Everybody wants to know why there are so many wasps

Anyone trying to barbecue burgers, enjoy a drink on a patio or shop at their local farmer’s market is noticing all the wasps buzzing around. 

Western yellowjackets, which are black and yellow in colour, are common from British Columbia to Manitoba during the summer and into the fall.  

There does, however, seem to be a lot more of the pesky insects this year.

“Everybody wants to know why there are so many wasps in Calgary right now,” says Dr. Jackie Lebenzon, PhD, an insect physiologist and assistant professor in Biological Sciences at the University of Calgary.

“It comes down to a few things: One is just the time of year. You go the whole summer with not many wasps, and then this is the time of year when their nests and their populations are at their largest. They have all summer to forage and eat, so now they are just growing and there is going to be a lot of them.” 

Another reason for the number of wasps could be the rainy spring and hot, dry summer. 

Lebenzon says the wet spring brought other types of insects such as aphids, which left a sticky substance — called honeydew — on the leaves of trees.

“Adult wasps that are out foraging really like that,” she explains. “It’s a good source of sugars and carbohydrates for them. That helped them grow faster in the early season, so there’s a lot of them.” 

The temperature could also be contributing. 

“It’s been a really hot summer. It’s been hot during the day; it’s been hot at night.” 

Insects, she says, can’t regulate their body temperature. “The term for that is that they are ectothermic. What that means is that when it’s really hot outside, high temperatures speed up their biological processes,” she says. 

“They are going to grow really fast and that could create a boom in population in the city.”

Lebenzon says the yellowjackets thrive in hot weather — and all the activities that come with it, especially barbecues.

“Wasps really like protein, because it’s what they bring back to feed their growing larva in the nests,” she says. “If you are having burgers and hot dogs, they are going to like that.” 

She says the insects will respond to feeling attacked: “If you swat them away or show any type of aggression toward them, they will release a pheromone and attract more wasps.

“It’s both the protein in the meat but also your reaction toward them that will bring more to your patio.”

Despite feeling like pests, Lebenzon says wasps are helpful. “All insects are integral to the ecosystem. They are about 70 to 80 per cent of all animal species, so we kind of need them around.  

“They are pretty annoying when they try to eat your burgers, but for the most part they are useful because they actually feed on a lot of other garden pest insects. They basically help keep all other insect populations at bay.” 

The easiest solution, she notes, may not be popular. 

“It might be difficult to let the wasp be, but that’s really your best bet,” says Lebenzon. “Maybe just take your food and go inside. 

“Everyone wants to enjoy the weather, but if you’re aggressive toward it, that may be worse. If it’s really an issue, call local pest control and they can help you deal with wasps.” 

Otherwise, Lebenzon says we can expect the wasps to stick around with the warm weather.

“A frost increases the likelihood that they are going to actually freeze,” she says. “They can’t maintain a body temperature, so if the temperature drops to a lethal level, that’s going to help deal with the population.”