Centipedes are animals that hunt other animals. They belong to the class Chilopoda, which is part of the group Myriapoda. This group also includes millipedes and other animals with many legs. Centipedes have long, segmented bodies, with one pair of legs on each body segment. All centipedes have venom and can sting. They use special legs called forcipules or toxicognaths to inject their venom. These legs are not fangs but are modified legs. Even though their name means "hundred legs," no centipede has exactly 100 legs. The number of leg pairs varies, ranging from 15 to 191 pairs.

Centipedes are generalist carnivores, meaning they eat a wide variety of prey they can overpower. They live in many places around the world, including tropical rainforests and deserts. However, they need damp areas because they do not have the waxy layer that helps insects and spiders keep water inside their bodies. This causes them to lose water quickly. To stay safe from drying out, centipedes avoid sunlight by staying in shaded areas or being active at night.

Description

Centipedes have a rounded or flat head with two antennae at the front. They have two long mandibles and two pairs of maxillae. The first pair of maxillae form the lower lip and have short palps. The first pair of limbs extend forward over the mouth. These limbs, called forcipules, end in sharp claws and contain venom glands that help the centipede kill or paralyze its prey.

Centipedes vary in size. Small species, like lithobiomorphs and geophilomorphs, are only a few millimeters long. The largest species, scolopendromorphs, can grow up to 30 cm (12 inches) in length.

Many centipede species do not have eyes. Some have a few ocelli, which may cluster to form simple compound eyes. These eyes can only detect light and darkness, not detailed images. In some species, the first pair of legs acts as sensory organs, similar to antennae, but they point backward. Some centipedes have a special group of sensory cells called the organ of Tömösváry, located near the base of the antennae. These structures likely help sense vibrations and may help detect sounds.

Forcipules are unique to centipedes. They are modified versions of the first pair of legs, forming a pincer-like structure behind the head. Although not used for eating, forcipules inject venom and grip prey. Venom glands connect from the head to the tip of each forcipule through a tube.

Behind the head, the body has at least 15 segments. Most segments have one pair of legs. The first segment has the maxillipeds, which extend forward. The last two segments are small and legless. Each pair of legs is slightly longer than the previous one, preventing them from overlapping and reducing the chance of tripping. The last pair of legs may be twice as long as the first. The final body segment has a telson and contains the openings for reproductive organs.

Centipedes use their antennae to find prey. Their digestive system is a simple tube with digestive glands attached to the mouthparts. Like insects, centipedes breathe through a tracheal system, which includes spiracles on each body segment. These spiracles lead to tracheae and tracheoles that carry oxygen to the body, except in Scutigeromorpha, where oxygen is delivered by a pigment called hemocyanin. Some centipedes can close their spiracles, and others have a waterproof covering to survive in dry environments. Waste is removed through a pair of malpighian tubules.

The first pair of legs becomes forcipules, while the back legs are modified into "ultimate legs," also called anal legs, caudal legs, or terminal legs. These legs are not used for walking. They may be thin, thick, or pincer-like and are often different between males and females. They may help in mating, sensing, or defense. Some species use them to grab prey, defend against predators, or hang from objects.

Centipedes in the genus Alipes rub their leaf-like ultimate legs together to make noise and scare predators. The species Rhysida immarginata togoensis makes a faint creaking sound when it moves its ultimate legs.

Centipedes and millipedes are both myriapods with long, segmented bodies, many legs, one pair of antennae, and postantennal organs. Centipedes have one pair of legs per segment, while millipedes have two. Centipede heads have long, threadlike antennae, small mandibles, two pairs of maxillae, and large venom claws. Millipede heads have short, bent antennae, strong mandibles, and one pair of maxillae fused into a lip.

Life cycle

Centipede reproduction does not involve mating. Instead, males leave behind a sperm packet, which females collect. In temperate regions, females lay eggs during spring and summer. Some species can reproduce without needing a male. Female centipedes care for their eggs and young by wrapping their bodies around them and cleaning them, likely to remove fungi and bacteria.

Centipedes live longer than insects. For example, the European Lithobius forficatus may live 5 to 6 years, and the Scolopendra subspinipes can live more than 10 years. These centipedes have few eggs, long development times, and slow growth, which scientists describe as "K-selected" traits.

Centipedes grow legs at different stages of their lives. In some groups, like Lithobiomorpha, Scutigeromorpha, and Craterostigmomorpha, development is anamorphic: they grow more body segments and legs between molts. For example, the house centipede, Scutigera coleoptrata, hatches with four leg pairs and gains more legs in each molt until reaching 15 pairs as an adult. Stages with fewer than 15 leg pairs are called larval stadia (about five stages). After reaching 15 leg pairs, they grow other adult features, such as reproductive organs and sensory structures, in postlarval stadia (about five stages). All mature Lithobiomorpha centipedes have 15 leg-bearing segments. The Craterostigmomorpha group only adds one set of segments during development, starting with 12 leg pairs and ending with 15.

The Epimorpha group, which includes Geophilomorpha and Scolopendromorpha, is epimorphic: all legs are present at birth, and no new legs grow after hatching. This group includes the longest centipedes. In Geophilomorpha, the number of leg-bearing segments varies by species and often depends on geography, with females typically having more legs than males. The number of leg pairs differs among species (usually 21 or 23 in Scolopendromorpha; 27 to 191 in Geophilomorpha), but it is always an odd number, so centipedes never have exactly 100 legs or 100 pairs, despite their common name.

Centipede body segments form in two stages. First, the head develops a fixed, odd number of segments, guided by Hox genes, as in all arthropods. Second, segments are added at the tail (posterior) end through a process involving prepattern units—double segments that split into two. This process is controlled by an oscillator clock, using the Notch signaling pathway. These segments are similar to legs in other arthropods, like trilobites. If the Notch clock runs faster, as it does in snakes, more legs could form.

Ecology

Centipedes are mostly generalist predators, meaning they eat a wide variety of prey. Common prey includes earthworms, fly larvae, springtails, and other centipedes. Centipedes are meat-eaters; studies of their stomach contents show that plants are not a major part of their diet. However, they may eat plants if they are very hungry in laboratory settings.

Some centipedes, especially those in the group Scolopendromorpha, such as species from the genera Scolopendra and Ethmostigmus, can hunt large prey, including big insects, small animals, and even vertebrates larger than themselves. For example, Scolopendra gigantea, the Amazonian giant centipede, hunts tarantulas, scorpions, lizards, frogs, birds, mice, snakes, and bats, sometimes catching them midair. Three species—Scolopendra cataracta, S. paradoxa, and S. alcyona—are amphibious, meaning they can live in water and on land, and likely hunt aquatic or land-dwelling invertebrates.

Many animals eat centipedes, including mongooses, mice, salamanders, beetles, and certain snakes. Centipedes are an important food source for many species, and some animals, like the African ant Amblyopone pluto, rely almost entirely on centipedes for food. The South African Cape black-headed snake (Aparallactus capensis) also primarily eats centipedes.

Some centipedes, including those in the groups geophilomorph, lithobiomorph, and scolopendromorph, produce sticky, toxic secretions to protect themselves. These secretions can repel or trap predators. Secretions from Scolopendra species contain hydrogen cyanide. The secretions of Geophilus vittatus, a geophilomorph centipede, are sticky, smelly, and also contain hydrogen cyanide.

The giant desert centipede (Scolopendra polymorpha) from Arizona has a black head and tail with an orange body. This bright color pattern may be a warning signal to predators, showing that the centipede is dangerous. Many centipedes also raise and spread their back legs to display spines as a defensive posture.

Centipedes lack the waterproof outer layer found in other arthropods, making them more likely to lose water through evaporation. To avoid drying out, they are usually found in areas with high humidity and are often active at night.

Centipedes live in many environments, including soil, leaf litter, tropical rainforests, deserts, and caves. Some geophilomorph centipedes live in coastal areas and eat barnacles.

According to the IUCN Red List, one centipede species is vulnerable, six are endangered, and three are critically endangered. For example, the Serpent Island centipede (Scolopendra abnormis) is vulnerable, and the Turk's earth centipede (Nothogeophilus turki) and the Seychelles long-legged centipede (Seychellonema gerlachi) are both endangered.

Evolution

Centipede fossils have been found dating back to 430 million years ago. This time period is known as the Late Silurian (Crussolum), though centipede fossils are rare during the Paleozoic era. The Devonian Panther Mountain Formation contains two centipede species: one is a scutigeromorph (Crussolum), and the other is Devonobius, which belongs to the extinct group Devonobiomorpha. Another Devonian site, the Rhynie chert, also has Crussolum fossils and possible scutigeromorph head material. Rhyniognatha, once considered the oldest insect fossil, is also found in the Rhynie chert. Three centipede species—Latzelia (a scutigeromorph) and Mazoscolopendra and Palenarthrus (both scolopendromorphs)—have been identified in the Carboniferous Mazon Creek fossil beds, which are 309–307 million years old. More centipede species appear in the Mesozoic era, including scolopendromorphs and scutigeromorphs during the Cretaceous period.

A cladogram from 2019 shows the position of centipedes (Chilopoda) within the arthropods. This group includes horseshoe crabs and spiders, millipedes and related species, and crustaceans and insects. Within the myriapods, centipedes are thought to be the first extant class to branch from the last common ancestor. The five centipede orders are Craterostigmomorpha, Geophilomorpha, Lithobiomorpha, Scolopendromorpha, and Scutigeromorpha. These orders are grouped into the clade Chilopoda by shared traits:

• The first postcephalic appendage is modified into venom claws.
• The embryonic cuticle on the second maxilliped has an egg tooth.
• The trochanter-prefemur joint is fixed.
• A spiral ridge appears on the spermatozoon’s nucleus.

Centipedes are divided into two clades: Notostigmophora (including Scutigeromorpha) and Pleurostigmophora (including the other four orders). Traits that distinguish Pleurostigmomorpha from Notostigmomorpha include:

• Spiracles are located on the sides of the body (dorsally in Notostigmomorpha).
• Spiracles are deep, complex, and always present in pairs.
• The head is somewhat flatter.
• Centipedes may develop through anamorphosis or epimorphosis.

Previously, centipedes were thought to split into Anamorpha (Lithobiomorpha and Scutigeromorpha) and Epimorpha (Geophilomorpha and Scolopendromorpha), based on developmental modes. The position of Craterostigmomorpha was unclear. Recent studies using molecular and morphological data support this classification. Epimorpha remains a group within Pleurostigmophora, but Anamorpha is not a single group.

All centipedes are venomous. For the first 50 million years of their evolutionary history, centipede venoms likely contained a simple mix of about four components. Specialized venom types developed after the five recognized orders formed. Venom evolution involved horizontal gene transfer, where genes moved between centipedes and organisms like bacteria, fungi, and oomycetes.

Interaction with humans

In China, some large centipedes are eaten as food. They are often cooked by skewering and grilling or deep frying. These centipedes can be found at street vendor stalls in big cities, such as Donghuamen and Wangfujing markets in Beijing.

To make centipede vodka, large centipedes are soaked in alcohol.

Some centipede species can harm humans because of their bites. A bite from a large centipede is usually very painful and may cause swelling, chills, fever, and weakness. While such bites are unlikely to be deadly for adults, they can be dangerous for small children or people who are allergic to bee stings. The venom from larger centipedes may cause a severe allergic reaction called anaphylactic shock in these individuals. Smaller centipedes typically cannot pierce human skin.

Even small centipedes that cannot bite humans are sometimes seen as scary. This is because they have many legs that move together and often quickly dart toward a person's feet from the dark. A 19th-century Tibetan poet told his fellow Buddhists, "if you enjoy frightening others, you will be reborn as a centipede."