Abstract

e"> Two-spotted spider mite, Tetranychus urticae Koch, belongs to the order Trombidiformes and family Tetranychidae. It has four immature stages: egg, larva, protonymph and deutonymph. There is a quiescent phase between each two of mobile stages. This polyphagous pest attacks plants in the field and greenhouses around the world. Information about differential developmental time is useful for some investigations such as prey preferences of phytoseiid predators on prey stages. In order to estimate the exact duration of each mobile stage and quiescent phases of T. urticae, firstly 40 adult females selected from the colony and transferred to a Petri dish containing a bean (Phaseolus vulgaris L.) leaf surrounded by wet cotton. After 24 hours, 63 same aged eggs were collected and transferred into separate Petri dishes with bean leaf and cotton. Observations were made at intervals of 8 hours and every stage and phase was recorded until adults emerged. The presence of exuvia was used as evidence of moulting. The sex of the emerging adult was recorded. The stock culture of T. urticae was maintained on bean plants in a growth chamber at 25±1ºC, 65±5% RH and 16: 8 hours (L: D). The experiments were done in a growth chamber with the same conditions mentioned above. The total developmental time of immature stages of females took more time (9.71 days or 233 hours) than immature stages of males (8.74 days or 210 hours). Mean developmental time of the seven stages and phases (egg, larva, protochrysalis, protonymph, deutochrysalis, deutonymph and teliochrysalis) in males were 89.1, 26.2, 20.5, 16, 18.2, 14.8 and 25.1 hours, respectively. The mentioned developmental times for females were 85.5, 33.9, 24, 22.6, 19.8, 22.8 and 24.5 hours, respectively. Mortality percent of the mentioned developmental periods were 20, 14, 6, 5, 2, 0 and 2.