Mild winter weather will get bugs buzzing sooner

A record mild winter and projected warm spring means black flies and mosquitoes could be showing up in our backyards earlier than expected within the next few months.
A record warm winter in most of Canada means that mosquitoes could be on the wing earlier than usual this year in many provinces. (James Gathany/Centers for Disease Control and Prevention/Canadian Press)

The onset of summer means longer days, warm, breezy nights — and a possible onslaught of winged pests dive-bombing onto the heads of Canadians.

A record mild winter and projected warm spring means black flies and mosquitoes could be showing up in our backyards earlier than expected within the next few months.

If you cue on temperature and we get a couple of freakishly warm days, you come out, start your life, and then get hammered when it gets cold again.

"The first black flies should be on the wing when the first buds on the trees start to come out," said Douglas Currie, associate professor of ecology and evolutionary biology at the University of Toronto. "If that's going to be a few weeks earlier, then the flies will be out, too."

Trees may very well be budding earlier than usual, too, on account of soaring temperatures. 

This winter was an exceptional one for most of the country, said Richard Moffet, a meteorologist with Environment Canada.

"The only area in Canada where they got normal or below-normal temperatures for the winter was on Vancouver Island and the coast of B.C. Other than that, it was above normal throughout Canada," he said.

The unseasonably mild winter was especially felt in the Prairies, which had a winter with temperatures that were on average six degrees above normal.

What does this mean for black flies?

While in a dormant state, most black flies are in the egg stage and remain that way for the winter, even a relatively mild one such as this year's.

"Because the eggs overwinter while in streams and rivers, they stay in that state regardless of what's going on over top of them," Currie said.

"However, it's quite likely if it's much warmer than usual that they'd hatch earlier than they normally do, especially if the ice is off the streams and rivers."

Currie said that while the black flies will likely show up sooner in a year as warm as this, there probably won't be an overabundance of them.

There are a number of factors, such as light and water temperature, that act as cues for black flies to emerge from the water and start buzzing about our heads.

The flies will grow until they reach a certain stage in their development but won't hatch until conditions are just right.

"Their developments are really under the control of temperature," said Stephen Heard, a professor of environmental ecology at the University of New Brunswick. "So, if the water is warmer earlier — and rivers and lakes are likely to warm up earlier — then they're going to start developing sooner and probably develop faster."

Black flies are most abundant in this country over the Canadian Shield, and they could be hitting hard this summer because of ideal weather conditions. (iStock)

Heard said insects often use the amount and earlier onset of daylight as their cue to hatch because it's a much more reliable indicator than temperature.

"If you cue on temperature and we get a couple of freakishly warm days, you come out, start your life and then get hammered when it gets cold again."

Currie said he doesn't expect to see as many black flies dying off this spring because of low water levels or the usual late-winter cold snaps.

"So, if the water is copious in spring, I'd expect either a good or bad black fly season, depending on your perspective," he said.

What does this mean for mosquitoes?

Unlike black flies, which breed in flowing waterways, mosquitoes breed in standing water, so a melting snow pack is essential to their development. They usually track the withdrawal of snow from the ground and appear as it recedes. 

"Large snow pack means lots of those little puddles in the woods and temporary ponds where mosquitoes breed," Heard said.

But as most parts of Canada haven't been buried under their usual amounts of snow this winter, mosquitoes could have fewer places than normal in which to breed, resulting in smaller populations.

"In warmer, drier weather, [mosquitoes] might develop faster, but there won't be as many," Heard said.

Currie agrees but doesn't discount the mosquitoes altogether, saying they do quite a good job of finding protected places in which to hide and breed when needed.

That adaptability is probably of little comfort to many Canadians, who would prefer to spend their summer months without inadvertently feeding both pests.

Rollover each region to see the black fly and mosquito outlook for Canada