During the early part of the 1 991-92 attack periods of the mountain pine beetle (MPB), ponderosa pine stands in the Black Hills were examined for primary focus trees-the first trees attacked by the beetles. Once found, a number of characteristics were recorded for each primary focus tree. Lightning strikes, MPB pitchouts, Armillaria infections, or physical breakage were present on 58% of the primary focus trees in 1991 and on 61% of the primary focus trees in 1992. The various predisposing

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... ors are discussed as to their relative importance and role in host selection. Keywords: Mountain pine beetle, Dendroctonus ponderosae, ponderosa pine, host selection, Armillaria, red turpentine beetle, Dendroctonus valens it A gt) 9 F764Un outhwest Great Plains ' Entomologist, formerly graduate student at Colorado State University. 2 Entomologist (retired), Forestry Technician, and Pathologist, Rocky Mountain Forest and Range Experiment Station. Headquarters is in Fort Collins, in cooperation with Colorado State University.