Although the fluctuation of the larch bud moth exhibits on a regional scale within the subalpine region a true cyclic appearance,i.e. being subjected primarily to birthrate and deathrate, the defoliation pattern of outbreaks on a larger scale throughout the Alps suggests wave phenomena which imply the significance of immigration and emigration of moths.
Population cycles are brought about at peak densities by the deterioration of the food resources induced by defoliation, a process which in turn selects during the regression phase of the cycle the robust intermediate colourmorph. It is hypothesized that at lowest population densities assortative mating between the dark fitnesstypes starts the new cycle again.
The impact of periodic defoliation on the larch tree is not crucial, it accelerates the nutrient cycling in the subalpine ecosystem. However, the killing of the young cembran pines in the understorey retards the succession to the climax forest.