الفهرس 
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Abstract
The effect of four constant temperatures (20,25,30, and 35°C) on the developmental periods , survival rates , Fecundity and fertility of Tetranychus urticae koch were studied. Temperature as a primary environmental variable affected the periods of development as well as the fecundity of T. urticae females . survival rates of developmental stages and egg fertility was not affected by increasing the incubated temperature from 20°C up to 30°C.
Statistical analysis of developmental periods (Incubation period of eggs , larval, nymph , immatures and generation periods) revealed that , as temperature increased (from 20°C--->30°C)the periods of development significantly reduced . Developmental periods at 30 and 35°C were statistically similar .fecundity and fertility of deposited eggs by virgin or mated females was statistically similar (data not shown) . Regardless the case of females (mated or virgin ), mean number of eggs laid significantly increased as temperature increased up to 30°C, at 35 °C fecundity significantly reduced as compared with it at 30°C.
The lower thermal thresholds of eggs , larvae , nymphs ,immatures and generation were 14.76, 7.94, 13.74, 12.95 and 12.37°C, respectively .