Population Dynamics of the Western Tent Caterpillar: The Roles of Fecundity, Disease and Temperature

Many populations of forest Lepidoptera exhibit regular periodic cycles in abundance. Explicit mechanisms for such dynamics however, remain a subject of debate in Ecology. I used annual field data (1977-2015) from a cyclical species of forest Lepidoptera native to southwestern B.C., the western tent caterpillar (Malacosoma californicum pluviale), to elucidate how fecundity, viral disease and temperature contribute to its dynamics. Using time-series analysis and relationships between lagged population density, disease prevalence and annual population growth rate, I demonstrated that cyclical dynamics can be generated. I then used AIC model selection to show that fecundity and lagged population density had the greatest contributions to annual population rate of increase, followed by disease prevalence and warmer spring temperatures during larval development. Using these factors, I constructed a population model capable of generating population cycles similar to those observed in the field. These results indicate that fecundity, density-dependent disease prevalence and temperature contribute significantly to the cyclical dynamics of these populations.