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The Great Dragonfly Migration

We seem to know everything about animal migration, it turns out that there is a huge migration of millions of individuals of dragonflies from India, through the islands of the Indian Ocean, South Africa, East Africa and back to India


Most of us have heard about the migration of herbivores: we protected in East Africa, the American buffalo, the reindeer and others, once a year we are exposed to news about the migration of butterflies from north to south in America, traditions tell about the migration of lemmings in Scandinavia.

Butterflies have long "flooded" the south of the Arabah and the Jordan Valley, a seasonal migration of millions of birds adorns our name twice a year, now there are those who claim to have located the longest known insect migration.

The dry facts that have been known for a long time are: in October every year, millions of dragonflies appear on the southern beaches of India ... and after a few days they disappear.

Every year around October 20, millions of dragonflies appear in the Maldives. In November and December, the dragonflies continue to arrive in "migration waves" when each wave stays for a few days and leaves, in December the dragonflies disappear and reappear at the end of April.

The islands that lie in the Indian Ocean about 500-1000 km from the mainland (southern India) and most of them are built of corals with no (visible) water sources are not a typical place for dragonflies, the dragonflies appear on the islands in geographical order from north to south and southeast. In November, dragonfly waves appear in the Seychelles, first in the north and then as far as Aldebra, the Seychelles are about 3,000 km from India.

In March and April, swarms with millions of dragonflies appear in East Africa (1,200 km from Seychelles), in May they appear in Mozambique and South Africa. Later in September the swarms appear again along the eastern coast of Africa and in December/January again in the south of the continent.

Around April, the appearance of dragonflies in the Maldives begins in reverse geographical order. Sailors in the Indian Ocean know how to tell that at that time thousands of dragonflies land on their ships. Information about swarms of dragonflies flying in the direction of the sea was accepted with the assumption that this is a flight resulting from a mistake and therefore the dragonfly's law is to the kidney.

We will also mention that dragonflies need water to complete their life cycle, the adult dragonfly lays its eggs in the water, the larvae that hatch grow and molt several times, at the last stage an adult insect emerges from the molt, leaving the water and flying.

So far, facts that were known to the inhabitants of the islands, to seafarers, to Indians in the south, to Africans in the east and even to biologists on the islands.
We will also add that although the appearance of dragonflies in the Maldives marked the beginning of the seasonal monsoon, the winds were not linked to migration.

The biologist Charles Anderson publishes in the monthly "Equatorial Ecology" (Tropical Ecology) his research on the aforementioned "appearances", according to him none of the inhabitants of the islands (including biologists) could explain where the dragonflies come from and where they disappear.

Starting in 1983, the biologist collects data on the arrival times of the dragonflies in the various places, after research and testing, Anderson came to the conclusion that the appearance of the dragonflies intermittently and in distant places constitutes the longest insect migration known in the world, according to his calculation, the length of the (circular) migration route is about 14000 to 18000 km M.

The dragonflies migrate from India to the Maldives, the Seychelles and the coast of Africa over vast expanses of open ocean, with some of the time the direction of flight is against the wind. It is possible that in order to overcome the headwind the dragonflies raise up to about 6,000 meters. Another part of the migration is done with and with the help of the winds in the equatorial circulation Inter-tropical Convergence Zone which produces wind at a height of about a thousand meters. On the way, the dragonflies eat small insects and are eaten by birds who take advantage of the opportunity, it is possible that the combination of "back wind" and "flying food" encourages the birds (which eat dragonflies) to set out and wander, and indeed together with the dragonflies, species of insect-eating birds appear: cuckoos , shrekraks, thamsims and others accompany the dragonflies on their way to Africa.

Anderson found that 98% of dragonflies are of the species Pantala flavescens. A dragonfly that is known for its ability to fly great distances at heights above 6 km. The dragonfly is able to travel the distance between India and the capital of the Maldives in 24 hours.

There is still the problem of a lack of water in the Maldives, which leads Andersen to claim that the dragonflies fly all the way from India to the coast of East Africa within one life cycle, meaning that the same individual makes a journey of up to 7,000 km. The migration cycle begins in India after the monsoon rains, in the resulting puddles the generation that will cross the Indian Ocean through the islands to the African coast grows. Upon arriving in East Africa, the dragonflies lay eggs in puddles and bodies of water created during the short rainy season (October/November). The adults continue south and breed in the puddles created during the summer rains (December/January) of South Africa. Now the dragonflies return to the long rainy season (March/April/May) of East Africa and another life cycle is developing whose graduates will fly all the way to India
And they will arrive in time to take advantage of the monsoon rains... to increase.

That is, a circular migration that lasts four generations and follows the rain for thousands of kilometers over the open ocean, partly against the wind, partly together with predatory birds, the well-known, well-known long migration of insects, because after such a discovery it is clear how lacking the knowledge we have... is.


6 תגובות

  1. It's quite amazing that those who come out continue the path their parents started (the road back to India to Doge) and end up where their parents started, and never make a mistake.
    Even with a map I would get lost.

  2. Among the native Indians, dragonflies are a miniature species of dragons.. (dragon fly) ha ha.
    They also symbolize "illusions".. and their distribution.

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