STUDIES ON THE POPULATION-DYNAMICS OF THE BARK BEETLE LEPERISINUS-VARIUS (FABR) (COL, SCOLYTIDAE) ON EUROPEAN OLIVE (OLEA-EUROPAEA)

Within-generation mortality of the bark beetle L. varius was studied i n a Spanish olive orchard by placing cut logs in the field for adult f emales to breed. Mortality was greatest at the larval stage with only 10 % of the original egg number surviving to adulthood. There was no e vidence that the density of eggs laid per maternal gallery affects sub sequent mortality at the egg, larval or pupal stages. The density of m aternal galleries on a log, however, was found to have a positive infl uence on the mortality of larvae, but not of eggs or pupae. Part of th is density-dependent mortality could be attributed to insect parasitoi ds, but the effects of intraspecific competition between larvae was al so important. However, the relative contribution of each of these comp onents to the density-dependent relationship was unclear. A simple mod el showed that the population is regulated by density-dependent larval mortality at an eqiulibrium of 11 newly-emerged females/dm2. Overwint ering adult mortality is unlikely to affect this equilibrium significa ntly. However, year-to-year variations in density-independent egg mort ality (or oviposition success) was shown by the model to have a major potential effect on both the equilibrium level and population stabilit y.