For the study, entomologists (scientists who study insects, that is) at North Carolina State University visited 50 randomly selected homes between May and October 2012 in Raleigh and within a 30-mile radius from the city. They performed a visual inspection of each room (they focused on attics, bathrooms, bedrooms, common rooms, basements, and kitchens), collecting a total of more than 10,000 specimens from visible surfaces.
“A lot of expeditions to collect biodiversity are done out in these remote places, and although we do know some things about pest species in our homes and [there are] some individual little studies about certain non-pest species in our homes, really nobody has looked at a complete picture on all the different types of arthropods you might be able to find in homes,” says Matthew Bertone, Ph.D., lead researcher of the study.
After analyzing the bugs at the North Carolina Museum of Natural Science’s research center, Bertone and team identified a whopping 579 arthropod morphospecies (a.k.a. bugs with different structures). However, Bertone notes that a lot of the specimens they found were “accidental wanderers” that came into the home and died.
That being said, the most common creatures living in homes were not giant roaches, but in fact flies (23 percent), beetles (19 percent), spiders (16 percent), and ants (15 percent). “The things that did appear to live in homes for long periods of time were actually extremely common [and] found in 100 percent of homes and over 50 percent of rooms,” says Bertone. “What really surprised me was that we found cobweb spiders, for instance, in 65 percent of rooms.”
Here’s a breakdown in pie chart form:
These bugs aren’t going to harm us, says Bertone, and there’s no need to go HAM trying to keep your house insect-free. “Most of them are very neutral and just going about their lives, staying out of our way,” he says. “They just enjoy our homes.” Bertone does add that they did find some pests like book lice, which can get into food if you leave something out, but still, he says it’s really NBD.
Meanwhile, certain predators like spiders and house centipedes (y’know, those creepy-crawlers with a million-and-one legs), feed on gross pests like roaches. “They can actually be beneficial despite being extremely scary to most people,” says Bertone.
Oh, and fun fact: While 100 seems like a huge number, these bugs are super teeny-tiny. If you put them all together, Bertone says they’d probably only fill up about half a shot glass, give or take. Not exactly scary when you think of it like that, right? “The fact that people are surprised by this just goes to show that they don’t interact with these organisms very often,” says Bertone.
While the study only represents homes in North Carolina, Bertone points out that the most common insects his team of researchers found are not actually from North Carolina or even the U.S. “Many of the arthropods we do find have been associated with humans for a long time, and they travel around the globe,” he says. Still, Bertone says some researchers are currently collecting specimens from different countries to get some variation, he says.
The bottom line: Maybe the next time you find a random bug on your bathroom wall, set it free instead of squishing the life out of it.