Millions of Insects Migrate Annually
A 30-meter gap in the Pyrenees mountains serves as a migration highway for insects, with up to 3,000 flies passing per meter per minute.
Scientists Discover High-Altitude Migration
Researchers from the University of Exeter in England have discovered that over 17 million insects annually migrate through the Puerto de Bujaruelo, a roughly 30-meter gap in the Pyrenees between France and Spain. The new study was published in the journal Proceedings of the Royal Society B Biological Sciences on June 11.
Stunning Scale of Insect Movement
"It's an astonishing sight to behold. You put your net out and it's just filling up with these tiny little flies, all part of this incredibly vast migration," said Will Hawkes, an ecologist and conservationist at the University of Exeter.
Historical Origins of the Discovery
The new study builds on observations made in the 1950s by British ornithologists Elizabeth and David Lack, who noticed the migration through the Puerto de Bujaruelo Pass, which sits at an elevation of 2,273 meters. "They saw large numbers of hoverflies [Episyrphus balteatus] migrating over the pass. We went there to see if that migration was still occurring and to record the species and numbers involved," Hawkes said.
Diverse Array of Insect Species
"Not only were large numbers of hoverflies still migrating over the pass, but so were many other insects. These insects originate from as far north as Scandinavia, flying south to Spain and probably beyond for the winter. On some days, there were over 3,000 flies passing per meter per minute," he added.
Along with hoverflies, the researchers observed large white butterflies (Pieris rapae), dragonflies (Odonata), and house flies (Musca domestica) passing through Puerto de Bujaruelo. The team used cameras, nets, and keen eyesight to detect and record the insect types.
Declining Insect Populations
Insect populations worldwide are in alarming decline, and it's likely that the number of insects migrating through the pass has decreased since it was first observed 70 years ago. The scientists hope their new findings can drive efforts to protect insect habitats. "Insects are incredibly resilient and can recover quickly," Hawkes noted.
A Rare and Visible Migration
The sight of so many insects moving in unison is a natural spectacle, according to lead researcher Karl Wotton. "The combination of high mountains and the prevailing wind patterns means that this high-altitude migration, which would normally be invisible, is squeezed into a narrow pass and becomes visible from the ground," Wotton said.
Summary
Puerto de Bujaruelo Gorge in the Pyrenees mountains serves as a migration highway for millions of insects each year. Over 17 million insects, including hoverflies, butterflies, and dragonflies, migrate through the 30-meter gap, potentially traveling from as far north as Scandinavia to Spain for the winter. Scientists are studying this high-altitude migration in the hopes of raising awareness about insect decline and protecting insect habitats.