Centipedes & Millipedes in the San Gabriel Valley
Centipedes and millipedes look similar but behave very differently. Here's how to tell them apart, why they turn up indoors, and how to keep them out.
- Centipedes: flat, fast, one pair of legs per segment
- Millipedes: round, slow, two pairs of legs per segment
- Centipedes are predators; millipedes eat decaying plants
- Both need damp conditions and come in from soil/mulch
- Millipedes curl into a coil; centipedes dart away
What they look like
The quickest way to tell them apart is to watch how they move and count legs. Centipedes are flattened, fast and a bit alarming, with one pair of legs per body segment, long antennae, and a pair of venomous pincers up front. Millipedes are rounded and slow, with two pairs of legs per segment, and they curl into a tight coil when disturbed rather than darting.
Most SGV millipedes are an inch or two and dark brown or grey. House centipedes — the leggy, fast ones people find in bathrooms — look the scariest but are harmless hunters that actually eat other pests.
Centipedes & Millipedes fast facts
| Detail | |
|---|---|
| Looks like | Flat & fast (centipede) or round & slow (millipede) |
| Where found | Damp soil, mulch, garages, bathrooms |
| What they do | Centipedes hunt pests; millipedes eat decay |
| Active when | Night; damp weather and seasonal migrations |
| Concern level | Nuisance; centipede pinch is rare and minor |
Where they live
Both live outdoors in the same damp places — under mulch, leaf litter, stones, logs and along moist foundation soil. Millipedes feed on decaying leaves and plant matter; centipedes hunt insects, spiders and other small prey in that same layer.
They come indoors when it's too wet or too dry outside, slipping into garages, bathrooms, crawlspaces and ground-floor rooms. Millipedes are famous for occasional mass migrations, where large numbers move at once after heavy rain and pile up at doorways.
Signs of a problem
Usually it's just sightings — a fast centipede in the bathroom at night, or millipedes wandering a garage or patio, especially after rain. Finding coiled, dead millipedes along the garage door or foundation is common after a migration.
Like pillbugs, steady numbers indoors are really a moisture and harborage signal: damp mulch or soil against the house, leaf litter, and gaps they can crawl through.
How they are controlled
Both are moisture-and-harborage pests, so the fix is the same: pull mulch, leaves and dense plantings back from the foundation, fix drainage and leaks, and seal gaps under doors, around the garage and at utility penetrations. A drier, clearer band around the house removes the reason they're at your door.
Centipedes are worth keeping around outdoors since they eat other pests, but nobody wants them inside. For repeated invasions or a millipede migration, a perimeter treatment of the damp harborage keeps them out. They share those zones with pillbugs and earwigs, so one round of moisture fixes helps with all of them. Ask for a free quote if they keep coming in.
Related Pests
Quick Answers
Quick Answers.
What's the difference between a centipede and a millipede?
Centipedes are flat and fast with one pair of legs per segment and dart away when disturbed; millipedes are round and slow with two pairs per segment and curl into a coil. Centipedes hunt other pests; millipedes eat decaying plants.
Are house centipedes dangerous?
Not really. The leggy, fast centipede in your bathroom looks alarming but is a harmless hunter that eats other pests. It can deliver a minor pinch if handled, but it isn't aggressive and the effect is usually no worse than a brief sting.
Do millipedes bite?
No. Millipedes have no bite and no venom. Their only defense is curling up and releasing a smelly fluid that can stain or irritate skin slightly, so it's best not to handle them, but they can't hurt you or your home.
Why do I suddenly have millipedes everywhere?
Millipedes migrate in large numbers after heavy rain or a sudden weather change, leaving soaked soil and piling up against foundations and doorways. It's a seasonal surge, not an infestation in your home — they're coming from the mulch and soil outside.
How do I keep centipedes and millipedes out?
Dry and clear the perimeter: pull mulch and leaf litter back from the walls, fix drainage and leaks, and seal gaps under doors, around the garage and at pipe penetrations. A drier band of soil around the house is the most effective deterrent.
Do I need pest control for them?
Often the moisture and sealing fixes are enough. If they keep invading or you get a millipede migration every wet season, a perimeter treatment of their damp harborage stops it — and it's worth addressing the moisture so other pests don't follow.
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