S. Mahunka szerk.: Folia Entomologica Hungarica 53. (Budapest, 1992)

on the ground and the wind speed were always measured. (Not for the purpose to find any correlation between capture results and the meteorological data but in cases we captured less than expected, this way we had a slight chance to find the reasons.) In 1988 12 samples were collected, in 1989 13 samples, in 1990 10 samples. Other than these samples, several other drosophilid materials were caught (on oozing sap of an oak tree, on leaves and young twigs of oaks infested by Kermes coccids, on kitchen refuse (compost heap), etc. These dipterous materials served as sources to judge the species richness of the given site. Altogether 9,563 drosophilid specimens were collected and identified. The taxonomical sequence and nomenclature follows the catalogue of Bächli and Rocha Pité (1984). When analysing the samples, the Shannon-Wiener index (polynomial entropy), evenness index, Berger-Parker (dominance) index and the Jaccard index (species identity index) were calculated. Some other numerical methods were also applied: the results of two similarity indices the Czekanowski index (for similarities in abundance), and the Renkonen index (for similarities in dominance) are given. Similarity values were processed by a group linkage method using average linkage to gain dendrograms. The results using some more sophisticated methods will be published in a second paper (Izsák and Papp, in preparation), where a wider cenological (ecological) interpretation of the primary results will also be given. RESULTS The results are summarized in Tables 1 and 2. Representatives of 40 species were caught (31, 31, 36 spp./year), some of them (A. (Amiota) rufescens, Chymomyza cauaatula, Drosophila (Sophophora) helvetica, D. (Sophophora) subsilvestris, D. (Drosophila) tsigana, D. (Drosophila) unimaculata) are new to Hungary (for details see Papp 1992). In 1988 six to 18 species/sample (n= 12) were collected, in 1989 seven to 16 spp./sample (n= 13), in 1990 five to 21 spp./sample (n= 10); 8, 8, and 9 spp. were caught only once, six spp./1988, five spp./1989, seven spp./1990 were represented by a single specimen. The ratio of the population size of the rarest and the dominant species is actually 1 to 2,845; however, we can suppose a value of 1 to 10

4 or even higher for the rarest but not yet detected species. The S.-W. diversity indices are never high, evenness is highly variable (medium to low) (Table 3). The highest diversity values - as a mean - were found at Magyarkút, the lowest ones at Aggtelek (the mean values of H' are A 1.4773, B: 1.5347, M: 1.6920, V: 1.6347). In 1989 the population size of D. phalerata and that of the related species ("yellow wild species", larvae mycophagous) were much lower than in 1988 as a consequence of the different climatic conditions of the consecutive years. Consequently, the relative frequencies of the "black species" (D. (S.), obscura, D. (S.) subobscura, larvae frugivorous, etc.) were higher (cf. Table 7/A); i.e. population frequencies in the assemblages profoundly changed from one year to another, probably as a natural process. Since the year of 1990 was a "intermediate one" compared to 1988 and 1989, the Czekanowski and Renkonen similarity values from the 1988 and 1989 samples