S. Mahunka szerk.: Folia Entomologica Hungarica 43/1. (Budapest, 1982)
m 1977 1978 1979 1980 Sh Wf Sh Wf Sh Wf Sh Wf O NSp p.c. NSp p.c. NSp p.c. NSp p.c. NSp p.c. NSp p.c. NSp p.c. NSp p.c. I. 19 54.28 15 34.88 18 51.42 12 31.57 16 50.00 12 34.28 16 51.61 19 42. 22 II. 11 31.42 13 30.23 9 25.71 1 0 26.31 10 31.25 10 28.57 7 22.58 13 28. 88 III. 4 11.42 7 16.27 6 17.14 8 21.05 4 12.50 8 22.85 5 16.12 6 13. ,33 IV. 1 2.85 8 18.60 2 5.71 8 21.05 2 6.25 5 14.28 3 9.67 7 15. 55 Sh: Sand hills; Wf: Wind furrows; NSp: Number of species. Groups of different ecological valence: I.: dry-grass specific species; II.: xerophilous species; III.: indifferent species; IV.: non-characteristic species. The changes of the leafhopper community have been indicated by the changes of the number of species belonging to the different groups and the dominance relations of these groups. 1. Change* of species composition: The experiences apparently negate the theory, because the number of specific and xerophilous species (groups I and II) decreased slightly during the four years (Table 4). At the same time, the number of species in group III were almost equal, and the number of not characteristic species increased slightly. We can say the same about the qualitative rates of the four groups. The number of all species decreased from 35 to 31. Both the number and rate of the species in group I in the wind furrows increased, the number of species in groups II and III hardly changed, and the number of species in group IV slightly decreased. The number of all species in the wind furrows decreased progressively until 1979, but it reached the highest value hitherto in 1980 (Table 4). 2. The changes of dominance relations: As it was expected, the populations of the dry grassland specific species became more and more dominant, their proportion in the leafhopper community increased from 47 p.c. to 64 p.c. during the 4 years. This increase proceeded to the detritment of the other groups, which dominance values decreased in almost equal rate of (Fig. 1). In, the wind furrows the species of group I had only a subordinate role, their dominance increased with about 2-3 p.c. during the 4 years. Group II was the most important one, and though its importance decreased by 10 p.c., it still remained the first group. By way of compensation, the rate of the indifferent populations increased (Fig. 1). It can be seen that the order of importance of the 4 groups are the same on the sand hills according to the number of species, the rate of the number of species and the dominance relations. The order is the following: group I, II, III, IV. Group I of the wind furrows was also dominant according to the number of species, but it was only the third according to its dominance. The number of species in groups II and III were less, but their dominances were higher than in group I. Thus it is demonstrated above, that not only the microclimatic conditions and plant associations of the two biotopoes in the mosaic-complex grassland are very different, but the leafhopper communities of them as well. Therefore we can investigate the changes of the structure of leafhopper communities according to the successive changes of plant associations. It appears to a lesser extent as the qualitative regrouping of the species belonging to the different groups of ecological valence. The changes in the quantitative proportions of the populations are more important because they anticipate and lead to qualitative changes. Summary In 1977-1980, from among the 94 lÄifhopper species found in the mosaic-complex sandy soil grassland of Bugac (Hungary) 66 species were on the sand hills and 71 species were in the wind furrows. Turrutus socialis , Anaceratagallia ribauti , Aphrodes bicinctus and Ribautodelphax albo striatus were important in both biotopes. Besides them 6 species were important in the wind furrows and ê species on the sand hills. Kelisia perrieri Rib, is a new species in Hungary. 41.3 p.c. of the species occurring in the wind furrows are univoltine, 26.9 p.c. are bivoltine
