The sound of stink bugs flying around indoors has become a harbinger of autumn. One has been circling above me the whole time I’ve been writing this story. She looks like she’s trying to get into the ceiling but each time she hits it, she bounces off.
Female stink bugs are slightly larger than males but both can get through the tiny openings in most shutters and soffits in houses and buildings.
Thom Kuhar is a professor of entomology at Virginia Tech. He and his graduate students studying the bug’s behavior “ have noticed that bugs will move up. When they land on a structure they will crawl upwards until they basically hit something that stops their progress and then they start searching for a crevice.”
Right now, he says, the bugs are “attracted to dark spaces because they’re looking to find a place to overwinter.”
That’s why, at this time of year, stink bugs can’t be fooled by one of those clever homemade water pan and incandescent lamp traps. They won’t fly toward the light because now it’s a very different urge that drives them: Warmth, comfort, the company of others like them.
“The bugs overwinter in huge masses (outdoors, often in dead trees, just beneath the bark). Most people don’t get to see that. They see the ones that have, basically, broken away from the overwintering pack and are likely losing their fat reserves that are going to help them get through the winter and they’re desperately looking to start the spring. It may not be spring. It just seems that way inside the warm house."
The stinkbugs that overwinter outdoors are the ones who make it to the actual spring to procreate. The ones who plague us indoors will usually die before they get that chance.
Kuhar points out that there are several species of native stink bugs that don’t invade people’s living spaces each autumn. It’s only the brown marmorated variety from Asia. First identified in Pennsylvania in 1989, it quickly gained a foot hold with no local predators to keep it in check.
But recently, some of our home-grown insects have begun to develop a taste for cilantro. That’s how people describe the scent of a crushed stink bug.
Tracey Lesky, an entomology researcher at the U.S. Department of Agriculture ran a study. She tried “to find out if spiders around people’s homes actually can attack, retain in their webs and consume Brown Marmorated Stink Bug. "And we found a couple of groups of spiders that do a pretty good job with that. So, for those homeowners that have stink bug issues, I would say let spiders do their work.”
Cobwebs may be the price you have to pay. So it's a tradeoff.
She says, researchers have also learned that there are a lot of insects that eat the eggs of Brown Marmorated Stink bug. "For example, we found that Katydids, of all things, eat the stink bug eggs in trees."
And reinforcements in the battle against stink bugs have also arrived, also from Asia
“That is the non-stinging wasp Trissolcus Japonicas, also known as the Samurai Wasp. This insect has been in quarantine for years. It’s a parasitoid. That means that this small, nonstinging wasp, about the size of a comma on a piece of paper, lays its eggs in the eggs of the BMS. However, this insect showed up accidentally, kind of like BMS and it was detected in the wild.”
Scientists first positively identified the tiny predator in Maryland in 2015. It’s now it’s being seen in large numbers in northern Virginia and several other states. But, right now, say the experts, the only line of defense against bugs desperate to get inside is, sealing up the crevices they seek ---and patience. This mad dash to get inside buildings lasts about 3 weeks and it’s almost over.