On-Bark Behavior of Dendroctonus frontalis: A Markov Chain Analysis

Abstract

Tree-killing species of the Scolytidae (Coleoptera) must locate suitable hosts at least once per generation for successful reproduction. The process used to select hosts is complex, involving a sequence of steps and many possible outcomes. Because more beetles land on bark (host-find) than bore galleries (host-recognize), postlanding behaviors appear to be important in determining whether a potential host is selected. We applied Markov chain analysis to on-bark behaviors of the southern pine beetle, Dendroctonus frontalis Zimmermann, that were described by previous investigators. Predictions obtained from our analysis agree well with earlier descriptions and provide additional information not heretofore apparent. By developing chains for each sex, sexually dichotomous fighting behaviors were revealed. Testable predictions were generated for outcomes of complex interactions that occurred when tree resistance and predator density were varied. Markov chain analysis also provides a framework for future host selection studies. Use of this type of analysis requires collecting data over the entire behavioral sequence of interest, with concentration on estimating the transition probabilities among states. This approach provides results for the many possible outcomes derived from a sequence of interrelated activities. We expect that such an integrated treatment will lead to a greater understanding of important facets of scolytid host selection behavior.