Almost 800 species of Chironomidae (non-biting midges) live in Canada. Pictured here is Chironomus plumosus. Non-biting midges are known for forming huge mating swarms in the evenings. (The Canadian Encyclopedia/Janet Graham) As warmer days approach, the city is seeing a rise in throngs of midges swarming around waterways. The midges are a common occurrence in Toronto in the spring around late April and early May. These pesky little creepy-crawlies can be hard to avoid, but experts say they are the sign of a healthy ecosystem. Midges, despite sharing similarities in appearance to mosquitoes, are harmless, non-biting insects from the family of flies and are primarily known to inhabit the bottoms of ponds and lakes, experts say. Here’s everything you need to know about these tiny insects: They only live a few days as adults There are many different species of midges across Ontario, but the ones that swarm together near water in Toronto are usually of one specific family dubbed the “Chironomidae,” also known as the non-biting midge, Darryl Gwynne, emeritus professor of biology at the University of Toronto’s Mississauga campus told CTV News. They live at the bottom of water bodies, feeding on organic matter and algae, before they rise to transform from larva into adults, experts say. Douglas Currie, curator of entomology at the Royal Ontario Museum and U of T professor in the department of ecology and evolutionary biology, told CTV News that they occur in huge numbers in the sediments of lakes, rivers and streams. Like all other flies and species like butterflies, moths and wasps, these insects have four stages to their life cycle – eggs, larva, pupa and adult, Currie says. Their life as adults only lasts a few days at most, he says. What is the function behind the swarms? Once the midges are ready to emerge as adults, they tend to do so synchronously, during the ice-free period, Currie says. “It’s very important that they come out en masse, so that they can take care of mating,” he says. “They typically will form swarms. The swarms will consist mainly of males and females will fly into these swarms to become mated.” The entire productions of swarms are formed for a singular purpose – mating. These swarms sometimes look like smoke hovering over a tree or a prominent rock, which are the markers adult males use to form their swarms. “The visual perception – the visual sight of a swarm is what attracts the females, like a lot of different animals in nature,” Gwynne says. “Each one is doing a display, and they’ll attract the female. From the female’s perspective, it gives them an opportunity to get into the swarm and perhaps even choose which male they want to mate with.” Each female can produce hundreds of eggs, experts say. However, they disappear as quickly as they appear due to their short-lived lifespan, Currie says. There are dozens of species of midges that reside in Lake Ontario, each with different life histories and characteristics. “What we’re going to be seeing is either different generations of the same species or different species altogether, that have their own characteristics about when they come out,” Currie says. Impact on the ecosystem “Midges are really important in ecological communities,” Gwynne says. Currie calls them “a keystone component of the aquatic food web,” explaining that they are one of the most important components because they serve as food for other invertebrates, fishes, birds, and when they emerge, they’re food for things like dragon and damselflies, aerial birds and more. “These are barometers of a healthy ecosystem,” Currie says. “They are very important if you like fishing, or if you like the aquatic birds that we see and so forth.” Some of the species of midges can act as indicators of poor habitat and others can be indicators of good habitats. It depends on the species, Gwynne explains. The only downside for humans is when they run through a swarm or walk near one, they get in your hair, eyes or mouth. “This, to me, is a small price to pay for having a healthy ecosystem,” Currie says. So what should you do if you encounter a swarm of midges in the coming weeks? Experts advise keeping your mouth closed if you ever get caught in a swarm, to avoid breathing in or swallowing them. These insects are attracted to light, so keeping a porch light on is an invitation for them. Keeping the windows of your house shut or screening your windows and patio doors is effective in keeping these insects outside your home.