Male behavioural plasticity depends on maternal mating status in the two-spotted spider mite

In haplodiploid organisms including the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), both unmated and mated females can produce male offspring. A previous study reported that males produced by unmated females (UM males) find pre-reproductive females more quickly than males produced by mated females (M males) in T. urticae . However, it remains unclear what factors cause the difference. We investigated effects of maternal mating status on mate-searching behaviour of their sons by changing the sons’ developmental environment. In T. urticae , the primary sex ratio of mated-female colonies is female-biased. For both UM and M males, half of individuals were reared with males to imitate unmated-female colonies, whereas the rest were reared with females to imitate mated-female colonies. In UM males, individuals that had developed with males found pre-reproductive females more quickly than those that had developed with females. However, such a difference was not observed in M males. This indicates that behavioural response to the developmental environment differs between UM and M males. It means that the behavioural plasticity depends on maternal mating status. When males were individually reared, however, there was no significant difference in the mate-searching behaviour between UM and M males, indicating that maternal mating status does not independently affect their sons’ mate-searching behaviour. This study showed that male mate-searching behaviour is changed by their developmental environment and maternal mating status. This behavioural plasticity depending on maternal mating status is the first reported in haplodiploid organisms.