Why do stink bugs and lady beetles come into houses?
They are looking for shelter that stays warm without freezing. Ohio State's Joe Boggs says they gather on sunny walls in autumn and enter wall voids, window casings and attics. Indoors they do not feed, and they die of starvation if they cannot leave. They do not damage the structure.
The sunny wall is not a coincidence. Warmth draws them, and the south and west faces of a building heat up most on a bright autumn afternoon. They then follow cracks and gaps to get inside.
Invasions tend to follow a cool spell and a warm-up. A chilly few days prompts them to start looking for shelter, and the warm day that follows sends them flying to the walls. That is why a house can seem clear one day and covered the next.
Where do they get in?
Around windows, chimneys, vents, soffits and air conditioner housings. Ohio State notes that stink bugs enter around windows, chimneys and air conditioners. Any small gap in siding, trim or a utility entry can serve, so a technician walks the sunny sides first.
Older houses tend to have more gaps, since materials shrink, caulk dries out and trim comes loose. Euclid has a lot of mid-twentieth-century housing, with sources differing on the median year, but one census-based profile pointing near 1956. That age often means weathered window frames and worn weatherstripping.
Attics and roof vents are another route. A damaged vent screen or a gap at the soffit lets them into a space that is hard to treat after the fact.
- Window frames and screens that do not fit tightly
- Door sweeps and thresholds that are worn
- Chimney flashing and cap gaps
- Air-conditioner units and their surrounds
- Soffit and fascia gaps, and unscreened vents
What should I do about the ones inside?
Vacuum them or sweep them into a container, and do not crush them. Crushing stink bugs releases the smell, and crushed lady beetles can stain light surfaces. Those that have already gone into wall voids will generally die there, so the better step is to keep further insects out.
A vacuum with a sock or a piece of stocking placed between the hose and the nozzle collects the insects without a mess. The bag is then sealed and thrown out, or the contents are flushed.
Spraying household insecticide into wall voids is not usually recommended, since it will not reach every insect and can leave dead insects that attract carpet beetles. The technician advises what is suitable for your house.
When is the best time to act?
Spring and summer, before the autumn flight. Ohio State advises replacing door sweeps, screening vents, repairing soffit gaps and caulking in those seasons. Treatment, where used, is timed before the main invasion. Acting during the invasion helps, but cannot close the routes already used.
Sealing is easier in warm weather. Caulk cures properly and ladders are safer. If you wait until the insects are on the wall, you can still remove those inside, but more will follow.
If you are reading this in autumn and already have insects, start with indoor removal and the main gaps you can see. A technician can then plan the exterior sealing for the warm months.
Are stink bugs and lady beetles the only autumn invaders?
No. Boxelder bugs and cluster flies also gather on walls and overwinter in attics and wall voids. They need different handling in some respects, so identification matters. These two are covered on their own page, and a technician can confirm which you have during the visit.
The patterns overlap, since all of these insects use sunny walls and small gaps. Boxelder bugs are linked to certain trees, and cluster flies are often found in upper floors and attics, though no Ohio count was sourced for either in this area.
See cluster fly and boxelder bug control for how those two are handled, and general pest control for a plan that covers the whole season.
