News > Overwintering: Which pests want to spend the winter in your house?

Overwintering: Which pests want to spend the winter in your house?

December 21, 2021

Pest control in winter


Different pests require different approaches

If you’re spending some time at the cottage in Ontario this fall, you may have asked yourself: “Why the heck are there suddenly so many ladybugs crawling around on the ceiling? Aren’t they more common in the spring – and why are they coming inside?”

Well, the truth is that they aren’t actually ladybugs. Those ladybug-like insects are Asian Lady Beetles, an invasive species which is now seen all across Ontario. They aren’t particularly dangerous to your home or to people, other than being annoying in large quantities.

However, they’re a good reminder that some pests will take every opportunity ‘overwinter’ with you. They’ll come inside in the fall, and drive you nuts all winter.

Here are the most common ones in southern Ontario, and what to do about them.

Asian lady beetles

Again, Asian lady beetles tend to get overlooked at first, because they’re mistaken for ‘cute’, non-invasive ladybugs – but then suddenly you’ll find a whole corner of your home is swarming with them. They will also sometimes bite, and can cause allergic reactions, so it’s best not to let them get a foothold.

How do you deal with them? Seal up any cracks you can find in your exterior, including little holes like between the siding and the foundation. If you’ve had an Asian lady beetle in the past, you should probably consider an exterior barrier treatment every fall, either a DIY solution from your hardware store or from a professional who can also help identify any ingress points.

Big brown bats

Bats generally aren’t a huge problem for residences, except in seasons where there are huge temperature spikes. Big brown bats are highly sensitive to temperature changes, so they will seek to overwinter in a place that has a more stable environment – like a quiet, insulated attic. Bats can be disease vectors (both via droppings and bites) and, let’s face it, a lot of people find them pretty creepy.

How do you deal with them? As with most pests, sealing up cracks in the walls or roofs that allow bats to enter is your first step in ensuring they don’t get into your home in the first place. But if you suspect you have bats, you really should call a professional to do an assessment and removal, to prevent getting bitten or your home contaminated by bat droppings.

Wasps and hornets

In the fall, wasps and hornets start to expand by establishing new colonies, and they definitely target warm, dry, secure places to set up, which is why sheds, garages and attics/crawlspaces are so appealing to them. Unlike Asian lady beetles, wasps and hornets do have painful stings and of course if anyone in your family is allergic, they can pose a real danger.

How can you deal with them? Your best defense is ensuring your home or outbuildings aren’t appealing to them: Go around your exterior with a caulking gun and seal up any holes where a wasp or hornet could get in and set up shop. And then through the fall, do a visual inspection every week to make sure there are no nascent nests.

But if you do suspect that you have a wasp or hornet nest in or on your home, please make sure you call an expert to remove it. Wasps and hornets can get aggressive and cause genuine pain, and it’s just not worth it to DIY.

Cluster flies

Of all the overwintering insects, cluster flies are probably the most infuriating, especially in the fall: They’re big, black, persistent, and somehow seem impossible to kill with a flyswatter or one of those electric tennis racquets.

They’re attracted to heat sources, so it’s not unusual for them to get into your home as they weather outside becomes cooler, and then just hang out in a warm basement, closet or attic. What’s worse is that they’ll then re-emerge when it gets warmer in spring.

How do you deal with them? The first step is ensuring that they don’t take up residence in your house in the first place. That means keeping doors closed, ensuring screens are in good shape, and sealing up any cracks or gaps in foundations or at the roofline. If you do find yourself constantly plagued by flies through the winter, it may be time to call a professional to help find and destroy the main cluster.


The good news is that rats generally don’t invade homes in the fall: They’re creatures of habit, so if you don’t have a rat problem in the summer, you’re unlikely to get a new infestation as the weather gets colder.

Mice, on the other hand, are always looking for food and warmth. When food becomes scarce in the fall, and the weather gets colder, they can definitely be attracted to homes and apartment buildings, especially if there is easily-accessible garbage nearby.

How do you deal with them? Make sure there are no access points on the exterior of your property: Again, walk around, examine everything, and carry a caulking gun to seal up even tiny holes. Remove all debris from around your foundation, whether it’s a stack of a few old bricks or just a tangle of weeds.

In multi-family residential or commercial properties, the primary access points for mice are garbage areas, so these should be kept away from walls and foundations as much as possible, and regularly cleaned and inspected.

Remember: Mouse droppings are allergenic and often toxic, and can get into ventilation systems in larger properties. If you start seeing evidence of mice indoors (mice droppings look like little black grains of rice), it’s time to consider calling a professional to help you deal with the problem safely and promptly.

Early detection saves time and money

The first step in protecting your property from overwintering pests is staying vigilant, because the sooner you notice signs of pests, the less time they’ll have to get established, and the easier (and cheaper) they’ll be to remove. For multi-family residential and commercial properties, monthly or quarterly professional pest inspections will make a huge difference in overall pest control and reducing spend in the long run.

Want to know more? Don’t hesitate to call us – we’d love to answer any questions you have!




Apex Pest Control Inc.

Commercial and residential pest control &
wildlife removal services
240 Magurn Gate
Milton, ON L9T 7B3
Phone: 1-888-434-2739

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Apex Pest Control Inc.