A house centipede is a grayish-yellow, flat-bodied creature with 15 pairs of long, spindly legs that make it look much larger than it actually is. The body itself measures only one to one and a half inches, but when you include the legs and antennae, the whole animal appears three to four inches long. That spray of legs is usually what catches your eye first, often as it darts across a bathroom wall or basement floor at startling speed.
Body Shape, Color, and Markings
The house centipede’s body is elongated and flattened, segmented like a chain of small plates. Its base color is grayish-yellow, and running down the length of its back are dark longitudinal stripes. These stripes are one of the easiest ways to confirm you’re looking at a house centipede rather than some other household bug. The legs themselves are banded in alternating light and dark segments, giving the whole animal a striped, almost feathery appearance when it’s still.
Legs and Antennae
The legs are the house centipede’s most distinctive feature. Adults carry exactly 15 pairs, and each pair is slightly longer than the one in front of it, so the legs near the back of the body are noticeably longer than those near the head. On adult females, the last pair of legs can be nearly twice the length of the entire body. Those elongated rear legs trail behind the centipede and can look almost like a second set of antennae, which sometimes makes it hard to tell which end is the front at a glance.
The actual antennae at the head are also long and whip-like, constantly sweeping the air as the centipede moves. Between the trailing rear legs and the forward-facing antennae, the animal’s silhouette is symmetrical enough to confuse people seeing one for the first time.
How Big They Actually Are
House centipedes look bigger than they are. The body alone tops out around one and a half inches in most adults, roughly the length of a paper clip. But with legs and antennae fully extended, the overall footprint stretches to three or four inches. That visual size is what makes them so alarming when they appear unexpectedly on a wall or in a sink. If you’re seeing a smaller version with fewer legs, it’s likely a juvenile. Young house centipedes add leg pairs as they molt and grow, so a tiny one with noticeably fewer legs is simply not fully developed yet.
How to Tell Them Apart From Similar Bugs
Several other household creatures get confused with house centipedes, but the differences are straightforward once you know what to look for.
- Silverfish are shiny silver or gray, uniform in color with no stripes, and have only six legs. They’re also smaller, typically half an inch to one inch long. They move quickly but lack the fan of long legs that makes house centipedes so recognizable.
- Millipedes are rounder in cross-section, with two pairs of short legs per body segment instead of one. They move slowly and curl into a coil when disturbed. A house centipede never curls up and is dramatically faster.
- Other centipede species found indoors tend to be darker brown or reddish, with shorter legs held closer to the body. They lack the long, banded, spidery legs that make the house centipede unique.
How They Move
Speed is part of the identification. House centipedes are among the fastest arthropods you’ll encounter indoors, capable of sprinting across floors, walls, and ceilings in short bursts. Their long legs ripple in a wave-like motion that lets them cover ground quickly, and they can stop and change direction almost instantly. If the bug you spotted was flat, striped, covered in long legs, and moved faster than you expected, it was almost certainly a house centipede.
Where You’re Most Likely to Spot One
House centipedes prefer damp, dark spaces. Basements, bathrooms, laundry rooms, and crawl spaces are their usual territory. You’ll often see them on walls or ceilings near moisture sources, especially at night when they’re most active. They’re predators that feed on other household pests like spiders, cockroach nymphs, and silverfish, so spotting one usually means there’s a food supply nearby. They don’t damage your home or belongings, and while they can technically deliver a mild bite if handled, they rarely do. Most encounters end with the centipede vanishing into a crack before you’ve had time to react.