Dragonfly stakes claim for animal kingdom's top long-distance traveller
A small dragonfly that migrates thousands of miles between continents could be the animal kingdom's most impressive long-distance traveller, scientists believe.
Pantala flavescens, which measures barely an inch and a half, has been found in locations as far apart as Texas, eastern Canada, Japan, Korea, India and South America.
The insects have strikingly similar genes, indicating that they have not had time to grow apart in their different homes.
There can only be one explanation for this lack of diversity, researchers believe. The dragonflies are undertaking breathtaking intercontinental journeys giving them a habitat range stretching across 4,400 miles or more.
Their secret is thought to be an ability to sail on wind currents that carry them between America and Asia.
Lead scientist Dr Jessica Ware, from Rutgers University in the US, said: "These dragonflies have adaptations such as increased surface areas on their wings that enable them to use the wind to carry them. They stroke, stroke, stroke and then glide for long periods, expending minimal amounts of energy as they do so."
The study, published in the journal Public Library of Science ONE, is the first to assess the insects' travelling habits by looking at their genes, said Dr Ware.
She added: "If North American Pantala only bred with North American Pantala, and Japanese Pantala only bred with Japanese Pantala we would expect to see that in genetic results that differed from each other. Because we don't see that, it suggests the mixing of genes across vast geographic expanses."
Direct evidence of the insect's migrations is still lacking, although dragonflies have been observed crossing the Indian Ocean from Asia to Africa.
Daniel Troast, who took part in the DNA analysis at Dr Ware's laboratory, said: "They are following the weather. They're going from India where it's dry season, to Africa where it's moist season, and apparently they do it once a year."
The dragonflies need fresh water to mate and lay their eggs. The scientists believe the hardiest fliers might make non-stop trips, while others could be "puddle jumpers" moving from one source of fresh water to another.
Confirmation of the findings would mean that P. flavescens easily breaks the 2,500 mile record for insect travel held by the monarch butterfly.
"Monarch butterflies migrating back and forth across North America were thought to be the longest migrating insects," said Mr Troast.
"But Pantala completely destroys any migrating record they would have."
Some other dragonflies never leave the pond where they are born, travelling no more than 36 feet in their entire lives, said Dr Ware.