Centipede vs Millipede: How to Tell Them Apart

Count the legs on one body segment. If the creature has one pair of legs per segment, it is a centipede. If it has two pairs of legs per segment, it is a millipede. This is the most reliable way to tell them apart. The second tell is movement. Centipedes scurry quickly and stay mobile. If you see a fast-moving creature with visible legs, it is almost certainly a centipede. Millipedes move slowly and steadily, taking their time to traverse the ground. If you see a slow-moving many-legged creature, it is likely a millipede. The third tell is body shape. Centipedes are flattened and look angular in cross-section. Millipedes are rounded and cylindrical. Finally, check the overall size and behavior. Centipedes are aggressive predators. Millipedes are peaceful and curl up defensively. These four signals checked in order will identify which creature you are observing.

Centipedes and millipedes differ noticeably in body structure. Centipedes have a flattened body that is somewhat angular in cross-section. This shape helps them squeeze into narrow spaces while hunting prey. Centipede segments are distinct and separate, with one pair of legs per segment. The first pair of legs are modified into venomous fangs called forcipules that they use to capture prey. Centipedes range from half an inch long in the tiniest species to 12 inches or more in the largest species found in tropical regions. Most North American centipedes are 1 to 6 inches long. Millipedes have a rounded, cylindrical body that looks like a tube or cylinder. The body segments overlap slightly, and each segment bears two pairs of legs. Millipedes are generally smaller, typically ranging from 1 to 4 inches long in North America, though some species reach up to 10 inches. The strong, sturdy build of millipedes provides protection when they curl into a defensive ball.

Both centipedes and millipedes are found throughout North America, preferring moist environments. Centipedes are active hunters found in gardens, leaf litter, under logs and rocks, and in soil across the country. They thrive in warm areas with plenty of prey and moisture. Learn more about centipedes in /wildlife/california/centipede or /wildlife/texas/centipede to understand regional variations. Millipedes also prefer damp areas but are more common in forests and heavily mulched gardens. Both creatures need moisture to survive because their skin dries out quickly in dry conditions. You will find these arthropods most active during spring, summer, and fall when temperatures are warm and soil moisture is adequate. In winter, both burrow deep into the soil to avoid freezing. Indoors, they sometimes show up in basements or bathrooms where moisture collects. Visit /wildlife for a complete guide to understanding North American invertebrates and their habitats.

Centipedes are active, aggressive predators that hunt at night and rest during the day. They use their speed and agility to chase down prey including insects, spiders, and small arthropods. When disturbed, centipedes run away quickly or defend themselves by biting. Centipede venom is rarely dangerous to humans but can cause pain and swelling. Centipedes are solitary creatures and do not interact with each other except to mate. They eat fresh prey regularly and must hunt to survive. Millipedes are passive, slow-moving detritivores that feed on decaying plant matter, fungi, and dead leaves. They move methodically along the ground, processing dead plant material as they go. When threatened, millipedes curl into a tight spiral ball for protection rather than running away. Some millipede species produce a defensive chemical spray that smells foul to discourage predators. Millipedes are often found in groups or aggregations, sometimes in large numbers. They do not bite or sting and are completely harmless to humans. Understanding these behaviors helps you know what each creature is doing when you encounter it.

If the arthropod ran away quickly when you approached, it was probably a centipede. Centipedes are the speedsters of the arthropod world. If it moved slowly or curled into a ball, it was likely a millipede. Count the legs on one segment if you can see them. One pair means centipede, two pairs means millipede. Check the body shape. Flattened and angular suggests centipede. Rounded and cylindrical suggests millipede. If you saw it in a very damp basement or bathroom, it could be either, but millipedes prefer damper areas. If you found it hunting in the garden at night or saw it catching prey, it was a centipede. Centipedes are active hunters, while millipedes are peaceful foragers. Learn more about these creatures by visiting /wildlife for identification guides.

The biggest myth is that centipedes and millipedes are insects. They are not. Both are arthropods, but they belong to the myriapod class, which is separate from insects. Another myth is that the name centipede means exactly 100 legs and millipede means exactly 1,000 legs. Neither is true. The words mean around 100 and around 1,000, but actual numbers vary. Most centipedes have far fewer than 100 legs, and no millipede has 1,000 legs. Some people think both creatures are dangerous pests. Millipedes are harmless. Centipedes are not aggressive toward humans, though they can bite if pinched or threatened. Another myth is that both creatures are insects that belong in the same family. They are both myriapods but belong to different classes with different life strategies. Some people believe millipedes are young centipedes or that they transform into centipedes as they grow. This is false. They develop separately from the time they hatch from eggs. Finally, some people think centipede and millipede bites are highly venomous. While centipedes do have venom, it is used only to subdue small prey and poses no serious threat to humans.