Stink bugs hide in wall voids, attics, window frames, and behind baseboards inside your home, and under tree bark, leaf litter, and rock crevices outdoors. Their hiding behavior is seasonal: during warm months they stay outside among plants and crops, but as daylight hours shrink in early fall, they move toward structures and squeeze into sheltered spots to ride out winter. Understanding where they go and why helps you find them, and more importantly, keep them out.
Why Stink Bugs Seek Shelter in Fall
Stink bugs, particularly the brown marmorated stink bug, enter a dormant state called diapause as autumn approaches. This isn’t triggered by cold alone. Research from Central Washington University found that the critical trigger is day length: when daylight drops to roughly 11 to 12 hours (typically early to mid-October in much of the U.S.), their metabolism suppresses significantly and they stop reproducing. Cooler temperatures reinforce this signal, pushing them to find a protected spot where they can essentially shut down for the winter.
This metabolic slowdown begins in late October and deepens through November. Once in diapause, stink bugs aren’t feeding, breeding, or doing much of anything. They’re just waiting. That’s why you can find dozens clustered together in a single wall void or attic corner, barely moving, for months at a time.
Indoor Hiding Spots
Inside a home, stink bugs gravitate toward spaces that offer warmth, dryness, and minimal disturbance. The most common indoor hiding places include:
- Wall voids: The hollow spaces between interior and exterior walls are prime real estate. Stink bugs enter through tiny gaps around window frames, door frames, siding, and utility penetrations, then settle inside the wall cavity itself.
- Attics and crawl spaces: Unfinished attics with exposed rafters and insulation provide exactly the kind of undisturbed, temperature-buffered environment they’re looking for. Crawl spaces under the house serve the same purpose.
- Behind baseboards and trim: The narrow gaps behind baseboard molding, crown molding, and window trim give stink bugs just enough space to tuck in.
- Around light fixtures and electrical outlets: These openings in the wall are easy entry points. Stink bugs are attracted to light, so they often buzz around lamps and ceiling fixtures in the evening before settling into gaps nearby.
- Curtain folds and window treatments: Heavy drapes, blinds, and the space between curtains and window glass can harbor stink bugs, especially on sun-facing walls that warm up during the day.
You might also find them behind picture frames, inside stored boxes, in the folds of seldom-used clothing, or tucked into the pleats of ceiling fans. Essentially, any tight, dark, undisturbed crevice is a candidate.
Outdoor Hiding Spots
During spring and summer, stink bugs are active outdoors and hide among their food sources. They feed on a wide range of plants, including fruit trees (apples, peaches, pears), vegetable crops (tomatoes, peppers, beans), and ornamental trees and shrubs. During these months, you’ll find them on the undersides of leaves, tucked into clusters of fruit, or resting along stems and branches.
As temperatures cool but before they move indoors, stink bugs gather on the sunny exterior walls of buildings, particularly south- and west-facing surfaces that absorb afternoon heat. They also hide under loose bark on trees, beneath stones, in woodpiles, inside sheds and garages, and in dead leaf litter. Any outdoor structure that creates a sheltered gap, from stacked firewood to the underside of deck boards, can host a cluster of stink bugs preparing to overwinter.
Why They Cluster Together
One of the more frustrating things about stink bugs is that they don’t hide alone. They release an aggregation pheromone that attracts other stink bugs, both male and female, plus immature nymphs, to the same location. This is different from the sex pheromones many insects use to find mates. The aggregation pheromone is essentially a “good spot over here” signal, which is why you can find dozens or even hundreds packed into a single wall void or attic space.
This also means that if stink bugs found a way into your home last year, the chemical traces they left behind can attract a new wave the following fall. The hiding spot itself becomes a recurring destination.
Signs of a Hidden Infestation
Stink bugs in diapause are quiet and mostly invisible, but a significant population leaves clues. The most obvious is smell: their scent glands produce a pungent, cilantro-like odor that becomes noticeable when many bugs are concentrated in one area or when they’re disturbed. If you catch an unexplained herbal or spicy smell near a wall or in your attic, stink bugs are a likely source.
Their droppings also leave small dark spots, similar to the fecal staining bed bugs produce. These marks can show up on walls, curtains, windowsills, and other surfaces near their hiding spots. On warm winter days, you may see individual stink bugs emerge from walls and wander toward windows or light fixtures, confused by the temporary warmth into thinking spring has arrived. These scouts are a reliable sign that more are hiding behind the wall.
How to Keep Them Out
Because stink bugs are flat-bodied and only need a small crack to enter, exclusion is the most effective strategy. The National Pesticide Information Center recommends sealing gaps around doors, windows, and foundation cracks before fall arrives. Focus on these areas:
- Window and door frames: Apply caulk to any visible gaps between the frame and the wall. Replace worn weatherstripping on doors.
- Foundation cracks: Even hairline cracks in a concrete foundation can admit stink bugs. Fill them with silicone caulk or expanding foam.
- Utility penetrations: Anywhere pipes, cables, or wires enter the house is a potential entry point. Seal around them with caulk or steel wool.
- Attic and soffit vents: Make sure these are covered with fine mesh screening (no larger than 1/16 inch) that allows airflow but blocks insects.
- Chimney caps and roof vents: Install or replace screens on these openings.
Timing matters. The window for exclusion is late summer, before stink bugs start migrating toward buildings in September and October. Once they’re already inside the walls, sealing entry points won’t remove them, it just prevents the next year’s invasion.
Removing Stink Bugs You Find
If stink bugs are already inside, the simplest removal method is a vacuum cleaner. Use a shop vac or a vacuum with a disposable bag, since the bugs’ odor can linger in the canister. Avoid crushing them: the chemicals they release when squeezed can irritate skin and will definitely stink. Flushing them down a toilet or dropping them into soapy water are low-odor alternatives.
Spraying insecticides inside wall voids is generally not recommended. Killing hundreds of stink bugs inside a wall doesn’t remove them, and the decaying bugs can attract other pests like carpet beetles. For large infestations that recur year after year, a pest management professional can apply targeted exterior treatments in early fall, timed to intercept the bugs before they enter the structure. But for most homes, consistent caulking, screening, and vacuuming will keep the problem manageable.