S. Mahunka szerk.: Folia Entomologica Hungarica 50. (Budapest, 1989)
ROVARTANI KÖZLEMÉNYEK L 1989 p. 165-168 Microhabitat preference of the pondweed bug Mesovelia furcata (Heteroptera: Mesoveliidae) By T. VÁSÁRHELYI (Received 10 May, 1989) Abstract: Microhabitat preference of the pondweed bug Mesovelia furcata (Heteroptera: Mesoveliidae*. - Microhabitat preference was investigated by using two different methods: estimations in the field and dispersion on an artificial arrangement of Hydrocharis, Lemna and open water surface. In both Lemna was preferred to Hydrocharis and water surface. In the framework of a recent project (Bakonyi and Vásárhelyi, 1987) attempts were made at sampling individuals of the semiaquatic bug genera Hebrus, Microvelia and Mesovelia^ 'Hebridae, Veliidae and Mesoveliidae). Considerable literature has been published on the bionomy, population biology as well as coexistence, habitat partitioning and microhabitat selection of Gej^ris species ie. g. Spence, 1980, 1981, 1983, Nummelin et al. , 1984* but data on the coexistence and/or microhabitat selection in smaller species of semiaquatic bugs are scarce (Andersen, 1982, Zimmermann, 1984). The smaller size, the smaller range of searching activity and the impression of their preference for certain vegetation types necessitated the development of new sampling equipments and the selection of a method suitable for density estimations. During these attempts microhabitat preference of the pondweed bug could also be investigated. Zimmermann (1984) listed the plants commonly found in the habitats of M. furcata (Table 6), also with literary references, latter however, with two mistakes. Besides him, Jansson (1916* and Stichel (1955) also mentioned Lemna as belonging to the habitat of the pondweed bug. Of the plants listed in the table Nymphaea alba and some submerse species occurred also in my study area. M. furcata was not observed on the open water surface here (including the areas densely grown in by submerse vegetation) and only a few specimens were found in a stand of N. alba, thus only two types of stands were investigated: Lemna sp. and Hydrocharis morsus-ranae. Field work and density estimations were carried out in a lacuna (about 100 m long and 15 m wide* of Lake Balaton, near Keszthely. The lacuna, that used to be an estuary of the stream Csókakő, was grown in by dense submergent and emergent vegetation, and was undisturbed disregarding the slow movements of boats of anglers In the middle of the water. The artificially built shore was steep, no zonation of shore vegetation existed. Along the shore stages and boats offered good observing possibilities. Of the emergent plants, Lemna sp. (probably L. minor) had the highest coverage and there were some stands of Hydrocharis morsus-ranae, each with an area of 0.04-0.25 square meters. Stands of Nymphaea alba were situated more closely to the open water of the Lake, and the density of the pondweed bug could be influenced by the waves, too. In an earlier attempt in 1986 a plastic cylinder attached with a polyurethane-foam belt was lowered into the water/plant surface and specimens captured on their two-dimensional habitat were collected. Although the equipment could be used on open water and
