Her home, like yours, is not a sealed-off fortress. Living creatures that aren’t on the lease will inevitably find their way inside. On the smallest level, your living space has a microbiome, with up to 500 to 1,000 species or microbes living in your dust. A few rungs up the size scale, silverfish, spider mites, ants, fungus gnats, and cockroaches can be mild nuisances or a huge problem. They can kill your houseplants and raid your cupboard. Just as introducing wolves back into Yellowstone National Park led to increased soil aeration, better songbird habitat, and stabilized river banks, a few household apex predators like earwigs, spiders, and harvestmen could change your home for the better. Most North American spiders, including the cellar spiders on Crawley’s sill, are not dangerous to humans (or pets) anyway. So don’t smush those helpful neighbors if you can help it, and think about employing some of the following strategies for backup.  And if anyone needs a platoon of eight-legged minions, it’s Crawley: She lives next door to a cattle farm and struggles with the inevitable houseflies that are drawn to the cows. “No matter what I do, I’m going to get a straggler in the house,” she says. But her windowsill spiders have come to the rescue, trapping three or four flies every few days. “The only issue is sometimes my dog will find them and boop them to death,” she says of her productive (if sometimes unlucky) roommates. If a pest problem is out of control, it is probably too late to rely on spiders, carnivorous plants, or any other DIY solutions. But aside from that, if you can control your squeamishness and begin to think of your home as a well-controlled garden rather than a sealed box, you might be able to make friends with your fellow residents and tend to your personal ecosystem.