Species richness and composition patterns across trophic levels of true bugs (Heteroptera) in the agricultural landscape of the lower reach of the Tisza River Basin

River basins are among the most threatened ecosystems. The species diversity of several European river basins decreased seriously during the last decade due to loss of habitats and increasing land use pressure on the remaining habitats. We studied true bug assemblages in various land use types of grassland fragments and dikes as linear grassland habitats in the agricultural landscape of the lower reach of the Tisza River Basin. We tested the effects of the recorded variables of habitat quality, surrounding landscape and land use type on the abundance, species richness and composition of true bugs. Altogether, 5,389 adult Heteroptera individuals representing 149 species in 13 families were collected. The factors which influenced significantly the species richness of different trophic levels (i.e. herbivors, predators) and degrees of food specialization (i.e. generalist and specialist herbivors) were concordant. Contrary to this, the factors which influenced the abundance of the different feeding groups varied strongly. We emphasise the vegetation and land use types as primarily influential factors for insects. Excluding the grass-feeding species, the number of both generalist, specialist herbivorous and predaceous species were lower in agricultural swards, i.e. hay-meadows and pastures than in old field and dike habitats and their number increased with increasing vegetation diversity. Due to the high species richness and abundance observed in dike and old field habitats compared to agricultural swards, we emphasise their importance for conservation of insect diversity and we stress the negative effects of agricultural intensification on the remaining grasslands of the lower reach of the Tisza River Basin.