Millipedes and centipedes are common multi-legged arthropods that frequently cause confusion due to their similar appearances. While they share a general body plan, distinct characteristics differentiate these invertebrates.
Telling Them Apart Visually
One of the most reliable ways to distinguish between a millipede and a centipede is by observing their legs per body segment. Millipedes (Class Diplopoda) possess two pairs of short legs on most of their body segments. In contrast, centipedes (Class Chilopoda) have only one pair of legs per body segment, which typically extend outwards and are more easily visible. This difference in leg arrangement also influences their overall body shape; millipedes generally have a more rounded, cylindrical body, while centipedes are typically flattened and elongated.
Their antennae also offer a visual clue for identification. Millipedes feature shorter, stumpy antennae, which they use for sensing their immediate surroundings. Centipedes, on the other hand, have longer, more slender antennae. The way they move provides another clear distinction; millipedes typically move slowly with a wave-like motion of their many legs, often appearing to glide across surfaces. Centipedes are known for their swift, darting movements.
How They Live and What They Eat
The dietary habits of millipedes and centipedes represent a fundamental difference in their ecological roles. Centipedes are carnivorous predators, actively hunting and consuming smaller invertebrates, including insects and spiders. They use specialized, venomous appendages called forcipules, located just behind their head, to capture and paralyze their prey. Millipedes, conversely, are detritivores, meaning they feed on decaying organic matter such as dead leaves, rotting wood, and other decomposing plant material.
Their defense mechanisms also differ significantly due to their distinct lifestyles. When threatened, a millipede often curls its body into a tight coil, protecting its softer underside with its hardened exoskeleton. Many species can also secrete defensive fluids, which may contain irritating or foul-smelling chemicals to deter predators. Centipedes rely on their speed to escape threats, but if cornered, they can deliver a venomous bite using their forcipules for self-defense.
Where They Are Found and Their Impact
Both millipedes and centipedes prefer environments that are moist and dark, commonly found under rocks, logs, leaf litter, and within soil. Millipedes are particularly prevalent in areas rich with decaying plant matter, such as compost piles and garden beds, where their food sources are abundant. Centipedes also inhabit similar damp outdoor spaces but are more likely to venture indoors, seeking shelter in basements, bathrooms, or other humid areas of a home.
Regarding human interaction, millipedes are generally considered harmless. Although their defensive secretions can cause minor skin irritation in sensitive individuals if handled, they do not bite and pose no significant threat. Centipedes, however, can deliver a painful bite if provoked, using their venomous fangs. While their bites are rarely medically serious for humans, they can result in localized pain, swelling, and redness comparable to a bee sting. From an ecological perspective, millipedes play a beneficial role as decomposers, contributing to nutrient cycling in soil, while centipedes serve as natural pest controllers by preying on other arthropods.