House Centipedes in Scarborough: What They Mean and How to See Fewer

A house centipede is the fast, grey, 1-to-2-inch bug with 15 pairs of long legs that shoots across the basement floor when you switch on the light. It is harmless to the house, your pets and your stored things, it almost never stings a person, and it is in your home for two reasons: the air is damp and there are other insects to eat. Dry the basement and cut the food supply and you will see fewer of them. Spraying the centipedes themselves is not the fix. If a centipede is pointing at silverfish, cockroaches or another real problem, our pest control in Scarborough starts with a free inspection so you pay for the right job.

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What is a house centipede?

The house centipede (Scutigera coleoptrata) is a predator, not a scavenger. The Connecticut Agricultural Experiment Station's house centipede fact sheet, the clearest government source on this animal, describes an adult as a segmented body 1 to 2 inches long with three dark stripes running down it and 15 pairs of long, striped legs, one pair per body segment. The two antennae at the front look so much like the legs that it is hard to tell which end is which. Young ones look like small adults with fewer legs and add legs each time they moult.

A few details explain why you keep meeting the same handful of them:

• They grow slowly and live a long time. The fact sheet puts sexual maturity at upwards of 3 years and lifespan at up to 7 years. That is very unlike a cockroach or a fruit fly. A house centipede population builds slowly, which is why most homes have a few rather than hundreds.
• They live indoors year-round in a climate like ours. In their native Mediterranean range they live outdoors in leaf litter and rotting wood. In a cold-winter climate they live and breed inside buildings all year. The University of Wisconsin Extension notes that this is the only centipede that breeds indoors.
• They hunt at night and avoid you. They are nocturnal and fast, and most of the ones living in a house are never seen. The one you do see is usually the one caught out when a light came on.

A house centipede is a symptom, not the problem. It tells you two things about the room you found it in: the air is damp, and something else is living there for it to eat.

Are house centipedes dangerous?

No, not in any practical sense. According to the Connecticut fact sheet, they do no harm to the structure of a house, to stored food or fabric, or to pets. Like every centipede they carry a pair of venomous claws under the head for subduing prey, and a sting to a person is very rare and comes from rough handling, such as grabbing one or pressing it against your skin. The fact sheet describes the result as temporary, localized pain. They are not aggressive and they run from people.

So the honest answer to "is this an emergency" is no. You do not need a same-day visit for a house centipede. What is worth your time is working out why it is there, because that is where the real problem, if there is one, lives.

Why you see more of them in October

Searches for "house centipede" from the Toronto area run highest in October and fall by more than half by December, going by the Google Keyword Planner figures we pull for Toronto. That lines up with what households report. The house gets closed up for the season, the heat comes on upstairs, the basement stays cool and damp, and more time is spent in rooms like the laundry room and the basement rec room where centipedes already live. Fall rain and a soaked yard also push moisture against the foundation walls.

In Scarborough the housing stock makes this worse in a few specific ways:

• Postwar bungalows and back-splits. Large parts of Wexford, Dorset Park and Cliffside are postwar housing. Basements that old have had decades to develop hairline cracks, tired window wells and a damp corner or two, which is exactly the cool, humid, dark habitat the fact sheet describes.
• Ravine-edge lots. Homes backing onto Highland Creek, the Rouge valley or the bluffs above the lake sit next to leaf litter, rotting wood and constant soil moisture, which keeps the insects centipedes eat close to the foundation.
• Basement apartments. A finished basement unit with a shower, a dryer and no dehumidifier is a damp space by design, and it is the part of the house centipedes already favour.

What a house centipede is eating in your home

This is the part that matters most. House centipedes are generalist predators. The Connecticut fact sheet lists cockroach nymphs, bed bugs, flies, ants, silverfish and spiders among their prey. A home with a steady centipede population is a home with a steady supply of something smaller.

Use the centipede as a pointer:

• Centipedes in the basement and bathroom, plus damage to stored paper or boxes: that is almost always silverfish. They need the same damp and they are a centipede's easiest meal. Our silverfish control in Scarborough page covers how we deal with them and why moisture comes first.
• Centipedes in the kitchen at night, plus small brown insects behind the stove or fridge: check for cockroaches, especially in an apartment or a semi with a shared wall. See cockroach control in Scarborough.
• Lots of webs in the basement corners: spiders and centipedes eat the same prey and often share the same rooms. Our spider control page explains when spiders are worth treating and when they are not.
• Centipedes in a bedroom, plus bites or small dark spots on the mattress seams: do not assume the centipede is biting you. Get the bed checked. Our bed bug inspection in Scarborough is free and tells you whether you have a bed bug problem before you spend anything.

How to get rid of house centipedes

The Connecticut fact sheet is direct about this: using pesticides to wipe out house centipedes is not recommended. The control that works is making the house a worse place for them and for the insects they hunt. In order:

1. Measure the humidity. A basic hygrometer from a hardware store is inexpensive. Put it in the basement for a day. Health Canada's guidance on humidity and mould recommends keeping indoor relative humidity between 30 and 50 percent and using a dehumidifier or air conditioner to bring it down when needed.
2. Run a dehumidifier in the basement and empty it, or run it to a floor drain. In most Scarborough basements this single step does more than anything else on this list.
3. Fix the water. Look for the source of damp rather than just drying the air: a dripping laundry tub, a sweating cold-water line, a downspout dumping beside the foundation, a window well that fills with leaves and holds water.
4. Seal the sump and the cracks. The fact sheet specifically recommends a properly caulked sump pump seal and filled cracks and crevices in the foundation. This also keeps out the insects centipedes come in to eat.
5. Get stored things off the floor. Cardboard boxes on a damp basement floor are shelter and food for silverfish and shelter for centipedes. Move papers, books and clothing into sealed plastic bins on shelves.
6. Clear the outside of the foundation. Pull mulch, leaf piles and firewood back from the walls, especially on the shaded side. On a ravine lot this matters more than on a street lot.
7. Use sticky traps as a survey tool. The University of Wisconsin Extension notes that small sticky board traps where centipedes are active can reduce their numbers. More useful still, the traps show you what else is moving along that baseboard. Check them after a week.

When to call a professional

You probably do not need us for house centipedes on their own. A few a month in a basement is normal in an older Scarborough home and is not worth paying to treat. It is worth a call when:

• You are seeing them every day, or upstairs in living areas and bedrooms. That usually means a prey population large enough to support them, and that population is the job.
• The sticky traps show silverfish, cockroaches or carpet beetles. Treat the prey and the centipedes thin out on their own.
• You have dried the basement and they keep coming. Something is still feeding them, often in a wall void, under a slab or in a crawlspace you cannot reach.

What it costs: the moisture-pest work most centipede calls turn into is covered on the silverfish control page, which starts from about $175, and a general one-off treatment in Scarborough runs $150 to $450. The pest control cost page breaks it down by pest. Every product used is registered by Health Canada's Pest Management Regulatory Agency and applied to the label. If the honest answer is a dehumidifier and a tube of caulk, that is what you will hear.

If you rent

If you are in a basement apartment or a rental tower and the centipedes come with a damp unit, the damp is a building issue, and so is any cockroach or silverfish problem behind it. Our guide to whether the landlord is responsible for pest control in Ontario explains who pays and how to put the request in writing. Keep a short log of what you see and where, with dates and photos. It makes the conversation with your landlord much easier.

House centipede, millipede or silverfish?

People mix these three up all the time, and the fix is different for each.

If you are not sure which one you have, send us a photo through the form or describe it on the phone and we will name it before anyone talks about treatment. For the other bugs that move indoors this time of year, our fall pest guide covers cluster flies, boxelder bugs, stink bugs and mice.

Common questions

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