Seasonal and diel flight activity patterns of aquatic Coleoptera and Heteroptera

1t is a well known fact that most aquatic insects can tly. Data collected by Jight trapping (BENEDEK & JÁSZAI 1972, NovtNSZKY 2003) and field observations are not suitable to analyze daily tlight activity patterns of aquatic insects because the attraction of light traps is considerably reduced by day due to the higher ambient light intensity. At the same time, the seasonal and diurna) tlight patterns have been investigated effectively only severa) times (FERNANDO 1958, PoPHAM 1964, PAJUNEN & JANssoN 1969, FERNANDO & ÜALBRAITH 1973, LANDIN 1980, BEHR 1990, 1993, BODA et al. 2003, CsABAI et al. 2003, 2004,). Aquatic insects recognize aquatic habitats by means ofthe horizontal linear polarization oflight retlected from the water surface (SCHWIND 1991 ). Numerous earlier field experiments (ScHWIND & HoRVÁTH 1993, HoRVÁTH 1995, HoRVÁTH & VARJÚ 1997) have shown that the horizontal polarization of retlected light is the major optical cue that attracts water insects to shiny surfaces; therefore, using horizontal shiny black plastic sheets is a suitable method throughout the day because it always polarizes the retlected light strongly and horizontally (HORVÁTH & VARJÚ 2003). Utilizing this phenomenon of aquatic insects landing on the shiny black plastic foils while foraging for water surfaces, we collected samples over one entire day per week for 2 years. In this paper, only the dispersa) activities of the most abundant species are discussed in detail.