Millipedes are terrestrial arthropods belonging to the class Diplopoda, often mistaken for their predatory relatives, the centipedes. These creatures are recognized by their cylindrical, segmented bodies, with most segments bearing two pairs of legs. Found across the globe in various ecosystems, a frequent question concerns what these slow-moving animals consume, particularly regarding other insects they share their habitat with. This article explores the typical millipede diet and clarifies why they do not consume ants.
Millipede Dietary Habits
The majority of the nearly 12,000 described millipede species are classified as detritivores, meaning they feed on dead organic matter (detritus). Their primary ecological role is recycling, breaking down plant material and returning nutrients to the soil. Millipedes mainly consume fallen, decaying leaves, moist wood, and other decomposing plant debris found within the soil and leaf litter.
This diet, rich in tough plant polymers like cellulose and lignin, requires a specialized gut microbiome. The millipede’s digestive system relies on microorganisms to break down these complex materials into absorbable nutrients. They also graze on fungi and molds, which grow on preferred food sources like rotting wood and damp mulch. Occasionally, some species opportunistically feed on soft roots or tender plant parts when decaying food sources become scarce or too dry.
Addressing the Ant Question
Millipedes do not eat ants because their diet and physical capabilities make ants an unsuitable food source. Ants are quick, agile, and possess strong defensive mechanisms, such as mandibles and formic acid, which deter predators. The millipede’s slow movement and lack of hunting instincts mean they rarely encounter active, defensive prey like ants.
The interaction between millipedes and ants is often antagonistic, with the millipede more likely to be prey than predator. Certain ant species, such as those in the genera Gnamptogenys and Leptogenys, actively hunt and subdue millipedes. Some smaller millipedes, like the bristly millipede Polyxenus fasciculatus, have evolved a specialized defense mechanism using detachable, barbed bristles to entangle attacking ants.
While millipedes are not hunters, they are opportunistic feeders. They may occasionally ingest small, immobile items found incidentally within the detritus, such as the eggs or larvae of insects, including ants. They may also consume the remains of dead insects, earthworms, or snails, but this is a rare supplement to their main diet. The vast majority of millipede species are strictly detritivorous, not carnivorous.
Millipede Feeding Mechanics and Habitat
The mouthparts of typical millipede species are structured for processing soft, decaying organic matter, which physically excludes hunting agile prey. Most millipedes possess mandibles designed for chewing and grinding, functioning to shred and crush the soft tissues of decaying leaves and wood. These mandibles feature complex structures like molar plates and internal teeth, which squeeze out the liquid contents of plant cells rather than tearing through an insect’s hard exoskeleton.
This chewing and grinding apparatus is ill-suited for capturing, biting, or tearing the hard-shelled bodies of active arthropods like ants. Their foraging behavior is limited by their need for moisture, confining them to damp, dark environments like under logs, rocks, and within leaf litter. This ground-level habitat naturally limits their food encounters to immobile, decaying material rather than active surface insects.
A small, specialized group of millipedes, such as those in the clade Colobognatha, presents an exception to the typical chewing mechanism. These species have reduced mandibles and utilize a fluid-feeding mechanism with a specialized sucking pump in their head. This modified anatomy is used to acquire liquid food, possibly from fungi or rotting plant material, illustrating a feeding specialization away from arthropod predation.