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 in 2020 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.
Desmoxytes, whose species are commonly known as the dragon millipedes, is a genus of millipedes of the family Paradoxosomatidae found in Southeast Asia. The genus was described by Ralph Vary Chamberlin in 1923, and reviewed by Sergei Golovatch and Henrik Enghoff in 1994. At least 18 species are known from to Malaysia, Myanmar, and Thailand. One species, D. planata, has also been observed in Sri Lanka, the Andaman Islands, Seychelles, Java, Great Coco Island, and Fiji; however, this species has expanded its range by being transported through human activity. Several species have only recently been discovered, and some have yet to be officially described.
Polydesmida is the largest order of millipedes, with more than 5,000 species, including all the millipedes reported to produce hydrogen cyanide (HCN). This order is also the most diverse of the millipede orders in terms of morphology. Millipedes in this order are found in all regions of the world other than Antarctica.
Xystodesmidae is a family of millipedes in the suborder Leptodesmidea within the order Polydesmida. The family Xystodesmidae was created by the American biologist Orator F. Cook in 1895 and named after the genus Xystodesmus. This family includes more than 390 known species distributed among 62 genera. Many species, however, remain undescribed: 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.
Motyxia is a genus of cyanide-producing millipedes that are endemic to the southern Sierra Nevada, Tehachapi, and Santa Monica mountain ranges of California. Motyxias are blind and produce the poison cyanide, like all members of the Polydesmida. All species have the ability to glow brightly: some of the few known instances of bioluminescence in millipedes.
Harpaphe is a genus of flat-backed millipedes native to the Pacific Northwest of North America. The genus contains three described species: two occurring only in northern California, and one with a large range extending from Southeast Alaska to Central California.
Platyrhacidae is a family of polydesmidan millipedes distributed in Southeast Asia and tropical Central and South America.
Haplodesmidae is a family of millipedes in the order Polydesmida. This family includes about 70 species. Species occur in East Asia, Southeast Asia, and Oceania, although some species have been introduced to the New world tropics.
Apheloria tigana, known as the yellow-and-black flat millipede, is a large North American flat-backed millipede in the family Xystodesmidae. It is reported to secrete cyanide compounds as a defense. It is recommended that one wash hands after handling this organism as the toxic compounds it secretes are poisonous and can cause extreme irritation if rubbed in the eyes.
Pleuroloma flavipes, commonly known as the traveling cherry millipede, is a species of flat-backed millipede in the family Xystodesmidae. It has the widest distribution of any species of xystodesmid millipede and is found in eastern North America from southeastern North Dakota, eastward to Connecticut, and southward to North Carolina, northern Louisiana, and southern Texas. Pleuroloma flavipes millipedes are occasionally observed in large aggregations of individuals where they appear to move en masse in a certain direction, hence the common name "wandering cherry millipede". In a report from 1950, an aggregation of about 6,000 individuals were encountered on a single bridge at McCormick's Creek State Park, Indiana. The species is extremely variable in coloration, and converges in appearance with several species of Apheloria and Brachoria as a result of mimicry.
Nearctodesmidae is a family of flat-backed millipedes in the order Polydesmida. There are about 7 genera and 17 described species in Nearctodesmidae.
Selenocheir sinuata is a species of flat-backed millipede in the family Xystodesmidae, endemic to Northern California. The Species was first described by Rowland M. Shelley in 1994 based on samples collected by J. S. Buckett and M. R. Gardner in 1966
Cherokia Chamberlin, 1949 is a genus consisting of a single species, Cherokia georgiana. Commonly known as the wrinkled flat-backed millipede, this species belongs to the order Polydesmida and the family Xystodesmidae. It inhabits forests in the southeastern United States, particularly those with hemlock, maple, tulip poplar, rhododendron, cedar, and spruce-fir trees.
Stenoniodes, commonly known as the Borneo tractor millipede, is a genus of millipede in the family Platyrhacidae. It contains six species, five of which occur on Borneo and one on Sibutu Island. Its common name originates from the likeness of its 20-segmented body to the tread of a tractor's tire.
Tubaphe is a genus of millipede in the family Xystodesmidae with a single described species, Tubaphe levii. The genus was erected by Nell B. Causey in 1954.
Chonaphe armata is a species of Xystodesmid millipede found in the Pacific Northwest of North America. The species was first described as Polydesmus armatus by O. Harger in 1872 and was later moved to the new genus Chonaphe, for which it is the type species, by O. F. Cook in 1904.
Selenocheir arcuata is a species of Xystodesmid millipede found in Northern California. The species was first described by Rowland M. Shelley in 1994 based on samples collected by C. Smith, J. Clover, and F. Ennik in 1972.
Thrinaphe is a genus of millipede in the family Xystodesmidae with a single described species. The genus was erected by Rowland M. Shelley in 1993 based on samples collected by Dr. Shelley in 1991 as well as museum type specimens collected by K. Goeden in 1968. The genus is found in the Cascade mountains on the Washington/Oregon border as well as down into the Willamette Valley.
Orophe is a genus of Xystodesmid millipede found in the Rocky Mountains of northern Idaho and western Montana.
Orophe unicus is a species of millipede in the family Xystodesmidae, which is found in the Rocky Mountains of northern Idaho. The species was originally described as Chipus unicus by H.F. Loomis in 1953 and was later transferred to Orophe by R.L. Hoffman in 1964. Hoffman also suggested that the differences in the gonopods of O. unicus and O. cabinetus were minor and so the relationship between the two may be "subspecific". Loomis and Schmidt later synonymized O. unicus under O. cabinetus based on the subtle nature of this feature. In 1993, Rowland Shelley reexamined the type specimens and based on the differences in the gonopods as well as the allopatric nature of the two populations, reinstated O. unicus as a valid species.
