American Houses Are Teeming With Bugs

Cobweb spiders, like the common house spider (Parasteatoda tepidariorum), were found in all 50 houses sampled in a new study. Matt Bertone

Even though you may think you're alone, you are not: You are probably surrounded by many more bugs than you thought possible.

In the first census of its kind, researchers combed through 50 American houses and found a surprising diversity of arthropods—creatures with hard exoskeletons, such as spiders and other insects. In the 50 houses, the scientists found more than 10,000 specimens from 579 species, and the average house had around 100 species. And the researchers found them in just about every room in every house searched, according to a study published Tuesday in the journal PeerJ.

The most common types of arthropods found were flies, beetles, spiders and ants. All of the homes contained cobweb spiders, carpet beetles, gall midge flies (which feed upon and create tumor-like growths in plants called galls) and ants. Book lice, insects that feed on mold and fungi, and dark-winged fungus gnats were also found in 98 percent and 96 percent of homes, respectively.

Generally, these household "roommates" are harmless. "The vast majority of the arthropods we found in homes were not pest species," study author Matt Bertone, from North Carolina State University, said in a statement. "They were either peaceful cohabitants—like the cobweb spiders...found in 65 percent of all rooms sampled—or accidental visitors, like midges and leafhoppers."

"We ought to consider them our quiet and benign roommates," co-author Michelle Trautwein, an entomologist at the California Academy of Sciences, told The Christian Science Monitor.

Typical pests, such as German cockroaches, termites and fleas, were found in a minority of homes (6, 28 and 10 percent of homes, respectively). Bedbugs weren't found in any of the houses, which were all in the Raleigh, N.C., region.

In another surprising finding, the majority of houses (58 percent) were home to camel or cave crickets, strange-looking insects that are typically found in subterranean locations. The researchers also found aphids and wasps in most of the houses. Some of the creatures, like gall midges (found in every home), weren't previously thought to be common indoor species and were not even mentioned as among the over 2,000 species listed in a supposedly exhaustive recent compilation of urban insects and arachnids titled Urban Insects and Arachnids: A Handbook of Urban Entomology.