Insect invasion: See millions of mayflies swarming in northern Ont.

CTV News Channel: Insects invade Northern Ontario Management Biologist, Ontario Ministry of Natural Resources Dave Fluri says the shadfly recommends that people leave the bugs be.

It’s a dreaded time of year for many residents of North Bay, Ont.

Aquatic insects known as mayflies or shadflies emerge by the millions from bodies of water, including Lake Nipissing in North Bay, and adhere to doors, windows, lampposts and any other surface they can find. The huge concentrations of mayflies may make you cringe, but Dave Fluri, management biologist at Ontario’s ministry of natural resources, says it’s perfectly natural.

The insects live most of their lives in the water. The nymphs develop wings, and emerge at this time of year because water temperatures are “essentially perfect for them to transform,” into adults Fluri said in an interview with CTV News Channel on Wednesday.

“They feed on organic matter in the water and then when they’re ready to reproduce they transform into adults, they leave the water and they reproduce and lay their eggs.”

The reason mayflies are mostly seen in North Bay due to the city’s location at the eastern end of Lake Nipissing, “most of which is excellent mayfly habitat,” Fluri said.

The wind tends to “push” the mayflies onshore, so residents within a kilometre of the lake will tend to see large swarms of the insects.

“I think they are in the millions,” Fluri said.

The swarming typically lasts 2-3 weeks, before it slowly peters out.

However frightful a sight, the insects are “completely harmless,” Fluri said. And they only live a day or two as adults.

“So I think it’s really futile to try to kill them all off,” Fluri said. “I would recommend that people just let them be.

“They’re kind of a beautiful and wonderful part of the natural system and we should feel happy that we can enjoy them.”