Will stink bugs survive winter inside the home?

It's tempting to think of overwintering stink bugs the way we think of a hibernating mammal — asleep, harmless, and eventually just gone. The biology is close to that in one respect (a dramatic slowdown) and completely different in another: this is a reproductive shutdown, not a nap. UC IPM and university research describe BMSB entering facultative diapause in early fall, a state that persists until spring warmth reactivates them. During that entire stretch, they are not feeding, not mating, and not laying eggs.

That matters more than it sounds like it should, because the diapause state is also what lets them survive being holed up in a dry wall cavity for months. A 2020 study in the Journal of Insect Physiology found diapausing BMSB tolerate desiccating conditions three to four times longer than non-diapausing bugs, through reduced water loss both through the respiratory system and the cuticle (the insect's outer shell). A dormant bug isn't burning through its moisture reserves the way an active one would. So the same physiology that stops them breeding indoors is also what keeps them alive indoors — which is why 'the dry heat in my house will kill them off' is more hope than plan.

The anxiety behind this question is usually about growth — the fear that a few stink bugs on the windowsill in November means hundreds by February. That's not how it works. Because reproduction is arrested during diapause, the number of BMSB in a given wall void is a closed, shrinking figure from the day the first hard frost hits: no new eggs, no new nymphs, nothing being added. Some individuals die over winter regardless — from desiccation, from getting trapped in an exposed, dry part of the house with no shelter, or simply from the stress of the season. None are being replaced from inside.

What you're actually watching, on a warm January afternoon when a few bugs show up at a sunny window, is a subset of last fall's arrivals waking up early and heading toward the light. It looks like new activity. It is old activity. The count only goes down from the day they entered until the day the survivors leave again in spring.

Because the insects are dormant and physically sealed inside a wall void, an interior insecticide application in December or January has nothing productive to do. The bugs aren't moving across surfaces to contact a residue, and they aren't taking bait. Extension guidance across land-grant universities is consistent on this: interior treatment for overwintering BMSB is not a recommended or effective use of a pesticide.

Worse, killing some of them in place creates a second problem. Dead insects accumulating inside a wall void are a food source for dermestid and carpet beetles, which can go on to damage stored fabrics, wool, and other natural materials — and a mass of dead bugs in a void causes lingering odor. You trade a dormant nuisance you could simply vacuum for a genuine secondary pest problem you can't see. The candid tool for a stink bug on a windowsill in February is a vacuum, bag removed and taken outside afterward — not a can of spray.