Overview
The house centipede (Scutigera coleoptrata) is one of the most startling insects people encounter in Montreal homes — its 15 pairs of extremely long, banded legs and lightning-fast movement make it deeply alarming to most people. Despite its fearsome appearance, the house centipede is completely harmless to humans and is actually a beneficial predator that feeds on cockroaches, silverfish, spiders, ants, and other household pests. Its presence indoors is almost always a sign of an underlying moisture problem and an existing insect population it is feeding on.
How to Identify House Centipedes
- Body length: 25–50 mm — medium-sized, elongated, and flattened
- Colour: Yellowish-grey with three dark longitudinal stripes running the length of the body
- Legs: 15 pairs of very long, banded legs — the last pair in females is nearly twice the body length
- Speed: Extremely fast — one of the fastest arthropods relative to body size
- Antennae: Very long, thread-like, constantly moving
- Eyes: Compound eyes — can see in multiple directions simultaneously
- Movement: Runs in short, rapid bursts; freezes when disturbed
- Habitat: Damp areas — bathrooms, basements, crawl spaces, and laundry rooms
Biology & Behaviour
- Lifespan: 3–7 years — unusually long for an arthropod
- Eggs per female: 35 per season, laid in spring
- Development: Hatch with 4 pairs of legs; add pairs with each moult until reaching 15 pairs
- Hunting method: Active predator — chases prey and injects venom through modified front legs (forcipules)
- Diet: Cockroaches, silverfish, spiders, ants, flies, and other small arthropods
- Activity: Primarily nocturnal; most active at night
- Preferred conditions: High humidity (above 70%), dark, undisturbed spaces
- Seasonal pattern: Present year-round indoors; most visible in fall as they move deeper into the structure
Health Risks
- Bite: House centipedes can bite if handled, but bites are extremely rare and require direct handling
- Venom: Mildly venomous — a bite causes localized pain and swelling similar to a bee sting; not medically significant
- No disease transmission: House centipedes do not transmit disease
- Beneficial: They actively hunt and eat cockroaches, silverfish, spiders, ants, and other household pests
- Psychological impact: Their appearance and speed cause significant alarm, but they are harmless
- Indicator species: Their presence reliably indicates high humidity and an existing insect population
Signs of Presence
- The centipede itself — seen running rapidly across bathroom floors, basement walls, or laundry room floors, usually at night
- Sightings concentrated in bathrooms, basements, and laundry rooms — high-humidity areas
- Increased sightings in fall as centipedes move deeper into the structure
- Presence of other insects (silverfish, cockroaches, spiders) that centipedes feed on
- High humidity readings in basement or crawl space (above 70% relative humidity)
Prevention
- Reduce basement and bathroom humidity with a dehumidifier — target 40–50% relative humidity
- Fix leaky pipes, faucets, and any moisture sources
- Seal gaps under doors, around utility penetrations, and through foundation vents
- Address the underlying insect population — centipedes follow their food source
- Keep basements and storage areas organized and clutter-free
- Seal cracks in the foundation and basement walls
- Ensure proper ventilation in crawl spaces
- Remove leaf litter and debris from around the foundation
Professional Treatment
House centipedes rarely require professional treatment. The most effective approach is addressing the root causes: reducing humidity with a dehumidifier and eliminating the underlying insect population they are feeding on. If centipede populations are high despite these measures, professional perimeter spray and crack-and-crevice treatment can reduce numbers. Individual centipedes found indoors can be captured and released outside. Call 514-809-1999 if you are seeing large numbers regularly.