In this study, development of the biological control agent, Deraeocoris pallens Reuther (Heteroptera: Miridae) was investigated on Tetranychus cinnabarinus Boisduval (Acarina: Tetranychidae), one of the most important pests of vegetables. T. cinnabarinus on host plants, bean (Phaseolus vulgaris L.) and eggplant (Solanum melongena L.) were given to D. pallens individuals for feeding. The experiment was carried out in a climatic chamber at 25+/-1 degreesC temperature and 65+/-5 % relative humidity. Total developmental time of nymph stages were 19.97+/-0.81 days on bean and 15.89+/-0.36 days on eggplant. Longevity of adults was 5.79+/-1.50 and 5.07+/-0.53 on the same host plants, respectively. Highest mortality rate occurred on bean plants. It was seen in the study that biological control with D. pallens was more effective on eggplant.