Dr. Murai Éva szerk.: Parasitologia Hungarica 25. (Budapest, 1992)

The original aim of this study was to test a well-known and very simple principle: any disturbance in an ecosystem is likely to be indicated earlier and more efficiently by changes in the structure of communities than by abundance changes or presence/absence relations of individual species. We selected two test groups of flies: the so-called synanthropic flies (collections made with Gregor-Povolny's traps baited with human faeces) and the drosophilids (results published elsewhere, see Papp 1992). Originally we intended to assess the deformation caused in the community structure of the dipterous assemblages by human activity (we thought that assemblages of species visiting human faeces were proper test groups). In the course of studies other aspects also arose: how the populations of rare species (discussed elsewhere) should be dealt with, and how wide the meaning of the term "synanthropic fly" should be. The term "synanthropic fly" has an obscure origin; I found the earliest use in the works of some Soviet dipterists from the early 40's (for a short review of the early literature see Stackelberg 1956). Most studies of this kind in Europe were done by F. Gregor and D. Povolny, who not only made invaluable, extensive and interesting collectings (also in Hungary, see Gregor and Povolny 1960) but also proposed a terminology for their grouping (Gregor and Povolny 1958). Our original plan and later work were much influenced by the results of Ferenc Mihályi, who collected synanthropic flies in all parts of Hungary in the late 'fifties and early 'sixties. He used the same traps as we did in the present study; he baited his traps with human faeces, decaying meat and fresh ripe fruits. Mihályi (1965,1967) published several interesting papers and made a comprehensive summary of results in his theses (Mihályi 1966). In accordance with his aims, he stressed connections with public health, human epidemiology etc. For us the species composition, abundance relations etc. are more important aspects. Nevertheless, we found his data very useful for comparison also in the latter respects. All the voucher specimens are preserved in the collection of the Zoological Department, HNHM, Budapest (pinned, or minutia-pinned and double-mounted, also those specimens which were originally kept in alcohol). MATERIALS AND METHODS In 1988-1990 collections were made in four localities of low mountain creek valleys in N and NE Hungary at an altitude range from 250 to 400 m a.s.l.. These four valleys are affected by tourism to a varying extent: least at Aggtelek, most strongly at Magyarkút. All the four sites are comparatively well-known as regards the faunistics of dipterous flies, e.g. they are characterized by a peculiar black brachypterous fly, the only pleciid species of Hungary, namely Penthetriafiinebris Meigen, 1804 (= holosericea) (see more in Papp 1992). The four sites are: Aggtelek National Park: Aggtelek, Ménes-völgy [=valley], Medvés-kert (below coded with A): below Ménes-forrás [source];