including human’s, is an evolutionary protective consequence of living on Earth, as a result of the Earth’s journey around the sun, rotating once every 24 hours, with a 23- degree tilt of its axis.Our internal clock is synchronised with the rotation of the Earth.
As temperature falls and food becomes scarce, young monarchs begin their flight from the east of the Rocky mountains and fly across the great plains of the central United States into the damp and cold of the south, braving on the way, all kinds of danger, such as bad weather with storms, predatory birds, sickness and infection.Every year, despitethe loss of many lives, millions of monarchs arrive in a single small area, Sierra Chinua in the heart of Mexico (the United Mexican States), and cluster on big tall fir trees.
They use the very same trees each and every year when they migrate, which is unique because they aren’t the same butterflies that were there last year.
Studies published in 2016, believe that, monarch’s ability to migrate such long distances is because they have developed unusual skills of navigation. They orient themselves using the position of the sun in the sky, and their internal clock.
Their eyes polarise the sun ie cut off the glare and they are able to see the exact position of the Sun.
They are also thought to use ‘spectral gradients’, which means, the precise mixture of colours in any given patch in the sky, which depends how close it is to the Sun, such as the red/orange colour of the Sun at sunrise or sunset.
After their hibernation in Mexico, monarch butterflies return home in spring.
But unlike other birds, they nevercome back to the place where they were born. They will go where milkweed is immediately available, as they are in a hurry to mate and breed before they die. The lifecycle goes on for thousands of years as their behaviour and biochemistry are intimately connected with their habitat.
The writer is based in the UK
Dr Irengbam Mohendra Singh