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Sri Lanka & Indian subcontinent Butterflies chat => Butterfly Chat => Topic started by: indunil on June 30, 2011, 05:06:46 pm

Title: The season of butterflies
Post by: indunil on June 30, 2011, 05:06:46 pm

It is in the fitness of things that their season should be towards the end of the year, for it is during this period of island-wide rain, brought about by the North-East Monsoon that the plants are green and fresh, affording excellent egg-laying sites, among the thick foliage and a constant food supply for the caterpillars of these winged insects.

Apart from their breeding habits, one of the phenomena during the latter of the year is the mass cross country migration of various butterflies. Impelled by some mysterious instinct, thousands and thousands of them may be seen flying past in an unending succession.

In hordes they come, winging their way a few feet above the ground and go on for hours, days or weeks on end. In home gardens, on the roads, over paddy fields, across irrigation reservoirs, and even inside homes, only to flutter on the walls and pass out through the windows, they fly like leaves fanned by the breeze.

Sometimes, as they issue forth like a dense cloud, small parties of them may be seen fluttering about the leaves of trees standing en route. Or at other times, they may settle on the herbage on land, as if to sip nectar of flowers. One would often see them alighting on the open forest road presumably to draw out the juice from the fallen fruits, or take in the moisture in the puddles of rain water.

But these stragglers soon join the main column in their uninterrupted migration.

An English lady who came ashore at Colombo in the month of October, over a hundred years ago, after observing a migratory horde of butterflies had stated thus, "I certainly thought I had stepped into the land of butterflies. The harbour, streets and large promenade, the Galle Face by the sea shore were alive with butterflies and being nearly comprised of Catopsilia (whites) looked like a snow storm."

Even Sir Emerson Tennent (an authority on all matters relating to natural history) referring to the uninterrupted passage of butterflies in Sri Lanka says, "Whence coming, no one knows; wither going, no one can tell."

Another foreign visitor commenting on the periodical movement of butterflies in the island has observed as follows:- "One of the mysteries of the Isle is the annual migration in November and December, and at intervals right on till February, of countless myriads of butterflies in vast flights. Whence they come and wither going no one can guess.

The migration commences with the setting in of the north-east monsoon, with its cool mornings and bright days; and when the stormy wind blows the strongest, these delicate insects, impelled by some inexplicable instinct force their way against it, and during a couple of months, successive legions pass on like an ever flowing stream.

"To quote L. G. O. Woodhouse (retired Surveyor-General of Ceylon)in his Butterfly Fauna of Ceylon he says, "Migration is an instinct possessed by certain butterflies and has been the subject of much speculation and wonder by all inhabitants of Ceylon, of diverse creeds and races. The flights in Ceylon are in various directions at different places, but in general, they appear to be towards the south on the east coast, and towards the north on the west coast of Ceylon, and chiefly towards the west in the hills near Kandy."

Very little is really known about these mass movements of the butterflies, which always seem to be in one direction. What causes them to start migrating, although there is evidence that the migration is often preceded by considerable overcrowding of the caterpillars. It is not known how these dainty creatures keep to more or less constant direction; or what makes them after all to resume a normal life. These are some of the perplexing problems that await solution.

In extensive studies carried out by the writer over a period of ten years, it has been found that the flights began about the last week of October and grew in intensity during the first three weeks of November and then decreased towards the end of the month. However in a lesser scale, movements of the insects continued sporadically through December and January to March or even June. In 1975 a very thin migration was observed in the 3rd week of September.

In South India major flights are reported to be towards south in October-November, with the return flight north in February and March. No return flight appears to have been recorded in Sri Lanka.

As far as I am aware, no convincing explanation has so far been advanced to solve the puzzle of the annual migration of the island's butterfly fauna. Some hold the view that these hordes are pilgrims on their way to Sri Pada (Adam's Peak), while others believe they are simply overflow movements. Whatever that may be, the very fact of its being hidden in mystery heightens our enjoyment and wonder of it.


By:K. G. H. Munidasa