Millipedes, the arthropods known scientifically as Diplopoda, burrow into the substrate below the surface. This subterranean habit is so widespread that nearly all millipede species adopt a lifestyle that is primarily underground or within dense leaf litter. As slow-moving detritivores, these creatures are essential decomposers, chewing and processing dead organic matter like fallen leaves and decaying wood. By breaking down this material, millipedes help recycle nutrients back into the soil, playing a significant role in maintaining ecosystem health and structure.
Role of Burrowing
Burrowing is crucial for millipede survival, driven largely by their physiology. Millipedes possess a hard exoskeleton but lack the waxy cuticle insects use to prevent water loss, making them highly susceptible to desiccation in dry air. They must constantly seek out high-humidity environments, and the soil provides a reliable, damp refuge from drying conditions and extreme temperatures.
The underground environment also offers protection from surface predators, such as birds, toads, and small mammals. Millipedes rely on burrows or secure underground chambers for two life cycle events: molting and reproduction. During molting, they shed their exoskeleton and are vulnerable, requiring a safe, undisturbed space. Females deposit their eggs in small nests or clutches within the soil, shielding the young until they hatch.
How Millipedes Dig
Millipedes employ a specialized method of movement to navigate and displace soil particles. Their numerous legs, which feature two pairs on most body segments, move in a coordinated, wave-like pattern known as a metachronal gait. This gait generates the thrust force required to push against and through dense substrate.
Rather than excavating and removing soil like a mole, millipedes use their bodies as a living plow or wedge. Species with cylindrical bodies, such as those in the orders Julida and Spirobolida, often use a method called “bulldozing,” lowering their heads and simply barging their way forward into the substrate. Other species, like the flat-backed Polydesmida, insert their front end into a crevice and then push upwards with their legs, using their body segments to widen the crack. This physical pressure against the soil is facilitated by the internal fluid pressure of their hydrostatic skeleton, transforming their segmented body into an effective, powerful digging tool.
Habitat and Human Interaction
Millipedes thrive in environments rich with decaying organic material and consistent moisture. Their preferred habitat is the top layer of soil, under leaf litter, or inside rotting logs. Their function in these damp areas is to consume detritus, which helps to aerate the soil and increases the rate at which nutrients are cycled back into the ecosystem.
Millipedes sometimes cross paths with humans when they are forced to migrate from their natural habitat. During periods of extreme weather, such as drought or heavy rain, they may seek refuge in structures like basements, garages, or crawl spaces where moisture is more stable. Although they can be an unwelcome nuisance when they enter a home, millipedes are non-aggressive and do not bite or sting. They are not considered destructive household pests, as they do not infest food, fabric, or sound wood, and typically perish quickly indoors due to low humidity.