Editing Millipede (section)

==Reproduction and growth==
{{anchor|Telopod}}
[[File:Mating millipedes.jpg|thumb|left|alt=Mating|''[[Epibolus pulchripes]]'' mating; the male is on the right]]
Millipedes show a diversity of mating styles and structures. In the basal order [[Polyxenida]] (bristle millipedes), mating is indirect: males deposit [[spermatophore]]s onto webs they secrete with special glands, and the spermatophores are subsequently picked up by females.<ref name="Shelley 1999"/> In all other millipede groups, males possess one or two pairs of modified legs called [[gonopod]]s which are used to transfer sperm to the female during copulation. The location of the gonopods differs between groups: in males of the [[Pentazonia]] they are located at the rear of the body and known as telopods and may also function in grasping females, while in the Helminthomorpha – the vast majority of species – they are located on the seventh body segment.<ref name=SierwaldBond2007 /> A few species are [[parthenogenesis|parthenogenetic]], having few, if any, males.<ref name=Blower85>{{cite book |last=Blower |first=J. Gordon |title=Millipedes: Keys and Notes for the Identification of the Species |year=1985 |publisher=Published for the Linnean Society of London and the Estuarine and Brackish-Water Sciences Association by [[E.J. Brill]] |location=London |isbn=978-90-04-07698-3}}</ref>

{{multiple image
| align     = right
| direction = vertical
| width     = 200
| image1    = Nipponesmus shirinensis anterior.jpg
| width1    = 
| alt1      = Gonopods are unlike walking legs
| caption1  = The gonopods of ''Nipponesmus shirinensis'' are quite unlike its walking legs.

| image2    = Oxidus gracilis gonopod SEM.png
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| alt2      = SEM image of gonopod
| caption2  = Left gonopod of ''[[Oxidus gracilis]]''. [[False colour]] [[Scanning electron microscope|SEM]] image, scale bar: 0.2&nbsp;mm
}}
Gonopods occur in a diversity of shapes and sizes, and in the range from closely resembling walking legs to complex structures quite unlike legs at all. In some groups, the gonopods are kept retracted within the body; in others they project forward parallel to the body. Gonopod morphology is the predominant means of determining species among millipedes: the structures may differ greatly between closely related species but very little within a species.<ref name="PolyGonopods">{{cite web |last=Mesibov |first=Robert |author-link=Robert Mesibov |title=Gonopods |url=http://www.polydesmida.info/polydesmida/gonopods.html |url-status=dead |archive-url=https://web.archive.org/web/20170709113924/https://www.polydesmida.info/polydesmida/gonopods.html |archive-date=9 July 2017 |access-date=27 October 2013 |work=External Anatomy of Polydesmida}}</ref> The gonopods develop gradually from walking legs through successive moults until reproductive maturity.<ref>{{cite journal|last1=Drago|first1=Leandro|last2=Fusco|first2=Giuseppe|last3=Garollo|first3=Elena|last4=Minelli|first4=Alessandro|title=Structural aspects of leg-to-gonopod metamorphosis in male helminthomorph millipedes (Diplopoda)|journal=Frontiers in Zoology|date=2011|volume=8|issue=1|page=19|doi=10.1186/1742-9994-8-19|pmid=21859471|pmc=3170261 |doi-access=free }}</ref>
[[File:Anamorphic development in Nemasoma.png|thumb|right|200px|alt=Growth stages|Growth stages of ''[[Nemasoma]]'' ([[Nemasomatidae]]), which reaches reproductive maturity in stage V]]
The genital openings ([[gonopore]]s) of both sexes are located on the underside of the third body segment (near the second pair of legs) and may be accompanied in the male by one or two [[Penis#Invertebrates|penes]] which deposit the sperm packets onto the gonopods. In the female, the genital pores open into paired small sacs called [[cyphopod]]s or vulvae, which are covered by small hood-like lids, and are used to store the sperm after copulation.<ref name=IZ/> The cyphopod morphology can also be used to identify species. Millipede [[sperm]] lack [[flagellum|flagella]], a unique trait among myriapods.<ref name=SierwaldBond2007/>

In all except the bristle millipedes, copulation occurs with the two individuals facing one another. Copulation may be preceded by male behaviours such as tapping with antennae, running along the back of the female, offering edible glandular secretions, or in the case of some pill-millipedes, [[stridulation]] or "chirping".<ref name="Wesener et al. 2011">{{cite journal|last1=Wesener|first1=Thomas|last2=Köhler|first2=Jörn|last3=Fuchs|first3=Stefan|last4=van den Spiegel|first4=Didier|title=How to uncoil your partner—"mating songs" in giant pill-millipedes (Diplopoda: Sphaerotheriida)|journal=Naturwissenschaften|date=2011|volume=98|issue=11|pages=967–975|doi=10.1007/s00114-011-0850-8|pmid=21971844|bibcode=2011NW.....98..967W|s2cid=12005617}}</ref> During copulation in most millipedes, the male positions his seventh segment in front of the female's third segment, and may insert his gonopods to extrude the vulvae before bending his body to deposit sperm onto his gonopods and reinserting the "charged" gonopods into the female.<ref name=Hopkin&Read>{{cite book|last1=Hopkin|first1=Stephen P.|last2=Read|first2=Helen J.|title=The Biology of Millipedes|date=1992|publisher=Oxford University Press|isbn=978-0-19-857699-0}}</ref>

Females lay from ten to three hundred eggs at a time, depending on species, fertilising them with the stored sperm as they do so. Many species deposit the eggs on moist soil or organic detritus, but some construct nests lined with dried [[faeces]], and may protect the eggs within silk cocoons.<ref name=IZ/> In most species, the female abandons the eggs after they are laid, but some species in the orders [[Platydesmida]] and [[Stemmiulida]] provide [[Parental investment|parental care]] for eggs and young.<ref name="Shelley 1999" />

The young hatch after a few weeks, and typically have only three pairs of legs, followed by up to four legless segments. As they grow, they continually [[ecdysis|moult]], adding further segments and legs as they do so, a mode of development known as [[Anamorphosis (biology)|anamorphosis]].<ref name="Blower" /> Some species moult within specially prepared chambers of soil or silk,<ref name="Enghoff cocoon">{{cite journal |last1=Enghoff |first1=Henrik |last2=Akkari |first2=Nesrine |title=A callipodidan cocoon (Diplopoda, Callipodida, Schizopetalidae) |journal=International Journal of Myriapodology |year=2011 |volume=5 |pages=49–53 |doi=10.3897/ijm.5.1995 |doi-access=free }}</ref> and may also shelter in these during wet weather, and most species eat the discarded exoskeleton after moulting. The adult stage, when individuals become reproductively mature, is generally reached in the final moult stage, which varies between species and orders, although some species continue to moult after adulthood. Furthermore, some species alternate between reproductive and non-reproductive stages after maturity, a phenomenon known as periodomorphosis, in which the reproductive structures regress during non-reproductive stages.<ref name=Blower85/> Millipedes may live from one to ten years, depending on species.<ref name=IZ/>