The common name for the arthropod known as the millipede suggests an impossibly high number of limbs, translating directly from the Latin words mille and pes to mean “thousand feet.” This widely accepted moniker creates a massive misconception regarding their actual anatomy. While these invertebrates are certainly multi-legged, the vast majority of species do not possess 1,000 legs. Millipedes are members of the class Diplopoda.
The True Leg Count of Millipedes
The vast majority of millipede species possess a leg count ranging from approximately 80 to 400 legs. This number varies significantly based on the species, gender, and age of the individual, as they gain segments and legs with each molt throughout their lives.
The reason for their dense arrangement of limbs is a unique anatomical feature called a diplosegment, the defining trait of the class Diplopoda. A diplosegment is a body section formed by the fusion of two embryonic segments, resulting in a single segment carrying two pairs of legs. Therefore, most of the millipede’s trunk segments have four legs attached, not just two like other arthropods. This double-legged structure gives the animal the appearance of having a continuous, dense line of movement. The first few segments behind the head are exceptions, typically bearing only one pair of legs or being legless.
The Difference Between Millipedes and Centipedes
The common confusion regarding leg count often stems from mixing up millipedes with their close relatives, the centipedes, which belong to the class Chilopoda. Millipedes are characterized by two pairs of legs per segment, while centipedes have only one pair of legs per body segment.
This structural difference dictates their roles and movements in the environment. Millipedes are generally slow-moving, using their numerous legs to propel their cylindrical bodies forward in a smooth, wave-like motion suited for burrowing into soil and leaf litter. In contrast, centipedes have a flatter body shape and longer legs that project out to the sides, allowing them to move quickly and deliberately.
The two groups also have distinct ecological functions and defense mechanisms. Millipedes are primarily detritivores, feeding on decaying organic matter, making them beneficial for decomposition and soil nutrient cycling. Centipedes are carnivores that actively hunt and capture prey using a pair of modified front legs called maxillipeds, which inject venom. When threatened, a millipede typically curls into a tight spiral to protect its soft underside, while a centipede often attempts to flee quickly or use its venomous fangs.
The Origin of the “Thousand Feet” Name
The name “millipede” originates from a time when zoological classification focused more on striking visual characteristics than on precise anatomical counts. The Latin root mille for “thousand” and pes for “foot” was a vast overestimation, likely inspired by the sheer density and rhythm of the animal’s leg movements. For centuries, no known species actually reached the 1,000-leg mark.
The previous record-holder, the species Illacme plenipes from California, possessed up to 750 legs, still falling short of the implied thousand. This long-standing misconception was finally broken with the discovery of the species Eumillipes persephone in Western Australia. This subterranean species, found deep underground in a mineral exploration drill hole, holds the current record for the most legs of any known animal.
A female Eumillipes persephone specimen was documented with an astonishing 1,306 legs, making it the first millipede species to truly live up to the thousand-foot name. The genus name Eumillipes was chosen to mean “true thousand feet,” acknowledging its unique status. This eyeless, elongated creature demonstrates an extreme adaptation to its dark, underground environment.