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.
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 or Singsamut school to California, however, also seen in northern Brazil and India. The dark coloration with contrasting yellow-tipped keels warn of its ability to exude toxic hydrogen cyanide as a defense. The cyanide secretions are not dangerous to humans, but can cause irritation and pain if it contacts sensitive areas such as the mouth, eyes, or nose.
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.
Chordeumatida is a large order of millipedes containing more than 1,400 species. Also known as sausage millipedes, they are found nearly worldwide. Chordeumatida is the largest order in the superorder Nematophora, a group also known as spinning millipedes because their telsons feature spinnerets used to build nests of silk. These millipedes produce this silk to create chambers in which to molt or to lay their eggs.
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.
Floridobolus is a genus of millipedes commonly known as Florida scrub millipedes containing three described species: Floridobolus penneri, F. orini, and F. floydi; the latter two described in 2014. All three species are endemic to Florida scrub habitat of peninsular Florida, and F. penneri is considered a critically imperiled species by NatureServe. Prior to the description of F. orini, the genus was considered the sole member of the family Floridobolidae, named by William T. Keeton in 1959, however studies in 2014 have argued that Floridobolus does not represent a distinct family but rather is a basal member of the family Spirobolidae, representing the subfamily Floridobolinae, and tribe Floridobolini.
Brachycybe (Greek for "short head") is a genus of social millipedes with species in the United States and East Asia. Species in this genus are often referred to as "feather millipedes" due to their shape.
Gosodesmus is a genus of platydesmidan millipede, described by Ralph V. Chamberlin in 1922, that is widely distributed in the U.S. state of California. It is monotypic, being represented by the single species, Gosodesmus claremontus, commonly known as the pink feather boa millipede. Individuals vary in color from bright pink to coral, and may possess a black or purple dorsal stripe. Body length ranges from 17 to 27 mm, with up to 81 body segments. Gosodesmus claremontus occurs on the Coast Ranges as well as the Sierra Nevada, and is often found within rotted wood, especially oaks. In 2020, chemist Dr. Tappey Jones at Virginia Military Institute and colleagues, discovered a novel natural product and alkaloid in the chemical defense secretion of G. claremontus: (1), 7-(4-methylpent-3-en-1-yl)-1,2,3,5,8,8a-hexahydroindolizine, known as gosodesmine.
Chonaphini is a tribe of flat-backed millipedes in the family Xystodesmidae. There are about 6 genera and 19 described species in Chonaphini.
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
Xystocheirini is a tribe of flat-backed millipedes in the family Xystodesmidae. There are about 5 genera and more than 40 described species in Xystocheirini.
Metopidiotrichidae is a family of millipedes in the order Chordeumatida. This family includes more than 70 species. These millipedes are found in Indochina, Australia, and on Pacific islands from New Zealand to Japan.
Anombrocheir is a genus of millipedes belonging to the family Xystodesmidae. The species of this genus are endemic to California where they are found in the inner Coastal mountain range of Colusa and Glenn counties.
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.
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.
Sigmocheir furcata is a species of millipede in the family Xystodesmidae. The species in endemic to California and found in the foothills of the Sierra Nevada mountains.
Anombrocheir bifurcata is a species of Xystodesmid millipede endemic to the inland coastal range of California. The species was described by Michael R. Gardner and John S. Buckett in 1969 based on samples collected by M.R. and R.C. Gardner.
