Polydesmida (from the Greek poly "many" and desmos "bond") is the largest order of millipedes, containing approximately 3,500 species,[2] including all the millipedes reported to produce hydrogen cyanide (HCN).[3]

Apheloria virginiensis
Scientific classification

Cook, 1895

Leach, 1815[1]

Proterospermatophora Verhoeff, 1900


Members of the order Polydesmida are also known as "flat-backed millipedes", because on most species, each body segment has wide lateral keels known as paranota.[4] These keels are produced by the posterior half (metazonite) of each body ring behind the collum.[5] Polydesmids have no eyes, and vary in length from 3 to 130 mm (0.12 to 5.12 in).[6] Including the telson, adults have 19 or 20 rings, while juveniles may have from 7 to 19 rings.[5] Mature males have a single pair of gonopods consisting of the modified forward leg pair of the 7th segment.[7] Many of the larger species show bright coloration patterns which warn predators of their toxic secretions.[7]


Polydesmids are very common in leaf litter, where they burrow by levering with the anterior end of the body.[4]


The c. 3500 species of Polydesmida are variously classified into four suborders (names ending in "-idea"), and 29 families, the largest (numerically) including Paradoxosomatidae, Xystodesmidae, and Chelodesmidae.[2]

Dalodesmidea Hoffman, 1980. 2 families
Leptodesmidea Brölemann, 1916. 13 families
Paradoxosomatidea Daday, 1889.[lower-alpha 1] 1 family
Polydesmidea Pocock, 1887. 12 families


  1. synonym: Strongylosomatidea Brölemann, 1916
  1. Robert Mesibov (2005). "A new genus of millipede (Diplopoda: Polydesmida: Dalodesmidae) from Tasmania with a pseudo-articulated gonopod telopodite" (PDF). Zootaxa. 1064: 39–49.
  2. Shear, W (2011). Zhang, Z.-Q. (ed.). Class Diplopoda de Blainville in Gervais, 1844. In: Animal biodiversity : an outline of higher-level classification and survey of taxonomic richness (PDF). Zootaxa. pp. 159–164. ISBN 978-1-86977-850-7.
  3. Thomas Eisner (2005). "Vinegaroons and other wizards". For Love of Insects. Harvard University Press. pp. 44–73. ISBN 978-0-674-01827-3.
  4. Colin Little (1983). "Onychophorans and myriapods". The Colonisation of Land: Origins and Adaptations of Terrestrial Animals. Cambridge University Press. pp. 127–145. ISBN 978-0-521-25218-8.
  5. J. Gordon Blower (1985). "Order Polydesmida". Millipedes: Keys and Notes for the Identification of the Species. Issue 35 of Synopses of the British Fauna (2nd ed.). Brill Publishers. pp. 192–221. ISBN 978-90-04-07698-3.
  6. William H. Robinson (2005). "Other arthropods in the urban environment". Handbook of Urban Insects and Arachnids. Cambridge University Press. pp. 389–440. ISBN 978-0-521-81253-5.
  7. Shelley, Rowland M. (1999). "Centipedes and Millipedes with Emphasis on North American Fauna". The Kansas School Naturalist. 45 (3): 1–16.
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