Mosquitoes and Moisture

July 17, 2012, 10:13 a.m.

Those who keep tabs on Edmonton’s mosquito population are part entomologist and part meteorologist.

Yes, you’ve got to know your insects. But you also have to keep an eye on the weather, because precipitation is an essential ingredient in a mosquito’s development. The wetter and warmer it is, the better for the bugs.

Some species love to lay their eggs in low-lying areas, where they await the next pooling rain or flood. Others lay eggs directly on the water’s surface, making puddles or rain barrels prime real estate for larval development. With the right conditions, mosquitoes can go from larvae to winged biter in four days. Typically in Edmonton, the cycle takes about a week.

“The traps are always showing us a week back in time,” said Edmonton’s biological sciences technician Mike Jenkins. “Anything developing right now will show up next week.”

Curious how spikes in mosquito numbers follow big dumps of rain, the Journal’s Lucas Timmons and Sarah O’Donnell compared the two on a weekly basis, using precipitation data published by Environment Canada and the mosquitoes counts from traps monitored by the city.

It appears that within a two-week after a period of heavy rain, the mosquito numbers spike. Take a look at the 2011 numbers and the 2012 numbers.

It is important to remember when looking at the data that the light traps used by the city attract certain breeds of mosquitoes, particularly that nighttime nuisance known as the Aedes vexans. Aggressive daytime biters like the Ochlerotatus spencerii that made last May and June so miserable are not attracted to the light traps.

In addition to publishing the detailed mosquito trap data since 2011 at www.edmonton.ca/opendata, the city has compiled other interesting mosquito data online, including:

— A mosquito meter that compares the average weekly mosquito count for the last five years http://www.edmonton.ca/for_residents/mosquito_meter1.pdf

— A mosquito meter dating back to 1978 that shows the average weekly counts http://www.edmonton.ca/for_residents/mosquito_meter1.pdf

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