How to Handle Home Insect Invaders

Cold winter temperatures provide a nice break from outdoor insect pests, but what’s worse than insects outside? When they’re in our homes.

In the winter, some common indoor pests are insects that spend just the winter inside, insects that infest food products, and ants.

Animals have developed an amazing array of ways to survive cold winters. Larger animals often migrate or hibernate, and insects also migrate south or enter a stage called diapause, which is essentially long-term hibernation.

One of insects’ other survival strategies is to congregate inside buildings. Insects frequently found inside homes during the fall and winter include boxelder bugs, multicolored Asian lady beetles, cluster flies, western conifer seed bugs and stink bugs.

It’s important to know that these overwintering insects are not reproducing inside. They’re just spending the winter indoors, and once temperatures warm up, they will exit the building. During the winter, however, they often gather in sunny windowsills or wander around during warmer days.

Preventing these insects from entering in the first place is key to managing them. Make sure that all windows and doors are properly sealed; replace damaged screens; and seal any openings around dryer vents, air conditioning units, utility wires or other places where insects could enter. Keep in mind that these insects can fit through very small spaces, so even gaps as small as 1/8 of an inch wide can be an entry point.

In severe cases, an insecticide can be used to treat the outside of the house in the fall to prevent them from entering, but it should not be used inside.

Once they’re indoors, there’s a limited population because they aren’t reproducing. Although the numbers may be much larger than you’d like, it’s not increasing. The best management tool at this point is a vacuum cleaner. When vacuuming, use a hose attachment rather than the floor brush rollers to avoid grinding insect parts into your carpet. When squished, these insects can stain surfaces and smell bad, which is another reason to avoid squishing them. After vacuuming, empty the vacuum bag so that any living ones don’t crawl out.

Another category of indoor insect pests is the one that enjoys eating carbs as much as we do. These insects, often called “pantry pests,” are commonly found in dry grain products and most other dried foods, including nuts, seeds (e.g., dried beans and popcorn), dried fruit, spices, tea and cured meats. Pet food, birdseed and dried flowers (and insect collections) can also harbor these pests.  

Pantry pests can be inside a food product before you buy it, or they can spread if they’re already inside your home. Often the first sign of a pantry pest is a moth flying out of your oatmeal container or small beetles (not to be confused with ants) in your cabinets. It’s typically fairly obvious when food is infested, so you don’t need to empty out your entire pantry unless you suspect an issue.

If you find pantry pests, you must locate the source of the problem. Throw away any infested products; carefully clean out cabinets and shelves; and store all new foods in sealed containers. Using cleaning solutions or disinfectants will not prevent pantry pests from infesting your food, and it may make the food hazardous to consume if it contacts those cleaning products.

Other insects often found inside homes are ants. Many different species can show up, but the most common ones seen in the winter are carpenter ants: large, black or black and red, and winged or wingless. Seeing some carpenter ants in your home in the spring may mean there’s a nest nearby, but if you find them in the winter, then likely there’s a nest inside.

Unlike termites (which are quite rare in Wisconsin), carpenter ants don’t eat wood, but they do nest in wet or decaying wood, which can lead to weakened structures. To get rid of carpenter ants, you must locate the nest, which can be very difficult. If you locate the nest, there are some treatments available to the public, but hiring an experienced pest-management company is recommended for the best and fastest results.

For more information about indoor insect pests, visit the University of Minnesota Extension’s website at

If you catch an insect inside your home and want to know what it is, take the sample to the Door County UW-Extension office at 421 Nebraska St. in Sturgeon Bay. Medication bottles or small Tupperware containers work well for transporting insects without damaging them. If you can’t make it to our office right away, place the container in the freezer until you can make a visit.

Despite our best efforts, there are always going to be some insects that live in our homes. None of the ones mentioned above transmit disease;  they’re mostly just a nuisance. With a little persistence and some careful note taking, you can be more successful at tracking down the problem and finding a solution.