Do stink bugs enter homes before winter?

The brown marmorated stink bug (Halyomorpha halys) is an invasive species that has become well established across much of the northeastern United States, including New Hampshire, and its fall behavior is genuinely well studied. As fall arrives, adults seek out sheltered locations to spend the winter, and buildings — with their gaps around windows, siding, soffits, and chimneys — offer exactly the kind of protected cavity they're oriented to find. Extension research is specific that this isn't a search for indoor warmth; it's a general shelter-seeking response to seasonal cues, and a home simply happens to provide that shelter.

Entry typically occurs from late September through October in the northern range that includes New Hampshire, which places it squarely within this hub's fall-invasion window. The detailed mechanics of that timing and the sealing calendar around it are owned by our fall-invaders guide; this page's job is confirming what happens for the rest of the winter once entry has already occurred.

Once a stink bug has made it into a wall void, attic space, or other undisturbed cavity, it settles into diapause — a dormant state, not sleep or hibernation in the mammalian sense, but a genuine physiological pause. It doesn't feed, doesn't reproduce, and doesn't grow during this period. What you occasionally see indoors during winter are individuals that have been roused from that dormancy, usually by warmth from sunlight on an exterior wall or heat escaping around a light fixture, wandering into living space rather than staying in the void.

This means the population you're seeing in January isn't a growing infestation — it's the same fall arrivals becoming intermittently visible, the same pattern seen with cluster flies and Asian lady beetles elsewhere in this hub. None of these overwintering insects reproduce indoors during winter; they're all waiting, not multiplying.

The practical winter response is straightforward: vacuum stink bugs you find rather than squashing them. Squashing releases their well-known defensive odor, which can linger and is unpleasant enough that it's worth the small extra effort of vacuuming instead, ideally into a bag or canister that can be emptied outside promptly.

Beyond removal of the individuals you encounter, there's realistically nothing more to do for a stink bug population that's already sheltering in a wall void for the winter — no treatment reaches them there without more disruption than it's worth, and none is necessary since they aren't reproducing or causing damage. The higher-value work is sealing the gaps that let them in during the next fall's entry window, which is exclusion timing this hub's sealing cluster covers, and which our fall-invaders guide covers in full phase-by-phase depth.