Often, centipedes and millipedes get thrown into a vague, miscellaneous category where the creatures are ‘not insects or arachnids.’ Many people also have difficulty telling the two apart. Both centipedes and millipedes are from the same subgroup called myriapods; the name for this category comes from a Greek word that means ‘countless legs.’
So what is the difference between a centipede and a millipede? Centipedes only have a single pair of legs for each body segment they have. Millipedes, on the other hand, have two pairs of legs for each body segment. Ironically, though, millipedes tend to be a lot slower than centipedes – which are incredibly fast-moving.
To put it very simply: there’s a world of difference. Not only are there some significant visible differences between the two, but they also happen to be from two completely different classes of arthropods. It’s like saying apples and oranges are similar because they’re both fruits.
How do you know if it’s a centipede or a millipede?
It’s not hard to tell if you’ve come across a centipede or a millipede. Even though they do look very similar, there are several visible differences between them too.
If you happen to come across one of these creatures under a pile of dead leaves and it runs, it’s a centipede. If it curls up and stays motionless, it’s a millipede.
Centipedes and millipedes can be similar in some ways. For example, they both have segmented bodies with many legs and can cause burns because of toxic and chemical compounds secreted by their bodies. They often have the same color and a pair of antennae for smelling and eating.
However, there are some key differences to tell them apart.
Differences in anatomy and appearance
Centipedes have long, segmented, and exoskeletal bodies. They often appear flat and are generally more flexible. Centipedes have one pair of legs per segment and two venomous legs that they use as a defense mechanism.
Unlike what their deceptive name suggests, they do not have 100 legs though they have a lot of them. Centipedes’ legs usually range from 20 to 350 in different species. It also depends on how many segments the centipede grows into, since each segment has a pair of legs. The back legs are also used to grab onto the prey and squeeze.
Centipedes also have a pair of antennae for smelling and feeding. They use these long antennae for catching their prey and injecting them with venom before feeding on them.
Millipedes, on the other hand, have elongated and segmented bodies that are more recognizable by their sub-cylindrical shape. Each segment of a millipede’s body has two pairs of legs, except for the first three segments that have one pair each. The most recorded legs on a millipede are 750.
Unlike centipedes, they do not have any poisonous legs. This may be because they are not predators and, therefore, do not any. In millipedes, the legs are not as easily visible because they are extended inwards towards the body. This position allows for maximum pushing and burrowing power, and also safeguards them from breaking while in narrow spaces.
Like centipedes, they have a pair of antennae for smelling and feeding, but these are shorter than those of millipedes.
Differences in defensive strategy
Being from the same class of arthropods, they both have toxic and chemical compounds that can harm humans. However, with centipedes being predators and millipedes being scavengers, they both have different behaviors when it comes to feeding and defending themselves.
Centipedes are part of the group of arthropods that bites predators and release venom with their bites that can result in severe skin burns and even death to some smaller insects. For people, the bite marks may take months to disappear, and the chemical compounds in the venom can cause allergic reactions and burns. However, centipedes will usually run from predators.
Millipedes also contain toxic chemicals for defense. Unlike centipedes, millipedes will usually curl in on themselves in case a predator comes around to protect their soft undersides, head, and legs. However, they are highly active in defending themselves. They release smelly, toxic compounds that can be harmful to other insects and humans.
For predators, this liquid is also extremely foul-tasting, which drives them off. It can cause allergies and burns in humans, which is easily treated with antiseptic s though it may take a while.
Differences in mobility
Because of the longer legs, centipedes can move faster than millipedes. They are quick to run when they come across danger, and also quick to bite their prey while hunting. Some species of centipedes move slowly and burrow, but most others are adapted for speed. Centipedes can comfortably run over long distances without trouble.
Millipedes are generally slow walkers and cannot catch their prey so fast. This is why they mostly live in wood and plants. They do not prefer moving over long distances and are adapted for burrowing, with at least three different burrowing mechanisms that are known to humans. Millipedes can, however, walk long distances during the rainy seasons to avoid drowning.
Differences in diet
When it comes to diet and feeding, there are some significant differences between the two. You already know that centipedes are predators. They can and do actively search long distances for food and are highly carnivorous. They kill their prey by biting them and injecting venom that makes the bite fatal for the prey. They also have a pair of legs which are used to attack prey and are also used to inject venom.
Millipedes, on the other hand, are detritivores, which means that they feed mostly on dead organic matter, such as decaying plants and animals. Because they are slow and cannot go over long distances looking for food or shelter, they tend to settle for whatever they come across first. They also seek refuge in houses where they feed on wood. Millipedes can live for several months in one place if they are not disturbed.
Although they are mainly detritivores, millipedes can also feed on small ants and insects that they can catch quickly, as well as from the roots, stem, and leaves of plants.
Differences in reproduction
Both centipedes and millipedes reproduce sexually. In centipedes, males leave their sperm bundles near females so they can impregnate themselves, or infuse the sperm inside to produce new offspring. They lay their eggs in the soil where they are kept for months and kept safe from environmental hazards. The soil provides them with food and moisture, and nymphs live on small insects for food. The house centipede will also reproduce indoors.
In millipedes, the male and female join for the mating (you can see this in the featured image above). They start at the age of two and mate during the whole year, particularly when they find a suitable environment for their offspring. Sometimes the male gives massages to the females. Millipedes also lay their eggs in the soil to keep them safe. Unlike the house centipede, however, the millipede does not reproduce indoors.
Differences in habitat
Centipedes are found in all sorts of environments but would prefer damp, moist habitats. They are usually found under rocks, leaf litter, logs, and sometimes, in burrows in the ground or rotting wood. Centipedes prefer to live in darker places, which is why they are also found in homes. They are rarely found in dry, desert regions, but some species can also survive these climates. Centipedes are almost exclusively land species, but some make their homes along the edge of coastal areas, and one species is also known to be able to swim.
Millipedes are found primarily in moist, deciduous forests because many species do not have the barrier to prevent water from leaving their bodies and can get dehydrated quickly. However, millipedes are good at adapting to their environment, and if faced with eco-unfriendly conditions, can move into different habitats. Millipedes can enter houses and live in basements or under furniture or anywhere where they can remain hidden. Here, they can live for months as long as they are able to find food. They are also found in the soil where they live on other insects for months.
Why do centipedes and millipedes have so many legs? Unlike many insects, having many legs has not proven to be a handicap for centipedes, and their evolutionary process reflects this. Since their bodies are made of segments, more segments mean more legs. More segments also mean more flexibility and easier movement, so maybe having many legs is actually an advantage.
Are centipedes and millipedes poisonous? Though both centipedes and millipedes contain toxic chemicals, neither one is fatal for humans and do not carry diseases. However, these chemicals can result in painful burns, so it is better to avoid them.
Are centipedes and millipedes worms? Centipedes and millipedes are myriapods. They have exoskeletons and have legs. Worms have long, slender soft bodies and no limbs, so centipedes and millipedes are not worms.