Herbivore exploitation of a fugitive plant species: Local survival and extinction of the Cinnabar Moth and Ragwort in a heterogeneous environment.

1. In the dune system under observation, Ragwort is distributed in small local populations that have only a restricted lifetime; (temporary) extinction has been observed frequently. 2. Cinnabar Moth attack on these populations is of even shorter duration. Colonization and extinction of the Cinnabar Moth is related to the amount of food present. 3. The presence of the predator Formica polyctena negatively influences the probability of local oviposition. 4. There is a continual shift of the Cinnabar Moth over its food-plant populations. When populations in a favorable food situation in Formica-free habitats became scarce, there was a shift towards populations in Formica habitats. 5. Negative effects of attack on the food-plant populations could be demonstrated, but they were small compared to fluctuations in these populations caused by other factors. 6. After dispersal each year new plant populations providing a favorable food situation are colonized. The heterogeneity of the populations in time and space is the factor that ensures survival of the insect in the system of plant populations.