Looking for a healthy variety of bugs? You might want to try searching in your wealthiest friend's house.
Neighborhood income is a good predictor of the number of kinds of insects found indoors, according to a recently-published study in Biology Letters. The researchers went searching in the dark corners of 50 homes in the Raleigh, North Carolina, area for bug life.
They explained that previous work shows wealthier areas tend to be more biologically diverse outdoors — and that's already proven true with "plants, birds, bats and lizards." That's because wealthier people tend to have more elaborate gardens that can impact animal diversity — known as the "luxury effect."
"It presented this paradox," entomologist and study lead author Misha Leong told Smithsonian Magazine. "You have this luxury effect known to happen outdoors and this public perception that low-income neighborhoods have major arthropod problems."
But: "that perception is based solely on our own prejudices," Leong told the publication.
Until now, very little research has focused on the ecology of the great indoors. In their paper, the scientists said recent research suggests the "indoor biome" actually "harbours more biodiversity than previously recognized."
Somewhat chillingly, they find that homes are teeming with these uninvited guests. "The average home contains more than a hundred anthropod species; the vast majority of these species being non-pests," the researchers state. In short: the luxury effect is as true indoors as it is outdoors.
The researchers found the most important predictor of insect diversity was the square footage of the home, followed by local ground vegetation cover, mean neighborhood income, and local ground vegetation diversity.
In a finding that surprised the researchers, the relationship between neighborhood income and bug diversity holds true even in high-value homes without particularly robust gardens. They said that's probably because these areas are more likely to have "enhancements at a neighbourhood scale" than lower income areas. That could mean a park or more greenery in public space along the roads.
As Leong told Smithsonian: "Choices made at the neighborhood scale by your neighbors or your local government can have an effect on what's going on in your kitchen floor."
In summary, the key determinant of bug diversity is "not only how much vegetation you have in your garden, but how much is present in the gardens and other habitats nearby."
This just shows "how much we have yet to learn about indoor ecology," the researchers concluded. Looks like plenty of mysteries could be waiting in your attic and basement.