When people inquire about a “bug” with many legs, they often use the term broadly to describe various small invertebrates, not just insects. Centipedes and millipedes are perhaps the most recognized for their numerous limbs.
Unraveling the Multi-Legged Mystery
Centipedes and millipedes belong to the subphylum Myriapoda, meaning “many feet.” These segmented arthropods are an ancient lineage of land-dwelling animals, with a widespread presence across various terrestrial habitats globally.
Despite their shared characteristic of having many legs and a segmented body, centipedes and millipedes possess distinct features. They both have a head and a trunk, along with a single pair of antennae. However, their body structures, locomotion methods, and ecological roles differ significantly.
Centipedes: Predators on Many Legs
Centipedes, classified under Chilopoda, are characterized by their flattened bodies and remarkable speed. They are agile predators, moving swiftly to catch their prey. Each of their numerous body segments bears a single pair of legs, aiding their fast movement.
The number of leg pairs on a centipede varies by species, typically ranging from 15 to 191 pairs, and notably, they always have an odd number of leg pairs. Despite their common name suggesting a hundred legs, no centipede species possesses exactly 100 legs. These creatures are carnivores, actively hunting a variety of small animals including insects, spiders, and sometimes even small vertebrates.
Centipedes subdue their prey using specialized venomous claws called forcipules, located behind their head. These modified legs inject venom to immobilize their victims. Centipedes generally prefer dark, moist environments, often found under rocks, logs, or in leaf litter, and are primarily active during the night to avoid dehydration and hunt.
Millipedes: Nature’s Little Recyclers
Millipedes, belonging to the class Diplopoda, typically have cylindrical bodies. Their movement is generally slower and more undulating, suited for pushing through soil and decaying matter. A distinguishing feature is that most of their apparent body segments possess two pairs of legs, giving them a denser appearance.
While their name means “thousand feet,” the actual number of legs on a millipede varies widely, ranging from as few as 24 to over 1,300 in some rare species, though most have fewer than 100 legs. Millipedes are primarily detritivores, meaning they feed on decaying plant material, such as dead leaves and wood. This diet makes them important contributors to nutrient cycling and soil health within their ecosystems.
Millipedes employ different defense mechanisms than centipedes. When threatened, they often coil their bodies into a tight spiral. Many species also release foul-smelling or irritating chemicals from glands along their bodies to deter predators.