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 ball. Although the name "millipede" derives from the Latin for "thousand feet", no known species has 1,000; the record of 750 legs belongs to Illacme plenipes. 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.
Gonopods are specialized appendages of various arthropods used in reproduction or egg-laying. In males, they facilitate the transfer of sperm from male to female during mating, and thus are a type of intromittent organ. In crustaceans and millipedes, gonopods are modified walking or swimming legs. Gonopods may be highly decorated with elaborate structures which may play roles in sperm competition, and can be used to differentiate and identify closely related species. Gonopods generally occur in one or more pairs, as opposed to the single (un-paired) reproductive organs such as the aedeagus of insects or the penis of harvestmen.
Harpaphe haydeniana, commonly known as the yellow-spotted millipede, almond-scented millipede or cyanide millipede, is a species of polydesmidan ("flat-backed") millipede found in the moist forests along the Pacific coast of North America, from Southeast Alaska to California. The dark coloration with contrasting yellow-tipped keels warn of its ability to exude toxic hydrogen cyanide as a defense. Despite the various common names given the species, the coloration pattern, cyanide defense, and associated almond scent occur in other flat-backed millipedes around the world.
Spirostreptida is an order of long, cylindrical millipedes. There are approximately 1000 described species, making Spirostreptida the second largest order of millipedes after Polydesmida.
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).
Paradoxosomatidae, the only family in the suborder Paradoxosomatidea, is a family of flat-backed millipedes in the order Polydesmida. Containing nearly 200 genera and 975 species as of 2013, it is one of the largest families of millipedes. Paradoxosomatids occur on all continents except Antarctica, and can generally be distinguished by dorsal grooves on most body segments and a dumb-bell shaped gonopod aperture. Notable groups within the Paradoxosomatidae include the dragon millipedes of Southeast Asia, and the widely introduced Greenhouse Millipede Oxidus gracilis.
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.
Antichiropus is a genus of millipede in the family Paradoxosomatidae. The genus is very distinctive in the form of the gonopod, which is typically coiled through at least a full circle. It is probably endemic to Australia. Some species have small ranges of less than 10000 km2, classifying them as short-range endemic invertebrates.
Orthomorpha is a genus of millipedes in the family Paradoxosomatidae containing approximately 50 species distributed in Southeast Asia.
Chordeumatida is a large order of millipedes containing some 1200 species with a nearly worldwide distribution. They possess around 30 body segments and reach about 25 mm (0.98 in) in length.
Orthomorpha coarctata, the long-flange millipede, is a widely introduced species of Polydesmidan millipede of the family Paradoxosomatidae. It is presumed native to Southeast Asia but due to transport by humans occurs in tropical and sub-tropical areas throughout the world, including the Hawaiian Islands, the West Indies, Gulf Coast of North America, and the Galápagos Islands.
Casimir Albrecht Willem Jeekel (1922–2010) was a Dutch myriapodologist and entomologist known for his major contributions to the taxonomy of millipedes. His 1971 monograph Nomenclator Generum et Familiarum Diplopodorum is credited as launching the "modern era" of millipede taxonomy, and has been considered the "most important single work ever published on the Diplopoda". He served as director of the Zoological Museum Amsterdam, and authored over 150 works on the taxonomy of millipedes and other myriapods.
The moss millipede is a keeled millipede of the family Platyrhacidae native to Colombia. It was described in 2011, and with several species of symbiotic moss found growing on its dorsal surface, it is the first millipede known with epizoic plants.
Ammodesmidae is a family of small millipedes endemic to Africa, containing seven species in two genera. Ammodesmids range from 1.4 to 5.0 mm long with 18 or 19 body segments in both sexes, and are capable of rolling into a tight sphere.
Hylomus rhinoceros is an aposematic species of dragon millipede in the family Paradoxosomatidae. It is only known from Champasak and Sekong Provinces in southern Laos.
Hylomus rhinoparvus is a species of dragon millipede in the family Paradoxosomatidae. It is only known from Houaphanh Province of northeastern Laos.
Chamberlinius is a genus of flat-backed millipedes in the family Paradoxosomatidae. There are five species; 3 of which occur only Taiwan, one only in the Ryukyu Islands of southeast Japan, and one occurring in both areas. Individuals are 25–37 mm (0.98–1.46 in) long and up to 5.5 mm wide, colored in pale yellow to brown, sometimes with dark brown markings on the anterior portion of body segments.
Anoplodesmus anthracinus is a species of millipedes in the family Paradoxosomatidae. It was previously thought to confined to Myanmar, the species was reported and documented from Malaysia and Sri Lanka in 2013.
Tonkinosoma tiani, is a species of millipede belonging to the family Paradoxosomatidae. It is found from caves in southern China.
