What Pests “Overwinter” Inside Houses?

 

When people talk about pests “overwintering,” it means certain insects and critters enter our homes to survive the cold months. They’re not usually setting up long-term homes or starting families indoors—they are just trying to stay alive when it’s cold outside. Once spring arrives and the weather warms up, many of these pests try to go back outdoors. However, while they’re inside, they can be a nuisance and even cause some damage.

 

Why Do Pests Overwinter in Houses?

 

When temperatures drop, food and water are harder to find outside. Many pests look for warmth and safety, and your house provides the perfect shelter. They’ll squeeze in through tiny gaps, cracks, or open doors and windows. Attics, basements, wall voids (the empty spaces inside walls), and even under furniture become hiding spots where they accidentally get trapped for months.

 

The Most Common Overwintering Pests in Homes

 

• Boxelder Bugs: These black and red bugs gather in huge numbers on sunny sides of homes in the fall. When it gets cold, they slip inside through cracks. While harmless to people and pets, they can stain curtains and walls with their droppings.
• Stink Bugs: Brown marmorated stink bugs are famous for their shield-shaped bodies and the strong, unpleasant odor they release if threatened or squashed. In autumn, they look for places to hide out the winter in homes and will become active again in spring.
• Ladies Bugs (Ladybird Beetles): Especially the Asian lady beetle, these beetles can come inside by the hundreds to cluster together for warmth. They aren’t dangerous, but they can scent-mark areas, stain surfaces, and sometimes even nip skin.
• Cluster Flies: Slightly larger than house flies, cluster flies sneak into attics and wall voids for warmth. In spring, they try to get back outside, but can blunder into living spaces, often sluggish and slow.
• Western Conifer Seed Bugs: These look a lot like stink bugs, but they’re actually a kind of “leaf-footed bug.” They get inside to hibernate, sometimes buzzing or startling people in the late winter.
• Spiders: Many spiders are accidental house guests. They enter seeking warmth or follow their prey indoors, and can hunker down for months, especially in basements, crawl spaces, or behind furniture.
• Rodents (Mice and Rats): While not insects, mice and sometimes rats enter homes in fall and winter, seeking warmth, food, and shelter. Unlike bugs, they may try to breed indoors and can cause serious damage or health risks.
• Cockroaches: Certain types—notably the German cockroach—will move indoors in cold weather. While often present year-round, their overwintering behavior makes them more likely to invade in larger numbers as it gets cold outside.
• Silverfish: These tiny, silvery insects like cool, damp spots such as basements and bathrooms. They enter homes year-round, but are more likely to move indoors for stable temperatures in winter.

 

How Do They Get Into Your Home?

 

Most overwintering pests are excellent at finding and squeezing through tiny openings to get indoors. Common entry points include:

• Gaps under doors, around windows, or in weatherstripping
• Cracks in exterior walls or foundations
• Vents, chimneys, or gaps around utility pipes
• Openings in attic or basement areas

They often gather on the sunny, south or west side of your home before searching for ways inside.

 

Prevention and What to Do if You Find Them

 

• Seal entry points: Check for and seal cracks, install door sweeps, and fix screens and window caulking.
• Reduce outdoor lighting at night: Many flying bugs are attracted to lights.
• Use a vacuum: For boxelder bugs, stink bugs, lady beetles, or cluster flies already inside, vacuum them up and empty the bag outside far from home (never crush stink bugs—they smell).
• Store food and trash securely: For rodents and roaches, sanitation is key.
• Consider professional pest control: If you’re overwhelmed or the pests are persistent, professionals can assess, trap, or safely remove infestations.

 

Summary of Key Points

 

• Many bugs and some rodents enter homes in cold weather to hibernate and survive the winter—this is called “overwintering.”
• The most common overwintering pests are boxelder bugs, stink bugs, lady beetles, cluster flies, western conifer seed bugs, spiders, rodents, cockroaches, and silverfish.
• They mostly seek shelter, not to breed, but some (like rodents or cockroaches) can establish real infestations.
• Prevent them by sealing entry points and keeping the home clean and tidy, and remove them promptly if you notice them indoors.