Science Insider

Wasp Woes

- September 1, 2019 - Alison McAfee - (excerpt)

yellow jacket

Yellow jacket wasps are more than just picnic crashers – they also raid beehives, killing off entire colonies. And climate change could be prodding the nest.

“How do you tell the difference between a wasp and a bee?” The twelve-year-old girl looked up at me expectantly, proud to be asking me a question that her classmates hadn’t thought of. “Well, the easiest way to tell,” I said, “is that wasps just look like . . . jerks.” I had to refrain from using a more profane word (I’m not used to spending much time around children). “If you’re having a picnic and a yellow stripy thing is trying to steal the food off your fork, it’s probably a wasp.”

It’s true: Wasps are jerks. They aren’t exactly fuzzy. They don’t have cute faces. Their angular bodies and colour patterns scream “troublemaker.” Their strong, menacing mandibles (mouthparts) are capable of cutting up chunks of meat or latching on to you as they repeatedly jam their stinger. If you’re a beekeeper, you probably have an exceptional hatred for yellow jacket wasps, particularly in the late summer and early fall when they relentlessly rob your colonies about as fast as you can feed them. And unfortunately, your seasonal wasp woes are probably only going to get worse.

“Yellow jacket” is the common name for several wasp species in the Vespula genus (such as V. germanica, V. vulgaris, V. maculifrons, V. atropilosa, V. pensylvanica, and V. squamosa). Though it varies between the species, their colonies are normally composed of a few thousand individuals. The nest normally dies off in the fall, leaving only the new, freshly mated queens to brave the winter, hibernating in a safe spot until spring (much like bumble bees do). When the winter ebbs, the foundress queen will emerge and begin to establish a new nest, foraging and caring for her first batch of brood until her daughters can take over the housekeeping and let her focus on laying eggs. But in some regions, a combination of mild winters and balmy springs are giving yellow jackets a head start. In the southern United States, some wasp colonies are even persisting through the winter, forming multi-queen “supercolonies” with tens of thousands of workers. I haven’t been able to verify this, but one nest in South Carolina reportedly contained in the neighbourhood of 250,000 workers.

But these supercolonies, though terrifying, are not entirely new. As the Huffington Post reported last July,1 2006 was exceptionally ripe with yellow jacket supercolonies, too. However, Charles Ray, a research fellow at Auburn University in Alabama, expects the number of supercolonies in the region to surpass the 2006 stats this year. The supernests are starting to appear earlier in the year (as early as May), which bodes badly for beekeepers in the region as we approach fall. “So normally,” Ray told The New York Times,2 “a surviving queen will have to start a colony from scratch in the spring. With our climate becoming warmer, there might be multiple surviving queens producing more than 20,000 eggs each.”

It’s unclear exactly how big of a role the warming climate is playing — it’s possible that mild winters could actually be bad for wasps, since it stimulates the queens to emerge too early in the spring, before there is sufficient forage. But in the southern states, winters are becoming so mild that the queens may not have to hibernate at all, facilitating these supercolonies to form. We don’t yet fully understand the factors involved, but even in the absence of supercolonies, yellow jackets are still a formidable pest to beekeepers.

To yellow jackets, honey bee colonies are like an all-you-can-eat buffet of sugar and protein at a time of dearth. Late in the season, there is not much else around for the wasps to eat, particularly sugars. Unlike honey bee brood, wasp brood consume pre-chewed insects and subsequently secrete sugars that they feed back to the adult workers. But late in the year, brood rearing is done, so the adult wasps have neither nectar nor brood dew to satisfy their sweet tooth. Conveniently for them, there also isn’t much around for the honey bees to eat, so we diligently fortify their overwintering stores with delicious syrup. That’s more than enough motivation your average wasp needs to take the risk of invading a beehive to steal their stores.

A strong honey bee colony should be able to defend itself against invading wasps, but that isn’t always the case. “Last fall, I lost 40% of my colonies due to wasp robbing,” Heather Higo — an experienced and well-respected British Columbia beekeeper — reports. For her, that was around 25 colonies. “I was killing about 100 wasps every 15 minutes [with an electric zapper], and I stopped at 800 in one afternoon in less than 2 hours!” That’s enough wasps to overwhelm even a strong honey bee colony, despite having entrance reducers to aid their defence.

In Canada, our winters are still too cold to enable wasp colonies to persist through the winter, and we don’t have supercolonies, but even the normal yellow jacket colonies are ferocious enough to ….