Thursday, July 16, 2009

Dragonflies migrate 14,000-18,000 km from India to S. Africa

Millions of dragonflies migrate thousands of kilometers across the Indian Ocean from southern India to Africa, reports the BBC.

The migration may be the longest of any insect, exceeding that the Monarch butterfly the moves 7000 kilometers (km) between Mexico and the United States, says Charles Anderson, the author of the study, which is published in the Journal of Tropical Ecology.

Anderson kept detailed records of dragonflies arriving in the Maldives, a chain of islands that lie 500 to 1000 km off the coast of Southern India. He found their dates of arrival across the islands show a steady movement from north to south. The insects, which flight at altitudes up to 6300 meters (20,475 feet), end up as far south as Mozambique, in Southern Africa, before returning to India, a round trip of 14,000 to 18,000 km.

The dragonflies appear to follow the Inter-tropical Convergence Zone weather system, taking advantage of rain puddles to breed. Maldivians, the people who inhabit the Maldives, "consider the dragonflies' arrival to be a harbinger of the north-east monsoon," according to the BBC.

Anderson told BBC that bird species seem to overlap with the dragonflies, suggesting they feed on the insects as they travel.

Over 98% of the dragonflies found in the Maldives are Globe skimmers (Pantala flavescens), although Pale-spotted emperors (Anax guttatus), Vagrant emperors (A. ephippiger), Twisters (Tholymis tillarga) and Blue perchers (Diplacodes trivialis) are also known to occur on the islands.

R. Charles Anderson. Do dragonflies migrate across the western Indian Ocean? Journal of Tropical Ecology, Volume 25, Issue 04, July 2009


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