Millions of moths descend on Quebec cities

Massive clouds of aspen moths swarmed over parts of Quebec, including Roberval, in the Lac Saint-Jean region, earlier this week.

A viral video shows the insects blanketing the vehicles in a LaSarre auto dealership parking lot.

After the moths reproduce, they die. The result was piles of dead insects, which had to be gathered using shovels.

"It was incredible," a store employee told Radio-Canada. "They were everywhere, and all over the ground, you couldn't even walk without stepping on them."

The phenomenon was likely caused by the city lights attracting the insects, according to tienne Normandin, an entomologist and collection manager at l'Universit de Montral.

He's identified the bug as the large aspen tortrix, which he said is present every year in the boreal forest, but the occurrence of swarms is increasing.

"This illustrates well the cyclical movement of this species," he said.

Normandin said the last time a swarm of large aspen tortrix of this size was seen in the region was about 15 years ago, but he anticipates it'll happen again within a decade.

"Their metabolism is activated by heat," he said. "If we have hotter springs and longer summers with overheat conditions, their metabolisms will be activated sooner than later."

The entomologist said while moths are typically spread out over a vast area of forest, when they're concentrated in a small area as was seen in Lac Saint-Jean this week, the swarms can sometimes be so large and dense they're detected on weather radar.

"In the video, the swarm was very impressive and had a Biblical aspect to it," he said.

Normandin warned that not only could such moth clouds make driving dangerous, because they can impair a driver's view, they can also have health repercussions.

When the small, brown insects fly in swarms, their microscopic scales detach. These can irritate the respiratory tract of some people.

Normandin said the cleanup may be a challenge for people, but the moth carcasses will provide a feast for predators like birds and other insects.