The mean number of beetles emerging from a tree of a given DBH, including the probability of attack on that tree, was calculated as follows (based on Eqs. (3) and (5)–(7) above and Eq. (14) in Safranyik (1988), which states that Tb = 48.0586(Xb 0.6386)(D1.3264)(Hi 0.7465); brood totals in individual trees; Xb = brood density per square metre at 1.22 mon the bole; D = tree