Regression equations for predicting diameter outside bark (DOBx) and bark thickness (BTx) as functions of height and diameter or bark thickness class were developed from data collected as part of aDendroctonus frontalispopulation dynamics study. The 2 equations were combined and integrated over height to provide estimates of the phloem area and bark volume infested by the insect.A graphic analysis using the BTxmodel showed that eggs/cm3of bark increase with height, indicating that factors other than BTxcontrol the egg density per unit area. An example is presented showing the use of the phloem area model to estimate the total number of insects inhabiting a tree.