In the evening, a creature with impossibly long legs races across the basement wall and vanishes behind a box. In Quebec homes that is almost always a house centipede. It looks like something out of a horror movie, but it is mainly an insect hunter. Its presence tells you two things: there is moisture, and there is something to eat.
House centipede or millipede?
People mix up two very different creatures:
| House centipede | Millipede | |
|---|---|---|
| Body | 2.5 to 5 cm, yellowish with dark stripes | Long, rounded like a worm, brown or black |
| Legs | 15 pairs, very long, clearly visible | Very many, short, under the body |
| Speed | Very fast | Slow |
| When disturbed | Runs | Curls up |
| What it eats | Insects, spiders | Decaying plant matter |
This guide is mostly about the house centipede. Millipedes sometimes come in by the dozen in the fall or after heavy rain, but quickly die in a house that is too dry for them.
Is it dangerous?
Not really. According to Health Canada, most house centipedes can’t break human skin; the few that can cause pain like a mild bee sting that fades within a few hours. They avoid people and only bite if handled. They are not dangerous to dogs and cats.
Why it is in your home
The house centipede needs two things:
- Moisture: basements, bathrooms, laundry rooms, drains, crawl spaces. Health Canada notes that it moves in when these areas are too damp, and also comes inside in the fall as it gets colder.
- Prey: silverfish, spiders, cockroaches, earwigs, fly larvae, bed bugs. It is a hunter: it eats bugs you would like to see even less.
In other words, a lot of house centipedes often means a lot of other bugs, which you don’t see because they are more discreet.
How to have fewer of them
Health Canada advises tolerating them as much as possible, because they are useful. If you see too many, going after their living conditions works better than chasing them:
- Dehumidify the basement to around 50% relative humidity; ventilate the bathroom and laundry room.
- Fix leaks and check floor drains.
- Cut the food supply: deal with the silverfish, spider or other insect problem feeding them.
- Declutter the basement: fewer cardboard boxes on the floor, more sealed bins on shelves.
- Seal foundation cracks, around pipes and under doors.
- Clear around the house: leaves, mulch and wood away from the foundation.
Sticky traps along basement walls catch a few and are mostly useful for spotting other insects.
When to call
One house centipede now and then needs no action. Call if:
- you see several a day, on more than one floor;
- you also find other bugs (silverfish, cockroaches): the real problem may be there;
- basement humidity stays high despite the dehumidifier.
A technician looks for what is feeding them and treats the areas where they travel. To make sense of what you are seeing, see also our guide to bugs in the house. For an assessment, contact us or call 514-638-8705. The estimate is free.
Frequently asked questions
Do house centipedes breed indoors?
Yes, in a damp, sheltered spot (basement, crawl space, under debris). It is one of the few creatures on this list that can live indoors year-round.
Why do I see more of them in the fall?
They leave the outdoors as it gets cold and look for a damp, mild place. The basement is perfect.
Should I kill them?
There is no need. A house centipede in the basement eats the insects living there. If their numbers bother you, deal with moisture and prey first.