Precopulatory mate guarding influences the development of quiescent deutonymph females in the two-spotted spider mite (Acari : Tetranychidae)

Individuals of some organisms have a specific stage sensitive to environmental cues that initiate developmental plasticity which subsequently influences their entire development. Females may use male behaviour such as precopulatory mate guarding as an environmental cue to change their developmental rate. In the two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae), only the first insemination results in fertilization and males guard quiescent deutonymph females. As quiescent individuals take on a silvery appearance before moulting, the period of the quiescent stage can be divided into two parts: from entering the quiescent stage to becoming silvery (1st period) and from becoming silvery to moulting (2nd period). Females may be sensitive to precopulatory mate guarding immediately before moulting (i.e. 2nd period). Thus, I examined whether precopulatory mate guarding during either period affects the total developmental duration of quiescent deutonymph females. When guarded by a male, the whole developmental duration of the quiescent deutonymph females became significantly shorter (by 3-5 %) than that of solitary ones, regardless whether the guarding occurred during the 1st period, the 2nd period or both periods. In conclusion, quiescent deutonymph T. urticae females use precopulatory mate guarding by conspecific males as an environmental cue for their developmental rate, although they are sensitive to the mate guarding not only immediately before moulting.