Detailed investigation of the within-tree population system ofDendroctonus frontalis Zimmermann has resulted in a large data base consisting of abundance estimates for various life stages. This data base was used to construct histograms for transformed estimates and several life stage indices. Histograms were also constructed for transformed values of adult residence time, brood development time, and several host-tree characteristics. Probability and cumulative density functions of the Weibull distribution were fitted, in tandem, to the scaled frequencies and interval means for each histogram. The inverse cumulative function is known, and with a uniform random number generator, allows the selection of random deviates from each distribution. This technique can be used for generating initial (starting) values inD. frontalis population models.