Millipedes are those brownish, cylindrical, many-legged creatures you find in woods and gardens within leaf litter, compost, and other moist substrates.
Although their name comes from the Latin words for “thousand” and “foot,” none actually have 1,000 legs. But millipedes do possess a lot of appendages — one species, in fact, holds the record at 750. There are some 12,000 species of millipedes worldwide, and scientists estimate there may be thousands more still waiting to be described.
Though wormlike in superficial appearance, millipedes actually are arthropods — relatives of insects, spiders, and crustaceans — with segmented bodies and a hard external skeleton. Some kinds of millipedes are less than an inch long, but others may reach lengths of fourteen inches.
Body segments vary in number, too, from eleven or so to over a hundred. Millipedes most closely resemble centipedes, another arthropod group. However, centipedes have just one pair of legs per body segment, whereas millipedes have two pairs. Also, centipedes are fast-moving carnivores with venomous fangs, but millipedes are slow-moving, burrowing creatures.
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Most lead inconspicuous but ecologically important lives, feeding on decaying organic matter and making re-cycled nutrients available to the roots of plants.
Although millipedes sometimes find their way into our homes, they don’t transmit diseases or damage clothing, food, or other items. When threatened, they coil up their body into a tight spiral. Some may also emit foul-smelling secretions that irritate the skin or eyes of humans, but unlike centipedes, millipedes don’t bite.
And while millipedes don’t score high on most people’s “favorite animal” list (pandas and tigers do, for example), what they lack in furry beauty they make up for in evolutionary interest.
In many ways, millipedes haven’t changed much since they first evolved. Looking at a millipede today gives you a glimpse into the distant history of life on Earth. Millipede-like creatures were among the first oxygen-breathing animals known to have lived on land. They breathed air via tiny spiracles (breathing holes) in their body, much as insects do today.
Some were much bigger than millipedes alive now — up to six feet long and a foot and a half wide. Fossils of these ancient millipedes are much older than those of dinosaurs, dating back over 400 million years.