The two-spotted spider mite, Tetranychus urticae Koch, is a very polyphagous pest with a worldwide distribution. In order to appraise population growth parameters of this pest, samples of two-spotted spider mites were taken from soybean (Glycine max) fields of Moghan region, Iran in June 2007 and are reared on bean plants var. Derakhshan (Phaseolus vulgaris) in a growth chamber. The life table parameters of this pest were calculated on three commercial soybean cultivars (Zane, Hach, and L17) and one hybrid (Hob 9 Will) at 25 ± 1°C, 60 ± 10%RH, and 16 h photophase. The developmental times of immature stages varied from 9.69 on Hach to 9.82 days on L17, whereas the immature survival was 57-79% on Hach and Hob 9 Will, respectively. On average, there were 65.5, 40.8, 38.8 and 34 eggs produced per female on L17, Hach, Hob 9 Will and Zane, respectively. The intrinsic rate of natural increase (r m ) for T. urticae on Hob 9 Will was the highest, whereas the values for r m ranged from 0.211 (females/female/day) on Zane to 0.292 on Hob 9 Will. Also, jackknife values of other life table parameters such as net reproductive rate (R 0 ), generation times (T), doubling time (DT), and finite rate of increase (k) on these cultivars were estimated. Overall, the two-spotted spider mite indicated a better performance on Hob 9 Will than on the other soybean cultivars.

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