The mean number of beetles attacking a tree with a certain DBH, including the probability that the tree will be attacked, was calculated as follows (based on Eqs. (3), (5), and (7) from the present study and Eq. (13) in Safranyik (1988), which states that Ta = 129.2189 (Xa 0.2964)(D1.7665)(Hi 0.9430); Ta = attack totals in individual trees; Xa = attack density per square metre at 1.22 m on the bole; D = tree diameter (m) at 1.37 m; Hi = infested bole height (m)):