SUMMARYOutbreaks of the red spider mite (Oligonychus coffeaeNietn.), the purple mite (Calacarus carinatusGreen) and the scarlet mite (Brevipalpus californicusBanks) of tea were closely associated with the monthly rainfall pattern. Peak numbers occurred during the intermonsoonal dry periods. The relationship between mite numbers and the rainfall pattern suggests that control measures should commence at the end of the first month after the dry season begins. More red spider mites, but fewer purple mites, occurred on tea grown under shaded conditions. Observations on the relationship between scarlet mite numbers and shade were inconclusive. It is suggested that, in addition to direct effects of rainfall and shade, mite numbers are determined by certain biochemical processes that take place within the tea leaves.