Entomologists assess bug impacts of 'weird NWT weather'

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The Northwest Territories' March heatwave has disrupted many human activities – and could have an impact on the territory's insects, both this spring and in the long term.

Warm conditions across much of the NWT may bring out "spring mosquitoes" earlier than usual, and could lead to a premature die-off.

However, experts said the summer bug season would be unaffected by warm March temperatures alone.

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"It takes time. The ground is still quite cold and frozen at this time of year, so the summer nuisance won't be a part of it," said Taz Stuart, an entomologist who has worked on mosquito identification projects with the territorial government for the past decade.

"But the spring nuisance may come out earlier than expected. What will happen is you would expect the weather to turn cold again, and you might get some early die-off of some nuisance mosquitoes – which is a good thing.

"It all depends on how long this warm spell is going to hit before you get that cold spell again," said Stuart.

"The overwintering adult mosquitoes that are out there, the females, they may start looking for a blood meal. And that's where if you drink blood, and then it gets cold again, blood has water in it that will crystallize – and then kill the mosquito before it can lay eggs."

Doug Currie, the Royal Ontario Museum's curator of entomology and a black fly specialist, said there would be no impact on black fly numbers or activity from the March heat.

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"The immature stages of black flies live exclusively in streams and rivers, with most NWT species overwintering in the egg stage. As eggs are safely buried in the stream bed this time of year, they are insulated from variations in air temperature, and thus are completely unaffected by the current warm spell," said Currie, who is also an associate professor at the University of Toronto, by email.

"Black flies, like most other insects, are relatively resilient to occasional bouts of unusual weather."

Disease mosquitoes

Stuart said while the impacts of a March warm spell are fairly minimal, longer-term climate shifts could introduce new threats to the NWT.

"There have been no disease mosquitoes that have caused diseases in humans in the Northwest Territories as of yet," he said. "But as we keep on getting these weird weather conditions and the world seems to be warming up, we may start seeing incidences of human cases in the Northwest Territories.

"There are lots of unknown diseases out there that haven't been detected up there. There could be activity that we're not detecting through our normal surveillance system. For people like myself who are looking for and tracking vector mosquitoes, especially in the summer, we want to know – what is the probability that that can happen?

"Are there enough degree days [where the temperature reaches a certain point] to make mosquitoes up there able to transfer those viruses or those other maladies that can cause illness in humans?

"It is concerning and the North seems to be getting the most effect, so lots of people are looking at: 'All right, what's happening up there?' What are the factors that we need to look at? Are we monitoring enough? Are we looking at all animals, all different susceptible populations, and making sure people are aware? Public education is very, very key."

In the short term, Currie advised looking at rain, and the snowpack, over the coming months to predict the extent of the 2019 bug season.

"The best way to predict whether this will be a 'good' or 'bad' season for black flies and mosquitoes is monitor the weather going forward," he wrote.

"Higher water levels in streams, or ponds in the case of mosquitoes, ensure that more overwintering eggs will hatch.

"If you have a good snowpack this year, and if you have a wet spring, then you’re pretty much guaranteed to have a 'bad' mosquito and black fly season."