O. Merkl szerk.: Folia Entomologica Hungarica 66. (Budapest, 2005)

VÁSÁRHELYI 2005). Previous studies revealed a certain indicator value of these bugs and their presence-absence data (HUFNAGEL et al. 1999). The use of species assemblages to monitor long-term changes requires the collection and analysis of such data. The present paper gives an overview of the species found so far, and characterises the lake by the found and searched habitats. The microhabitat preferences of species populations, or the detailed composition of habitats are not dealt with. HISTORY OF COLLECTINGS During seven decades a considerable amount of data has been accumulated on the aquatic and semiaquatic bug fauna of Lake Balaton (Hungary). GÉZA HORVÁTH (1847-1937), the outstanding hemipterist, collected materials around the lake and published his faunistic results giving the names of 21 settlements as the localities of the species (HORVÁTH 1931). ÁRPÁD SoÓS (1912-1991), after research in altogether six years between 1936 and 1965 treated the human impacts on the fauna of the lake (SoÓS 1977). Since only a few species names were mentioned by him in connection with human impacts, his data have not enriched the faunistic list. The Hungarian Natural History Museum conducted a research programme around the lake, and this supported the first thorough investigations of the present authors. Between 1984 and 1986 40 collecting localities were visited, several repeatedly, and as many species as possible were collected (VÁSÁRHELYI & BAKONYI 1988). These data allowed the first evaluation of the significant changes (VÁSÁRHELYI & BAKONYI 1991) and were later used for investigating the indicator value of species assemblages (HUFNAGEL et al. 1999). After two years of collectings BÍRÓ and HUFNAGEL gave a list of their 44 collecting localities in the watershed of the lake (BÍRÓ & HUFNAGEL 2001 ). Thirteen localities are mentioned in their paper, which do not belong to the lake itself: channels, streams, springbasins or remote settlements. In some cases it is difficult to determine where the margin of the lake is, and where channels, estuaries and harbours end. MATERIAL AND METHODS During our investigations, systematic sampling by common water net, and singling with specific water nets were used. Sampling time was not limited. We tried to catch all species currently present in the habitat. Sampling localities were selected according to the authors' knowledge (field experience) about the lake and around the lakeshore. In the course of recent explorations