Cobwebs often conjure up images of creaky old houses and dark attics where scary things might lurk. But if you look around your own perfectly not-scary, well-lit house, chances are good you, too, will probably find a few cobwebs. Maybe more than a few. The mysterious tangles of sticky thread seem to appear (and reappear) out of nowhere, no matter how many times you use the Swiffer on those upper corners.
What gives? There’s not a spider in sight, so where do cobwebs come from? Could there be some supernatural involvement after all?
To keep a clean house—and ensure yours doesn’t accidentally look like it’s decorated for Halloween year-round—you should know a few things about webs and the spiders that make them. We asked a scientist to give us all the sticky details.
The difference between cobwebs and spiderwebs
Let’s start with some trivia, shall we? Spiders have special glands in their abdomens that allow them to make powerful silk threads (stronger, in relative terms, than steel). They use this silk to weave a web.
But don’t use “cobweb” and “spiderweb” interchangeably unless you want to make an arachnid expert shudder. A cobweb is a web spun by members of the spider family Theridiidae (aka “house spiders”). The family has over 200 species of spiders in the U.S., including black widows.
Cobwebs are sticky. (Some other types of spiderwebs are simply fuzzy.) Cobwebs are also messy—and lack the front entrance or emergency exit built into more sophisticated structures spun by other types of spiders.
“Unlike beautiful orb webs, funnel webs, and other more regular web constructions, cobwebs are irregular mesh-works,” explains Jerome S. Rovner, professor emeritus of biological sciences at Ohio University in Athens, and a member of the American Arachnological Society. “In placing the threads, cobweb spiders don’t follow the series of behavioral steps that would result in a more regular or symmetrical web.”
It doesn’t matter, though, because webs exist primarily to immobilize prey. Once an insect’s stuck fast, the spider can elegantly finish it off with its teeth.
Are cobwebs made by spiders? Wait, why are spiders inside your house to begin with?
Relax, spiders are (most likely) not coming to get you.
“It’s not a choice [that they’re indoors]; it’s an accident,” Rovner says. “They wander throughout the environment and sometimes, without any actual intent to do so, wander into a building through a gap. Once inside, they do what they would otherwise do on the outside—build a web.”
To figure out where to spin, spiders “assess the presence of appropriate supporting structures for attaching the ends of the threads of their web,” Rovner says.
They do this primarily using their sense of touch. Sight’s far less important. Spiders don’t have great vision and most are nocturnal, so they do just fine in the dark. By reaching out their long legs, they make sure they have enough contact with nearby surfaces.
As long as they occasionally catch insects to eat, a spider will continue to happily hang out, waiting for a big (insect) payday. But if they start getting hungry, they’ll ditch their web and build in another location.
And if another corner isn’t successful either?
“They sometimes eventually manage to find a way back outside,” Rovner says, and leave their web.
Where do cobwebs come from? A web without a spider is still (st)icky
Once a spider dies or abandons its hanging home, “the web still maintains its sticky texture, grabbing hold of every dust and dirt particle, pet hair, and any other debris floating around your home,” says Debra Johnson, Merry Maids’ home cleaning expert. (It’s likely that you don’t notice the cobwebs until these tiny particles start clinging to it.)
OK, ready for another disturbing fact? If protected from the weather and left untouched, cobwebs can last for years, “with only minimal structural change—that is, sagging of threads,” Rovner adds.
That’s where you come in.
To make your home more spider-unfriendly, you can spray an insecticide around any gaps and openings in your home. Do this every month or so during spring, summer, and fall to reduce the number of arachnid invaders you get.
You can also take the following steps:
Get rid of the dust: “The key here is consistency,” Johnson says. “Ideally, you should dust your house on a weekly basis, but if life gets in the way, as it so often does, you can get away with dusting every two weeks to keep cobwebs at bay.”
Work from top to bottom, making sure you hit the upper corners where cobwebs tend to form. Cover any furniture or items below the corners with a towel so they don’t get dusty and you create even more work for yourself.
Afterward, vacuum the floor to prevent the dust and dirt from recirculating.
“Make sure to check corners of the floor and corners where furniture sits, as spiders have a tendency to make webs in these spots,” Johnson says.
Clean your blinds: Spiders might be fans of darkness, but the insects they eat are drawn to light.
“That makes window blinds and other window treatments a prime area to build webs,” says Johnson. Other areas of the home to check for webs include ceiling fans and air-conditioning vents.
“Since these items move or circulate air, they play a large role in spreading dust and dander about your home and onto webs,” Johnson says.
Kill the clutter: “Piles of clutter throughout a home create a source of shelter for spiders, so make sure everything has its own place,” Johnson says.
And if you come across a web that’s still inhabited? Twist the web onto a dust mop, although “most homeowners would prefer to just vacuum up the spider from its web,” Rovner admits.
But spiders are our friends (no matter if they make your skin crawl) because they catch and eat so many types of pests. Because of that, consider taking a tenderhearted approach. Push a small jar into the web, get the spider inside, put the lid on, and release your eight-legged friend outside with some good wishes.
