Centipedes are predatory arthropods belonging to the class Chilopoda, part of the subphylum Myriapoda, or “many-footed” creatures. These elongated, segmented animals are found worldwide in various terrestrial habitats, often hiding beneath rocks or logs to maintain required moisture. The common name “centipede” comes from the Latin roots centi (hundred) and pes (foot), leading many to assume the creature possesses exactly 100 legs. However, this name is misleading regarding their actual anatomy.
The Actual Number of Legs
Despite the popular misconception suggested by their name, no known species of centipede possesses exactly 100 legs. The number of legs depends entirely on the number of body segments, which varies between species. Centipedes have a minimum of 15 pairs of legs (30 legs total), seen in common species like the house centipede (Scutigera coleoptrata). Some long, slender soil centipedes (order Geophilomorpha) can have up to 191 pairs of legs, totaling 382 appendages. Centipedes always have an odd number of leg pairs. This means they cannot have 50 pairs, which would equal 100 legs, a result of their specific embryonic development sequence.
Segment Anatomy and Movement
The body of a centipede is a series of repeating segments, with one pair of legs attached to each segment. This consistent arrangement is a defining feature of the class Chilopoda, and the number of these segments determines the animal’s overall leg count. The number of segments can vary even within species, especially in the Geophilomorpha order, where the count may differ between males and females.
This structure allows the centipede to move quickly across the ground in pursuit of prey. To avoid tangled limbs, the legs become progressively longer toward the posterior end of the body. This differential leg length ensures that each footfall clears the path of the leg behind it, allowing for smooth, rapid locomotion.
The Specialized Front Legs
The first body segment behind the head features a pair of appendages called forcipules. These are structurally modified legs, not used for walking, that are unique to centipedes. These pincer-like claws are used exclusively for capturing and subduing prey.
The forcipules are connected to venom glands and act as a delivery system for injecting paralytic toxins into small animals like insects and spiders. The venom is delivered through a duct that opens at the tip of the sharp, curved claw. While this venom is effective for hunting, a bite to a human is typically not medically serious, though it can cause localized pain, redness, and swelling.
Centipedes Versus Millipedes
The confusion between centipedes and millipedes is common, but their anatomical differences reflect distinct lifestyles. The clearest distinction is the number of legs per body segment: centipedes have a single pair of legs per segment, while millipedes have two pairs of legs per segment. This feature gives the millipede class its scientific name, Diplopoda, meaning “double foot.”
Centipedes have a flattened, compressed body that facilitates their speed and predatory nature. Conversely, millipedes possess a more rounded, cylindrical body that is rigid and better suited for burrowing through soil and leaf litter. Centipedes are active, carnivorous hunters, whereas millipedes are slow-moving detritivores, meaning they feed on decaying organic matter.