The featherlight long-distance fliers with parchment-thin wings

Dragonflies and damselflies are predatory insects with powerful jaws, compound eyes and spectacular colours. What is less well known is their ability, like migratory birds, to travel long distances and overcome geographically challenging barriers such as the Indian Ocean and the Alps.

For a long time, scattered observations and papers have indicated migratory behaviour in a number of dragonfly species. Now, a comprehensive study of this global phenomenon has been completed. After several years of work and a review of 392 papers, the researchers have identified 100 species with documented migratory behaviour and a further 85 that are also likely to migrate. The results reveal a unseen world above our heads - where insects undertake journeys that can in some cases rival those of migratory birds.

“Many people see dragonflies as something that hovers over a forest pond for a few days in July. But some species fly across continents and open seas. It is truly staggering when you begin to grasp the scale,” says researcher Johanna Hedlund at Lund University, who led the study.

The research also shows that the ability to migrate has evolved several times over the course of evolution, mainly as a way to escape cold, drought, and environments where reproduction has become impossible. Most dragonflies, like other migratory insects, complete their round-trip migration over several generations. Others do something even more unusual: they fly from their hatching sites in hot valleys up to cooler elevations in the mountains - only to return later.

“I was genuinely surprised by how many examples there are of dragonflies completing an entire migration cycle, that is, a round trip journey, within a single lifetime. That is rare in insects and, oddly enough, something research has not paid much attention to before,” says Johanna Hedlund.

The researchers suggest that dragonflies can serve as guides to the vast, largely invisible mass migration of insects taking place globally. Because dragonflies are easy to recognise, they can help scientists understand how other insects move between ecosystems - from pollinating hoverflies to pests and disease vectors. Their migration routes can also reveal which environments are especially important to protect for migratory insects. In addition, dragonflies are sensitive to water quality and environmental changes, making them important indicator species.

“Dragonflies function almost like nature’s own sensors. By tracking their movements and where they thrive, we can better understand how ecosystems and the climate are changing,” concludes Johanna Hedlund.

FACTS: SPECTACULAR MIGRANTS

In Japan, the species Sympetrum frequens - the red dragonfly known as “Akiakane” - migrates from valleys up to cooler mountain areas during the summer, then returns again in the autumn. Another extreme migrant is the globe skimmer (Pantala flavescens), which is believed to carry out annual migrations between India, the Maldives and eastern Africa. These journeys take place partly over open ocean and cover thousands of kilometres.

Several migratory species are also found in Sweden, including the migrant hawker (Aeshna mixta) and the four-spotted chaser (Libellula quadrimaculata). At the same time, the vagrant emperor (Anax ephippiger) - a species originating from Africa and the Middle East - is being seen increasingly farther north in Europe, even in Sweden.