Glasswing butterflies:

Rare, tropical gems

Fragile and delicate beauties of the wild, butterflies are a group of insects that have captured the imagination of poets, artists and authors from time immemorial. Fluttering from flower to flower with the sunrays reflecting the vibrant multi-colours on their delicate wings, they resemble tiny fairies. Most children gasp in wonder at their first encounter with one of these beautiful creatures.

Who can resist the beauty of these tiny winged jewels that visit our gardens in search of nectar? Few I guess. Butterflies are easily one of the most admired and written about creatures in the insect world which comprises millions of insect species. Our beautiful isle too is home to a number of these enchanting butterfly species, some of whom are endemic.

The butterfly species we feature today is a rare tropical gem and you are not likely to ever see it alive in the wild unless you make a trip to South America.

The name alone speaks volumes about its spectacular appearance. This rare brush-footed butterfly species native to South America (anywhere from Mexico to Panama in Central America), is commonly known as the Glasswing butterfly in English because of its enchanting transparent wings. It is one of the most exquisite and little known species of butterfly on the planet that confounds science with its unusual appearance. Like its English name its Spanish name too is very fascinating. It is called espejitos which literally means 'little mirrors.' Even its scientific name Greta oto sounds like the name of a famous movie star - perhaps it deserves to be classed as such among its species due to its enchanting beauty.

Now let's check out some interesting facts about this unique species with transparent wings.

The glasswing butterfly (Greta oto) is a part of a specific clade called the clearwing. If you are wondering what a clade is, it is the scientific term meaning branch and is used in the taxonomy (science classification) of species. When groups of species have a single, common ancestor (which does not necessarily need to be extant) then it is known as monophyletic.

If you look closely at the pictures of this butterfly featured here it will be evident that its wings spanning about six centimetres are virtually see-through or translucent as they are properly called.

While most butterflies have coloured scales which pattern their wings in a spectacular manner, quite often to ward off predators, this particular species has transparent wings which make them virtually invisible. The only way that you can tell the insect has wings at all are by the opaque borders on them. They are of a dark hue, sometimes appearing as orange or red. What's hard to understand is how and why they ended up with transparent wings in the first place. According to science, transparency can be achieved only if light is not absorbed by the tissue. In addition, the tissue, must not scatter the light too. So, for this to happen, the clearwing must be having wings that have the same refractive index (passing of light from one medium to another all the way through them). Otherwise it would reflect colour.

The reason we humans can never become 'transparent' is because we have chemical and biological compounds with different refraction. Try to imagine what we would have looked like if we had the ability to be transparent like the glasswing butterflies? Some scientists are of the view that the glasswings have a single refractive index and also think (it is not proven) that the surface of their wing has a covering of protrusions which are extremely tiny (submicroscopic).

Butterflies we all know are delicate creatures and glasswings, with their transparent wings must surely be more fragile than the rest of the members in the butterfly family. You will be surprised to learn that they are not; their wings are as strong as those of other butterflies.

It is a resilient species and is fortunately not listed as endangered because it is common in its native habitat - the rainforests of South America. The glasswing like all butterflies survives on the nectar of flowers. It feeds off the nectar of a variety of rainforest flowers such as the lantana. But, when it comes to laying eggs, the glasswing butterfly mum is really selective.

Wherever possible, she will lay her eggs on a plant called the nightshade of the genus Cestrum. The nightshade is a highly poisonous plant. The caterpillars, vibrantly coloured in red and purple stripes, feed on these toxic plants. They are not the best of meals for birds and other predators. The akaloids, a chemical which occurs naturally in the plant and is full of Nitrogen, are retained in the bodies of caterpillars into adulthood making even the adult butterflies distasteful to predators.

Pix and facts : Internet

***********

Butterflies in Sri Lanka

There are about 245 species of butterflies in Sri Lanka and of these 23 are endemic to our country. In size, they range from the large, aptly named Birdwing butterfly, which was declared the National Butterfly of Sri Lanka to the tiny (just as aptly named), Grass Jewel.

Some of the endemic butterflies are Ceylon Tree Nymph, Cingalese Bushbrown, Ceylon Palmfly, Ceylon Tiger, Ceylon Teabrown, Ceylon Hedge Blue, Ceylon Indigo Royal, Clouded Silverline, Green's Silverline and Ceylon Forester.

There are eleven families of butterflies found in Sri Lanka. They are Danaidage, Satyridae, Amathusiidae, Nymphalidae, Acraeidea, Libytheidae, Riodinidae, Lycaenidae, Pieridae, Papilionidea and Hesperiidae.

These butterflies habitats range from the hottest areas in the arid zones to the coolest areas in the forested hills. Some butterflies are seasonal but others can be seen all year round. A large number of species can be found in the foothills up to 3,000 feet elevation. About half a dozen species occur above 4,000 feet. Twenty species are strictly confined to the dry zone below 500 feet.

***********

[Fact file]

* The common ancestor of the glasswing had become extinct long ago, but the clade it belongs to is known as the clearwing clade.

* The glasswing uses its transparent wings to camouflage itself and the toxics in its body to avoid becoming a tasty meal of birds and other predators.

* Rainforest sociologist use the presence of this rare tropical butterfly as an indication of high habitat quality. Its demise alerts them of ecological changes.

* This beautiful species found in the Amazon rainforest of South America is so delicate in appearance that some liken it to finely blown glass. Others say they are similar to the beauty of refined stainglass as the translucent wings shimmer in the sunlight like polished panes of green, red orange and turquoise.

***********