1 The presence and abundance of arthropods were compared in three olive orchards under organic, integrated and conventional management regimes. In each olive orchard, trees were sampled in the canopy by beating branches and soil arthropods by placing pitfall traps. Contrary to expectations, the highest abundance of arthropods occurred in the integrated management orchard. The most abundant groups were Formicidae and the species Euphyllura olivinae (Homoptera: Psyllidae). 2 Canopies and the soil under the tree canopy (interior soil) were selected as the most informative sites for sampling. The months with the strongest differences were May, June and July, especially June. In the canopy, Araneae, Coleoptera, Diptera, Heteroptera, Hymenoptera, Homoptera, Lepidoptera, Neuroptera and Thysanoptera were the most abundant, and showed significant differences in abundance among orchards with different management regimes. Moreover, in the canopies, Coleoptera and Lepidoptera showed a seasonal pattern of abundance and consistent significant differences between the organic orchard vs. the integrated and conventional ones in both years of study. In the soil, 12 orders showed significant differences in abundance among management regimes at some point of the sampling season. 3 In a search for biological indicators that could help to distinguish between management regimes, a discriminant analysis applied to the data indicated that only the samples from the canopy were classified according to their management regime in a consistent way over time. The groups selected by the analysis to establish differences among management regimes were Coleoptera, Diptera, Heteroptera, Lepidoptera and Thysanoptera. The analysis applied to compare organic vs. non-organic olive orchards, again identified Coleoptera and Lepidoptera as suitable groups. The results suggest that these two orders are potential bioindicators to distinguish, in a simple way, organic olive orchards from non-organic ones.

Within‐generation mortality of the bark beetle L. varius was studied in a Spanish olive orchard by placing cut logs in the field for adult females to breed. Mortality was greatest at the larval stage with only 10% of the original egg number surviving to adulthood. There was no evidence that the density of eggs laid per maternal gallery affects subsequent mortality at the egg, larval or pupal stages. The density of maternal galleries on a log, however, was found to have a positive influence on the mortality of larvae, but not of eggs or pupae. Part of this density‐dependent mortality could be attributed to insect parasitoids, but the effects of intraspecific competition between larvae was also important. However, the relative contribution of each of these components to the density‐dependent relationship was unclear. A simple model showed that the population is regulated by density‐dependent larval mortality at an equilibrium of 11 newly‐emerged females/dm2. Overwintering adult mortality is unlikely to affect this equilibrium significantly. However, year‐to‐year variations in density‐independent egg mortality (or oviposition success) was shown by the model to have a major potential effect on both the equilibrium level and population stability. Zusammenfassung Zur Populationsdynamik von Leperisinus varius (Fabr.) (Col., Scolytidae) in Olivenbäumen (Olea europaea) Die Mortalität des Borkenkäfers Leperisinus varius im Laufe einer Generation wurde in einer spanischen Olivenplantage mit Hilfe ausgelegter Baumabschnitte als Brutplätze untersucht. Die Mortalität war im Larvenstadium am größten mit etwa 10 %. Es gab keine Hinweise darauf, daß die Eidichte pro Muttergang die nachfolgende Mortalität der Eier, Larven und Puppen beeinflußte. Die Dichte der Muttergänge in einem Stammabschnitt jedoch zeigte eine positive Korrelation zur Mortalität der Larven, nicht aber zu jener der Eier und Puppen. Anteil an dieser dichteabhängigen Mortalität hatten zweifellos die Parasitoiden, doch war auch die intraspezifische Konkurrenz zwischen den Larven von Bedeutung. Allerdings blieb der relative Anteil jedes einzelnen der genannten Faktoren unklar. Ein einfaches Modell zeigt, daß die Populationsdichte durch die dichteabhängige Larven‐Mortalität mit einem Gleichgewicht bei elf frischgeschlüpften Weibchen/dm2 reguliert wird. Die Mortalität der überwinternden Adulten nimmt auf dieses Gleichgewicht keinen bedeutenden Einfluß. Jedoch zeigt das Modell, daß Jahr‐zu‐Jahr‐Variationen der dichteunabhängigen Ei‐Mortalität von wesentlicher Bedeutung sowohl für den Gleichgewichtslevel, als auch für die Populationsstabilität sind.

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