Your home may host 100 different 'quiet and benign' bugs, scientists say

In an unprecedented analysis of arthropod biodiversity inside the human home, a group of entomologists found that there are on average about 100 different species of bugs in every house. 

Don’t freak out, but there may be more than 100 identifiable types of bugs in your home right now. Most of them, you will be happy to know, are harmless.

In the first study ever to analyze the biodiversity of arthropods – insects, spiders, centipedes, mites, and other crawly things – inside the human home, a team of entomologists visited 50 houses in the Raleigh, N.C. and gathered specimens, both dead and alive, from every visible surface.

The result was nothing short of astounding. From the 554 rooms sampled, the scientists collected over 10,000 bugs and identified at least 579 morphospecies, a term used for organism types that have no discernible physical differences, but may have genetic differences. On average, individual homes had about 100 morphospecies.

“The truth is that we’re all living with this vast diversity of arthropods and the majority of them are not overtly harmful,” says Michelle Trautwein, an entomologist at the California Academy of Sciences and co-author of the study. “We ought to consider them our quiet and benign roommates.”

The study, published Tuesday in the journal PeerJ, entailed hundreds of hours of field biology – all inside people's homes. In collaboration between the CAS and North Carolina State University, the collection process in each house took between two to seven hours.

“Our visits were full-on indoor expeditions,” Dr. Trautwein tells The Christian Science Monitor. “We’d be all decked out in knee pads, headlights, forceps, and vests full of vials.”

And the scope of the analysis, she says, is unprecedented. After documenting the collected specimens, her team found that the most common bugs were gall midge flies, cobweb spiders, ants, carpet beetles, and booklice, though it’s worth mentioning that 82 percent of the homes had cockroaches. But to the scientists’ surprise, pests in general were not as common as they’d predicted.

“Because previous studies of indoor arthropods have largely focused on pest groups of economic and human health importance, we expected common pests to be among the most frequently found groups of arthropods in the homes,” the study reads. “In fact, we found a relative dearth of typical household pests.”

So, pest or no pest, why exactly are there so many bugs inside human homes?

Historically, bugs have been evolving alongside people since the days of cavemen. “As human society changed over time, arthropods successfully – and rapidly – made use of our bodies and resources for food and shelter,” the scientists write.

For instance, having pets is one reason for the presence of certain bugs. Proximity to foliage and heavy greenery is another. It could be as mundane as bringing home a bouquet of flowers, or even the dirt residue from your shoes. But whatever the reason, it’s nothing to worry about, says Matt Bertone, an entomologist at North Carolina State University and lead author of the paper.

"While we collected a remarkable diversity of these creatures, we don't want people to get the impression that all of these species are actually living in everyone's homes," Dr. Bertone explained in a statement. "Many of the arthropods we found had clearly wandered in from outdoors, been brought in on cut flowers or were otherwise accidentally introduced. Because they're not equipped to live in our homes, they usually die pretty quickly."

The bugs may actually provide benefits for their accidental hosts. A working hypothesis for Trautwein (whose expertise is flies), Bertone, and their colleagues is that similar to microbial diversity, your household bugs could fend off other pests.

“It’s like how we’ve learned that microbial diversity in your house can prevent the infestation of other pathogenic bacteria,” Trautwein says.

In addition to the possible effects of these bugs, further correlations between the residences’ physical characteristics and the specific biodiversity of their arthropod dwellers will be topics of follow-up research.

The study, in fact, has already been expanded to different locales. This summer, Trautwein and her team in California conducted the same sampling research in San Francisco homes. Then, they repeated the procedure in Amazonian Peru and Sweden.

“It’s funny, because we’re field biologists collecting in someone’s living room instead of trekking through the Sierras or something,” says Misha Leong, co-author and a postdoctoral researcher at CAS. “But it’s very intensive work, getting on your hands and knees, working up a sweat, and looking into corners where people don’t necessarily clean or notice.”

Up next? Dr. Leong tells the Monitor that the team will check out Australia, China, and Mozambique. The goal is to explore arthropod biodiversity in human homes on all seven continents.