Photo: The Canadian Press

The millions of black-and-orange butterflies that have carpeted flower beds across the Montreal area in recent days are waiting for winds to carry them south to warmer weather, according to an expert at the Montreal Insectarium.

Southern Quebec has become host to an "unprecedented" number of painted lady butterflies in the last ten days, said Max Larrivee, the museum's head of research and collections.

"It's extremely unusual," he said in a phone interview Wednesday. "This is the largest on record — no doubt."

One factor that can explain the increase, Larrivee said, is that the butterflies arrived early this year and therefore benefited from an extra reproduction cycle.

Their large numbers, he continued, allowed the insects to cover a bigger territory than they normally would.

"In the spring they came really early and in really high numbers in April, which allowed them to take advantage of a much larger territory to reproduce, but also to reproduce one more time than they normally do," Larrivee said.

Most of the painted ladies will probably leave Quebec to continue their southwest migration towards Texas and Mexico within a week or so, or whenever the winds shift, Larrivee said.