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.
Mammamia profuga is a species of cave-dwelling millipede in the family Julidae. The only known species of the genus Mammamia, it was described in 2011 from a specimen discovered in a cave in Italy.
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, 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.
Tridontomidae is a small family of millipedes. Its members are endemic to Guatemala. These millipedes range from 22 mm to 28 mm in length and are uniformly grayish in color; their legs and antennae are unusually long and slender. This family includes the remarkable species Aenigmopus alatus, in which adult males feature no gonopods. This millipede is the only species in the infraclass Helminthomorpha without gonopods.
Ommatoiulus is a genus of millipedes in the family Julidae.
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.
Glomeridesmida is an order of millipedes in the infraclass Pentazonia containing 2 families and at least 31 species. Glomeridesmida is the only living order of the superorder Limacomorpha. Also known as slug millipedes, glomeridesmidans are small and somewhat flattened, and unlike other orders of Pentazonia, are unable to roll into a ball. Ocelli (eyes) are absent.
Callipodida is an order of millipedes containing around 130 species, many characterized by crests or ridges.
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.
Siphoniulus is a poorly known genus of millipede containing only two living species: S. alba from Indonesia, and S. neotropicus from Mexico and Guatemala. An additional two fossil species are known from Cretaceous amber. Siphoniulus species are the only members of the family Siphoniulidae and order Siphoniulida, making Siphoniulida the smallest millipede order. Few specimens are known, and their classification is contentious, although most recent studies place them as basal members of the Helminthomorpha.
Titanophyllum spiliarum is a species of cave-dwelling millipede in the family Julidae. The only known species of the genus Titanophyllum, it was described in 2011 from specimens discovered in a cave in Greece. It has several unusual characteristics including eyelessness and a small hook on its hind-most body section that may be involved in keeping the animal ‘locked’ when it coils-up defensively.
Bollmania is a genus of millipedes with around six species occurring from Central through East Asia, including Iran, Pakistan, Tajikistan, and China. The genus was established by entomologist Filippo Silvestri in 1896, and is named in honor of Charles Harvey Bollman. Bollmania is the sole genus of the family Caspiopetalidae.
Burmanopetalum is an extinct genus of millipede containing the single species Burmanopetalum inexpectatum from the Cretaceous of Myanmar. It is a member of the order Callipodida and is the only member of the suborder Burmanopetalidea and family Burmanopetalidae.
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.
Chordeumatidae is a family of millipedes belonging to the order Chordeumatida. These millipedes range from 7 mm to 18 mm in length and are found in Europe. Adult millipedes in this family have either 28 or 30 segments. This family features distinctive sex-linked modifications to the legs in adults: In the adult female, a legless sternite replaces the third pair of legs, and in the adult male, five pairs of legs are modified in the gonopod complex. These modifications are more extensive than those found in other adult males in this order, which often have only two leg pairs modified into gonopods. With the more extensive modifications to the legs in this family, species with the usual 30 segments feature adult females with only 49 leg pairs and adult males with only 45 pairs of walking legs, and species with only 28 segments feature adult females with only 45 leg pairs and adult males with only 41 pairs of walking legs.
Speophilosomatidae is a family of millipedes belonging to the order Chordeumatida. These millipedes are found in Japan and range from 4 mm to 6 mm in length. Adult millipedes in this family are notable for being among the few in this order with only 26 segments instead of the 30 usually found in chordeumatidans. The adult males in this family are also notable for involving three leg pairs in the gonopod complex rather than the two pairs typically modified into gonopods in this order.
Peterjohnsiidae is a small family of millipedes belonging to the order Chordeumatida. The family was first described in 1987 by Jean-Paul Mauriès. These millipedes range from 3 mm to 8 mm in length and are found in Australia. Species in this family exhibit sexual dimorphism in segment number: adult males have 30 segments, but adult females have 32 segments. In adult males in this family, the gonopod complex involves three leg pairs rather than just the two usually modified into gonopods in this order.
Golovatchiidae is a family of millipedes belonging to the order Chordeumatida. This family contains a single species, Golovatchia magda. This species ranges from 15 mm to 17 mm in length and is found in the Russian Far East. Adult millipedes of this species have 30 segments. In the adult male of this species, the gonopod complex involves three leg pairs rather than just the two that are usually modified into gonopods this order.
Hoffmaneumatidae is a family of millipedes belonging to the order Chordeumatida. This family includes two genera, one (Hoffmaneuma) found in the Russian Far East and the other (Japanoparvus) found in Japan. Millipedes in this family range from 4 mm to 6 mm in length. Adult millipedes in this family have only 28 segments, not the 30 segments usually found in this order. Adult males in this family feature a reduced leg pair 10 in addition to the two pairs normally modified into gonopods in this order. In the adult male of the species Hoffmaneuma exiguum, for example, the gonopod complex derives from all three leg pairs rather than from just the usual two.
