15 Most Fascinating Facts About Millipedes

The back of a millipede is protected by hard exoskeletal segments called tergites, while the underside is soft and vulnerable. Millipedes are not fast movers, making it difficult for them to escape predators that are always on the lookout. Instead, when a millipede senses danger, it curls its body into a tight spiral to protect its softer underside.

Due to their slow movement and lack of biting or stinging ability, the primary defense mechanism of millipedes is to roll up into a spiral, using their hard exoskeleton on the back to shield their legs and other delicate body parts. Although millipedes don’t bite in defense, many species can release foul-smelling chemicals to deter predators.

In some cases, these chemicals can cause burning sensations, pain, or temporary discoloration of the predator’s skin. Large tropical millipedes can even spray toxic compounds into the eyes of their enemies.

Many millipedes possess a secondary defense mechanism that involves secreting toxic substances or hydrogen cyanide gases through tiny pores along their bodies. These toxins are caustic and can corrode the exoskeletons of ants and other predatory insects, as well as cause burns to the skin and eyes of larger predators.

Some animals, like Capuchin monkeys, have been observed rubbing millipedes on themselves to coat their skin with the millipede's toxic secretions, helping protect them from mosquito bites. At least one species, Polyxenus fasciculatus, has hard bristles to fend off ants.

For humans, the venom of millipedes is generally not dangerous. It typically causes only mild effects, such as temporary skin discoloration. However, some stronger toxins may lead to pain, swelling, redness, blisters, eczema, and cracked skin. If the venom enters the eyes, it can cause eye pain or more severe consequences, like conjunctivitis or corneal inflammation. First aid involves washing the affected area with water to reduce the effects of the venom.

Unfortunately for the male millipede, the female often perceives his courting gestures as a threat. The female will curl up tightly, preventing the male from releasing his sperm. So what does the male do? He needs a plan to literally loosen her up.

The male climbs onto the female's back and gently massages her with his hundreds of legs, trying to convince her to relax. In some species, the male may even produce loud sounds to soothe his mate. Other males use sex pheromones to capture the female’s interest.

Male millipedes can be distinguished from females by one or two pairs of modified legs that serve as copulatory organs. These legs are typically located on the seventh body segment and are used to transfer sperm into the female during mating. Some species of millipedes are parthenogenetic, meaning they reproduce without males, with very few or no males in the population.

If the female accepts the male’s courtship, he will then use his specially modified legs to transfer sperm or his sperm sacs to her. The sperm is received in her genital opening, just behind the second pair of legs. In most millipede species, the copulatory legs replace the regular legs on the seventh body segment. You can determine whether a millipede is male or female by examining this segment. A male will have shorter legs in this area, or no legs at all.

Each brood of millipedes lays around 10-300 eggs, depending on the species, and the eggs are fertilized immediately upon laying, using sperm stored in the female's genitalia. While many millipede species leave their eggs on damp ground or organic debris, others create protective nests for the eggs using dried feces.

Female millipedes dig and turn the soil to create a nest, where they place their eggs. In many cases, they use their own feces to form a protective barrier around the eggs. In some species, the millipedes may push soil with their heads to form the nest. They place around 100 eggs, or more, in the nest, and the young millipedes emerge in about a month.

While most arthropods have short lifespans, millipedes are far from ordinary in this regard.

They live surprisingly long lives, following the motto 'slow and steady.' As you can observe, millipedes are never in a hurry. They lead relatively uneventful and sluggish lives. Their passive defense strategies and camouflage abilities help them outlive many of their arthropod relatives.

These many-legged creatures breathe through two pairs of spiracles on each body segment. Each spiracle connects to an internal sac and is linked to a system of air tubes. The heart runs along the body’s length, with a main artery extending toward the head. The excretory system consists of two pairs of Malpighian tubules located in the midgut.

Millipedes thrive in groups in damp environments, such as rotting leaves or piles of gravel.

Millipedes are considered one of the first animals to have moved from water to land during the Silurian period. Fossil evidence shows that they were among the earliest creatures to breathe air and make the transition from aquatic to terrestrial life. Pneumodesmus newmani, a fossil found in Siltstone, Scotland, dates back 428 million years and is the oldest known millipede fossil, with spiracles present on its body.

These early millipedes likely fed on mosses and primitive vascular plants. The oldest known millipede, Pneumodesmus newmani, lived 428 million years ago and was only about 1 centimeter (0.39 inches) long. During the early Carboniferous period (340 to 280 million years ago), Arthropleura, a millipede relative, grew to be the largest known invertebrate ever to exist, reaching lengths of up to 2.6 meters (8 feet 6 inches).

The head of a millipede has a pair of sensory organs called Tömösváry organs. These are located at the front and sides of the antennae, arranged in an oval ring at the base. These organs are believed to detect environmental humidity and possibly chemicals. Millipedes have compound eyes, which consist of multiple flat individual eyes clustered together at the front and sides of the head. In some species, especially those that live in burrows like Causeyella, the eyes degenerate as they mature.

The head of a millipede is usually round on top and flattened underneath, with large mandibles for chewing. The body is cylindrical or flattened, covered with plates made of chitin on the back, with one plate on each side and two or three plates on the underside.

In many species, these plates fuse to form a ring-like structure. These plates are hard and contain calcium salts in their chemical composition. Because millipedes lack a waxy waterproof coating, they can easily lose water through their skin, so they spend most of their time in moist soil or humid environments.

Most millipedes feed on plant matter, particularly decaying leaves, parts of plants, or organic material mixed into the soil. Some species are omnivorous or carnivorous, preying on smaller arthropods like insects, centipedes, or earthworms. A few millipedes have needle-like mouthparts, allowing them to pierce and suck the juices from fruits.

Millipedes have a simple digestive tract, aided by two salivary glands that help break down food. Many species use their saliva to moisten and soften food before consuming it.

As detritivores, millipedes primarily consume decomposing plant material, like dry leaves and other plant debris. They use their saliva to soften the food, then chew it with their mandibles. Occasionally, millipedes may harm crops, especially young seedlings in greenhouses, by feeding on newly sprouted plants. Signs of damage include peeling outer layers of young plants and irregular wounds at the tips.

Scientists accidentally discovered a fossil of an ancient millipede over 2.6 meters long, living around 326 million years ago.

The fossil belongs to the millipede genus Arthropleura, which lived during the Carboniferous period, approximately 326 million years ago, long before dinosaurs appeared. When it was alive, this creature is estimated to have been 55 cm wide and 2.63 meters long, weighing 50 kg. This made it the largest known invertebrate of all time, surpassing even ancient sea scorpions.

The fossil is set to be displayed at the Sedgwick Museum in Cambridge, UK, in 2022. This is only the third Arthropleura fossil ever found, with the previous two specimens found in Germany being much smaller than the new discovery.

To achieve such a size, this ancient millipede must have had a highly nutritious diet. At that time, Britain was located at the equator, and the region's ancient invertebrates and amphibians likely thrived on plants growing in rivers and waterways.

Researchers believe the fossil might be a cast of exoskeletons that were shed during molting, filled with sand, which helped preserve it to this day.

Millipedes can be a nuisance, especially when they damage plants like orchids or roses, or cause an unpleasant odor. It’s important to get rid of them as soon as possible. Here are some natural, chemical-free methods to control them:

• Regularly clean your garden: Areas with tall grass or flower pots are ideal hiding spots for millipedes. To keep them at bay, make sure to clean these spaces regularly. Specific steps include:
  • Remove tall, damp grass as millipedes cannot thrive in dry, airy places.
  • Water your garden in the morning instead of the evening since millipedes are more active at night.
• Remove or relocate hiding spots: Cleaning up areas where millipedes can hide, like leaf piles, will encourage them to leave. Without a hiding spot, millipedes won’t invade your living spaces.
  • Remove unnecessary debris and store it away from your house and garden.
  • Eliminate decaying organic matter to remove their food source and help reduce their population.
  • Keep mulch layers between 7.5 to 10 cm thick, and place them at least 60 to 90 cm from your home’s foundation.
  • Trim bushes in spring to improve air circulation and keep the environment dry.
• Avoid rainwater pooling near your house: If you have drainage near your home, make sure it doesn't lead water directly into your living space. Millipedes are attracted to damp environments, so directing rainwater away from your home can prevent them from entering.
• Seal cracks and gaps: Repair cracks in your foundation or walls to prevent millipedes from entering your home.
• Sweep them out: A simple solution is to use a vacuum cleaner or broom to remove millipedes from your home.
• Reduce indoor humidity: Since millipedes thrive in moist environments, reduce indoor humidity using a dehumidifier to make your home less inviting.
• Mix ash into the soil: To discourage millipedes outside, mix dry wood ash into the soil around your home, especially in damp areas. The ash will dry out the soil, making it an unsuitable breeding ground for them.

Millipedes have several defense mechanisms, but biting or stinging is not one of them (they have poor vision, and some species even lack eyes, relying primarily on their antennae for navigation). The most effective defense for a millipede is to curl up and release a chemical substance to ward off predators. Although the chemicals secreted by millipedes vary, the amount released is typically so small that it is not harmful to humans. In fact, research shows that in some tropical regions, monkeys use the chemicals produced by millipedes to repel mosquitoes.

In contrast, centipedes can bite with their sharp pincers, which inject venom. While the bite may be painful, it is generally not dangerous to humans.

Looking at their legs, centipedes have legs that spread outward, while millipedes' legs point downward. Centipedes have one pair of legs per body segment, whereas millipedes have two pairs. If you're not keen to get too close to confirm this, you can observe the creature's behavior. If it moves quickly, it's a centipede. If it curls up, it's a millipede.

Currently, millipede species are divided into 15 orders and 3 subclasses. The Penicillata subclass includes 160 species with uncalcareous exoskeletons, covered by tough bristles. Other millipedes, by stricter definition, belong to the Chilognatha group.

The Pentazonia subclass includes rock millipedes with very short bodies, which, when curled, resemble balls. The Helminthomorpha subclass includes most of the known millipede species.

The evolutionary classification of millipedes, from the most primitive to the most advanced species, is as follows:

• Primitive genus Eileticus (fossils)
• Subclass Penicillata
• Subclass Arthropleuridea
• Subclass Zosterogrammida
• Subclass Pentazonia
• Subclass Archipolypoda
• Subclass Helminthomorpha

In English and several other languages, millipedes are often referred to as 'milipede' (derived from the Latin words mille, meaning 'thousand', and pes, meaning 'foot'). However, no known millipede species has ever been found to have 1000 legs. Most millipedes have fewer than 100 legs, with the species holding the record having only 750 legs.

Millipedes, or simply 'thousand-leggers', belong to the class Diplopoda within the subphylum Myriapoda. They are called 'millipedes' because each body segment typically carries two pairs of legs, except for the first segment behind the head, which lacks legs. This phenomenon occurs because each segment of a millipede is the result of two fused body segments. Most millipedes have cylindrical, tube-like bodies, though some species are flattened along the belly and back. Millipedes in the Oniscomorpha infraorder are particularly short and curl up into a ball, resembling pill bugs (Armadillidiidae).

The term 'millipede' comes from their habit of curling up into a ball, resembling a rolled-up mat. In some regions, they are also known as 'hundred-leggers'.

If you closely examine the image of the millipede above, you'll notice that nearly every body segment has two pairs of legs. The first segment, right after the head, lacks legs, and segments two through four usually have only one pair of legs. However, from the fifth segment onward, each segment has two perfectly symmetrical pairs of legs. In contrast, centipedes have only one pair of legs per segment, which is an interesting and clear distinction between millipedes and centipedes.

Unlike centipedes or similar creatures, millipedes have two pairs of legs on each segment (hence their name 'Diplopoda', meaning 'double-foot'). This is because each 'segment' of a millipede is actually formed by two fused segments during the early stages of development, which is why they are sometimes called 'double segments.' Some of the initial segments, directly behind the head, do not follow this pattern: the first segment is legless and referred to as the 'collar segment,' and segments two through four each have only one pair of legs.

In some millipede species, a few of the final segments also lack legs, with the very last segment featuring a specialized structure called a 'telson.'

Millipedes undergo an incomplete metamorphosis, consisting of three stages: egg, larva, and adult. When they first hatch from the egg, they only have three pairs of legs on three body segments.

To reach their adult form, the larvae must molt several times. Each molt causes the millipede's body to grow longer and develop additional pairs of legs. After each molt, their protective exoskeleton is shed, and they seek refuge in safe places to avoid predators.

Millipede eggs hatch within a few weeks, and the newly hatched millipedes usually have only three pairs of legs, followed by four legless segments. As they grow, the number of segments and legs increases with each molt. Some species molt only in specially prepared burrows, which also serve as shelters during dry seasons. After molting, most species consume their old exoskeleton. Millipedes typically live for 1 to 10 years, depending on the species.