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Summary 1.During the last few years a variety of methods have been applied in Switzerland to preserve and enhance biological diversity in agricultural systems. The purpose of this study was to evaluate grassland management techniques in respect of their effectiveness within a managed area and to examine how these areas contribute to species diversity at a landscape scale. 2. We examined insect diversity in grasslands subject to different management in a heterogeneous landscape in part of the Swiss Jura. Four study areas with varying landscape structure were selected and, in each area, meadows of two grassland management types were investigated. 3. The true bugs (Heteroptera) were chosen as an indicator group for insect diversity on the basis of previous work that had shown that the richness of the bug fauna correlates strongly with total insect diversity. 4. The variance of the heteropteran species data was partitioned into spatial (area) and management components. Area accounted for 35·4%, management for 29·7% and the interaction management × area for 7·2% of the species variance. The species diversity was greater in extensively managed meadows than in intensive ones; extensive sites had more individuals and showed a more even rank abundance distribution. 5. Individual species differed in their responses to management. Two species benefited from intensification whereas six species were affected negatively by intensive management. Two main groups of species did not appear to respond to management; these were mostly widespread species occurring in a variety of habitats, and polyphagous species which live in a wide range of grasslands but which show a certain affinity to managed meadows. 6. Our study indicates that extensive management of grasslands can enhance both local and regional insect diversity in agricultural landscapes. Extensively managed meadows were species-rich habitats that supported some rare and specialized species. In contrast, the bug community of intensive meadows was dominated by more widespread and less specialist species.

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Abstract. 1. In a laboratory experiment, the influence of host plant diversity and food quality, in terms of nitrogen content, on the larval survival of two oligophagous bug species (Heteroptera, Miridae: Leptopterna dolobrata L., Notostira erratica L.) was investigated. Both species are strictly phytophagous and capable of feeding on a wide range of grass species. Moreover, they typically change their host plants during ontogenesis; it has been suggested that this behaviour is a response to the changing protein content of the hosts.2. To investigate the importance of host plant diversity for these insects, the development of insects reared on grass monocultures was compared with that on mixtures of four grass species. In addition, the host grasses were grown under two nitrogen regimes to test whether nitrogen content is the key factor determining host plant switching.3. Both species had a significantly higher survival rate when feeding on several host plants but only L. dolobrata showed a significant response to food nitrogen content. Furthermore, there was no correlation between the nitrogen content of the host plants and the survival rate of N. erratica larvae.4. The study suggests that at least some Stenodemini need a variety of host plants during larval development but that the level of host plant nitrogen is not the main factor responsible for the observed diversity effect.