Millipedes are a group of arthropods that are characterised by having two pairs of jointed legs on most body segments; they are known scientifically as the class Diplopoda, the name derived from this feature. Each double-legged segment is a result of two single segments fused together. Most millipedes have very elongated cylindrical or flattened bodies with more than 20 segments, while pill millipedes are shorter and can roll into a tight ball. Although the name "millipede" derives from Latin for "thousand feet", no species was known to have 1,000 or more until the discovery of Eumillipes persephone, which can have over 1,300 legs. There are approximately 12,000 named species classified into 16 orders and around 140 families, making Diplopoda the largest class of myriapods, an arthropod group which also includes centipedes and other multi-legged creatures.
Chilognatha is a subclass of the class Diplopoda, which includes the vast majority of extant millipedes, about 12,000 species.
Myriapods are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial.
Orator Fuller Cook Jr. was an American botanist, entomologist, and agronomist, known for his work on cotton and rubber cultivation and for coining the term "speciation" to describe the process by which new species arise from existing ones. He published nearly 400 articles on topics such as genetics, evolution, sociology, geography, and anthropology.
Polydesmida is the largest order of millipedes, containing approximately 3,500 species, including all the millipedes reported to produce hydrogen cyanide (HCN). Polydesmids grow and develop through a series of moults, adding segments until they reach a fixed number in the adult stage, which is usually the same for a given sex in a given species, at which point the moulting and the addition of segments and legs stop. This mode of development, known as teloanamorphosis, distinguishes this order from most other orders of millipedes, which usually continue to moult as adults, developing through either euanamorphosis or hemianamorphosis.
Xystodesmidae is a family of millipedes. Its members often have very small distributional areas, with many species only known from a single locality. They are found across the northern hemisphere, with peak diversity in the Appalachian Mountains, where one-third of the 300 or so species occur. They are particularly abundant in deciduous broadleaf forests in the Mediterranean Basin, Africa, Asia, Central and North America, and Russia. Information on basic taxonomy is scant for this family; for example, it is estimated that the genus Nannaria contains over 200 species, but only 25 were described as of 2006. By 2022, 78 species in Nannaria have been described.
Polyxenida is an order of millipedes readily distinguished by a unique body plan consisting of a soft, non-calcified body ornamented with tufts of bristles – traits that have inspired the common names "bristly millipedes" or "pincushion millipedes". There are at least 86 species in four families worldwide, and are the only living members of the subclass Penicillata.
Chordeumatida is a large order of millipedes containing some 1200 species with a nearly worldwide distribution. Also known as sausage millipedes, they grow and develop through a series of moults, adding segments until they reach a fixed number in the adult stage, which is usually the same for a given sex in a given species, at which point the moulting and the addition of segments and legs stop. This mode of development, known as teloanamorphosis, distinguishes this order from most other orders of millipedes, which usually continue to moult as adults, developing through either euanamorphosis or hemianamorphosis.
Harold Frederick Loomis was an American botanist and myriapodologist known for his contributions to agronomy, plant pathology, and millipede taxonomy. He worked for the U.S. Department of Agriculture for over four decades, studying diseases of crop plants, and was a colleague of Orator F. Cook. He also made major contributions to the natural history of Central America and the West Indies, naming over 500 species of millipedes in total. He co-described with Cook the leggiest animal on earth: Illacme plenipes, with over 700 legs.
Siphonorhinidae is a family of millipede in the order Siphonophorida. There are at least 4 genera and about 12 described species in Siphonorhinidae.
Siphonophoridae is a family of millipede in the order Siphonophorida. There are about 12 genera and more than 110 described species in Siphonophoridae.
Andrognathidae is a family of millipede in the order Platydesmida. There are about 17 genera and more than 30 described species in Andrognathidae.
Illacme tobini is a species of millipede in the family Siphonorhinidae. It was discovered in California at Sequoia National Park in 2016. This millipede is part of the Illacme genus, which contains only two other species, Illacme plenipes and Illacme socal.
Illacme is a genus of millipedes in the family Siphonorhinidae. It includes three species. Illacme plenipes was first described in 1928 from San Benito County, California, and rediscovered in 2005. In 2016, Illacme tobini was described based on a single male specimen collected in 2006 from Lange Cave, in Sequoia National Park, 240 km (150 mi) east of the known habitat for I. plenipes. In 2018, Illacme socal was discovered in Whiting Ranch Wilderness Park.
Cleidogonidae is a family of millipedes in the order Chordeumatida. Adult millipedes in this family have 28, 29, or 30 segments. This family includes the genus Tianella, notable for featuring adult millipedes with 29 segments, a number not found in the adults of any other chordeumatidan species. All Tianella species have adults with 29 segments except for two in which adults have only 28 segments. In the Tianella species with 29 segments, adult females have 48 pairs of legs, as one would expect in adult female chordeumatidans with one segment fewer than the 30 usually found in this order. There are seven genera and at least 140 described species in Cleidogonidae.
Conotylidae is a family of millipedes in the order Chordeumatida. Adult millipedes in this family have 30 segments. There are about 19 genera and at least 60 described species in Conotylidae.
Rhachodesmidae is a family of flat-backed millipedes in the order Polydesmida. There are more than 20 genera and at least 80 described species in Rhachodesmidae.
Metopidiotrichidae is a family of millipedes in the order Chordeumatida. These millipedes range from 4 mm to 17 mm in length. Adult millipedes in this family have 32 segments, not the 30 segments usually found in this order. Adult males in this family often feature a reduced or vestigial leg pair 10 as part of the gonopod complex, in addition to the two leg pairs typically modified into gonopods in this order. There are about 9 genera and at least 70 described species in Metopidiotrichidae.
Eumillipes is a genus of millipede in the family Siphonotidae. It contains a single species, E. persephone, known from the Eastern Goldfields of Western Australia. The species was first collected in 2021, discovered in three drill holes, living at depths of between 15 metres (50 ft) and 60 metres (200 ft).
Illacme socal is a species of millipede in the family Siphonorhinidae. It was discovered in California at Whiting Ranch Wilderness Park in 2018.
