Huge quantities of bugs undertake intense journeys.
Every autumn, millions of insects - including cabbage whites, eye flies, and grass flies - flee the cold and head towards warmer climates, crossing a narrow 30-meter-wide gap between two peaks in the Pyreenees. This stunning migration is closely observed by researchers who admire the process up close.
This spectacular event happens annually at the Pyreenees' Puerto de Bujaruelo, where an estimated 17 million insects move in synchronization through the narrow passage on the French-Spanish border. According to a team of researchers reporting in the journal "Proceedings B" of the British Royal Society, witnessing such a mass journey of insects is a true marvel of Mother Nature. Co-author Karl Wotton from the University of Exeter comments, "To see so many insects moving purposefully in the same direction is truly one of the great wonders of nature."
Notable species include the cabbage white butterfly (Pieris rapae), the eyefly (Musca autumnalis), and even minuscule grass flies (Chloropidae), measuring just three millimeters long. The study leader, Will Hawkes from the University of Exeter, expressed his awe at the experience, saying, "It was magical. When I swung my net through what seemed like empty air, it was full of tiny flies - all on this incredible journey."
It's been calculated that billions of insects cross the Pyrenees every year, continuing their journey to Spain and sometimes even Africa. These migratory insects, especially the flies, have a significant role in our ecosystem. The University of Exeter found that almost 90% of the recorded insects were busy as pollinators, transferring genetic material across long distances between different plant communities, improving overall plant health.
As climate change progresses, the future of insect migration will be threatened. However, Hawkes is optimistic, asserting, "Insects are resilient and can recover quickly."
The researchers seized the opportunity to observe the insects as they flew south during the day, staying low and easy to count. Wotton commented on the fascinating occurrence, explaining, "The mixture of high mountains and wind patterns transforms an otherwise invisible high-altitude migration into a spectacle that can be observed from the ground." Overall, about 90% of the insects captured over the course of four years were flies. Less common insects like butterflies and dragonflies accounted for less than two percent of the total.
This particular pass, Puerto de Bujaruelo, is situated at about 2,270 meters and is one of the many mountain passes in the area. The area attracts not only insects but hikers, with several well-used trails passing through the region. Numerous species can be found in the area, including the common field hoverfly (Eupeodes corollae). Despite these numbers, studies from other European regions have revealed a significant decline in migrating hoverflies, often more than 90% since 1970, indicating a likely higher number of insects present during previous migration seasons.
Hawkes and his team returned to Puerto de Bujaruelo to see if the migration continued and to determine its scale and species composition. They employed video recordings of butterflies, targeted observation of moths, and a flight trap. The results were quite remarkable, as Hawkes recounts, "The number of hoverflies was still astounding: There were days when the number of flies exceeded 3,000 individuals per meter and minute." However, research from other parts of Europe reveals alarming drops in the numbers of migratory hoverflies, with decreases as high as 90% since 1970. So, it's possible that there were many more insects on the move in the past.
Read also:
In comparison to the insect migration in the Pyrenees, educational programs in Spain often cater to the study of various insect species, providing children with an understanding of their importance in ecosystems. Meanwhile, researchers in France have also conducted studies on the impact of climate change on insect migrations, aiming to predict future changes and protect these vital organisms.
