Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada

Class Diplopoda - Millipedes

Millipede - Chicobolus spinigerus Diplopoda nest of wigglies - Oxidus gracilis Unknown Millipede  - Pseudopolydesmus serratus spotted snake millipede - Blaniulus guttulatus Is this an American Giant Millipede (Narceus americanus)? - Narceus americanus-annularis-complex Miliipede 1 Greenhill Sector 4 - Apheloria virginiensis Greenhouse Millipedes (?) - Oxidus gracilis
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Myriapoda (Myriapods)
Class Diplopoda (Millipedes)
Other Common Names
thousand-leggers, millipeds
Explanation of Names
'double-legged'
Numbers
worldwide, >12,000 described spp.(1), many more undescribed (estimated 80,000 spp., based on known degrees of endemism), arranged in 2 subclasses, 16 orders, and 145 families; >900 described spp. in 217 genera of 52 families (of which 17 are endemic to NA, and 7 are non-native) in our area, but hundreds await description, particularly in the Glomeridae, Parajulidae, Atopetholidae, Cleidogonidae, Trichopetalidae, Striariidae, Polydesmidae, and Nearctodesmidae(2)(3); 66 documented & ~100 estimated spp. in Canada(4)
Families represented in our area
Classification adapted from(2). Taxa not yet in the guide are marked (*), non-native taxa in brackets.
CLASS DIPLOPODA
Subclass PENICILLATA
Order Polyxenida
Subclass CHILOGNATHA
Infraclass Pentazonia
Superorder Oniscomorpha
Infraclass Helminthomorpha
Subterclass Colobognatha
Subterclass Eugnatha
Superorder Juliformia
Order Julida
Superfamily Juloidea [Julidae]
Suborder Spirostreptidea
Superorder Nematophora
Suborder Striariidea
Superorder Merocheta
Suborder Leptodesmidea
Suborder Polydesmidea
Infraorder Oniscodesmoides
Infraorder Polydesmoides
Size
3-270+ mm worldwide; the longest millipede of our fauna (Paeromopus paniculus) up to 160 mm
Identification
Two pairs of legs on all but the first three body segments (47-375 leg pairs and 25-189 body segments, not counting head and tail segment). Body flattened or cylindrical. In some groups, notably Polydesmida, body segments are laterally explanate. Pill Millipedes (Glomerida) are short-bodied, can roll into a ball, and look similar to pillbugs.
Sexing: Mature males usually have modified legs (gonopods). Most have 1-2 pairs of gonopods on segment 7, but in the Glomerida they are on posterior segments, while Polyxenida lack gonopods altogether.
Range
worldwide and throughout NA
Habitat
Moist habitats under rocks, rotting logs, organic debris, etc.
Food
usually decaying plant material; a few spp. occasionally carnivorous. Some may feed on living plant tissue.
Life Cycle
Millipedes hatch with just 3 pairs of legs, and add segments/legs as they molt and grow; some live up to 7 years.
Remarks
To protect themselves, millipedes coil or roll into a ball; many emit poisonous (e.g., cyanide-containing) or foul substances (e.g., benzoquinones). It is sometimes assumed some species can produce hydrochloric acid, but this has never been tested and Shear (2015) makes no mention of this substance.
"Millipedes lack the structures to bite, pinch, or sting, and are harmless to humans, although the defensive secretions burn if they get into the eyes. Millipedes are non-toxic to humans and can be picked up by hand. Some secretions discolor the skin, with no lasting effects. Some large, cylindrical, tropical species squirt defensive secretions up to a half meter and can blind chickens and dogs." --Rowland Shelley
See Also
Centipedes have only one pair of legs per body segment, and the last pair of legs extends backwards behind the body; they can run fast and can bite. Millipedes are slow-moving and unable to bite.(5)
Print References
Shear, W. A. 2015. The chemical defenses of millipedes (diplopoda): Biochemistry, physiology and ecology. Biochemical Systematics and Ecology 61: 78-117. http://dx.doi.org/10.1016/j.bse.2015.04.033
Works Cited
1.Sierwald P., Spelda J. (2021) MilliBase
2.Shelley R.M. The myriapods, the world’s leggiest animals
3.Sierwald P. et al. Milli-PEET: The class Diplopoda
4.Myriapoda of Canada
Langor D.W., deWaard J.R., Snyder B.A. 2019. ZooKeys 819: 169-186.
5.Spiders and Their Kin: A Golden Guide from St. Martin's Press
Herbert W. Levi, Lorna R. Levi, Nicholas Strekalovsky. 2001. St. Martin's Press.