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Edmonton’s entomologist explains why mosquito season is on hold

City of Edmonton biological sciences technician Mike Jenkins holds a mosquito sample in his lab in Edmonton, Alberta on Friday, July 24, 2015.

Amber Bracken/The Globe and Mail

In one of the driest summers on record, the Canadian Prairies have been parched by drought and covered with thick smoke from raging forest fires. The dry conditions have, however, severely reduced the mosquito population that typically plagues the area at this time of year. Mike Jenkins is Edmonton's biological sciences technician, but everyone just calls him the "bug guy." He spoke with Justin Giovannetti.

The mosquito population is down 98 per cent in Edmonton this summer compared with the five-year average. What's going on?

It's largely a product of the dry season we've had so far. We started out with low levels of water in the spring and, since then, we've had no significant rainfall. We're only seeing a few mosquitoes in every mosquito trap we've set, where several hundred would be the average for this time of year.

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Winnipeg remains the mosquito capital of Canada. They see in their traps nightly what we see every week, but Edmonton isn't that far below Winnipeg in Canada's mosquito hierarchy.

What does a mosquito trap look like?

What Edmonton uses is called the New Jersey light trap. It's the standard across North America. It's essentially a 25-watt bulb on a timer over a barrel. The fan turns on at night, and insects drawn to the light bulb are sucked in by the fan. There's a pointy hat on top to keep out the elements, so it looks like a stubby rocket hanging in a tree.

How are the mosquitoes counted?

Each week, we go and pick up the catch jar under the trap and get everything drawn in there. We bring it back to our lab and pick out all the mosquitoes from the little spiders and moths also drawn to the light. We dump them in a tray and pick them out with tweezers. Then we put those mosquitoes under the microscope and identify the species. Each is individually counted. This year hasn't been bad. We've only had about a half-dozen mosquitoes in each trap weekly. But when we have thousands of mosquitoes in there, it can take quite a while – up to a week to identify them all. In the 1980s, we sometimes had over 100,000 mosquitoes per trap weekly.

While you're sitting there for a week counting mosquitoes, do you ever question why you're doing this?

It does cross your mind. But this gives us a historical basis to compare results year over year. The species identification also has big implications for our control program. Different species have different habitats, so if we're getting a lot of one species in our light traps we know what areas we may have missed in our campaign.

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While the mosquito population has been low so far this year, how likely is it that numbers could rebound?

The mosquito numbers could change very quickly if we got significant rainfall. There are eggs just lying there dormant for years waiting to get activated by water. Within days of rain, especially with the warm temperatures at the end of summer, huge numbers of adults could be on their way. Each female has left up to 500 eggs along ponds after each blood meal. That's billions of eggs in our region. Our mosquitoes are really well adapted for drought on the Prairies, so there could be no rain for years and the eggs will be fine.

Last year, we were doing fine in terms of mosquitoes, and then we get rain and humidity at the end of July and we were left with one of the highest mosquito populations in decades. It could turn depending on what happens with the rain – that's one of the joys of mosquitoes on the Prairies.

This interview has been edited and condensed.

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