Stink bugs and Asian lady beetles: why they invade in fall and how to keep them out
Published Updated
By John Stopka, Co-Founder & CEO · Reviewed by John Stopka
Stink bugs and Asian lady beetles gather on homes in the fall and squeeze inside to spend the winter [1][2][3]. In Kentucky, stink bugs start moving in around early to mid September, and Asian lady beetle flights peak in October [1][2]. They don't breed or damage the house indoors, and sealing gaps before fall is the most lasting way to keep them out [1][2].
Why do stink bugs and Asian lady beetles come into houses in the fall?
To spend the winter. Shorter days and cooler temperatures trigger the urge to find a sheltered place to overwinter [1].
In nature, brown marmorated stink bugs look for cool, dry, protected spots like rock outcrops and dead trees with loose bark. A house offers the same kind of shelter [1]. Asian lady beetles fly to buildings looking for overwintering sites, too [2][3].
Once inside, lady beetles tuck into cracks around window and door frames, behind siding and fascia boards, and into soffits, attics and wall voids [2]. Stink bugs favor the upper parts of a building and often get in through attics and chimneys [1].
When do they come inside in Kentucky and Illinois?
Stink bugs come first. In Kentucky, brown marmorated stink bugs start entering buildings in early to mid September [1].
Asian lady beetles follow. In Kentucky, their flights to buildings peak in October, but they can run from September into November depending on the location and the weather [2]. Flights are heaviest on sunny afternoons after a cool spell, once temperatures climb back to at least the mid-60s [2]. Stink bug flights also peak on warm, sunny afternoons [1].
University of Illinois Extension describes the same fall pattern for both insects in Illinois [3].
How do you identify stink bugs and Asian lady beetles?
The stink bug is shield-shaped and mottled brown. The Asian lady beetle is about 1/4 inch long, with a dark M or W mark behind its head [1][2][3].
| Feature | Brown marmorated stink bug | Asian lady beetle |
|---|---|---|
| Shape and size | Shield-shaped, about 5/8 inch long | A lady beetle about 1/4 inch long |
| Color | Mottled or marbled brown | Tan, yellow or red-orange |
| Key marks | White bands on the antennae, and light and dark bands on the legs and the edge of the abdomen | A dark M- or W-shaped mark on the whitish area behind the head, and anywhere from none to 19 spots |
| When disturbed | Gives off a strong smell, often compared to cilantro | Gives off a sharp odor and a yellowish fluid |
Other bugs come inside in fall too. Boxelder bugs and western conifer seed bugs are sometimes mistaken for stink bugs [1].
Do stink bugs and lady beetles damage your home?
Not the house itself. Neither insect breeds indoors, and the ones you see in late winter or spring are the same insects that came in during the fall [1][2]. Asian lady beetles don't attack wood, food or clothing [2], and stink bugs cause no structural damage [1].
They're still a nuisance:
How do you keep stink bugs and Asian lady beetles out?
Seal them out before they arrive. University of Kentucky entomologists call sealing entry points the most permanent way to keep fall invaders out, and the best time to do it is late spring or summer [1][2].
- Caulk cracks around windows, doors, soffits and fascia boards, and where pipes and wires enter the house [1][2].
- Put tight-fitting door sweeps or thresholds on exterior doors [2].
- Fix holes in window screens, and make sure windows and doors fit tightly [1][2][3].
- Add screening behind attic vents [1][2]. Use fine mesh: in UK testing, many adult stink bugs got through 1/4-inch screening [1].
- Remove or seal around window air conditioners in the fall [1].
- Keep siding, eaves and soffits in good repair, and seal gaps around the foundation and chimney [3].
How do you get them out of the house without chemicals?
Vacuum them up or move them out by hand.
- Vacuuming is the easiest way to remove lady beetles [2]. A vacuum may smell like stink bugs for a while afterward. A nylon stocking placed in the hose catches the bugs before they reach the bag [1].
- To pick up stink bugs by hand, use gloves or a tissue. You can also hold a container under a bug and nudge it to drop in [1].
- Illinois Extension suggests emptying vacuumed bugs into soapy water [3].
How does Liberty treat stink bugs and Asian lady beetles?
Here's what we do.
On your first visit, your Service Specialist does a thorough inspection inside and outside to see how many stink bugs there are, where they're getting in and what draws them, like sunny walls and gaps around windows, siding and attic vents.
- Treat windows and eaves: Outside, your Service Specialist treats around window and door frames and eaves, where stink bugs gather and look for a way in.
- Treat siding and vents: They also treat the sunny sides of your home, siding and attic vents, where stink bugs rest before moving inside.
- Inside treatment: Your first visit always includes treatment inside where stink bugs gather, like around windows, and on later visits they treat inside only if it's needed and ask you first.
For Asian lady beetles:
- Outside, your Service Specialist treats around window and door frames and eaves, where lady beetles cluster in the fall.
- They also treat the sunny sides of your home, siding and attic vents, where lady beetles gather in the fall.
If covered pests show up between visits, just text us.
In Western Kentucky and Southern Illinois, our stink bug and Asian lady beetle calls usually start in October.
When to call a professional
Call if large numbers keep getting inside after you've sealed what you can, or if the gaps are in places you can't reach, like soffits and roof lines.
Stink bugs and Asian lady beetles are covered by every Liberty pest control plan. Learn more on our pest control page, or read about stink bugs and Asian lady beetles in our pest library.
Common questions
When do stink bugs come inside in Kentucky?
Brown marmorated stink bugs start entering buildings in Kentucky in early to mid September, looking for a place to spend the winter [1].
When do Asian lady beetles invade homes?
In Kentucky, Asian lady beetle flights to buildings peak in October and can run from September into November. They're heaviest on sunny afternoons after a cool spell [2].
Do stink bugs lay eggs in your house?
No. Brown marmorated stink bugs don't breed or reproduce indoors. The stink bugs you see in winter and spring are the same ones that came in during the fall [1].
What's the best way to keep stink bugs out?
Seal cracks around windows, doors, soffits, fascia boards, pipes and wires, and fix screens, ideally in late spring or summer before the bugs arrive [1][2].
Why do Asian lady beetles gather on one side of the house?
They're drawn to the sunnier southwest sides of buildings that get afternoon sun, and to contrasting light and dark features like dark shutters on a light wall. Homes near woods tend to get more [2].
Sources
- University of Kentucky Entomology. "Stink Bug Infestation of Dwellings." https://entomology.mgcafe.uky.edu/ef654 (opens in a new tab)
- University of Kentucky Entomology. "ENTFACT-416: Asian Lady Beetle Infestation of Structures." https://entomology.mgcafe.uky.edu/ef416 (opens in a new tab)
- University of Illinois Extension. Ken Johnson, "Fall House Guests." October 1, 2019. https://extension.illinois.edu/blogs/good-growing/2019-10-01-fall-house-guests (opens in a new tab)