The midges are back. Here's what they are and why they matter

Going for a walk on a sunny day can mean walking through a swarm of black flies.

These mosquitoes, known as midges, are common along Ontario's lakeshores, wildlife areas and parks. Most years, they begin to appear in early spring and continue throughout the summer before dying in the fall.

Doug Curry, a professor in the Department of Ecology and Evolutionary Biology at the University of Toronto, said that's a small price to pay for a healthy ecosystem.

“I think if they were to disappear, it would be a warning that things aren't going so well,” Kerry said of the bugs in and around Lake Ontario. “So I think it's a small price to pay for a clean lake considering they've been around for such a short period of time.”

Because midges can tell us a lot about our ecosystems, he said. When midges are abundant above reservoirs, oxygen levels are a constant indicator of healthy water. In their absence, it indicates water pollution.

In addition, adult midges are eaten by larger insects such as spiders and swallows.

Every month, in the spring and summer, new types of these bugs appear. There are over 4,000 species, all of which form in flocks as a way to mate.

“When you get these big herds, it's really a mating ritual,” Curry said. “So they have to communicate with each other to mate.”

Large swarms are usually male midges that band together to attract females. After pairing, Curry says the cycle begins again.

“(They) leave and mate and then the cycle starts again. (They) lay their eggs in the lake or in the street, and then the cycle starts again.”

Most of the species found in Ontario do not bite, but they are female because they need protein to mature their eggs.

Curry says they don't bite and there is no reliable repellent against them.

“They are certainly harmless creatures,” he said