It’s that time of year again when it’s hard to enjoy a meal outdoors without a wasp stopping by to bug you. Have you ever wondered why wasps become so irritating at the end of summer?

The answers lie in the ecology of social wasps.

Firstly, what is a wasp?

Depending on the context, the term ‘wasp’ can mean a number of things – including mud dauber wasps, gall wasps, parasitoid wasps or yellowjackets. The term covers any flying hymenopteran (the order of insects that contains ants, bees and wasps) with a narrow waist.

The “annoying” wasps that people talk about are typically yellowjackets, hornets or paper wasps. One thing they all have in common is that they are social wasps, which means they live in nests with a queen and workers.

As social insects these wasps are driven to protect their nests and will sting if their nest is disturbed. Unlike bumble bees and honey bees, the stingers of yellowjackets and hornets are not barbed – meaning they can sting multiple times without getting stuck. They even release an alarm pheromone when they attack, alerting other workers to come help defend the nest!

A buzzing wasp nearby can be unnerving, but yellowjackets, hornets and paper wasps aren’t likely to sting unless you provoke them. Learning about the biology of these species might help you avoid some nasty stings and begin to appreciate them.

Let’s have a look at different types of wasps:

Vespinae: Hornets
The only true hornet in North America is the introduced European hornet. It’s a large wasp with orangey-brown colouring. They live in woodlands and rarely bother humans. They usually build their nests in hollow trees and can be a tree pest when they strip the bark to make their nests.

Bald-faced Hornet (Dolichovespula maculata)

Vespinae: Dolichovespula yellowjackets
The bald-faced hornet is a large, black and white wasp. Despite its size, it’s one of the less aggressive species. It makes large papery-covered nests, usually high up in trees or on roofs or telephone poles. The aerial yellowjacket is yellow and black. This species also makes a large papery nest, but they often make their nests lower down on houses or in trees. It’s easier to avoid stings from this species because their nests are pretty obvious. Both species prey on living insects, mostly caterpillars, to feed to their larvae.

Vespinae: Vespula yellowjackets
Vespula yellowjackets can be predators, but mostly scavenge decaying flesh to feed to their larvae. They also have a sweet tooth! These are the nuisance visitors at your bar-b-que because they love to snack on human food. Some of their favorites are sugary or meaty things (like your burger) as well as garbage and rotting fruit. Vespula nests are usually hidden underground or behind walls, making it easier for you to get stung. Two of the most common species are the eastern yellowjacket and the introduced German yellowjacket. Vespula species can be yellow and black or white and black, with varying amounts of colour and banding.

Polistinae: Polistes paper wasps
Paper wasps make small open-celled paper nests, without a papery covering like yellowjacket species. You’ll often spot their nests under sheltered areas like eaves and roofs. Watch out! They’ll aggressively defend their nests if they need to. All Polistes species are predators that feed their larvae living insects. Common species in urban areas include the northern paper wasp and the introduced European paper wasp. The northern paper wasp varies in colour, ranging from mostly orangey to yellow and black banded.

European Paper Wasp (Polistes dominula)

The end of summer feeding frenzy

In yellowjacket, hornet and paper wasp nests only new queens survive the winter while all the workers die off. That means each spring, the colony starts again and the queen must build up her population by laying eggs and raising larvae. By the end of the summer there’s very high numbers of wasps within each nest, and many more workers are out looking for food. That’s why it seems like they’re everywhere this time of year.

If you have a garden, you may want to give thanks to these hungry wasps. As generalist predators, they’re great at controlling caterpillars and other insects that feed on your plants.

Now that you know a little more about wasps, hopefully you can enjoy the last days of summer despite the busy buzzing all around!

To learn more about other insects around the Credit River Watershed, visit Insects of the Credit.

By CVC’s Laura Timms

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