People mix these two up constantly. Fair enough, they're both long, leggy, and live under logs. But millipedes and centipedes are about as similar as a cow and a wolf. One eats plants. The other hunts and bites. Getting them confused in a pet shop has consequences.
The short version
Millipedes (class Diplopoda) are slow, gentle detritivores. They eat rotting wood, leaf litter, and decaying organic matter. Centipedes (class Chilopoda) are fast, aggressive predators. They eat other animals, and they have venomous modified front legs called forcipules that they use to subdue prey.
Both belong to the subphylum Myriapoda, which is where the similarities largely end.
Legs and body segments
This is the easiest way to tell them apart. Millipedes have diplosegments, meaning most of their visible body rings carry two pairs of legs. Pick one up (gently) and look at the underside: you'll see legs in pairs of two on each segment. Centipedes have one pair of legs per segment, and those legs splay outwards from the body rather than tucking underneath.
Centipede legs are longer and more visible. They need them to be, because they chase down prey. Millipede legs are short and numerous, working in a wave-like motion that pushes the animal forward through soil and leaf litter. It's a burrowing body plan versus a hunting one.
One thing that catches people out: millipedes don't actually have a thousand legs. The number varies by species and increases with each moult. Most common pet species have somewhere between 100 and 400 legs as adults. The record holder, Eumillipes persephone, was described in 2021 from Western Australia with over 1,300 legs, but that's genuinely unusual.
Defence
When threatened, a millipede curls into a tight spiral and may release defensive secretions from glands along its body. Depending on the species, these chemicals can include benzoquinones (common in the order Spirostreptida) or even hydrogen cyanide (produced by some flat-backed millipedes in the order Polydesmida). The secretions can stain skin, smell unpleasant, and irritate your eyes if you touch your face afterwards. Wash your hands after handling.
Centipedes, on the other hand, bite. Their forcipules are modified front legs that inject venom, and while a bite from a small European centipede is unlikely to do much, larger tropical species like Scolopendra subspinipes can deliver a bite that's genuinely painful and medically significant. Centipedes don't curl up. They run, or they fight.
Keeping them as pets
Millipedes are popular pets for good reason. Species like Archispirostreptus gigas (the giant African millipede) are docile, tolerate handling, and are interesting to watch. They need deep, moist substrate with plenty of rotting hardwood and calcium supplementation, but their day-to-day care is fairly straightforward.
Centipedes are kept by some hobbyists, but they're a completely different prospect. They're fast, defensive, and their bite hurts. They need secure enclosures with no gaps whatsoever. Handling is strongly discouraged. A centipede is a display animal for someone who already has experience keeping tricky invertebrates, not a starter pet.
If you're shopping for your first myriapod, the millipede is the one you want. I've had people come in confused about which is which, and the conversation usually goes: "Do you want something you can hold?" Yes. "Then you want a millipede."
Feeding differences
Millipedes are detritivores. They eat decaying plant matter: rotting hardwood, leaf litter, cucumber, courgette, the odd bit of banana. Their substrate is also their food. They process dead organic material and return nutrients to the soil, which is why they work so well in bioactive setups.
Centipedes are obligate predators. They eat live insects, and larger species will take pinkie mice. You'll need a supply of feeder insects, and you'll need to feed them with long tweezers rather than your fingers.
Speed and temperament
Millipedes are slow. Properly slow. Even the quicker small species like Trigoniulus corallinus aren't going to outrun your hand. Large millipedes trundle along at a pace that makes them easy and relaxing to handle.
Centipedes are fast in a way that makes your heart rate spike. They bolt. If one gets out of its enclosure, you're in for a stressful time catching it, and you need to be careful doing so because they will bite when grabbed.
A quick reference
| Feature | Millipede | Centipede |
|---|---|---|
| Class | Diplopoda | Chilopoda |
| Legs per segment | Two pairs | One pair |
| Diet | Detritivore | Predator |
| Venom | None | Yes (forcipules) |
| Defence | Curling, chemical secretions | Biting, fleeing |
| Speed | Slow | Fast |
| Handleable | Yes (most species) | No |
If you're still not sure which one you've found under a rock in the garden, check the legs. Two pairs per segment means millipede. One pair means centipede. And if it's moving fast enough that you can't count, it's almost certainly a centipede.