Hikers swarmed by black flies in Troms

Hiker Sissel Eriksen encountered an extreme swarm of black flies during a mountain trip to Storhaugen in Sjøvegan, Troms, Dagbladet reports.

“When we got above the tree line, there were flies everywhere. They covered our backpacks—it was just completely black,” Eriksen said.

The group pressed on despite the conditions, hiking for four to five hours as the flies swarmed around them. Though the insects did not bite or sting, their sheer numbers made the experience overwhelming.

“We could barely take photos without flies on the phone. It was intense. We had to put on jackets and cover up,” Eriksen said. She added that she had never seen anything like it in her years of hiking.

After sharing her experience in a Facebook outdoor group, she received over a thousand reactions and hundreds of comments. Many confirmed that such swarms are normal in the mountains under the right conditions.

Biologist and professor Anne Sverdrup-Thygeson of NMBU explained that the insects are likely black flies, also known as sweat flies, which can appear in massive numbers this time of year, particularly in the mountains.

“If there’s been a wet spring followed by sudden warmth and still air, huge numbers can emerge. It’s a natural phenomenon,” she said, noting that the flies are harmless, seeking only sweat and bodily fluids.

Her advice for hikers caught in such a swarm: move to higher, windier ground or choose a different route. Otherwise, she said, “you just have to endure it.”

Eriksen said she does not regret the hike, despite the ordeal. “It was beautiful up there. But I hope I don’t experience that again anytime soon.”