Low Temperature Induces Embryonic Diapause in the Spider Mite, Eotetranychus smithi

The spider mite, Eotetranychus smithi Pritchard & Baker (Acari: Tetranychidae), exhibits a facultative diapause that occurs at the egg stage. Diapause was induced by low temperatures alone (≤ 17.5°C) and averted by high temperatures (≥ 20°C). Photoperiod had little effect on diapause induction. This is the first example of temperature-induced diapause in spider mites. The diapause eggs became larger and darker (orange) than non- diapause eggs (white to pale yellow), suggesting that egg size and egg color are associated with diapause. When mites that were reared from eggs at 25°C and 16:8 L:D were transferred to 15°C and 16:8 L:D just after the start of the teleiochrysalis stage (the final molting stage before adulthood), all females laid non-diapause eggs during the first 30 days and then switched over to laying diapause eggs. The switch to diapause may be caused by the aging of mothers.