Invertebrates
Millipede
Diplopoda · also called millipedes, thousand-legger
A millipede is the opposite of a centipede in almost every way. It is slow, round, and harmless, it eats dead leaves rather than live prey, and it defends itself not with a bite but by curling into a spiral and oozing an evil-smelling, sometimes cyanide-laced fluid. It also has far more legs — and one species has genuinely broken a thousand.
Overview
Millipedes are the class Diplopoda, around 12,000 named species, on every continent except Antarctica. They are slow, cylindrical detritivores of damp, dark places — leaf litter, rotting wood, soil, compost — and among the most important recyclers of dead plant matter in forests. The name means “double foot”: most body segments carry two pairs of legs, the result of ancestral segments fusing.
The leg count
Most millipedes have 40 to 400 legs, and the name “thousand-legger” was hyperbole for centuries — until 2021, when Eumillipes persephone, a thread-thin, eyeless species from 60 m down in Western Australian soil, was found with up to 1,306 legs, the first animal on record to pass a thousand. A millipede hatches with just three pairs of legs and adds more at each moult.
Chemical defence
A threatened millipede coils into a tight spiral and releases a defensive fluid — a mix that can contain hydrogen cyanide, quinones, and other irritants that stain skin and repel ants. Some capuchin monkeys and lemurs deliberately rub agitated millipedes on their fur as an insect repellent.
An ancient pioneer
Millipedes are among the oldest land animals, with 400-million-year-old fossils, and the extinct millipede relative Arthropleura, up to 2.5 m long, was the largest land invertebrate ever.
Status
Millipedes as a class are Not Evaluated. Most are common decomposers, but many have tiny ranges tied to one cave, mountain, or forest and are poorly known, and the Madagascan giant pill millipedes are collected for the pet trade.
Millipede: common questions
Do millipedes really have a thousand legs?
Almost never, and for most of history none did. The vast majority of the roughly 12,000 millipede species have somewhere between 40 and 400 legs, and even the long tropical giants top out around 700 to 750. The name thousand-legger was pure hyperbole until 2021, when scientists described Eumillipes persephone, a pale, eyeless, thread-thin millipede found 60 metres down in a drill hole in Western Australia, with up to 1,306 legs on 330 body segments, the first animal on record to have more than a thousand. It is an extreme adaptation for pushing through tiny gaps deep in the soil.
What is the difference between a millipede and a centipede?
Legs and lifestyle. A millipede has two pairs of legs on most body segments, a rounded body, and moves slowly with a smooth rippling motion, and it eats dead plant matter and defends itself by curling up and releasing chemicals. A centipede has one pair of legs per segment, splayed out to the sides, a flattened body, and moves fast in a weaving run, and it is a predator that kills with a pair of venom claws under the head. In short, a slow, round, dead-leaf eater that curls into a spiral is a millipede, and a fast, flat, biting hunter is a centipede. Millipedes are harmless to people; large tropical centipedes are not.
Are millipedes dangerous or poisonous?
They have no bite, no sting, and no way to actively attack, so they are not dangerous in the way a large centipede or a wasp is. But most millipedes are chemically defended. The fluid they release when handled can irritate and stain the skin brown or purple, and in the large tropical species it may contain enough hydrogen cyanide and quinones to blister sensitive skin and to cause real harm if it gets into the eyes or mouth. The sensible precautions are to handle millipedes gently and briefly, or with gloves, not to let a child put one near the face, and to wash your hands afterward. Ingesting a millipede, which pets sometimes do, can cause drooling and stomach upset.
Why are millipedes important?
They are among the primary recyclers of dead plant material on land. Millipedes shred and consume enormous quantities of fallen leaves, rotting wood, and other litter, and by fragmenting it, mixing it into the soil, and passing it through a microbe-rich gut, they greatly speed up the release of nutrients back into the ecosystem and the formation of humus. In many forests millipedes process a large fraction of the annual leaf fall. They also aerate the soil through their burrowing, are food for birds, amphibians, reptiles, small mammals, and many insects, and, being sensitive to soil moisture and chemistry, serve as useful indicators of soil health.