Courtesy of Matt Bertone

Your house is bugged.

According to a new study, our houses can contain more than 500 different kinds of arthropods, a category that includes insects, spiders, mites and centipedes. The most commonly identified critters in the study were flies, spiders, beetles and ants.

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How did the researchers determine this great abundance of biodiversity inside human dwellings? By scouring them from top to bottom and collecting over 10,0000 specimens.

A group of entomologists from NC State, the California Academy of Sciences and the North Carolina Museum of Natural Sciences went through 50 houses near Raleigh, North Carolina, gathering all the arthropods they could get their hands on. Of the 554 rooms they searched, only five didn't have any bugs.

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"We think our homes are sterile environments, but they're not," Matt Bertone, an entomologist at North Carolina State University and lead author of the paper, said in a statement. "We share our space with many different species, most of which are benign. The fact that you don't know they're there only highlights how little we interact with them."

Still, not need to bug out. According to Bertone, not all of these creatures are actually living inside—many of them just wandered in or were accidentally brought in, and are passing through. Most of the other ones are not so-called "pest species" but rather "peaceful cohabitants" such as cobweb spiders, which were found in nearly two-thirds of the rooms sampled. German cockroaches, termites and fleas were only present in a few homes, and no bed bugs were found. However, around 75% of the homes hosted more common Blattidae cockroaches, which are not considered pests.

In sum, the specimens represented over 300 families of arthropods and at least 579 species. The average house contained around 100 different species, which the authors consider an extremely conservative estimate.

Part of the reason why this is likely an underestimate of the actual number of bugs in our homes is that the researchers were only looking at visible surfaces and didn't get into walls, under large furniture or inside drawers and cabinets. Which makes you think that just because they didn't identify many of the more unwelcome critters, doesn't mean they weren't around hiding in deeper recesses.

According to the study, which was published on January 19 in the journal PeerJ, more types of flies are associated with human homes than any other group of animals. Almost all of the houses contained booklice, a harmless, tiny insect that eats mold and mildew.

Proportional diversity of arthropod orders across all rooms.
Courtesy of

In the end, many of the insects found weren't able to be identified as specific species and were rather categorized by morphospecies: a term used to characterize animal types that are identifiable by their form and structure without extensive taxonomic training.

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Due to this ambiguity, the study may actually end up identifying some new species—of which there are millions remaining in the insect world.

With around 18,000 new plants and animals being cataloged every year, some two million of Earth’s species have been discovered. Scientists estimate that this leaves at least 10 million more species yet to be classified, according to a 2012 study.

For instance, 60 new dragonfly species were recently discovered throughout Africa, bringing the total number of known dragonfly species to 760.