Every summer, we hear reports of cottagers bemoaning the summer’s bug population (typically in some form of, “Do the X seem worse to you this year?”). From irritating, itch-inducing mosquitoes to aggressive wasps, we’ve all encountered some pesky forms of nature at the cottage.
This year’s star insect? Deer flies.
And if you’ve found yourself noticing them, well, everywhere this season, your eyes are not deceiving you.
“Yes, there are more deer flies this year,” says Alice Sinia, an entomologist with Orkin Canada. North and southwestern Ontario have been hit particularly hard with ballooning populations, leading to more calls and complaints to the pest-control company.
Here’s why.
‘Perfect breeding conditions’
There are a few reasons why deer fly populations are growing. The first is—you guessed it—climate change.
Deer flies thrive in hot, humid environments near bodies of water with moist soil. In other words, they’re made for forested, lakeside or marshy areas.
Generally speaking, most of the population dies off in the winter when hit with dry, freezing temperatures. But thanks to climate change, more flies are surviving the recent mild winters we’ve experienced. This starts the spring season off with a higher breeding population, leading to a spike in numbers by mid-summer, when they’re most active.
This year in particular, a combination of sticky heat waves and summer storms has created “perfect breeding conditions for deer flies,” says Sinia. “With all these changes in humidity, moisture, and temperatures, people should anticipate that this will continue to happen.”
Another factor is linked to population growth in another cottage country creature—the white-tailed deer. Female deer flies feed on large mammals, including humans and deer, to sustain their larvae. With white-tailed deer populations growing in Ontario, Sinia says that this will inevitably give deer flies a nutritional boost.
Should cottagers be worried about more deer flies?
If you’ve ever been bitten by a deer fly, you know that the experience is less than pleasant. Their scissor-like mouths make a cutting motion when biting into your skin, leaving a painful mark behind.
Unfortunately, with a higher population comes more bites.
On the bright side, despite their seemingly-relentless nature, you’re very unlikely to contract any form of disease in North America. A deer fly bite is one of the ways tularemia, a potentially serious disease, can be transmitted to humans, though instances are very rare. According to the B.C. Centre for Disease Control, there are only 0–2 cases per year in the province.
How to keep deer flies away
Unlike rodents or other home-invasive pests, there’s little we can do to stop deer flies from moving into the cottage or the surrounding property. “The best option to fight deer flies is our own behaviour,” says Sinia.
The first piece of the preventative puzzle is knowing when and where you’re most likely to find these insects. Deer flies are most active during mid-day to late afternoon—when it’s hottest—and tend to be in heavily wooded areas near a body of water.
During these peak times, deer flies can bite up to 11 times per minute, says Sinia.
If you can’t avoid deer fly havens during the day, your next strategy is all about trying to stop those painful bug bites. Similar to staving off ticks or mosquitoes, Sinia suggests wearing long-sleeved, light-coloured clothing to prevent deer flies from landing on exposed skin. Hats with netting can also be helpful.
“Deer flies, like mosquitoes, like dark objects,” she says. “Dark clothing is like a magnet, especially when you’re moving.”
While the science is iffy on the effectiveness of insect repellents (including DEET) on deer flies, it’s still good practice to give yourself a generous spritz before heading out to insect-dense areas. Repellents help to keep away mosquitoes, ticks, and other biting creatures.
As their populations grow, you might notice an increase of flies inside your cottage. During extremely high temperatures, bugs are drawn indoors by the coolness (especially if you have A/C).
Some deer flies might be inevitable, but Sinia suggests keeping up-to-date on your cottage maintenance to help stave away too many unwanted visitors. Check your doors and windows for gaps or tears in your screens that could let pests in.
This article has been updated to clarify that while it is exceedingly rare to contract a disease from a deer fly bite, it is possible to get sick.
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