If you’ve ever walked into your kitchen on a warm spring morning and spotted a slow-moving, shield-shaped insect crawling across the counter, you’ve met the brown marmorated stink bug (Halyomorpha halys). And if you’ve made the mistake of squashing one, you already know how it got its name.

Stink bugs aren’t dangerous. They don’t bite, they won’t damage your furniture, and they’re not a sign that your home is dirty. But they are deeply annoying—and once they find their way inside, they tend to show up in numbers. Understanding why they emerge in spring, and what drives them indoors in the first place, is the first step to keeping them out for good.

What Are Stink Bugs, Exactly?

The brown marmorated stink bug is an invasive species originally from East Asia. It was first detected in the United States in Allentown, Pennsylvania, in the late 1990s and has since spread to nearly every state in the country. Its name comes from the foul-smelling chemical it releases from glands on its abdomen when it feels threatened or is crushed—a defense mechanism that works surprisingly well against predators.

Adult stink bugs are roughly ¾ of an inch long, with a mottled brown, shield-shaped body. They’re slow fliers and even slower crawlers, which makes spotting them fairly easy. The challenge is that where there’s one, there are usually many more hiding nearby.

Why Stink Bugs Emerge in Spring

They Spent the Winter in Your Walls

Stink bugs are what entomologists call “overwintering” pests. As temperatures drop in fall, they seek out warm, sheltered spaces to enter a dormant, low-energy state called diapause. Homes are ideal for this—wall voids, attics, crawl spaces, and gaps around window frames offer the kind of stable, cool-but-not-freezing temperatures they need to survive the winter.

This is why you’ll often see a surge of stink bugs inside the home in late fall as they try to get in, and again in early spring as they try to get out.

Warming Temperatures Wake Them Up

When spring arrives and temperatures consistently climb above 70°F (21°C), stink bugs emerge from diapause. Their metabolism kicks back in, and they become active again—seeking food, light, and eventually a way back outside to feed and reproduce.

The problem is that many of them have been overwintering inside your home. So when they “wake up,” they don’t always find their way back out. Instead, they wander into living spaces, attracted to light from windows and warmth from heating systems. This is the source of those baffling spring appearances on curtains, light fixtures, and kitchen benchtops.

They’re Looking for Food and Mates

Once outside, stink bugs become highly active feeders. They use a piercing mouthpart to feed on the juices of fruits, vegetables, and ornamental plants—making them a serious agricultural pest as well as a household nuisance. As days lengthen and temperatures stabilize, they also begin mating, which drives them to congregate in large numbers around host plants and sun-warmed surfaces like south-facing walls and windows.

How to Stop Stink Bugs From Getting In

Seal Entry Points Before Fall

The most effective way to deal with stink bugs is to prevent them from entering in the first place. Since their fall migration into homes typically begins in September and October, late summer is the ideal time to seal up your home.

Focus on:

• Door and window gaps – Install or replace weatherstripping and door sweeps on exterior doors. Check that window screens are intact with no tears or loose edges.
• Utility penetrations – Seal gaps around pipes, cables, and wiring that enter through exterior walls using caulk or expandable foam.
• Roof and attic vents – Cover these with fine-mesh insect screening to block entry without restricting airflow.
• Chimney openings – Fit a chimney cap if you don’t already have one.

Even small gaps matter. Stink bugs can squeeze through openings as narrow as a few millimeters, so thorough sealing pays off.

Reduce Outdoor Attractions

Stink bugs are drawn to warmth, light, and food sources. A few simple changes to your yard and outdoor lighting can make your home less attractive to them:

• Switch to yellow or sodium vapor outdoor lights, which are less attractive to insects than standard white or cool-spectrum LEDs.
• Keep firewood, compost, and debris piles away from the house, as these provide shelter and harbor the bugs before they migrate indoors.
• Trim plants and shrubs away from exterior walls—dense vegetation gives stink bugs easy access to your home’s exterior and entry points.

Manage Them Indoors Without Making It Worse

If stink bugs are already inside, resist the urge to squash them. The defensive odor they release can attract more bugs and, in enclosed spaces, leave a lingering smell that’s hard to shift.

Instead:

• Use a vacuum to collect them, then immediately seal and dispose of the bag outside.
• Place them in soapy water—dropping them into a container of dish soap and water kills them quickly without triggering the odor release.
• Avoid pesticide sprays indoors unless the infestation is severe. Stink bugs overwintering in wall voids are largely inaccessible to sprays, and indoor pesticide use carries its own risks.

Consider Professional Treatment for Severe Infestations

For homes with a significant overwintering population, a professional pest control treatment in late summer or early fall—before bugs enter—can be highly effective. Exteriors are typically treated with residual insecticides along foundation walls, window and door frames, and other likely entry zones.

If you’ve dealt with large numbers of stink bugs for multiple years in a row, professional treatment combined with thorough exclusion work is likely your most reliable long-term solution.

Frequently Asked Questions About Stink Bugs

Are stink bugs harmful to humans or pets?
No. Stink bugs do not bite, sting, or transmit disease. They are a nuisance pest only. The odor they release is unpleasant but not toxic.

Why do I suddenly have so many stink bugs in my house?
A sudden increase in spring is almost always caused by bugs that overwintered inside your home becoming active as temperatures rise. It’s not a new infestation—they’ve been there all winter.

Do stink bugs cause damage to homes?
No structural damage. However, they can stain light-colored surfaces with their secretions, and large numbers can leave a persistent odor.

What smells keep stink bugs away?
Some homeowners report that essential oils like clove, lemon, and spearmint act as deterrents when applied around entry points. The evidence is largely anecdotal, but these are low-risk options worth trying alongside more effective exclusion measures.

When is the best time to act?
Late summer to early fall—before stink bug migration begins—is the most strategic time to seal your home and apply exterior treatments. Acting in spring addresses the current season but won’t prevent next year’s overwintering.

The Smartest Move Is a Seasonal One

Stink bugs are predictable. They follow the same seasonal cycle every year, which means you have a reliable window to get ahead of them. Seal your home in late summer, reduce outdoor attractants, and manage any indoor bugs calmly and carefully—and you’ll dramatically reduce the number you see each spring.

There’s no silver bullet, but there is a clear strategy. Start with exclusion, stay consistent, and you’ll find that the annual spring stink bug invasion becomes a non-event rather than a recurring headache.