Scientific Name: Class Diplopoda
Description: Millipedes are cylindrical or slightly flattened invertebrates. The word “millipede” translates to “1,000 feet,” which is a semi-accurate description of the animals. They have many feet, but not quite 1,000. Most species have fewer than 100. Millipede bodies are split into a number of segments, and each segment has two sets of legs attached underneath the body. Millipedes look quite different from their centipede cousins, which have one set of legs per segment that stick out to the sides. Millipedes are not insects—they’re actually more closely related to lobsters, shrimp, and crayfish.
Size: There are 7,000 species of millipede in the world, and 1,400 of these occur in the United States and Canada. The smaller ones are less than an inch in length, but the common spirobolid millipede can grow to over 5 inches.
Diet: Millipedes move slowly through soil and organic matter, breaking down dead plant material and rejuvenating the soil, much like earthworms. When they become overly abundant, they sometimes damage seedlings in gardens.
Predation: Millipedes lack stingers or pinchers to fend off predators like birds, toads, and small mammals. Instead, they rely on their hard exoskeleton as a first line of defense. Some species can even produce hydrogen cyanide, a noxious liquid which is toxic to small animals.
Typical Lifespan: Lifespan varies widely among species. Non-native giant African millipedes are often kept as pets and can live upwards of 7 years.
Habitat: Moist soil beneath decaying leaf litter or mulch is prime millipede habitat. Millipedes sometimes find their way into basements, but they’re mostly harmless to homes and people. Some produce toxic substances on their exoskeletons, so millipedes should not be picked up.
U.S. Range: Millipedes are found in every U.S. state, including Alaska and Hawaii, as well as in Puerto Rico and the U.S. Virgin Islands.
Life History and Reproduction: Millipedes lay their eggs in the soil each spring. When the offspring hatch, they have only a few pairs of legs. After each molt, they gain new segments and legs until they reach adulthood. After molting, millipedes consume their exoskeletons to gain back valuable nutrients.
Fun Fact: Californian millipedes in the genus Motyxia are bioluminescent. They glow greenish-blue in the dark!
Conservation Status: There’s still much we don’t know about millipedes and their conservation. Many people only become concerned with millipedes when the critters venture into their gardens or homes. Millipedes do not bite, sting or infest food, fabric or wood, and they are usually beneficial to gardens as they break down decaying plant matter. When they do become nuisances they can be controlled by removing leaf litter, decaying plants, and moisture sources from near the home.