Tóth Sándor: A Bakony természettudományi kutatásának eredményei 25. - A Bakonyvidék zengőlégy faunája (Diptera, Syrphidae) (Zirc, 2001)

HOVERFLY FAUNA OF THE BAKONY REGION (SUMMARY)

To lesser extent, material of light-traps of lepidopterists working on different locations of the mountains was also utilized. Occassionally bowl-traps were also placed (yellow bowls), especially to investigate hoverflies which were overwintering in adult form. For identification of hover flies, handbooks of ROTHERAY (1993), SACK (1928-1932), STACKELBERG (1970), STUBBS - FALK (1983) and TORP (1994) were used. In addition, several papers dealing with the revision of genera to some extent were of great help in identification of the species. Zoogeographical assessment Assessment of the hover fly fauna by small geographical units was carried out based on the work entitled "Zoogeographical conditions of the Bakony Mountains" (PAPP 1968). In this work the author distinguishes 5 zoogeographical units within the mountains (1. Balaton Highlands, 2. Keszthely Mts, 3. Southern Bakony, 4. Northern Bakony, 5. Eastern Bakony). The most significant modification was to separate Bakonyalja (involving Pannonhalmi Hills) as the sixth unit. In the frame of this research we have investigated which species were found in each geographical unit. So far Northern Bakony proved to be the richest in hoverflies as exactly 92 percent of the species were found here (312). Further order of succession: Balaton Highlands: 270 species (79.4%), Keszthely Mountains: 246 species (72.3%), Bakonyalja: 227 species (66.8%), Southern Bakony: 224 species (65.9%), Eastern Bakony: 196 species (57.6%). It is obvious that some small geographical units of the Bakony cannot be considered equally well investigated from the point of dipterology. However, we cannot say that it is the sole reason for the significant differences in species number found in each unit. Not considering some taxa having unknown distribution, most of the species found exclusively in the Northern Bakony are more or less montan elements. Also, most species found to occur only in the Balaton Highlands are having southern (at least partly Mediterranean) distribution. Composition of the hover fly fauna Fauna composition can be investigated from several point of view. Strictly speaking, fauna investigation based on small geographical units which we were discussing in the previous chapter can also be involved. An evident way of grouping can be based on feeding habits of the larvae, which was mentioned when giving a general characterization of hoverflies. Also, experiences considering qualitative and quantitative composition of the fauna are worth presenting briefly. Qualitative composition of the hoverfly fauna Quantitative composition of the fauna is normally characterized by the occurrence of rare species. However, it might cause some problems that determining how rare a species is can be subjective. In between rare and frequent (common) taxa researchers generally differentiate 5-7 categories, according to the number of known places of occurrence in the given country. As a contrary, the author used a different method which is based on the assessment of relative categories of frequency determined on the basis of data on occurrence and on UTM maps and which was proven to work well in practice (DÉVAI -