S. Mahunka szerk.: Folia Entomologica Hungarica 56. (Budapest, 1995)

Fig. 1. Changes of abundance of the three grasshopper communities during sampling time. Trend in the shapes of the curves on that of the two grazed grasslands - alfalfa site (AL), pasture (PL) - is similar to each other number of grasshoppers was also the highest on the PL site (9 species), while on the AL site 6 and on the SM site 7 species. The caught species number - by sweep netting method - was relatively low on each site. We could find similarities between the dominance curves of the species according to the species rank on the AL and the PL sites, but they were different from the curve of grasshopper community on the SM site. On this latter there was only one species (Chortippus parallelus) that had strikingly high dominance value.On the other sites the dominance values were lower and more equalized, there were a dominant and at least one or two sub-dominant species. The dominant and subdominant species were Chortippus albomarginatus, Chortippus dorsatus on the AL site, while Euchortippus declivus and Chortippus parallelus on the SM site (Fig. 2). The presence of these species in large numbers reflected the microclimate conditions of the different sites as well. The high dominance values of Chortippus albomarginatus, Chortippus dorsatus indicated more moderate microclimate close to the ground surface and higher moistuere content in the soil and in the air among the vegetation. On the one hand, the presence of Euchortippus declivus with high individual number indicated drier and warmer conditions, while Chortippus parallelus medium moisture conditions and higher average height of the plant species. The Shannon-Wiener diversity indices slightly increased from July to September on each site, but got the highest values in the AL site, and a somewhat lower ones on the PL. The lowest values were found in the SM (Fig. 3). The hierarchical cluster analysis revealed two main groups in the grasshopper communities. One of them contained the PL and the AL sites. These are the so called disturbed sites (grazed sites), but the other group contained grasshopper communities in the SM site. The analysis also revealed that the early summer (July) communities of the three fields have light similarity. The mid-summer and the late summer states were divided into two groups. The cluster analysis also divided the disturbed group into two subgroups, namely the PL and the AL site communities (Fig. 4).