O. Merkl szerk.: Folia Entomologica Hungarica 66. (Budapest, 2005)
( 1998-2002) new localities were selected by further search (by car and by foot) in the collecting season. Appropriate sites were also discovered by observation from lakeshore trains during the winter season when sites are less hidden by the foliage of trees. The observation point on the railway bed is often above that of a car. A few localities were also discovered in winter, when the reeds was harvested. Many sites were visited once. Repeatedly visited sites were selected according to the character of the locality, the found or assumed richness of the fauna, and the location along the entire shoreline. Altogether 37 localities and 83 samples were collected between 1998 and 2002. Fifteen localities were sampled twice or more times. Collectings were made annually in June-July and September-October. Species accumulation curves were constructed and fitted by the y = a ( 1 -e" bx ) equation (HYAMS 1995), where a: saturation level of the curve e: natural logarithm, b: curve fitting parameter. Habitats were grouped by their geomorphological characteristics, botanical composition and the degree of direct human influence. Partly different habitat characteristics are important for the aquatic and the semiaquatic Heteroptera, respectively. Characteristics which were considered while selecting collecting sites, and which, according to authors' opinion, influence presence or absence, and the density of different species populations are listed below. Water depth: 0-1 m. Collectings were made from wet mud, from among tussocks, as well, as from the deep water of harbours where the length of water net limited the depth of collecting. Size of open water surface: It varies substantially, e.g. from narrow surface of water-stripe behind reeds, channels of 1-5 m width in reeds, bays differing in size from that made for an anglers boat in reeds through open bay of public beaches up to open water along stoned shore, or along the reed belt. Connection to open water surface: This basically influences the intensity of waves, with all the consequences to the water quality characteristics for insects. The range varied from the on the surface totally isolated water margins behind reeds, through water within reeds, to basins or built channels at 1-80 m distance from, but connected to open water. Material and character of bed: The bed was, in most cases, composed of sand or sandy mud. In basins closed or those with hardly turbulent water, anaerobic conditions may develop and the benthos consists of decaying plants. In a few areas along the northern shore the bed is covered by stones. Pebbles and larger stones are covered by algae in the whole waterbody. Material and character of shore: The free shoreline was largely stabilised by embankment, set with stone or rock-packing (0.5 m or higher above average water level) during the 20th century. Hardly any natural shores have been left. In such places, tussocks of grass and roots of trees alternate with flat sand or pebbles. The shoreline is often grown in by reed belt of various width. If the water or the macrophyte vegetation in the water is backed by a built shore, the habitat does not offer possibilities to landing for semiaquatic bugs in escape or before overwintering. Submersed vegetation: Hairweeds of different species {Potamogeton, Elodea, Myriophyllum, Stratiotes, as well as underwater parts of emersed plants). In some places in the Keszthely Basin as also in other basins, local algal bloom may appear. Emersed, floating vegetation: Besides algae and hairweeds, Lemna spp., Hydrocharis morsus-ranae, Nuphar luteum and occasionally Nymphéa alba were noticed. Lemna may totally cover the entire water surface (water bugs were absent in such channels). Hydrocharis is preferred by Mesovelia (VÁSÁRHELYI 1989), its stands may be inhabited even near open water. Macrophyte vegetation: At shallow shores, grass, sedge (Carex), Glyceria, in deeper water Typha angustifolia and T. latifolia, Scirpus lacustris and reeds (Phragmites australis) was present. Microvelia species preferred microhabitats with not dense stands of sedges and Glyceria. If reeds is harvested, there is no shelter during the first months of the vegetative season.
