You don’t just see one stink bug. You see seemingly infinite stink bugs: in the couch, among the dishes, somehow under your pillow. Sure, try to kill them—they’ll just come right back.
New research from scientists in Virginia measures just how small the smallest gaps must be in order to keep stink bugs out of your house.
“Based on experimental data and size data, we conclude that most H. halys individuals will be excluded by slits smaller than 3 mm and holes smaller than 7 mm,” according to the paper published in the Journal of Economic Entomology. That’s pretty small—3 millimeters is the width of two dimes stacked on top of each another, and 7 millimeters is the length of a long grain of rice.
Halyomorpha halys, the brown marmorated stink bug, is a beetle-sized Japanese insect first found in Allentown, Pennsylvania in 1998, which likely entered the U.S. in shipping containers from Asia. It has since spread across the country and become an agricultural pest. They’re most famous for their cold-weather behavior, when they enter warm homes, sometimes by the thousands.
Most research aims to learn about the stink bug’s effects on crops, but some scientists are looking into how best to keep them out of homes. Thankfully, while the bugs seem like they can get just about into anything, there are ways to keep them out. “Everyone talks about stink bugs like they can get into anything,” study author Benjamin Chambers told Gizmodo, “but they’re not that small.”
Chambers’ research essentially involved putting the stink bugs into wooden boxes and slicing holes and slits of various sizes into the walls, then heating up the box on a radiator to encourage the stink bug to try to leave. They wanted to see just how big a hole the stink bug could escape through. The 7 mm holes and 3 mm slits are a little smaller than the openings in meshes typically employed at openings in order to keep rodents out.
But the study is limited. The experiment didn’t test soft surfaces, and there’s a chance smaller stink bugs than the ones used in the study could pass through smaller openings, of course. And there are simply places where houses require larger holes, such as vents—Chambers suggested talking to an expert before going around and plugging all the holes in your house.
Stink bugs are scary, but we don’t have to let them win.