Mating Millipede

The production of eggs and sperm is achieved in organs called 'Gonopores' associated with the second pair of legs, which as the first segment is always apodous (without legs) and the second only has one pair of legs is the 3rd body segment.
In some species i.e Glomeris marginata males and females are brought together by means of pheromones emitted by the male but it is generally considered that these are not effective over anything but very small distances. Before mating, in nearly all species, the male millipede has to charge his secondary sexual organs from his primary ones, to do this he has to curl his body forward so the spermatophore from his Gonopores on the 3rd body segment can be transferred to his Gonopods (means 'sex-legs') on the 7th body segment. Millipedes courtship involves the male walking along the females back and stimulating her with rhythmic pulses of his legs. When the female raises her front segments the male entwines his body around her and when their genitalia are opposed sperm transfer occurs. The sperm is passed to the female as a packet called a spermatophore. The 'Gonopods' or secondary sexual organs used in the transmission of this spermatophore vary in shape with different species, this helps stop closely related species form hybridizing. Females can and will mate several times in the Iulid types but female Polydesmoid types tend to mate only once a season as far as we know. Females of the larger Iulid species can apparently be damaged or even killed by larger males which can force them to bend backwards to far (though I have never seen this happen). Parthenogenetic reproduction is known from a number of species such as Polyxenus lagurus and Proteroiulus fuscus.

Female millipedes make an underground nest into which they lay their eggs The nest is made by excreting soil they have eaten and using their anal folds to shape it as required. Either as a nest for a number of eggs or as a coating for individual eggs i.e. Glomeris balcanica. Female millipedes may lay as many a 2 000 eggs but a few hundred is more likely. There is great variation in the number laid within a species depending on the size and condition of the female. Some species such as Tachypodoiulus niger are iteroparous, i.e. they can lay more than one lot of eggs and may live for more than one year as mature adult. Other species such as Ophyiulus pilosus are semelparous, i.e. they lay one batch of eggs and then die.

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