Late summer in Saskatchewan is a beautiful time to enjoy barbecues and outdoor concerts.

Or it would be, if not for wasps: specifically, yellowjackets.

Like bees (with which they share a similar coloration, but from which they can be easily distinguished: bees have thick waists, wasps have skinny ones, bees are hairy, wasps are smooth) yellowjacket wasps are social insects.

Each spring a single reproductive female, or queen, crawls out of whatever crack she has spent the winter in, makes a golf-ball-sized nest, and lays her first batch of eggs (fertilized the previous fall). Soon she has her first crop of sterile female worker wasps to continue building the nest and feeding the larvae, allowing her to focus on laying even more eggs.

The nest is made of paper—wood fibers stuck together with saliva. Over the course of the summer it can swell to impressive size, housing 5,000 wasps or more.

Other species of wasps also make nests from paper, especially the paper wasp, which we also have in Saskatchewan. Paper wasps are shy and retiring as wasps go, though, so they’re rarely a problem unless they build a nest right over your porch. Whereas yellowjacket nests are covered with a tough outer wrapping and typically have a single entrance, paper wasp nests are open, so you can look inside them and see the eggs and larvae (if you really want to stick your nose in a wasp nest, which most people don’t). Paper wasp nests are also much smaller, since they typically contain only a couple of dozen wasps.

There’s more than one species of wasp we call yellowjackets. While we’re more aware of the ones that make aerial nests, under eaves or in trees, there are others who build their nests in rodent holes, which they’ll sometimes enlarge by moistening the soil and digging. If they get inside a wall or attic, they may do the same thing, which can lead to a wet patch in a wall or ceiling which can eventually develop into a hole that allows wasps inside the house.

The eggs laid by the queen hatch into white, grublike larvae, which in turn become white pupae from which adult wasps emerge. You probably won’t see the larvae unless you tear open a nest. This would be a bad thing to do: yellowjackets are extremely aggressive about defending their nests, and they can both bite and sting. Not only that, unlike bees, which sting once, then die, wasps can sting repeatedly, and are quite willing to do so, especially if they get trapped inside clothing.

We see more wasps in late summer than in spring partly because there are so many more of them (since they’ve been hatching all summer) and partly because, whereas early in the season they’re more focused on finding protein to feed all the little larvae, late in the season they’re more interested in nectar (and sweet drinks) to maintain themselves and the queen.

Something else happens in the late summer: males are produced. Eventually new queens and males swarm from the nests and mate. The newly fertilized queens look for places to spend the winter, the males and workers die off, and in the spring, the cycle begins anew.

However bad the wasps may have been around here this year, it could be worse. In July the Montgomery Advertiser in Montgomery, Alabama, reported that “to the bafflement of insect experts, gigantic yellowjacket nests have started turning up in old barns, unoccupied houses, cars and underground cavities across the southern two-thirds of Alabama.”

How large? There was one as large as a Volkswagen Beetle, and another (the newspaper published an alarming photo of it) that filled the interior of junked 1955 Chevrolet parked on a farm. “I had to sneak down there at dark and get my tractor out of the barn,” said the farmer.

Experts estimated some of those giant nests may have 100,000 wasps in them—and (the key to their size) multiple queens. Unwilling to share space with other queens, each queen might have ordered her workers (by whatever means wasps communicate) to make her nest as large as possible, resulting in runaway nest building. A warm winter that allowed wasps to continue feeding instead of forcing them into cover may have contributed, as well.

A wasp nest the size of a Volkswagen Beetle? A wasp nest filling an old car?

Scientifically, there’s only one word to describe such phenomena:


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