Millipede

Millipedes are myriapods in the class Diplopoda, distinct from insects and closely related to centipedes, characterized by long, cylindrical (or sometimes flattened) bodies divided into numerous segments, most of which bear two pairs of legs each—a hallmark that distinguishes them from centipedes, which have only one pair per segment. Species like the large North American millipede exemplify the group's slow, methodical, ground-dwelling lifestyle.

Millipedes are primarily detritivores, feeding on decaying plant material, and are considered important decomposers in forest and garden ecosystems, helping break down leaf litter and dead wood and returning nutrients to the soil. Their gentle, plant-material diet contrasts with the predatory habits of centipedes, despite the two groups' superficially similar many-legged appearance.

Globally there are many thousands of described millipede species, ranging from a few millimeters to many centimeters long, occupying leaf litter and soil habitats on every continent except Antarctica.

• Long, cylindrical (in most common species), segmented body, ranging from about 20 mm to over 100 mm in larger species.
• Two pairs of legs on most body segments, giving a dense, rippling row of legs along each side—more legs per segment than centipedes.
• Slow, deliberate crawling movement in a straight line, in contrast to the fast, darting movement of centipedes.
• Short antennae and no visible pincers or fangs at the head.
• Common defensive behavior: coiling into a tight flat or cylindrical spiral when disturbed, protecting the softer underside and legs.
• Lookalikes: centipedes (flattened body, one pair of legs per segment, fast movement, and pincer-like front appendages, versus the millipede's rounded body, two leg pairs per segment, and slow gait).

Millipedes are found worldwide in a wide range of climates, favoring consistently moist microhabitats such as leaf litter, mulch, rotting logs, compost, and damp soil. They are most active during warm, humid conditions, often emerging after rain, and are typically found under bark, stones, or organic debris during dry or cold periods.

They generally avoid direct sunlight and dry conditions, remaining in sheltered, humid spots close to the ground where decaying organic material is abundant.

Millipedes feed primarily on decaying plant matter, including leaf litter, rotting wood, and other organic debris, making them significant decomposers that recycle nutrients into the soil. They move slowly and deliberately, using their many legs in a coordinated wave-like motion to push through soil, litter, and tight spaces.

When disturbed, many species curl into a tight coil, a passive defensive posture that protects the more vulnerable underside and legs. Some species can also produce defensive secretions from glands along the body as an additional deterrent. They are generally not aggressive and are considered beneficial decomposers within their ecosystems.

Females lay eggs, often in small clusters in soil or moist debris, sometimes within a simple nest or chamber constructed from soil and secretions. Hatchlings emerge with fewer body segments and legs than an adult and gain additional segments and leg pairs with each successive molt, a growth pattern distinctive to millipedes.

Development to full adult size can take from several months to a few years depending on species and environmental conditions, and some larger species may live for several years. Millipedes typically overwinter as juveniles or adults in sheltered soil or leaf litter, becoming active again as temperatures and moisture levels rise.