Wasps get a bad rap. And sometimes, they deserve it. Bumblebees don’t swarm your barbecue the moment you pour the lemonade. Butterflies won’t nest by the hundreds in your rafters, then sting you for the crime of walking by.
But they’re not all “murder hornets,” and there’s another side to these so-called pests. Wasps have a place in the whirl of summer life. They raise families, stage complex battle royals and make paper with their own spit. Some even help us by hunting caterpillars and other crop-munching bugs.
They’re also your neighbors. As you’re mowing, gardening or dining al fresco this summer, you’ll probably meet some of them. Here’s how to appreciate — and not tick off — these creatures we share the season with.
Uninvited guests have arrived at your picnic. They’re striped and kind of stocky, with black dots on their faces. They’re German yellowjackets, and they will not leave you alone.
There is method in their madness. Are they hovering around your ham sandwich? They’re looking for protein to bring to larvae back at the nest. Trying to hijack your soda can? They want to slurp up the sugar, which powers their surprisingly zippy flight. Beer or wine is even more tempting, because it reminds them of their favorite treat, fermenting fruit.
“They seem like they’re trying to ruin our day,” said Jennifer Jandt, a zoologist at the University of Otago in New Zealand who has studied the species for years. “In actuality, they’re just foraging.”
Why are there so many of them at this time of year? Like ants and honeybees, German yellowjackets are social insects. Each colony is founded by a single queen, who starts laying eggs in late spring and doesn’t stop until her death, in autumn. Most of these eggs become workers, who spend the summer feeding their proliferating population of younger siblings: grabbing live caterpillars, bits of roadkill or your tuna salad, then chewing it into mincemeat for the next generation.
German yellowjackets make short work of carcasses and rotting produce, Dr. Jandt said: “They’re really important decomposers.” The invasive species, which first established itself on the East Coast about 50 years ago, is now found across much of the country and is the dominant yellowjacket in many states.
If one is trying to dominate your picnic as well, Dr. Jandt suggests playing along. “Let it land, let it do its thing,” she said. When she collected data for her master’s thesis at the University of Wisconsin-Madison, she shared a P.B. and J. with her research subjects every day, an experience she said helped her learn to appreciate the insects’ personalities, and “really forced me to be calm all the time.”
But if, instead of a few foragers, you find yourself dealing with an endless, vengeful stream of yellowjackets, you might have accidentally disturbed a nest. These are hidden underground, or in attics, ceilings or walls, and can be home to thousands of insects. Vibrating a nest is the insect equivalent of setting off a security alarm: Now you’re the uninvited guest, and it’s time to leave.
“Odds are pretty good that if you stumble across a wasp nest, you’re going to get stung at least about 10 times — while running away,” said Dr. Jandt, whose research now focuses on why some wasp colonies are more aggressive than others.
A tan mass in the shape of an amphora is hanging from a tree. It brings to mind Winnie the Pooh, who in cartoons often seeks out such structures, assuming they’re filled with honey.
“Winnie the Pooh gets it wrong,” said Norman Patterson, a wasp removal specialist based in Connecticut. “They don’t have honey.” If the Hundred Acre Wood were the real world, Pooh Bear would reach into the nest and instead scoop out a pawful of bald-faced hornets.
Bald-faced hornets, which are technically yellowjackets but nest above ground, are found in much of the United States. They’re named for the black and white patches on their heads, as if they’re wearing Guy Fawkes masks. While you might find their iconic summer homes in a tree in your yard, some tuck them under the eaves of houses or hide them cheekily in ornamental hedges.
Construction begins in late spring, when a queen builds a small core nest and lays a batch of eggs. By early summer, these eggs have hatched into workers. The workers scrape up wood pulp, sometimes from nearby decks or fences, and chew it to form long ribbons. They then add these strips to the nest one at a time — a collaborative, midair papier-mâché project.
A single bald-faced hornet dwelling may grow to the size of a rugby ball. It can house hundreds of workers, including a cadre of guards primed to defend it. Mr. Patterson is regularly called to remove these nests, which he said people often come upon “the hard way, when they’re trimming their bushes.” (He recommends all summer yard work be preceded by a check for wasp traffic.)
Mr. Patterson supplies these and other wasps to medical labs, which harvest their venom and use it to create immunizations for people who are allergic to stings. So he captures the bugs alive, usually with a vacuum. If he finds a nest full of larvae, he will take them home and raise them before shipping them off.
He’s not alone in seeing the good in bald-faced hornets. Farmers often like a nest or two around, because bald-faced hornets — like most wasps — are good at pest control. (Mr. Patterson has seen one pluck a fly straight from a cow’s back.)
But nests in busy areas should always be removed, Mr. Patterson said.
If yours is out of the way, though, and you feel like spicing up your summer, “just leave it and watch it,” he said. But don’t touch.
The Smarty Pants
It’s perfect barbecue weather. You flip the grill open for the first time all summer. As it turns out, others have been using it: a colony of paper wasps.
Longer and skinnier than yellowjackets, paper wasps are distinguished by their back legs, which hang down when they fly like a “pair of pants,” said Megan Asche, an entomology Ph.D. candidate at Washington State University. There are a number of paper wasp species native to particular areas of the United States, as well as an invasive one, a European variety that has spread nationwide since its arrival in the 1970s.
Paper wasps have complex social lives. While some colonies are founded by one wasp, many start out with a few queens, who brawl to establish dominance. The winner lays most of the eggs, and the others shoulder most of the foraging, maintenance and child care.
Elizabeth Tibbetts, a biologist at the University of Michigan who studies paper wasp behavior, is investigating how the insects form these hierarchies. She has found that Northern paper wasps can recognize one another, thanks to distinct markings on their faces.
More recently, Dr. Tibbetts found that Northern paper wasps can also “keep track of a social network of interaction,” she said: Even if they haven’t fought a particular queen, they have an idea of her strength from watching her fight others and will treat her accordingly. “You have to be pretty smart to be able to do that,” she said.
The males have their own rituals. Each fall, male European paper wasps in the Southern United States gather in huge swarms at the tallest point they can find to wait for potential mates. This could be a high-rise building, a granary or an amusement park ride. On military bases or at airports, it’s often an air traffic control tower.
Male wasps can’t sting. But this behavior is understandably distressing to people who witness it, including those working inside the control towers. “They really freak people out,” Ms. Asche said.
So Ms. Asche, whose research is funded by a grant from the United States Air Force, is also doing behavioral studies, testing whether the wasps can learn to associate a particular scent with a reward. (If they can, the scent could be used to trap them or to lure them away.) In the lab, without a home to defend or larvae to raise, they are “a pleasure to work with,” she said, and spend most days lounging in the sun “like little tiny cats.”
Outside the lab, they aren’t so bad, either. They’re pretty uninterested in picnic food, and “you have to try hard” to be stung by them, Dr. Tibbetts said. But they are “very, very comfortable around human dwellings,” and like to build their small, open nests in places like porch rafters, Ms. Asche said.
If you don’t want European paper wasps near your house, you don’t need a military-style intervention, just some forethought. In the springtime, if a small nest with just a few paper wasps appears in your eaves, wait for a cool morning — below 60 degrees — and “just take a stick and knock it down,” she said. The queens, who don’t fly in cold weather, will fall down with it. Then they will build a home somewhere else. But if it’s summertime, best to call a professional.
The Big Ones
An enormous wasp is investigating your flower bed. It is black with caution-yellow markings and the size of a USB stick. You are picking up the phone to call your local bug expert.
Whomever you plan to ring will be ready for you. Your new friend is a female cicada killer. She and her peers are about to emerge en masse throughout the eastern half of the United States to hunt cicadas — and to worry people. “I’ll be getting lots of calls very shortly,” said Michael J. Raupp, a professor emeritus of entomology at the University of Maryland who does insect outreach through his blog and YouTube channel, both called Bug of the Week.
Cicada killers are solitary wasps: They build nests, have offspring and gather food all on their own, no colony involved. At the beginning of July, the smaller male cicada killers establish territories, often in people’s yards. Females come out of the ground a few weeks later.
When they do, many people “become concerned,” Dr. Raupp said. Some are put off by their size. Others confuse them with other large wasp species, like the Asian giant hornet, which kill honeybees and have a very painful sting. (In the United States, Asian giant hornets have not been found outside Washington State. Yet.)
Cicada killers aren’t aggressive and can be quite fun to watch, Dr. Raupp said. But their lifestyle is a bit gnarly. After mating with a male, a female will dig a burrow, called a gallery, in soft dirt, perhaps a flower bed. She will then head up to the treetops.
When the wasp finds a cicada, she will sting it, paralyzing her prey without killing it. She will then carry it home. If you wait patiently near her hole, you can see her “fly back with this ginormous cicada,” often as big as she is, Dr. Raupp said. “You wonder how in the world they can even lift this thing.”
The wasp will drag her prey into her gallery and lay an egg. She seems to know the sex of the egg ahead of time and apportions cicadas appropriately: one or two for males, and two or three for the much larger females. When the egg hatches, the larva will eat the still-living lunch. (Charles Darwin, lover of most life-forms, once wrote that the existence of similar wasp species that prey on caterpillars made it hard for him to believe in “a beneficent and omnipotent God.”)
After its meal, the larva spins a cocoon and stays put, staying underground for the remainder of the summer, autumn, winter and spring until its re-emergence as an adult next year, Dr. Raupp said.
As summer wanes, colony life for German yellowjackets, bald-faced hornets and paper wasps also starts to slow down. In the fall, you may notice a rush of workers fending for themselves, seeking sugar where they can. By the time winter comes, the queens will be hibernating; the males and workers dead; and the old nests abandoned.
But if you missed them, don’t be sad. They’ll all come back next year.