Sex on the beach: Swarms of mating midges descend on Canada

If you’ve spent any time near a lake in the past few weeks, you’ve likely noticed relentless swarms of tiny, barely visible flies hovering near the water. But they won't hurt you - they're just in mating mode.

Non-biting midges emerge from lake bottoms to mate in swarms multiple times a year, experts say

Hundreds of species of non-biting midges thrive in Canada alone, with an estimated 10,000 species worldwide. They emerge from their larval layers in lake sediments multiple times a year to find a mate. (ChinellatoPhoto/Shutterstock)

If you’ve spent any time near a lake, river, pond or stream in Canada in the past few weeks, you’ve likely noticed relentless swarms of tiny, barely visible flies hovering near water.

But don’t be alarmed by the bugs, experts say. The swarms are just thousands upon thousands of non-biting midges that are in mating mode.

“The midges spend most of their lives as tubular larvae buried in the sediment of lakes or rivers, feeding on organic matter on the lake bottom, and in turn serving as food for fish and waterfowl,” says Douglas Currie, associate professor in the department of ecology at the University of Toronto and curator of entomology at the Royal Ontario Museum.

I think the best advice for people is to keep your porch lights off, keep your window and door screens shut, and relax. It will soon pass.- Douglas Currie, curator of entomology at the Royal Ontario Museum 

“But what we are seeing above ground is mating swarms. The midges emerge from the sediment periodically, sometimes two or three or four times in a year, and they mate.”

Midges of the same species try to synchronize when they emerge for mating in an effort to maximize the chances of reproductive success. That’s why, Currie says, there are so many of them swarming at any particular time. 

“If you come up by yourself, then you’re not going to have anyone to hook up with.”

Midges 'live to mate'

Male midges tend to fly free of the lake bottom before the females midges, then fly into the huge swarms of males to find a mate.

The sheer number of midges swarming means that birds and larger insects, which feed on the adult midges, simply cannot eat them all.

“It’s a strategy,” says Antonia Guidotti, an entomologist at the Royal Ontario Museum. “Midges are part of the ecosystem, so if you think of them as bird food, it might help you to tolerate them a bit better.”

There are hundreds of species of non-biting midges, which belong to the Chironomidae​ family, in Ontario alone, and an estimated 10,000 species worldwide. The insect family is closely related to blackflies and their peskier cousin, the biting midges, which are commonly known as “no see ‘ems.”

Adult non-biting midges only live for a few days, maybe a week, before dying, says Guidotti.

“They essentially live to mate. Soon they’ll be gone and then there will be another insect that people will get bothered by.”

While the long winter and heavy snowfall experienced throughout much of the country this winter will result in more standing water and increased water levels in lakes and rivers, it’s virtually impossible to discern if there are more non-biting midges swarming in any given year compared to another, according to Currie.

“Not a lot of people study the midges ecologically, especially in Canada. No one goes out and counts numbers and compares numbers to previous years. So it’s very difficult to pinpoint any reasons for why it may seem like there are more in a certain year."

Wait out midge mating times, expert suggests

According to Currie, while the adult midges will likely return in mid-summer or sometime in autumn for another lakeside orgy, the spring swarms will be gone within weeks, making them a minute problem “certainly not worth controlling.”

“In terms of insect pests, these midges are fairly well-behaved. I think people just don’t like to be bothered with large numbers of insects and sort of have a short memory about them.”

Like other insects, non-biting midges are attracted to light, and will swarm around lights on balconies and porches. With the exception of turning off outdoor lights and closing windows, there isn’t much that can be done about the mating swarms.

Bug zappers, while effective at killing individual flies, tend be very destructive and kill far more beneficial insects than ones that are bothersome, says Currie.

“I think the best advice for people is to keep your porch lights off, keep your window and door screens shut, and relax. It will soon pass.”


To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.