To witness astounding biodiversity, one need not trek to a remote nature preserve. In fact, research published today shows it’s not even necessary to leave home.
In a study sure to make insectphobes tremble a team of scientists visited 50 houses in the Raleigh, N.C., area and documented nearly 600 species of bugs. Some of these creatures are notorious pests. German cockroaches, for example, had infested three of the houses surveyed whereas 14 houses had termites and five had fleas. Yet the vast majority of bugs in what the scientists described as the “great indoors” are considered benign and go largely unnoticed by their human co-habitants. “I like to think of them as good roommates,” says study co-author Michelle Trautwein, an entomologist at the California Academy of Sciences in San Francisco. “They’re quiet and unobtrusive.”
The scientists conducted their research from May to October 2012, arriving at each house equipped with headlamps, kneepads, nets, forceps and aspirators, which were used to suck up tiny critters along windowsills and baseboards. “We looked like intense expeditioners,” Trautwein says, laughing. “It looked like we could be going to the middle of the Amazon.” Methodically moving from room to room, they ended up collecting more than 10,000 specimens in 304 invertebrate families.
Each house averaged about 100 species. Ants, spiders, carpet beetles and gall midges—otherwise known as gall gnats—were found in every single residence, and all but one contained book lice, which Trautwein describes as “cute” and “the friendly cousins of parasitic head lice.”
Whether or not residents employed pesticides to combat the critters seemed to make little difference: The bugs were everywhere, regardless. Of the 554 rooms examined, the scientists discovered and collected specimens in all but five (four bathrooms and a bedroom—they aren’t sure why these rooms were clear of bugs). Because they did not check behind walls, in drawers or under heavy furniture—and also did not identify every bug to the species level, something that’s exceptionally difficult to do with insects—the researchers believe their total of 579 species is likely a significant undercount. “These are very small arthropods, or very hidden and cryptic arthropods,” says lead author Matt Bertone, an entomologist at North Carolina State University.
This study, which appeared in PeerJ, represents the first-ever comprehensive survey of indoor invertebrates. “When we think of unexplored places, we often think of the bottom of the ocean or the top of the rainforest canopy,” Trautwein says. “But the truth is even our houses are these relatively new and unexplored ecosystems.”
In addition to the common bugs, the scientists encountered several unexpected surprises. For example, neither Trautwein nor Bertone had ever seen live ant-loving crickets prior to spotting them in a few homes with ant infestations. They likewise came across carrion-feeding flesh flies emerging from a dead rodent, two nearly microscopic hermit crabs trapped dozens of kilometers from the closest seashore and a larval-stage beaded lacewing, which immobilizes termites with a chemical released from its anus before eating them.
Most bugs cannot survive indoors long-term. Trautwein likened such herbivores as gall midges and leafhoppers to “ill-fated tourists” that get lured in by light or shelter only to find that there’s nothing to eat. “Some groups are definitely just coming in and dying,” Bertone says. “They wander into places and they can’t get out.” On the other hand, a core community of parasites, predators and scavengers appears to thrive best with a roof overhead.
The impact of all these many-legged critters on human health remains unclear. It’s well known that bugs can spread diseases and trigger allergies. Yet they also bring potential benefits, such as “good” bacteria. Evidence suggests that a diverse community of invertebrates may even inhibit pest infestations. “I don’t think anyone should change their lifestyle or start spraying more chemicals or burn down their house or anything like that,” says Bertone, who adds that if household conditions cannot support arthropods, it could be a “bad sign for us.”
To further uncover the world of indoor wildlife the scientists now plan on surveying dwellings on all seven continents. (They’ve already finished work in Peru, Sweden and San Francisco, although the data remain unanalyzed.) “When I was a kid learning about science, I sort of had this assumption that all the cool stuff had already been discovered,” Trautwein says. “[But] gosh, we don’t even know a lot about the animals in our own house.”