Function of quiescence of Tetranychus kanzawai (Acari : Tetranychidae), asa defense mechanism against rain

We compared the mortality of quiescent female deutonymphs and adult females of the kanzawa spider mite, Tetranychus kanzawai, on leaf-discs that recei ved simulated rain. The mortality of adult females was significantly higher than that of quiescent nymphs under the simulated rain. This may be due to a difference in water tolerance between the two stages, because the mortal ity rate did not differ in the absence of the simulated rain. The quiescent period was extended under increased moisture caused by the rain, and the q uiescent deutonymphs emerged in response to a decrease in moisture. This pl asticity in development seemed to ensure their molting safely after rainfal l. The presence of both active and quiescent stages in the life cycle may f unction as a bet-hedging strategy against unpredictable rain.