Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 51. (Budapest 1959)

Kovács, L. ; Gozmány, L.: Data to the quantitative relations of the Lepidoptera of the Alderwood Marshes in Ócsa, Hungary

bilineata L., of which we have disturbed very many from the shrubs and but 2 specimens were caught on the lamp. The results of the indirect survey methods are furthermore influenced also by external conditions, first of all weather conditions. Aside of these, lunar changes too have a strong effect on the results of the collectings by an artificial source of light. The effects of weather conditions and lunar changes wrought on the results of our Ócsa surveys are shown on Graph I. Naturally, Graph I. The effects of weather conditions and of the full moon on the numbers of the captured imagos (individuals) as related to one lamp. Vertical axis denotes numbers of individuals in hundreds ; horizontal coordinate shows the several dates of the surveys. Abbreviations : c = cold ; m == mild ; s = squall ; nft = nocturnal fall in temperature ; ^fm = full moon ; w = warm. if the surveys be made systematically during a number of years, the fluctuation caused by the Moon and weather conditions will not be apparent from the values of the annual means. We raised the question whether external conditions influence also the number of species or but their individual numbers. Observations up to now seem to indicate that they do it in a much smaller rate than in the case of specimens. This is shown, first of all, by the fact that the number of species worked out indespendently of the ways of the Moon and the weather conditions in 1952. It was low and medium in June and in the beginning of July, it was high in the middle of July, from then on medium till the middle of August, and low from the end of August ; therefore there was no monthly fluctuation. This was also supported by the control surveys of 1953. The number of species on 12 June was but slightly higher than that observed on 10 June 1952, even though external conditions were favourable. On 10 July, and at considerably more favourable external conditions, the number of species equalled the one found on 8 July 1952, — at full moon ! Another important deficiency of the surveys made by artificial light sources is the fact that the effectivity of the light source will decrease by the increase of the distance from it ; furthermore it depends on whether it radiates in an open or within a closed space. For this very reason, no concrete area can be determined on which to relate surveys made by this method, and therefore the number of specimens collected is not an abundancy value.