The population dynamics of Quadraspidiotus perniciosus Comstock was studied on three host plants (apple, plum and pear). It proved that host plant was an important factor. Changes in the developmental period from settling crawlers to newly adult female ranged 28.4 – 34.8 days on apple , 32.6 – 43.9 days on pear and 30.1 – 39.7 days on plum trees.
The construction of life table for Q. perniciosus indicated that the total mortality from settling crawlers to the reproducing stage was considerably fluctuating between host plants and generations. On twigs of apple, plum and pear, it ranged 73.1 – 87.8, 81.5 – 87.6 and 86.0 – 96.4%, respectively. This value was extremely high (87.8, 87.6 and 96.4%) in the 4^th generation (winter generation) on apple, plum and pear, respectively.
Analysis of the stage specific mortality of life table indicated that mortality of 2^nd instar female is the Key-stage specific mortality, which can induce population changes in comparison with other specific stage mortalities.