Occasional Invaders
NuisanceWhat it is
A broad category for pests that enter buildings incidentally but usually do not reproduce indoors. Examples can include boxelder bugs, lady beetles, millipedes, ground beetles, and other seasonal invaders.
How to recognize it
- Stink bug: shield-shaped and mottled brown, and it releases a bad smell when crushed.
- Boxelder bug: black with red-orange lines on its back, gathered on sunny walls.
- Cluster fly: a dull gray fly with golden hairs, slow and sluggish near windows.
- Asian lady beetle: orange to red, with a white "M" shape behind the head.
- Other common ones include pill bugs, earwigs, crickets, and millipedes.
Where you will find it
On sunny walls in fall, then in attics, wall voids, and around windows. Some come out on warm winter days.
Why it matters
They usually do not reproduce indoors, so seeing them points to how they are getting in.
What to do
- Vacuum up the ones that get in and empty the vacuum right away.
- Skip indoor sprays and bug bombs. They don't reach the insects in the walls.
- Fix or report moisture problems, since damp areas attract some of them.
- Contact a professional in late summer, before they move in. Closing entry points and treating the outside at the right time works best.
When to call a professional
- You get large numbers every fall.
- They keep coming back year after year.
- You're not sure what you have.
Questions
Why do they come inside?
In fall they look for a warm, sheltered place to wait out the winter, and your house qualifies.
Will they breed in my house?
No. They don't reproduce indoors, so seeing them in spring or on a warm winter day usually means ones that spent the winter inside.
Are they harmful?
Mostly they're a nuisance. Some stain surfaces or smell when crushed, and a few can trigger allergies.
Related pests
Boxelder Bugs
Black-and-red true bugs associated with boxelder and some maple trees. They often gather on sunny exterior walls and enter buildings in large numbers to overwinter.
Read more →Clover Mites
Tiny reddish mites that feed on grasses and ornamental plants. They often invade buildings in large numbers around windows and foundations but do not bite people or damage household items.
Read more →Cluster Flies
Slow-moving flies that enter buildings in late summer or fall to overwinter in attics and wall voids. Their larvae develop as parasites of earthworms outdoors; indoor adults do not breed in garbage or drains.
Read more →Lady Beetles
Predatory beetles, many of which are beneficial because they feed on aphids and other plant pests. Some species, especially multicolored Asian lady beetles, enter buildings in large numbers to overwinter.
Read more →This page is general information, not a diagnosis. Pests vary by region and situation, and an on-site inspection is the reliable way to know what you have.