Centipedes are predatory arthropods belonging to the class Chilopoda, characterized by their segmented bodies and fast movements. The name centipede, derived from Latin, means “hundred-footed,” a label that has led to a common misunderstanding about the animal’s actual anatomy. These creatures are widespread across terrestrial habitats, where they function as active hunters, relying on speed and venom to capture prey.
The Actual Number of Centipede Legs
Despite the popular name, no known species of centipede possesses exactly 100 legs. The total number of legs is determined by the number of body segments, and this count varies significantly among the different orders of centipedes. Centipedes typically have a range of 15 to 191 pairs of legs, which translates to a total number between 30 and 382 individual legs. For instance, common house centipedes have 15 pairs of legs.
A biological rule for all centipedes is that the total number of leg pairs is always an odd number. This means a centipede will never have an even number of leg pairs, such as 50 pairs, which would result in exactly 100 legs. This odd-number pattern is a result of their unique embryonic development, where segments are added sequentially, ensuring the final leg-bearing count remains uneven.
Structure and Locomotion
Centipedes are characterized by having exactly one pair of legs attached to each body segment. For most of the body, these legs are primarily used for rapid locomotion, enabling the centipede to move quickly to catch prey or escape danger. The legs of many species are progressively longer the farther they are from the head, a structural feature that helps prevent the legs from tangling during their fast, coordinated movement. The final pair of legs, known as ultimate legs, are often modified and do not contribute to walking, sometimes serving a sensory role.
The first pair of legs behind the head is highly modified into pincer-like appendages called forcipules or toxicognaths. These forcipules are the animal’s primary weapon, featuring a sharp, claw-like tip connected to venom glands. Centipedes use these specialized appendages to quickly inject venom into prey, which includes insects and other small creatures.
Centipedes Versus Millipedes
Centipedes are often confused with millipedes, though the two belong to different classes within the subphylum Myriapoda. The most reliable way to tell them apart is by looking at the number of legs per body segment. Millipedes generally have two pairs of legs on each segment, giving them a dense, “double-footed” appearance, while centipedes maintain only one pair per segment. Centipede legs extend out from the side of a flatter body, and millipede legs point downward from a more rounded, cylindrical body.
These structural differences reflect their different lifestyles and diets. Centipedes are active, fast-moving carnivores that hunt and kill their food using venom. Millipedes are slower-moving detritivores that primarily feed on decaying plant matter and fungi. When threatened, a centipede typically flees quickly or uses its venomous forcipules for defense, whereas a millipede’s primary defense is to coil up and release irritating fluids.