As Toronto hits the height of wasp season, we’re resurfacing this story first published on Aug. 27, 2024 to break down what’s happening and why.
Nothing screams fall in Toronto like being swarmed by dozens of buzzing wasps while trying to enjoy a meal outdoors.
Wasp season is underway, and raiding parties of the hungry insects are emerging from their nests in force, their sights trained on our sugar-laden patios and picnics.
But before you reach for the bug trap, have some pity for the little guys — they’re going through a lot right now.
Here’s everything you need to know about wasp season.
When does wasp season start and end in Toronto?
Every year in Toronto, beginning in late July or August, hoards of wasps — primarily yellowjackets — invade human spaces in search of sweets, said Antonia Guidotti, an entomologist with the Royal Ontario Museum.
Despite their surging numbers now, the vast majority will be dead by the first hard frost of the year, usually in late September or early October.
The colony will be survived by a new queen, who, after mating in autumn, will soon enter hibernation to start the cycle anew next spring.
What causes wasp season?
Wasps are only after your food now because there isn’t enough of it at home, Guidotti explained.
After gorging on meat, the carnivorous larvae of yellowjackets produce a sweet nectar — a key food source for their adult caretakers, who no longer eat meat and survive off sugary substances.
But by late summer, most of these babies have grown into adults themselves, and the queen has stopped laying eggs.
“The workers no longer have the nutrition they get from the (sugary nectar),” Guidotti said. “So what they’re doing is trying to find other sources of sweetness, and they’re going after the sugary drinks or even sometimes the meaty stuff that we have on our picnic tables.”
Earlier in the year, when the larvae were still growing, the bugs were more preoccupied with hunting and bringing home meat than scavenging for sweets, she said.
Now, with their babies grown, the bugs are also coming off a peak in their population numbers, said Darryl Gwynne, a professor emeritus of biology at the University of Toronto. It’s their large numbers, coupled with the loss of a food source, that leads to what we know as “wasp season,” he said.
How to deal with wasps
If you notice wasps hovering around your patio, resist the urge to swat them away or flail your arms in panic — “that just aggravates them more,” Guidotti said.
“I know this is really difficult to do, but the best thing is actually to freeze,” she continues. “If it’s after your food, calmly step away and either let them have it or you can do a little wave” to shoo them away.
Make your patio less attractive to wasps by keeping food covered, cleaning up spills or crumbs when they happen and keeping your garbage sealed and away from frequently trafficked outdoor areas. It could also help to trim bushes and other vegetation near your home to reduce potential nests.
Don’t reach for the swatter — a smashed wasp will emit alarm pheromones that can cause nearby wasps to become more aggressive. Similar pheromones are laced in its venom, marking people it stings as targets for further attack.
Peter Kevan, a professor emeritus and entomologist at the University of Guelph, said he’s not aware of any diseases that can be transmitted to people from wasps: “I don’t think there’d be any harm in continuing to drink that soft drink” after a wasp fell into it, he said.
“Just make sure you’re not ingesting food with (a wasp) in it,” Gwynne added, recalling a time a guest at his cabin got stung on the lip after drinking from a cup.
Wasp traps do work in a pinch, Kevan said.
What to do if you are stung by a wasp
Unlike bees with their barbed stingers, wasps can sting you multiple times in a row. If you notice swelling after a wasp sting, seek medical attention immediately, Guidotti said — that’s an indication of an allergic reaction.
Otherwise, clean the sting with alcohol, soapy water or hand sanitizer, Guidotti said. She also recommended gently rubbing a cut piece of onion over the wound until the pain subsides — a common remedy for insect stings.
Johns Hopkins also recommends applying a cold pack to the region for 10 minutes on, 10 minutes off, for 30 minutes up to an hour.
“Yellowjackets are actually a really important part of our ecosystem — they visit flowers, they contribute to pollination … and they’re really good for pest control,” Guidotti said. “You just don’t want to mess with them, especially at this time of year.”
