Millipedes are arthropods found in terrestrial environments like gardens and forests. They are part of the class Diplopoda, encompassing over 12,000 known species globally. These creatures are characterized by their segmented bodies and numerous legs, often leading to their common, though inaccurate, nickname of “thousand-leggers.” Millipedes play a significant role in ecosystems as decomposers, contributing to nutrient cycling.
Physical Characteristics
Millipedes have elongated, cylindrical bodies, though some species can be flattened. Their most defining feature is a segmented body, with most segments bearing two pairs of jointed legs. This arrangement gives them a characteristic appearance. While their name suggests a thousand feet, most species have fewer than a hundred legs, with the highest recorded number around 750.
A millipede’s head features a single pair of antennae, used for sensing the environment, especially given their limited vision. Their eyes detect light and dark. Millipedes are covered by a tough exoskeleton, providing protection. Their size can vary, ranging from less than an inch to over five inches, with some species reaching up to 11 inches.
Habitat and Diet
Millipedes inhabit terrestrial environments across nearly all continents, excluding Antarctica. They generally prefer dark, damp conditions, making them common inhabitants of forest floors, where they reside in leaf litter, under dead wood, and within soil. They are often found in gardens, under rocks, logs, and mulch. If outdoor habitats become too dry, they may seek refuge in damp areas of homes like basements or crawl spaces.
Millipedes are primarily detritivores, meaning their diet consists mainly of decaying organic matter. They consume dead leaves, rotting wood, and other decomposing plant material. This dietary habit makes them important contributors to nutrient cycling, as they help break down plant litter and return nutrients to the soil. Some species may also feed on fungi or algae.
Behavior and Defense
Millipedes are known for their slow, deliberate movement, adapted for burrowing and navigating through tight spaces. When threatened, millipedes rely on defense mechanisms. They do not sting or bite.
Their most common defense is to coil their bodies into a tight spiral. This action protects their soft undersides by presenting their hardened exoskeleton to potential predators. Many species also secrete fluids from pores along their bodies. These secretions can be foul-smelling or irritating. While generally harmless to humans, they can cause minor skin irritation or discoloration, and eye exposure should be avoided.
Millipedes vs. Centipedes: Key Differences
Millipedes are frequently confused with centipedes, yet several key distinctions set them apart. The most apparent difference lies in their leg arrangement: millipedes have two pairs of legs per body segment, giving them a rounded, cylindrical appearance. Centipedes, conversely, possess only one pair of legs per segment, and their bodies tend to be flatter.
Their diets and behaviors also differ significantly. Millipedes are primarily slow-moving detritivores that consume decaying organic matter. Centipedes, however, are fast-moving predators that hunt other insects and small invertebrates. All centipedes are venomous, injecting toxins through fangs to subdue prey. Millipedes are not venomous and do not bite or sting; their defensive secretions are irritating.