dark winged fungus gnat Photo: Matt Bertone

There are uninvited guests crashing at your house, and they likely number in the hundreds or more.

As part of a University of North Carolina study, researchers combed 50 detached homes within 30 miles of state capital Raleigh for arthropods, invertebrates that can be identified by their exoskeletons, segmented bodies and jointed limbs.

Their findings were recently published in academic journal PeerJ, and it’s not recommended reading for the squeamish.

The search turned up 579 different kinds of arthropods, with flies, spiders, beetles, ants and book lice among the most popular.

In all, researchers collected close to 10,000 samples both living and dead, averaging out to about 200 per home and only five of the 554 rooms didn’t yield any arthropods.

“We basically used forceps, tweezers, and aspirators, which are little devices to suck up insects without getting them in your mouth,” explains Matthew Bertone, a University of North Carolina entomologist, and lead author of the scholarly paper.

“A few times we had to use an insect net to catch a flying insect, but it wasn’t too often, luckily,” he adds.

Armed with these tools, as well as knee pads and flashlights, Bertone and others spent two to three hours at each home from May to October 2012.

None of the homes looked like a hoarder’s dwelling, nor were any “sparkling clean,” says Bertone. “These were all fairly typical homes,” says Bertone.

Almost all of the creepy crawlers Bertone and his team came across were harmless — almost.

A black widow found in an unfinished basement crawlspace, but that was the only “dangerously venomous” arthropod uncovered. “Unless you count wasps and bees that can cause… allergic reactions,” Bertone adds.

little black ants Photo: Matt Bertone

Nearly every spider is venomous, same with house centipedes, the researcher says, but these don’t pose much of a threat to their human landlords.

“It’s really more that they are dangerous to other arthropods and really not dangerous to us,” Bertone explains.

The household expeditions resulted in some uncommon finds. “We found a few types of insects that are either very rarely encountered or that I had never seen specimens captured anywhere.”

The telephone pole beetle is perhaps most notable due to its unique reproductive biology. “They have babies that can have babies,” as Bertone puts it.

Bertone believes there’s a wealth of knowledge to be gleaned from this study.

“For instance, why are some groups of arthropods well adapted to humans… but their close relatives are found only outdoors and really don’t establish in homes?” he asks. “Is there something they’ve evolved to, some adaptation to living in homes?”

He also hopes to bring the word “arthropod” to the mainstream. “It’s a good way to describe all these many-legged critters and creatures,” he says. “They are a very diverse group.”

Bertone says the real number of arthropods in homes could be much higher than the 10,000 he and his colleagues found.

“We just collected for diversity, rather than abundance,” he explains. Researchers also didn’t check behind walls, under floorboards, or down pipes.

“Many of the specimens we collected had come in from outdoors,” says Bertone, who points out “a lot” of them were dead upon discovery.

“We do get a lot of accidental intruders, or guests — whatever you feel like calling them,” he adds.

Not every region has the same bugs flying, crawling, and slithering around outside, but many of the hardier arthropods that can survive inside homes in North Carolina are found in other regions, so the study can provide some insight into household populations elsewhere.

“We all have similar things,” says Bertone. Citing a common house centipede, he explains, “People in Colorado and people in Canada and people in Texas will all be familiar with that, because it does spend its time indoors and doesn’t really care about the outdoor environment.”

It’s difficult to say right now what factors led to one home having more arthropods than another, but a survey should help give an idea.

Participating households were asked to fill out a form that asks things like how often windows are left open at home, what temperature they keep their home at, and whether or not they have plants or pets.

“One of our future studies is to take this data and look at all the variables, either based on the physical aspects of the home or people’s behaviors,” says Bertone.

“We really haven’t crunched that data yet, because it’s really complex.”

If anyone can make sense of it, a group of academics who spent months searching for (and counting) approximately 10,000 bugs probably has a pretty good shot.

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