House Centipedes in Ontario: Why You Have Them and How to Get Rid of Them

Quick answer: House centipedes are predators, not scavengers. If you are seeing them, they are hunting something else in your home — silverfish, spiders, carpet beetle larvae or springtails — in a space damp enough to keep that prey alive. Killing the centipede you can see does nothing about the moisture and food supply that brought it in. Drop the humidity below 50%, remove the prey, seal the ground-level gaps, and the centipedes leave on their own. Seeing them several times a week means a food supply worth identifying: a $95 inspection, credited when you book the treatment, tells you what is actually living behind the drywall. Call Sani IQ at (705) 302-1887.

The thing nobody tells you about house centipedes

Almost everything written about house centipedes treats them as the problem — so the advice is always about killing the one that just sprinted across the basement floor. That has the logic backwards.

Scutigera coleoptrata, the house centipede, does not eat your food, your drywall, your insulation or your wiring. It does not chew fabric or carry the disease risk rodents do. It eats other arthropods, and it is very good at it. A house centipede in your basement is doing what a hawk over a field is doing: it is there because there is something to hunt.

So the sighting is information. One centipede is a hunter passing through. Several a week is a symptom — a moisture problem somewhere in that part of your house is sustaining a population of softer-bodied insects, and a predator has found the buffet and moved in.

Treat the centipede and you have treated the messenger. That is why so many homeowners kill them all autumn and see them again the following autumn.

What house centipedes actually eat

Understanding the menu is what makes removal permanent. House centipedes hunt:

• Silverfish — the classic basement co-tenant, and a strong indicator of humidity above 60%
• Spiders — including the common house spider in corners and window wells
• Carpet beetle larvae — living quietly in stored wool, felt and lint
• Springtails — tiny, jumping, tied to a damp slab or over-watered soil
• Earwigs, sowbugs, small flies and ants that wandered indoors

Penn State Extension describes them as beneficial predators of household insects, and Michigan State’s extension service makes the same point about their diet. Useless as reassurance when one runs over your foot — but it tells you where to aim.

For identification detail, see our centipede library page. Short version: centipedes are flat and fast, one pair of legs per segment. Millipedes are round and slow, two pairs. Different animals, different reasons for being in your house.

Why Ontario homeowners suddenly see them in September and October

Centipedes are in Ontario homes year-round. Fall is when you notice them, for three reasons that stack.

Humidity moves indoors. Through August, a basement in Vaughan or Ajax is often drier than the air outside. As temperatures drop in September that reverses — warm indoor air holds moisture against cool foundation walls, and relative humidity in the lowest level climbs. Condensation on cold-water pipes, damp along a block wall, a sump pit that never dries. That humidity supports the prey, and the prey supports the centipedes.

Everything comes inside at once. The same week centipedes become obvious is the week cluster flies hit south-facing walls and spiders appear in garages. The insects centipedes eat are also moving in from the yard.

They are moving more. Cooling temperatures push centipedes out of wall voids and crawlspaces into heated areas — which is why the sighting is almost always a floor-level sprint, not a discovery inside a box. Older stock feels this most: a 1960s bungalow in Barrie with a block foundation, floor drain and unsealed cold room has far more centipede habitat than a 2015 build with a poured wall and sealed sump.

Where they are coming from

House centipedes do not chew their way in. They walk through openings that already exist:

• Floor drains and unsealed sump pits — the most common route, and permanently damp
• The foundation-to-sill-plate gap, especially behind finished basement framing
• Window wells holding leaf litter and water against a basement window
• Utility penetrations — water service, gas line, conduit, the hole a cable installer never foamed
• Crawlspaces with exposed soil, which is outdoor habitat under your floor
• Cardboard stored on concrete, which wicks moisture and shelters predator and prey alike

Every one of those is also a mouse route, an ant route and a spider route — sealing them is never single-purpose work.

How to get rid of house centipedes, in the order that works

1. Drop the humidity first

This does the most and gets skipped the most. Target below 50% relative humidity in basements and crawlspaces. A dehumidifier draining to the floor drain, run through fall rather than retired in September, beats any product sold for the purpose. Fix the obvious water first: downspouts discharging at the foundation, negative grade against the wall, a dripping shut-off, a dryer venting into the crawlspace. Below 50%, silverfish and springtails struggle — and when the prey population falls, centipedes have no reason to stay.

2. Remove the prey

Centipedes are a lagging indicator. Get cardboard and stored textiles off concrete and into sealed bins. Vacuum window wells, corners and the undersides of stored furniture, where carpet beetle larvae and spider egg sacs sit. Clear leaf litter away from the foundation. If you already know you have silverfish or carpet beetles, treat that directly and the centipede sightings end as a side effect.

3. Seal the entries

Foam and caulk the utility penetrations. Fit a proper sump pit cover. Keep floor drain traps filled — a cup of water down a rarely-used drain monthly, because a dry trap is an open door. Weatherstrip the basement walkout. Cover crawlspace soil with a sealed vapour barrier.

4. Skip the baseboard spray

A can of general-purpose insecticide along a basement baseboard is close to worthless here. Centipedes live in voids, under slabs and inside wall cavities, and they cross treated surfaces quickly on long legs that keep most of the body off the ground — while the moisture and prey go untouched. This is the approach that produces homeowners who have “been spraying every fall for six years.”

Professional treatment targets the harbourage and the prey species together, which is why it holds. Our residential pest control service follows that sequence: identify the prey, treat the harbourage, close the moisture and entry problems.

Cottages and seasonal properties

Centipedes at a cottage are almost always a moisture story. A place sitting closed through a humid Ontario summer, over an unvented crawlspace with exposed soil, is ideal habitat. Owners open up in spring, see centipedes, and assume something went wrong over winter. Nothing did — the crawlspace has been a habitat the whole time.

The fix is the crawlspace: vapour barrier over soil, ventilation or conditioned air, and a look at how water moves around the foundation. That work also removes what brings in mice, sowbugs and the spiders that follow them. Our Muskoka team handles most of these during a closing inspection rather than a separate visit.

When a sighting becomes a pest control problem

One centipede in October is normal. Book an inspection when:

• You see them multiple times a week, or several in one evening
• You find them on upper floors — usually the population below has grown enough to push outward
• You are also seeing silverfish, carpet beetles or springtails, confirming a prey population
• There is visible dampness — efflorescence on block, musty smell, condensation on the slab
• The basement is finished, hiding both moisture and harbourage from casual inspection

A $95 inspection, credited in full when you book the treatment, is the efficient move, because the useful answer is not “yes, those are centipedes” — it is what they are eating and where it lives, which needs someone looking inside wall cavities, crawlspaces and utility chases. Households across Vaughan, Ajax and Barrie call about centipedes and turn out to have a silverfish or carpet beetle population that went unnoticed for a year.

What year-round protection actually changes

Here is the economics, plainly. A one-time General Insect Control treatment runs from $395 exterior or $475 interior and exterior, carries a 60-day guarantee, and will clear the current population. That is the right entry point when you want an active problem handled now.

But centipedes are a conditions problem, and conditions come back every autumn. The prey rebuilds. The humidity climbs again next September. The gap you did not find stays open.

That is what an annual plan is for. The Insect Control plan at $845/year covers the seasonal cycle rather than one moment in it — scheduled exterior work before the fall migration, interior attention when it matters, and the entry-point and moisture observations that stop the population re-establishing. Households wanting rodents covered too move to Essentials at $1,195 or VIP from $1,395. The comparison worth making is not “$395 versus $845” — it is one treatment a year, indefinitely, versus a year of protection that addresses why they keep coming. Our Plans & Pricing page lays out each level, or the free quote quiz will point you at the right one in about two minutes.

Sani IQ is licensed under the Ontario Pesticides Act, registered with the MECP, BBB Accredited, carries $5M liability coverage, and holds a 5.0 rating across 126 Google reviews. Our technicians are employed, licensed and background-checked, and we use reduced-risk products wherever they will do the job.

Frequently asked questions

Are house centipedes dangerous? Not meaningfully. They have modified front legs that deliver venom to the insects they hunt. A bite to a human is uncommon, usually only happens if one is pressed against skin, and is generally compared to a bee sting. They do not transmit disease, damage property or infest food.

Should I kill them if they eat other pests? You can, but it solves nothing. Removing a predator does not remove the prey — it usually means the silverfish or carpet beetle population you did not know about grows unchecked. Treat what they are eating and fix the moisture, and the centipedes leave without intervention.

Why do I only see them at night? They are nocturnal and light-avoidant. Daytime sightings usually mean the harbourage is crowded or disturbed.

Do they lay eggs in the house? Yes — in damp, protected spots like crawlspace soil, under stored cardboard, or in block wall gaps. That is why the problem persists year after year with no new arrivals from outside.

How long does it take to get rid of them? The visible centipedes go quickly. The conditions take a season, and the real confirmation is next autumn, when the sightings do not come back.

Ready to find out what is actually living in your basement? Call (705) 302-1887 or start with the free quote quiz.