Millipedes, whose common name derives from Latin for “thousand feet,” are arthropods often associated with an extraordinary number of legs. However, this is largely a misconception. These creatures, belonging to the class Diplopoda, exhibit a wide range of leg counts.
The Truth About Millipede Legs
The scientific name Diplopoda refers to their defining characteristic: two pairs of legs on most body segments. These segments are known as diplosegments. Each diplosegment forms from the fusion of two embryonic segments.
Millipedes do not hatch with their full complement of legs; they gain more segments and pairs of legs each time they molt their exoskeleton. The number of legs varies significantly among species. While some common species have fewer than 100 legs, the range typically falls between 24 and over 700 legs.
Why Millipedes Have So Many Legs
The multitude of legs on a millipede is a specialized adaptation for movement. Their numerous, short limbs contribute to a powerful, wave-like motion, known as a metachronal gait, which allows for efficient forward propulsion. This coordinated movement provides significant thrust, crucial for their primary activity: burrowing.
Millipedes use their heads to push through soil and leaf litter, with their many legs providing the necessary power and traction to move through dense substrates. This adaptation allows them to navigate tight spaces and access decaying plant matter, their main food source. When threatened, their cylindrical body enables them to curl into a tight coil, protecting their softer underside from potential harm.
Millipedes Compared to Centipedes
Millipedes are often confused with centipedes, but these two arthropod groups have distinct differences. Centipedes typically have one pair of legs per body segment, in contrast to the millipede’s two pairs. This difference in leg arrangement is reflected in their body shapes; millipedes generally have a more rounded or cylindrical body, while centipedes are often flattened.
Their lifestyles also diverge significantly. Millipedes are primarily detritivores, feeding on decaying plant material, and are generally slow-moving. Centipedes, conversely, are fast-moving predators that use venomous fangs to capture prey. Millipedes typically defend themselves by coiling or secreting defensive chemicals, rather than biting.
Millipede Leg Records
For many years, no millipede species was known to truly live up to the “thousand feet” implied by its name. The record for the highest number of legs was previously held by Illacme plenipes, a species from California, which could possess up to 750 legs. However, a discovery in 2020 in Western Australia changed this understanding.
Scientists unearthed a new species, Eumillipes persephone, which holds the current world record for the most legs of any known animal. One female specimen of this species was found to have 1,306 legs. This pale, eyeless creature was discovered 60 meters underground, showcasing adaptations to its subterranean habitat.