The combined effect of the three weather factors (temperature, photoperiod and relative humidity) on percentage of diapaused pupae of Lobasia botrana was estimated under field conditions. Percentage of dia­paused pupae were highly influenced by daily means of both temperature and photoperiod, while relative humidity had no effect on active or dia­paused insects. Long days (16 L : 8 D), especially when combined with high temperature, Increased the rate of diapause development and de­creased the time to subsequent adult emergence. Also, the exposure of diapaused pupae to low temperature (OM) for 15 days then reared at 25⁰0 and long photoperiod of 16 hrs. till emergence significantly short­ened the pupal duration, but did not affect the pupal mortality. Diet and temperature may exert an effect on the percentage of pupae that enter diapause, however, these effects were not readily apparent except under short days less than 12 hours illumination.