House Centipedes in Ontario

Overview

The house centipede is the fast, many-legged shape that darts across a basement floor or freezes on a bathroom wall before vanishing into a crack. Its speed and fringe of long legs make it one of the most alarming-looking household pests in Ontario — and one of the most misunderstood. House centipedes are harmless predators. They don’t damage homes, don’t spread disease, and very rarely bite. What they do is hunt: silverfish, cockroaches, ants, spiders, flies, and other small insects are all prey. That makes a house centipede less a pest in its own right than a living indicator. If you have them, your home is supplying both the dampness they need and the insects they eat — and both are worth addressing.

Identification

A house centipede has a flattened, yellowish-grey body 25–35 mm long, marked with three dark lengthwise stripes, and 15 pairs of long, jointed, striped legs that get progressively longer toward the rear. Two very long antennae extend from the head, and the rearmost legs are so long the animal can look double-ended. Leg-tip to leg-tip, a large one spans well over 75 mm, which is why it looks bigger than it is. It moves in rapid bursts and can climb walls and ceilings.

The most common confusion is with millipedes, but the two are easy to separate: centipedes are fast, flat, and long-legged with one leg pair per segment, while millipedes are slow, round, and worm-like with two pairs per segment and coil up when touched.

Life Cycle

House centipedes develop through gradual metamorphosis and are notably long-lived for arthropods, surviving several years. A female lays eggs in damp soil or protected indoor cracks, and the young hatch with just a few pairs of legs, adding more segments and leg pairs with each moult until they reach the adult complement of fifteen. Development is slow and depends on temperature and prey availability. Because they live for years and reproduce indoors where conditions allow, a stable damp basement can host a small resident population that persists quietly, replenished as long as prey and moisture last.

Habitat & Behaviour

House centipedes are nocturnal hunters that favour damp, dark spaces — basements, crawl spaces, bathrooms, laundry rooms, and floor-drain areas. They don’t build webs or nests; they roam actively at night, running down prey with speed and seizing it with venomous front legs modified into fangs (harmless to humans). By day they hide in cracks, under boxes, and in undisturbed corners. They’re solitary and secretive, so a sighting usually means several more are hidden nearby. Crucially, they go where the food is: a centipede population tracks the insect population, which tracks moisture. Reduce any one link and the others fall.

Diet

House centipedes are pure predators. Their prey list reads like a who’s-who of household nuisance insects: silverfish, cockroaches, ants, spiders, flies, moths, and other small arthropods. They hunt actively, using long antennae and legs to detect and capture prey, then inject venom to subdue it. This diet is exactly why their presence is diagnostic — a centipede indoors is proof that other insects are present in enough numbers to feed a predator. They eat nothing structural and contaminate no food; they’re strictly hunters of other bugs.

Signs of Infestation

• Live centipedes darting across floors or walls at night, especially in basements and bathrooms.
• Sightings in damp rooms — near floor drains, sump pits, laundry areas, and under-sink cabinets.
• The presence of prey insects — silverfish, cockroaches, or ants — which the centipedes are there to hunt.
• Occasional daytime sightings when disturbed from harbourage under boxes or clutter.

Because centipedes hide well, seeing even one occasionally usually means a small resident population supported by ample prey.

Damage Caused

House centipedes cause no damage whatsoever. They don’t chew wood, fabric, paper, or wiring; they don’t feed on stored food; they don’t stain surfaces or leave droppings of concern. Their only “impact” is the fright of encountering one and the discomfort some people feel about their appearance. If anything, they reduce damage by preying on pests — like silverfish — that do harm belongings. The real cost associated with centipedes is indirect: their presence flags a moisture problem and an insect population that may include species you’d rather not host.

Health Risks

House centipedes pose almost no health risk. They don’t transmit disease, don’t infest food, and don’t provoke allergies the way cockroaches can. Bites are rare and only occur if a centipede is handled or pressed against skin; even then, the jaws of a house centipede usually can’t penetrate human skin, and any bite is minor — comparable to a small bee sting at worst, with brief localized soreness. They are not aggressive and flee from people. For homes and businesses aiming for zero pest activity, the concern is appearance and what centipedes signal, not any medical danger.

Seasonal Activity in Ontario

Outdoors, house centipedes are most active in the warm months and seldom seen in winter. Indoors, in heated Ontario homes, a resident basement population can stay active year-round wherever moisture and prey persist. Activity peaks in the humid stretch of summer, when — as our June 2026 spiders-and-centipedes alert described — rising humidity across the GTA and Simcoe County drives moisture-loving insects indoors and the centipedes that hunt them follow. Homeowners in Mississauga and Vaughan see the same July pattern each year, which is why getting ahead of it in June keeps numbers low all season.

Where They Hide

Damp, dark, undisturbed spaces: basements and crawl spaces, around floor drains, sump pits, and foundation cracks, under bathroom and kitchen sinks, in laundry rooms, behind storage boxes and clutter, and in wall voids adjoining damp areas. They gravitate to wherever humidity is highest and prey is most concentrated.

How They Enter Homes

House centipedes enter through foundation cracks, gaps around basement windows and doors, utility penetrations, floor drains, and weep holes. Once inside, a damp basement can support them indefinitely, and they may not need to re-enter at all — they simply persist as long as conditions hold. They can also migrate indoors from damp exterior harbourage like leaf litter, mulch, and stones against the foundation when outdoor conditions dry out or cool.

Prevention Tips

1. Run a dehumidifier in basements and crawl spaces; target indoor humidity below 50%.
2. Fix leaks, dripping taps, and damp spots — moisture is the primary draw for both centipedes and their prey.
3. Reduce the insects they feed on by sealing entry points and treating the perimeter.
4. Seal cracks around the foundation, basement windows, pipes, and floor drains.
5. Clear clutter and stored boxes that provide daytime harbourage.
6. Remove exterior harbourage — leaf litter, mulch, and stones piled against the foundation.
7. Improve ventilation in bathrooms and laundry rooms to keep surfaces dry.

Lower the humidity and thin out the prey, and centipedes lose both reasons to stay.

DIY vs. Professional Treatment

You can vacuum up the centipedes you see and dehumidify a basement, and doing so genuinely helps — but because centipedes track the insects they hunt, lasting control means dropping the whole food chain. That’s the honest DIY trade-off: you can chase individual centipedes indefinitely, or address the moisture and prey that keep drawing them. A professional general insect treatment targets the perimeter and entry points, reduces the prey insects centipedes feed on, and identifies the dampness behind it all, so the population collapses at once rather than persisting. Sani IQ backs its integrated approach with a Pest-Free-Or-It’s-Free guarantee. Explore general insect control pricing or residential pest control.

References

• University of Minnesota Extension — Sowbugs, Millipedes and Centipedes
• University of Missouri Extension — Millipedes and Centipedes

Last updated: July 16, 2026 · Reviewed by Sani IQ licensed technicians