The seychellarum mealybug, Icerya Seychellarum (Westwood) (Homoptera: Monophelibidae) is one of the most important mealybug species in Egypt attacking guava orchards in Qalubyia Governorate. The present study aimed to study the population fluctuations of this pest during two successive seasons, (2013-2014) and (2014-2015), in guava orchards (at Shebein El-Qanater district , Qalubyia  Governorate ) in addition to explain the effects of certain weather factors (temperature degrees and relative humidity) on its population. The obtained data showed that I. seychellarum  had two annual peaks of seasonal abundance on guava trees in the two years of study were recorded during (November and Jun.), its highest activity during autumn season of the first and second years (with means of 56and 53 individuals/leaf). On contrary, the lowest activity of I. seychellarum was recorded during early February of the first and second studied year. Also, it recorded three generations during the two studied years. To study the relationship between the metrological factors and the total population of the tested pest, each year of study was divided to two periods. During the first period of each year leaf age is the effective factor but during the second period metrological factors were the effective factors. Data illustrated that there were simultaneous occurrence of the total population of I. seychellarum and its associated predator Rodolia cardinalis