Mosquitoes, the scourge of cottage country. Last year, a mild winter with warm, wet conditions in the spring led to a spike in the blood suckers’ numbers.
“The mosquito numbers were crazy because we never had a freeze event again that killed all those babies that were first laid,” says Rosalind Murray, an evolutionary ecologist at the University of Toronto Mississauga, who studies insects.
This summer, however, may not be as severe. Warm temperatures in mid-March stirred female mosquitoes from hibernation. But the ice storm at the end of the Month killed off any eggs laid.
That doesn’t mean we won’t see a surge in mosquitoes this summer, though—they may just be delayed compared to last year. The province’s current wet and warm conditions are ideal for mosquitoes. After hibernating in leaf piles, gutters, and other hidden places, the insects emerge at around 12 degrees, says Murray. By 16 degrees, you’ll start to see the mosquitoes in noticeable numbers, especially if temperatures aren’t dropping overnight.
Mosquitoes lay their eggs in stagnant water. This could include clogged gutters, tire swings, flowerpots, or even parking lot puddles. “They can survive pretty grotesque conditions,” says Murray. When the temperature of the water they’re laying eggs in is cool—around 10 degrees—it can take the mosquitoes more than a month to mature from egg to adult. But as the temperatures warm, they mature faster. “Their metabolism speeds up,” says Murray.
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Twenty-four degrees is the sweet spot. Once the water hits that temperature, mosquitoes mature from egg to adult in four days.
But mosquitoes do have their limits. Murray says Canadian species are generally more cold tolerant than heat tolerant. Stagnant water baking in the sun could be too hot for them to reproduce. That’s why mosquitoes often reproduce in dense vegetation. The plants provide shade, which prevents the pools of water from evaporating.
Vegetation also provides protection from predators. “If you go to a lake, you don’t see a thousand baby mosquitoes because it’s filled with fish,” says Murray. “But as soon as you get a tiny pool of water that might be there for about a week, that’s when you get a mosquito-only breeding habitat.”
As climate change brings more adverse weather conditions and warmer temperatures, we are seeing southern mosquito species travel further north, bringing with them tropical diseases, such as dengue fever and the Zika virus. “Usually, they’ve moved north throughout the summer, or they’ve piggybacked on human transportation,” says Murray. But she adds that Canadian winters tend to wipe them out. “We are pretty safe from some of the more dangerous vectors of diseases,” she says.
Canadian species do, however, carry the West Nile virus. With last year’s increase in mosquitoes there was a jump in West Nile cases: 72 compared to 61 in 2023.
People can limit the number of mosquitoes on their property by removing stagnant water, trimming excess vegetation, and using a Health Canada approved bug repellant. But the only surefire thing that will drastically decrease the mosquito population is hot, dry weather.
“If there’s a heat wave and all of those puddles, those stagnant pools, the temporary wetlands that show up in spring, dry out by late summer, you’ll see no mosquitoes,” says Murray. “If there’s no water, there are no mosquitoes.”
But as much as we cottage owners cross our fingers for mosquitoes to disappear this summer, Murray points out that no mosquitoes is bad for the ecosystem. The insects are an important food source for fish, birds, dragonflies, and other species. “We wouldn’t have dragonflies and birds without mosquitoes,” says Murray.
For those who want to see what the mosquito situation looks like in their area, they can look it up on OFF’s OFFCast Mosquito forecast.
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