12 Facts About the Brown Marmorated Stink Bug

iStock.com/claudiodivizia
iStock.com/claudiodivizia

There are about 5000 species of stink bugs, shield-shaped insects that belong to the family Pentatomidae. One of the most notorious stink bugs is the brown marmorated stink bug (Halyomorpha halys Stål), a.k.a. BMSB, which The New Yorker called “the most destructive, the most annoying, and possibly the ugliest” of all the stink bugs, an invasive species that’s taking North America by storm … and not in a good way. Here’s what you should know.

1. IT MADE ITS WESTERN HEMISPHERE DEBUT IN PENNSYLVANIA.

A stink bug
iStock.com/sdominick

Native to East Asia, the first BMSB specimens in the U.S. were collected in Allentown, Pennsylvania in 1998, but the bugs likely arrived a few years prior to that. (They may have come to the states in a shipping container, but no one’s sure.) Since then, they’ve spread to 43 states and will probably be continent-wide soon.

“It’s an incredible hitchhiker,” Dr. Tracy Leskey, an entomologist with the Agriculture Department’s Appalachian Fruit Research Laboratory, told The New York Times of the BMSB. Less than 10 years after it was identified in the States, it was in Switzerland and other parts of Europe, too.

2. IT TOOK YEARS TO IDENTIFY IT.

A magnifying glass on a yellow background.
iStock.com/solidcolours

When the bugs were delivered to Karen Bernhard, an entomologist at Pennsylvania State University’s Extension Service, she had no idea what they were—and neither did anyone else. (Many assumed it was the native Euschistus servus.) It wasn’t until 2001, when Bernhard sent specimens to Richard Hoebeke, an entomologist specializing in invasive species who was then working at Cornell, that they were identified as brown marmorated stink bugs.

3. IT’S NOT CUTE.

Brown marmorated stink bug eggs hatching on a leaf.
iStock.com/flowerino

After they hatch, the black-and-red nymphs go through five molts, growing into mottled, dull-brown bugs—up to .66 inches long—with white banded antennae and legs, alternating dark and light bands on the abdomen, and smooth, rounded shoulders. All of these features distinguish them from lookalikes like the brown, rough, and one-spotted stink bugs. BMSBs can live for up to eight months.

4. THEIR SPRAY HAS SOMETHING IN COMMON WITH CILANTRO.

A bunch of cilantro tied together with a string
iStock.com/MmeEmil

Skunk. Old socks. Coriander. These are just some of the things the stink of the brown marmorated stink bug has been compared to. The two main chemicals responsible for the BMSB’s stinky spray are trans-2-octenal and trans-2-decenal. The latter is what gives cilantro its smell.

The chemicals in the spray might have a purpose besides scaring away predators: According to a 2016 study, they “inhibit the growth of bacteria”; the results of the study “suggest that brown marmorated stink bug aldehydes are indeed antibacterial agents and serve a multifunctional role for this insect.”

5. THEY EAT YOUR APPLES …

Brown marmorated stink bug feeding on an apple
iStock.com/saraTM

Brown marmorated stink bugs chow down on more than 100 types of crops. According to StopBMSB.org, apples, Asian pears, green beans, sweet corn, peaches, tomatoes, peppers, and Swiss chard are among the crops BMSBs pose the most risk to. Apricots, blueberries, broccoli, cauliflower, sweet potatoes, and turnips are also on the menu (though they’re less at risk).

To feed, the bugs pierce the skin of the plants with their mouthparts and drink the fluids, which in fruits like apples “results in a characteristic distortion referred to as ‘cat facing,’ that renders the fruit unmarketable as a fresh product,” according to a Penn State Extension article on the bugs. In 2010, mid-Atlantic farmers estimated that BMSBs caused $37 million in damage to apple crops alone. Some farmers of apples and other crops reported total losses that year.  

6. … AND COULD INVADE YOUR HOME BY THE THOUSANDS.

A stink bug on a model of white house
iStock.com/ibunt

Come winter, BMSBs are looking for a warm place to shack up so they can enter diapause, a hibernation-like state that lasts until spring (a.k.a. mating season). Outdoors, they’ll overwinter in dead trees—but often, they find their way into peoples' homes through open windows and doorways, in the gaps around window air conditioning units, down chimneys, and basically any crack they can find.

According to The New Yorker, “Studies have shown that, despite their relative heft, stink bugs can crawl through any crevice larger than 7 millimeters, which means that, no matter how much caulk and weather-stripping and patience you possess, it is virtually impossible to stink bug-proof a home.” But that doesn’t mean you shouldn’t try; experts recommend placing screens over windows and vents and making liberal use of caulk to patch cracks.

Once a stink bug has found a warm spot it likes, it will release an aggregation pheromone (which can linger for up to a year) that draws other BMSBs to the same area, where they’ll gather in sometimes staggering numbers: One study found more than 26,000 of them living in a Maryland home.

The good news is, beyond being a smelly nuisance, they won’t mate in your home or cause structural damage (though they might clog chimneys ... or your pipes).

7. ONCE INSIDE, THEY’RE HARD TO GET RID OF.

A stink bug on a piece of wood.
iStock.com/drnadig

Some suggested stink bug removal approaches include knocking the bugs into soapy water, placing fly traps or double-sided tape in entryways, and spraying various concoctions (like garlic water) around your house. Vacuuming them up is also an option, though as the Penn State Extension article notes, “the vacuum may acquire the smell of stink bugs for a period of time,” so it might be best to avoid that tactic if your vacuum doesn’t have a bag you can easily toss.

A study showed that traps baited with the aggregation pheromone are only effective half of the year. And though foggers will kill stink bugs around your house, “it will not prevent more of the insects from emerging shortly after the room is aerated” and therefore “is not considered a good solution to long-term management of the problem.” Even expensive professional extermination efforts can be for naught.

Research by Virginia Tech has suggested that the most effective method of removal is to line a roasting pan with foil, fill it with soapy water, and place it in a dark room with a light above it to attract the bugs. According to a press release, this method—which was tested in 16 homes over a period of two years—“eliminated 14 times more stink bugs than store-bought traps that cost up to $50.”

8. THEY’RE PRETTY GREAT FLIERS.

In the home, stink bugs are lethargic, buzzing around clumsily thanks to diapause. But in the wild, they’re good fliers: Research has shown that, in flight mill tests, the bugs can fly 1.2 miles in a 24-hour period, and in field observations, they fly in a straight line at 6.7 mph. You can see one flying in slow motion here.

9. THEY’RE GENERALLY NOT HARMFUL.

A puppy with a leash in its mouth.
iStock.com/sawiemander

BMSBs don’t sting or bite—their main defensive mechanism is their stinky spray. But some people can have allergic reactions, including rhinitis, conjunctivitis, or dermatitis, to the spray. The bugs aren’t toxic, so they won’t hurt your pets—though the chemicals in their spray might make your pets vomit or drool.

10. THEY MIGHT BE MESSING WITH YOUR RED WINE.

Pouring red wine into a glass.
iStock.com/debyaho

Not only do these pests feed on grapes, but they can end up in the mix as grapes are turned into wine, where the bugs give off stress compounds that affect the quality of the vino. Researchers at Oregon State University placed live and dead stink bugs on wine grapes and measured the stress compounds the insects released as they and the grapes were squeezed during the winemaking process. According to a press release, “They found that pressing was a key step in the release of two of the most common stress compounds—tridecane, which is odorless, and (E)-2-decenal, which produces an undesirable musty-like, coriander or cilantro aroma.” Red wine was more affected than white, maybe because the grapes are pressed at different points in the production process. The researchers found that more than three stink bugs per grape cluster resulted in contaminated wine.

11. THEY LEAVE TRACES OF THEIR PRESENCE ON PLANTS.

Brown marmorated stink bug on a plant.
iStock.com/ibunt

Scientists at Rutgers University recently discovered that they could detect the eDNA (or environmental DNA—things like skin flakes, scales, exoskeletons, or fecal matter) of brown marmorated stink bugs in the water farmers used to wash their produce before the crops go to market. They visited two farms—one in New Jersey with a known stink bug infestation and another that was just outside the bugs’ range in New Hampshire—where they both tested water and set traps for the bugs. As expected, they found stink bug DNA at the Jersey farm … and they found it at the New Hampshire farm, too. There, on the last day of testing, an immature stink bug ended up in a trap—visual confirmation of what their data was telling them. They hope that farmers can use the test to detect stink bugs before there’s a full-fledged infestation.

12. ONE OF ITS NATURAL PREDATORS IS A PARASITIC WASP THAT JUST MADE ITS WAY TO THE STATES.

A samurai wasp lays an egg in a brown marmorated stink bug egg
Oregon State University, Wikimedia Commons // CC BY-SA 2.0

In the U.S. the BMSB has few predators—so when scientists were looking for a way to combat the pests, they went to Asia. There, the stink bugs are kept in check by samurai wasps (Trissolcus japonicus), a tiny, stingerless parasite that lays its eggs in the stink bugs’ eggs, where its larvae eat the contents before emerging as wasps to continue the cycle. Sixty to 90 percent of BMSB eggs in Asia are parasitized by the wasps.

Scientists brought some of the wasps back and began testing to see if they would be a good candidate for release in the states. But before they could release any, the wasps showed up on their own, in Maryland in 2014. (Genetic testing showed that they weren’t escaped wasps that the scientists had been studying.) According to Science, “Although in laboratory tests it has parasitized some eggs laid by native species, [the wasp] has shown a strong preference for brown marmorated stink bug eggs.” Still, scientists are proceeding with caution: Though they can release the wasps in states where they’ve already been found, there are rules and regulations to follow and permissions to get before they can be released anywhere new.

10 Products for a Better Night's Sleep

Amazon/Comfort Spaces
Amazon/Comfort Spaces

Getting a full eight hours of sleep can be tough these days. If you’re having trouble catching enough Zzzs, consider giving these highly rated and recommended products a try.

1. Everlasting Comfort Pure Memory Foam Knee Pillow; $25

Everlasting Comfort Knee Pillow
Everlasting Comfort/Amazon

For side sleepers, keeping the spine, hips, and legs aligned is key to a good night’s rest—and a pain-free morning after. Everlasting Comfort’s memory foam knee pillow is ergonomically designed to fit between the knees or thighs to ensure proper alignment. One simple but game-changing feature is the removable strap, which you can fasten around one leg; this keeps the pillow in place even as you roll at night, meaning you don’t have to wake up to adjust it (or pick it up from your floor). Reviewers call the pillow “life-changing” and “the best knee pillow I’ve found.” Plus, it comes with two pairs of ear plugs.

Buy it: Amazon

2. Letsfit White Noise Machine; $21

Letsfit White Noise Machine
Letsfit/Amazon

White noise machines: They’re not just for babies! This Letsfit model—which is rated 4.7 out of five with nearly 3500 reviews—has 14 potential sleep soundtracks, including three white noise tracks, to better block out everything from sirens to birds that chirp enthusiastically at dawn (although there’s also a birds track, if that’s your thing). It also has a timer function and a night light.

Buy it: Amazon

3. ECLIPSE Blackout Curtains; $16

Eclipse Black Out Curtains
Eclipse/Amazon

According to the National Sleep Foundation, too much light in a room when you’re trying to snooze is a recipe for sleep disaster. These understated polyester curtains from ECLIPSE block 99 percent of light and reduce noise—plus, they’ll help you save on energy costs. "Our neighbor leaves their backyard light on all night with what I can only guess is the same kind of bulb they use on a train headlight. It shines across their yard, through ours, straight at our bedroom window," one Amazon reviewer who purchased the curtains in black wrote. "These drapes block the light completely."

Buy it: Amazon

4. JALL Wake Up Light Sunrise Alarm Clock; $38

JALL Wake Up Light Sunrise Alarm Clock
JALL/Amazon

Being jarred awake by a blaring alarm clock can set the wrong mood for the rest of your day. Wake up in a more pleasant way with this clock, which gradually lights up between 10 percent and 100 percent in the 30 minutes before your alarm. You can choose between seven different colors and several natural sounds as well as a regular alarm beep, but why would you ever use that? “Since getting this clock my sleep has been much better,” one reviewer reported. “I wake up not feeling tired but refreshed.”

Buy it: Amazon

5. Philips SmartSleep Wake-Up Light; $200

Philips SmartSleep Wake-Up Light
Philips/Amazon

If you’re looking for an alarm clock with even more features, Philips’s SmartSleep Wake-Up Light is smartphone-enabled and equipped with an AmbiTrack sensor, which tracks things like bedroom temperature, humidity, and light levels, then gives recommendations for how you can get a better night’s rest.

Buy it: Amazon

6. Slumber Cloud Stratus Sheet Set; $159

Stratus sheets from Slumber Cloud.
Slumber Cloud

Being too hot or too cold can kill a good night’s sleep. The Good Housekeeping Institute rated these sheets—which are made with Outlast fibers engineered by NASA—as 2020’s best temperature-regulating sheets.

Buy it: SlumberCloud

7. Comfort Space Coolmax Sheet Set; $29-$40

Comfort Spaces Coolmax Sheets
Comfort Spaces/Amazon

If $159 sheets are out of your price range, the GHI recommends these sheets from Comfort Spaces, which are made with moisture-wicking Coolmax microfiber. Depending on the size you need, they range in price from $29 to $40.

Buy it: Amazon

8. Coop Home Goods Eden Memory Foam Pillow; $80

Coop Eden Pillow
Coop Home Goods/Amazon

This pillow—which has a 4.5-star rating on Amazon—is filled with memory foam scraps and microfiber, and comes with an extra half-pound of fill so you can add, or subtract, the amount in the pillow for ultimate comfort. As a bonus, the pillows are hypoallergenic, mite-resistant, and washable.

Buy it: Amazon

9. Baloo Weighted Blanket; $149-$169

Baloo Weighted Blanket
Baloo/Amazon

Though the science is still out on weighted blankets, some people swear by them. Wirecutter named this Baloo blanket the best, not in small part because, unlike many weighted blankets, it’s machine-washable and -dryable. It’s currently available in 12-pound ($149) twin size and 20-pound ($169) queen size. It’s rated 4.7 out of five stars on Amazon, with one reviewer reporting that “when it's spread out over you it just feels like a comfy, snuggly hug for your whole body … I've found it super relaxing for falling asleep the last few nights, and it looks nice on the end of the bed, too.” 

Buy it: Amazon 

10. Philips Smartsleep Snoring Relief Band; $200

Philips SmartSleep Snoring Relief Band
Philips/Amazon

Few things can disturb your slumber—and that of the ones you love—like loudly sawing logs. Philips’s Smartsleep Snoring Relief Band is designed for people who snore when they’re sleeping on their backs, and according to the company, 86 percent of people who used the band reported reduced snoring after a month. The device wraps around the torso and is equipped with a sensor that delivers vibrations if it detects you moving to sleep on your back; those vibrations stop when you roll onto your side. The next day, you can see how many hours you spent in bed, how many of those hours you spent on your back, and your response rate to the vibrations. The sensor has an algorithm that notes your response rate and tweaks the intensity of vibrations based on that. “This device works exactly as advertised,” one Amazon reviewer wrote. “I’d say it’s perfect.”

Buy it: Amazon

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

10 Facts About Argentine Ants

A pile of genetically-related Argentine ants
A pile of genetically-related Argentine ants
Marc Matteo, Flickr // CC BY-NC 2.0

A supercolony of invasive Argentine ants (Linepithema humile) stretches for 560 miles beneath California, from San Diego to San Francisco. The billions of Argentine ants are unlike other ants in many ways—and they are virtually indestructible. Along with their supercolonies in Europe, Japan, and Australia, L. humile’s global domination is rivaled only by that of human beings. Here’s what you should know about these prolific pests.

1. Argentine ant colonies are ruled by hundreds of queens.

Most ant colonies revolve around a single queen. Growing much larger than the worker drones, she is programmed to mate as quickly as possible, then to leave her nest of origin and establish a new one. In some species, a single queen can lay millions of eggs in a lifetime, producing an army of worker drones and future queens who will go off to build their own nests. But unlike most ants, Argentines are polygynous: Each nest contains multiple queens. In some, they can form up to 30 percent of the population.

2. Argentine ants move their nests frequently.

Nest types vary from ant species to ant species, but those who live in soil commonly dig tunnels and chambers deep into the earth that will protect the colony throughout the life of the queen. L. humile, though, is transient and ever shifting. Argentine ants frequently pack up their eggs and move the entire colony, queen and all, to a new nest, even when there is no apparent threat. Biologist Deborah Gordon told Ars Technica that the ants typically have 20 to 30 shallow nests at any one time, which can be built up in a matter of just weeks.

3. Argentine ants traveled the U.S. before settling down in California.

Argentine ants arrived in the United States from Northern Argentina in the late 19th century, when the first recorded Argentine ant was found in Louisiana in 1891. Researchers believe that the ants hitched a ride to North America in Argentinian shipments of coffee or sugar off-loaded at the Port of New Orleans. From there, they traveled—most likely by train—across the South and into California. Enticed by the Mediterranean climate, one similar to that of its original home in South America, the ants set up shop. By 1907, they’d displaced local native ants and begun their first steps towards total soil domination along 560 miles of California coastline.

4. California’s Argentine ants are more laid-back than their South American cousins.

In side-by-side comparisons of Argentine ants from their South American homeland and California, researchers have found that those from the West Coast are far more mellow than those from Argentina. In studies, it was typical for two ants from different nests to fight when placed in the same vial in Argentina, but in California, ants from different nests rarely fought, even when they were collected from locations several hundred miles apart.

A DNA study of ants from both locations in 2000 revealed a stark difference. In the ants from Argentina, microsatellites—short, uniquely patterned DNA sequences passed down from generation to generation—had more than twice as much variation as the microsatellites of the Californian ants. When two individuals from different nests in California were placed together, they recognized one another as family. The ants from Argentina didn’t, making them more likely to display territorial aggression.

The difference is rooted in the genetic bottleneck the ants encountered on their arrival to the Golden State over a century ago. According to biologist Neil D. Tsutsui, who conducted the DNA study, the ants in California today are all descendants of that founding colony. “It would be as if all of the people in the United States were descended from the Pilgrims who came here in 1620,” he told the Stanford Report in 2004. Instead of competing with one another, generation after generation has worked together to take out native ants and build an immense California colony.

5. Argentine ants protect other insects in exchange for sweet, sweet honeydew.

Argentine ants
Two Argentine ants share a tiny blob of honeydew.
Davefoc, Wikimedia Commons // CC BY-SA 4.0

Argentine ants love to feed on sweet nectar, but flowers and suburban kitchens aren’t the only source of such desirable foodstuffs. Insects that feed on plant sap, like mealybugs, scales, and aphids, naturally excrete sugar-rich liquid “honeydew” from their butts. To secure a steady flow of the sticky-sweet substance, Argentine ants will fight off the predators of their insect chefs, including soldier beetles and midges. They’ll even relocate their honeydew producers to better food sources or microclimates to get the most they can out of their anal secretions.

6. The California Argetine ant supercolony is one-sixth the size of Southern Europe’s.

The California supercolony, which scientists have named the “Californian large,” is only the second-biggest conglomeration of Argentine ants in the world. The biggest colony is found along Southern Europe’s Mediterranean coast, where it stretches 3700 miles from northern Italy to the Atlantic coast of Spain. The ants, introduced around 80 years ago, now number in the billions. Smaller supercolonies also exist in Japan and Australia.

7. Argentine ants are second only to humans in their scale of world domination.

In 2009, researchers discovered that Argentine ants from three of the world’s largest supercolonies (Southern Europe, California, and Japan) are so closely related that they actually form a single mega-colony. The study, led by Eriki Sunamura from the University of Tokyo, found that when placed together, ants from the three supercolonies refused to fight. Instead, they rubbed antennae in greeting the way L. humile does when interacting with genetically-related individuals.

The researchers believe that the Argentine ant mega-colony isn’t just the largest insect colony ever identified; it rivals that of human colonization around the globe. Presenting their findings in the journal Insect Sociaux, they wrote, “the enormous extent of this population is paralleled only by human society.”

8. A mass execution of Argentine ant queens takes place every spring.

Each spring, just before mating season begins, worker ants go on a killing rampage and assassinate 90 percent of their queens. Entomologists aren’t sure exactly why the large-scale execution occurs, but one hypothesis, published in the Journal of Evolutionary Biology in 2001, suggests that it is a “spiteful behavior” to kill the queens that are less related, on average, to the workers.

In their study, researchers from the University of Lausanne hypothesized that Argentine ants are regularly separated from direct family members through free exchange among the nests. Before mating season begins each year, those that are genetically related band together to kill more distantly related queens. Doing so decreases the nest’s genetic diversity and allows it to be rebuilt with a queen who is directly related to the greatest majority of workers.

The study’s results were inconclusive and the question remained unanswered, yet researchers learned something unexpected in the process. Instead of finding genetic diversity among worker ants, those belonging to each nest were actually a homogenous population. Only the queens were genetic outliers with relatively few familial relationships in each nest.

9. Climate change is making Argentine ants more of a nuisance to humans.

Argentine ants thrive in a Mediterranean climate where winters are cool and wet and summers are warm and dry. When conditions are ideal, they largely keep to themselves, but when conditions are drought-like or extremely wet, the ants move indoors in search of more hospitable climes. Experts at survival, Argentine ants can find food or water that’s been left unguarded in just minutes.

With the climate crisis, conditions in California are becoming more extreme. Hot days, no longer relegated just to the summer months, are becoming more numerous and prolonged. Droughts are becoming more frequent. While these changes are unlikely to harm much of the California supercolony, they are likely to drive the residents of urban nests more frequently into people's homes, making the ants a major nuisance for residents from San Diego to San Francisco.

10. Argentine ants are almost impossible to eradicate.

Individual Argentine ants are easy enough to kill, but an Argentine ant colony is a different story. The California colony has no natural predators and, thanks to their high levels of cooperation and massive numbers, L. humile has effectively destroyed possible competitors and disrupted the ecological balance of native species in the process. Insecticides, which are unable to penetrate into the underground nests, aren’t particularly effective. And because the ants can pick up and move their entire nest so quickly, neither are household control measures such as ant bait. After just over a century in California, Argentine ants are now virtually invincible.