Why do the millipede curl up when touched?


Millipedes are fascinating creatures that belong to the class Diplopoda. These segmented arthropods are known for their long, cylindrical bodies and numerous legs. When disturbed, millipedes have a unique behavior of rolling into a tight ball, which has puzzled scientists and nature enthusiasts alike. In this article, we will explore the science behind this curious behavior of millipedes.

What is a millipede?

Millipedes are arthropods that belong to the class Diplopoda. They are characterized by their long, cylindrical bodies, numerous legs, and segmented exoskeleton. Millipedes are found all over the world, and there are approximately 12,000 known species. They primarily live in soil or leaf litter, where they feed on decaying plant matter. Although they are often confused with centipedes, millipedes are distinct in that they have two pairs of legs per body segment, while centipedes have one pair of legs per segment.

Anatomy of a millipede

The body of a millipede is divided into numerous segments, with each segment bearing two pairs of legs. The legs of millipedes are not attached to the body like those of insects but instead are modified extensions of the body segments. The exoskeleton of millipedes is made up of chitin, a tough, protective protein that also forms the exoskeleton of other arthropods, such as crustaceans and insects.

Why do millipedes curl up?

When threatened, millipedes have a unique behavior of rolling into a tight ball, which is known as curling. This behavior is a defense mechanism that protects millipedes from predators. Curling helps to protect the vulnerable underside of the millipede’s body, which is not covered by the exoskeleton. By curling up, the millipede is able to shield its legs and other appendages, making it harder for predators to attack.

The function of millipede curling

The primary function of millipede curling is to protect the millipede from predators. When a millipede is attacked, it will immediately curl up and remain in this position until the threat has passed. Once the danger has subsided, the millipede will uncurl and continue with its activities. Curling also helps to conserve moisture, which is especially important for millipedes living in dry environments.

The role of millipede defense mechanisms

In addition to curling, millipedes have other defense mechanisms that they use to protect themselves from predators. Some species of millipedes produce toxic or noxious secretions that deter predators from attacking. These secretions may be produced from glands located along the sides of the body, and they can cause irritation or even chemical burns in predators.

When do millipedes curl up?

Millipedes will curl up in response to any perceived threat. This may include predators, such as birds, rodents, or other animals, or even humans who accidentally step on or touch them. Millipedes may also curl up as a response to extreme temperatures or dehydration.

The science behind millipede curling

The exact mechanism by which millipedes are able to curl up is not fully understood. However, it is believed that this behavior is controlled by a combination of muscles and the nervous system. When a millipede curls up, it contracts its muscles to create a tight ball. The nervous system also plays a role in coordinating this behavior and allowing the millipede to sense threats and respond accordingly.

Other defense mechanisms of millipedes

In addition to curling and producing noxious secretions, some species of millipedes also use camouflage as a defense mechanism. They may have coloration or patterns that blend in with their environment, making them harder to spot by predators. Some species of millipedes also have spines or other structures on their exoskeleton that make them harder to swallow.


Millipedes are fascinating creatures that have developed a variety of defense mechanisms to protect themselves from predators. Curling is one of the most unique behaviors of millipedes, and it serves as an effective way to shield their vulnerable underside from attack. While the exact mechanism behind this behavior is not fully understood, scientists continue to study millipedes to better understand their fascinating adaptations.

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