The snow scale insect, Lineaspis striata (Newstead) was recorded as an important insect pest of Thuja orientalis in Alexandria Governorate, Egypt. The present study revealed that the total individuals were in high numbers, (143.7[plus or minus]43; 141.8[plus or minus]20.7 and 149.0[plus or minus]48.5) during May, June and January, respectively. The fluctuating numbers of the immature stages have two peaks during June and November (6.9[plus or minus]0.7) and (20.5[plus or minus]5.0), respectively. The numbers of adult males reached the maximum (73.9[plus or minus]7.5) in October, while the females reached the maximum (88.7[plus or minus]2.2) in January. The insect has two annual generations. It is usually parasitized with Encarsia citrina (Aphelinidae), with maximum parasitization rate of 17.8[plus or minus]2.8 during August.