If you've seen a long, leggy creature wriggling across the floor and weren't quite sure what you were looking at, you're not alone. Was it a centipede? Or wait, was it actually a millipede? What's the difference? Millipedes and centipedes are both common arthropods that often find their way indoors — especially in damp, cool spaces. And they're very different in behavior, diet, and how they interact with humans.

Let's talk about what sets them apart, where they tend to live, and why they show up inside. More importantly, we'll tell you what you can do to keep them from invading your home.

Like other arthropods, millipedes and centipedes go through a few key life stages: egg, juvenile, and adult. Most species lay their eggs in soil or under debris outdoors, where it's moist and protected. Juveniles hatch with fewer legs and segments than adults and add more with each molt.

Millipedes typically live longer (sometimes several years) while centipedes tend to have shorter lifespans.

Millipedes are detritivores, meaning they feed on decomposing organic matter like leaves, mulch, and decaying wood. So they're not interested in your pantry or your belongings.

Centipedes, on the other hand, are actual predators. They hunt other insects, including silverfish, cockroaches, and even spiders. They can actually help reduce other pest populations in small numbers, but you still probably don't want them running around your home.

Millipedes and centipedes are small and flexible enough to squeeze through cracks, weep holes, or gaps under doors. If there's excess moisture inside your property, especially near entry points, they have the perfect invitation to go ahead and come inside. Centipedes may also wind up inside while chasing prey, while millipedes seek out cool, damp hiding spots.

Basically, any moisture-rich area with poor ventilation is a likely entry and hiding point — and it's even more so if the space hasn't been sealed or maintained.