Comparative Studies on Life Histories of Three Species of Spider Mites (Acarina : Tetranychidae)

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Abstract
Biological studies of 3 spider mite species, Oligonychus ununguis (Jacobi), Panonychus citri (McGregor) and Tetranychus urticae Koch, [a pest of forestry and agriculture] were conducted under constant temperature (25.degree. C) and moisture (52% relative humidity) conditions. Total developmental time was shorter in T. urticae than in the other 2 spp. and the total fecundity and average egg production per day were significantly greater in T. urticae. Egg hatchability was high in all 3 spp., while it was slightly lower in O. ununguis. High proportions of females, about 70-80% in P. citri and 65-70% in T. urticae, were observed; in O. ununguis, it was 50-55%. The intrinsic rate of natural increase (rm), the net reproductive rate (R0) and the mean generation time (T) were evaluated as follows: O. ununguis (rm = 0.178, R0 = 24.72 and T = 18.02); P. citri (rm = 0.162, R0 = 24.36 and T = 19.71); and T. urticae (rm = 0.259, R0 = 65.00 and T = 16.16). T. urticae had significantly high reproductive potential; this probably caused its high adaptability to its herbaceous host plants.