Friday, November 6, 2009

Where have the dragonflies gone?

There are so many amazing things happening around us in nature that we are not aware of. Take the case of dragonflies, the pretty but feeble looking insects.


Have you noticed that some species of dragonflies are found only seasonally? If you are in South India and you ask someone during off season where the insects have gone, don’t laugh if the answer is “Africa”. That is likely to be true.


Now, how do the dragonflies get to Africa? Simple. They fly. Not as stowaway on an aeroplane, but on their own motion. All across the Indian Ocean/Arabian Sea. They cover a distance of 7000-9000 kilometers. They fly across in hordes. Millions of them.


Almost the entire lot of migrant dragonflies is made up of Globe skimmers (Pantala flavescens). A sprinkle of Twisters (Tholymis tillarga), Pale-spotted emperors (Anax guttatus), Blue perchers (Diplacodes trivialis) and Vagrant emperors (A. ephippiger) are also involved


Flocks of dragonflies taking off towards the sea had been observed by many in the past. The general presumption was that it was a kind of mass suicide mission or something of the sort. Only recently their destination was discovered – Africa via Maldives and Seychelles. And they come back to India. Well, at least their descendants.


The credit for this recent discovery goes to Charles Anderson, a biologist attached to the Maldives Marine Research Center. He noticed the seasonal (October-December) arrival of the insects in Maldives, their departure after a few days and their return in April-June. The scientist pursued the matter.


Anderson was able to establish a pattern to the migration. From Maldives the dragonflies mostly went to Seychelles and from there to Africa. He also linked the mass movement to Inter-tropical Convergence Zone, an extraordinary weather system in which there is a seasonal shift in the wind direction. The deduction is that the dragonflies could be taking advantage of this phenomenon.


The migration cycle appears to be linked to the monsoons. The dragonflies reach Maldives and Eastern Africa just ahead of the rains at those places and return to India in time for the monsoon.


Amazing world, isn’t it?


(Note: I don’t think the insect in the photo is the migrating type. Click on photo to enlarge. Copyright reserved.)


Links:


http://ecoworldly.com/2009/07/22/14000km-dragonfly-migration-discovered-longest-of-any-insect/


http://news.bbc.co.uk/earth/hi/earth_news/newsid_8149000/8149714.stm


Connected posts:


Photos: Dragonflies by KO Isaac


Dragonflies, Onathumpi



6 comments:

YOSEE said...

Yes, certainly amazing ! But with weather and climate systems going awry, insect and bird migrations too are begining to show drastic changes in pattern. It has already been noticed and documented that certain butterflies that used to mass-migrate across the deccan plateau towards the Western Ghats have not done so in the past two years. Sad.

Sunita said...

What a sight that must make! Imagine swarms of dragonflies flying across the ocean en masse, going to 'phoren'.
Incidentally, I think some of them have been diverted to Mumbai. It's literally swarming with dragonflies right now.

Abraham Tharakan said...

Yosee, how the climate change affects nature is so sad.

Abraham Tharakan said...

Thank you for the comment, Sunita.

Kariyachan said...

Very interesting post, I just wonder what makes these dragonflies migrate, how do they learn to migrate? What guides them? ..

We humans think we only have the capability of thought and reasoning and intelligence.

Wonder how we can equate Darwin's evolution theory with our past, present and the future.. In another million years (if our planet is intact), would creatures like dragon flies also evolve and posess intelligence like us Homosapiens, by the nurturing of the mother nature/universe or the power of creation(God)?

Abraham Tharakan said...

Kariyachan, a profound thought, I must say.