When millions of insects cross a gorge in the Pyrenees: News

“A blizzard of yellow and white butterflies, like a storm of petals”: ​​More than 17 million insects cross a gorge in the Pyrenees every year, according to a study that describes for the first time in detail this great migration of nature.

On a hot September day, in the Bugaruelo Pass on the border between France and Spain, British scientist Will Hawkes found himself surrounded by a cloud of insects buzzing in a “determined” manner.

The researcher at the University of Exeter (United Kingdom) and first author of the study published Wednesday in Proceedings B of the British Royal Society, told AFP that he saw a “living carpet” at his feet.

Houseflies, butterflies, dragonflies…: Every year more than 17 million insects cross the Pujaruelo Pass, which is only 30 meters wide, according to the work carried out by this specialist in insect migration.

At the peak of the wave, more than 3,000 people rush into the breach every minute. Coming from continental Europe, head south.

This phenomenon had already been documented in 1950 by the British ornithological couple Elizabeth and David Luck, who spoke of “the most remarkable migrants of all time.”

But this mass migration cannot be quantified. That's why, every fall since 2018, Will Hawks' team of researchers has gone to Pujaruelo Pass, where they have installed video cameras and traps where the insects pass, in order to count and identify them.

Most (90%) are hoverflies with orange and black stripes. Will Hawks explains that these flying insects from the fly family feed on aphids and are therefore ideal for ridding crops or gardens of pests.

They're also talented pollinators, he adds, and because they travel hundreds of miles, they may prove better pollinators than “relatively sedentary” bees.

The scientist, who relies on a 2020 German study indicating a collapse in the numbers of similar species, says their numbers have declined due to climate change, the use of pesticides and habitat loss.

In the past, the migration of collared hoverflies must have been more dramatic, according to Will Hawks. Still, the scenery remains “enchanting,” he comments, and he recommends going to Bujaruelo Pass on a sunny day in September or October. Especially if the wind blows from the south.

Posted on June 12 at 7:07 p.m., AFP

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