House Centipedes

Two questions, and the second one is the useful one. The first is whether the animal can hurt you, and it is answered below from eight publications that do not fully agree. The second is why it is in the house at all — and the answer to that is not about the centipede.

What This Page Carries

The Bite Question: Eight Sources, One Range

This is the question people arrive with, and the honest answer is that the published positions run from “cannot bite through skin” to “an occasional threat to humans”. All eight are set out, in order, from the most reassuring to the least. None is averaged.

• Colorado State University Extension: “Except for the largest species, centipedes cannot bite through skin, so hazard to humans is remote.” It also explains why encounters are rare: “Bites are extremely rare, because centipedes are light shy and bite only when being picked up or crushed.”
• Penn State Extension, of the house centipede specifically: “While they are fast and have long legs, which may frighten some people, they are harmless.”
• University of Wisconsin-Madison: “Centipedes have fangs and can possibly bite if handled, but this rarely happens and the bite is not dangerous.”
• Utah State University Extension: “Centipede bites on humans are rare.”
• Mississippi State University Extension: “Bites to humans are uncommon unless centipedes are handled or accidentally pressed against the skin.”
• Washington State University: “They may inflict a painful bite if handled.”
• University of Georgia Cooperative Extension, the least reassuring of the eight: “Centipedes, which have poison glands and can bite, pose an occasional threat to humans.”

What survives the disagreement is the condition attached to every one of them. Colorado State says a bite happens only when the animal is picked up or crushed, Wisconsin and Washington State both say if handled, and Mississippi State says “unless centipedes are handled or accidentally pressed against the skin”. No source read here describes a house centipede biting a person who left it alone.

On severity, one source offers a comparison and the rest do not. Colorado State: “The bite of the largest species is reported to cause a sharp, temporary pain, similar to a bee sting.” Read what that sentence is careful about — it concerns the largest species, it is reported rather than measured, and the same source has already said that anything smaller cannot break skin. This site is not a medical source and assesses nobody’s symptoms.

What You Are Looking At

The leg count is the identification, and it is exact. Penn State Extension: “Adult house centipedes have 15 pairs of legs with the last pair (on adult females) nearly twice the length of the body, which is one to one and one-half inches in length”. The Connecticut Agricultural Experiment Station gives the same number with the marking: “They have 15 pairs of long striped legs (one pair per body segment).” Washington State adds the quality that makes them look alarming: “Adults have fifteen pairs of long, fragile legs.”

Fifteen pairs is thirty legs, not a hundred, and the apparent size is mostly leg: Penn State notes the animal looks three to four inches long once the legs and antennae are counted, against a body of one to one and a half inches.

It is the one that lives indoors on purpose. Penn State: “House centipedes do not survive winters outdoors in Pennsylvania, but readily reproduce in heated structures.” That is why this animal turns up in a heated bathroom in February when nothing else does.

Why It Is in the House

Damp, dark and at night. Washington State: “House centipedes prefer damp areas; frequently they are found in basements, bathrooms, closets, or potted plants.” Penn State gives the daily rhythm: “During the daytime, the centipedes inhabit dark, damp locations in the home and come out at night to forage for prey.”

Penn State also lists the specific ways in, and they are worth reading as a checklist rather than as biology: expansion cracks and sump pump openings beneath concrete slabs; uncapped blocks, missing mortar and pipe penetrations in cement block walls; floor drains without water traps, especially those connected to dry sumps; cardboard boxes stored on slabs; and any damp, cool unexcavated space under the house.

If the animal is slow, round and curls up, it is not this one. Colorado State publishes the house centipede in the same fact sheet as the millipede for the same reason — both need damp and both die as it dries — but they are told apart at a glance: a millipede has two pairs of legs per body segment and curls into a coil when disturbed, where a centipede has one pair per segment and runs. Our millipedes page covers the autumn invasion, why it ends on its own, and the one source that advises against handling them.

Three other pages on this site describe the same damp spaces for different animals. Our silverfish and firebrats page covers two of the animals Penn State names as this one’s prey; our camel crickets page covers the humpbacked jumping one of crawl spaces; and our earwigs page covers the one that comes in from the mulch outside. None of them repeats the others.

The Part That Matters: It Is Eating Something

A house centipede is a predator, and a recurring one is a receipt. Penn State names the menu: “House centipedes feed on silverfish, firebrats, carpet beetle larvae, cockroaches, spiders, and other small arthropods.” The Connecticut Agricultural Experiment Station puts it more generally: “House centipedes are generalist predators of insects, spiders, and other arthropods, many of which are considered household pests.”

And then Penn State draws the inference, which is the most useful sentence on this page: “If house centipedes are seen frequently, this indicates that some prey arthropod is in abundance, and may signify a greater problem than the presence of the centipedes”. Its own summary says the same thing: “House centipedes feed on small arthropods, including pest insects, so their presence in large numbers may indicate another underlying pest issue.”

One sighting is one sighting. Several, repeatedly, is a signal that something else is living in the building in numbers — and killing the centipede does not touch that.

Two sources make the case for the animal outright. Utah State: “Centipedes are predatory relatives of the insects, and are considered beneficial.” Penn State: “House centipedes are of little concern to homeowners, despite their long legs and scary appearance.” That is the sources’ position, reported. Nobody has to like sharing a bathroom with one.

What the Sources Say to Do, in Their Order

Penn State puts the steps in an order and the order is the advice. First: “Reduction in the centipede food source is the first step in managing a house centipede population.” Second: “Harborage reduction is the second most important management tactic.” Its harborage measures are sealing cracks and crevices in slabs and block walls, screening and caulking sump pump covers, screening basement floor drains, and grading soil so water runs away from the foundation.

Third, and stated without a number: “Reduce the humidity by utilizing dehumidifiers.” No source read here gives a target humidity, a capacity or a room size — which is why no dehumidifier is named on this page, exactly as on our silverfish page and our camel crickets page, both of which reached the same conclusion on the same question.

Colorado State is blunter and shorter. Its control position is to wait out the problem and control moisture sources in and around the home, it observes that infestations usually involve only a few individuals, and it states that interior applications of insecticides are not recommended. That last sentence is paraphrased rather than quoted, because the PDF sets one of its words with a soft hyphen and reproducing it would mean either carrying an invisible control character into the page or silently altering the source.

The two sources are not identical in emphasis and this page does not pretend they are. Penn State does go on to describe insecticide formulations labeled for home use; Colorado State advises against interior application. Both put the non-chemical work first, and both treat the centipede itself as the least important part of the problem.

Why No Product Is Named Here

The only product class any of these eight sources names is a monitor, not a control. Penn State describes distributing sticky insect traps around the house to determine what other arthropods are providing a meal — a diagnostic step, aimed at the prey rather than at the centipede. It publishes no size, no adhesive, no count and no placement specification, and it points the reader to a pest control company for the traps and the identification service together.

That is a practice, not a criterion. There is nothing in it to rank one listing against another, so nothing is named. This site does not measure products against a vocabulary.

The dehumidifier fails for a different reason and it is worth keeping the two apart. The sources support dehumidifying; none of them publishes a figure. A recommendation with no number is not a specification either.

And the insecticide is not an absent card but a discouraged one. Colorado State advises against interior application outright. A page that quietly omitted that sentence and named a product anyway would be misreporting its own sources.

Questions

Sources