“Start with your windowsills,” advises Rob Dunn. “Light fittings are often a graveyard, too.”
As households across the United States decorate their homes with plastic spiders for Halloween, Dunn, an applied ecologist at North Carolina State University, is encouraging people to search out the real thing — and then to photograph whatever they find, rather than squash it.
His new project, Never Home Alone, aims to gather at least 10,000 observations of arthropods — insects and their kin — from around the world. Anyone can participate, using the online nature-identification platform iNaturalist; the only condition is that the bugs must be observed indoors.
That is where humans, too, are mostly to be found. “We spend more than 90 percent of our lives inside,” Dunn said recently, citing a 2001 study funded by the Environmental Protection Agency.
In the world’s densest cities, the indoor biome is bigger than the outdoor space, at least in terms of floor area. (Indoor Manhattan, Dunn calculates, now exceeds outdoor Manhattan by a factor of 3-1.) Yet scientists know almost nothing about the spiders and flies and book-lice that inhabit this space alongside us.
“There’s no shortage of papers on cockroaches and termites,” said May Berenbaum, an entomologist at the University of Illinois who was not involved in the project. “But there are hundreds, potentially thousands of house dwellers that are neutral to beneficial that we know nothing about.”
Even Dunn was, until recently, guilty of ignoring his six-legged housemates. A few years ago, he and his colleagues decided to take a census of 50 homes in Raleigh, North Carolina, including his own.
“I would have told you I had four species of spiders,” he admitted. “When we looked, we found 10 in my house — and that turns out to be the average.”
Indeed, some houses in Raleigh had more than 200 arthropod species in total; Dunn and his team have found a similar multiplicity of bugs living in homes as far afield as Sweden and Peru.
For Dunn, the domestic interior suddenly seemed more exotic than the Amazon, filled with opportunities for discovery. (Dunn’s previous surveys include studies of the microbial diversity in armpits and sourdough.) A couple of the insects he and his colleagues saw were entirely new to science, but even the named ones were deeply mysterious. In most cases, researchers don’t know what the creatures eat, what their closest relatives are or from which habitats they originally hailed.
At the same time, the extent of this ignorance was overwhelming. It took the team hours to survey a single home, and even longer to identify each specimen. At that pace, Dunn would never have enough data to understand even the basic patterns of indoor insect life, or how they differed throughout the United States, let alone the world. iNaturalist — a citizen-science app with users across the globe, and the ability to geolocate and even identify specimens from photos using artificial intelligence — offered a way through this bottleneck.
In July, Dunn created a page for the project, and began asking the platform’s most active users to contribute. By mid-October, the project page had received more than 3,000 submissions, representing more than 800 species, from more than 1,000 participants around the world.