The periodic outbreaks of the larch bud moth in the subalpine larch forests intrigues the ecologists and layman alike. The spectacular discoloration of the larch forests reappeared since 1900 13 times in the European Alps more or less widespread. Many different hypotheses have been proposed to explain this phenomenon but it becomes increasingly more obvious that only a set of several processes may result in such a complex manifestation.
It is generally agreed that peak densities of the cycle are regulated by the exhaustion of the food resource and the induced reaction of the larch which, due to the loss of nutrient reserves, produces a less favourable food for the subsequent generations of bud moth larvae (Baltensweiler et al., 1977). However this hypothesis is not sufficient to explain the regular oscillations of population densities, i.e. the immediate recommencement of the following cycle after a regression phase of 2-3 years only. It is the intention of this paper to investigate whether the dispersal behaviour of moths could provide an answer to this question.