/ 3 March 2016

Sex-crazed dragonfly on ‘suicide mission’

Research shows that these dragonflies fly 7 000km in a single journey.
Research shows that these dragonflies fly 7 000km in a single journey.

It’s not the journey that matters, it’s the destination. That’s all fine and well if you’re a human and can jump on a jet-propelled plane. But in the natural world, getting somewhere requires that serious calories are burned.

For a long time we thought that monarch butterflies were the hardiest fliers, flapping their way to locations more than 4 000km from their departure branch.

But science is ready to hand the crown to a tiny new champion: the Pantala flavescens, a type of dragonfly measuring about 4cm in length.

Research by biologists at Rutgers University-Newark in the United States – published in the PLOS ONE journal – shows that they fly 7 000km in a single journey.

The record-smashing trip is all about sex. The hardiest proponents can travel that distance in one go, stroking their elongated wings to get into the path of strong winds. Some hop on the whirling mass of a tropical cyclone to get a bit more speed. The laziest dragonflies leapfrog from island to island, taking in some fast food along the way. Most die.

The Rutgers research started from observations made of dragonflies winging their way across the Indian Ocean, from Asia to Africa. They were following the same trade winds that allowed sailors to undertake a similar trip two centuries ago. In this case, dragonflies are migrating to take advantage of wet weather. Moisture is a must for their reproduction because they lay eggs in small pools of water.

Jessica Ware, assistant professor of biology at the university, says the need to procreate drives dragonflies through a “kind of suicide mission”.

The findings come from the genetic tracing of dragonfly populations across four continents. This showed that the genes of dragonflies that lived implausibly far apart to be related were too similar for them to not be related. Ware says if local variants only bred with each other, it would be reflected in the data. “Because we didn’t see that, it suggests a mixing of genes across vast geographic distances.”

This wanderlust makes the Pantala different from their cousins – the average dragonfly struggles to leave the pond where they’re born. Maybe Pantala just don’t find each other that attractive.