O. G. Dely szerk.: Vertebrata Hungarica 8/1-2. (Budapest, 1966)
Topál, Gy.: Some observations on the nocturnal activity of bats in Hungary 139-166. o.
with reference to the former species,that the activity graph taken at the Pisznice Gave in the end of June is divided (cf. Table l). On this day, the first Myotl 3 appeared at 2057, and by this start the hypothetical curve, to he attained in the case of a pure Myoti s population, would have "been satisfactorily completed. The duration of the exit, as far as I was able to establish from my records (when I have noted the appearance of the first Myoti s specimens), fluctuated between 38 and 66 minutes. In Héviz, I had to study the nocturnal activity of this species together with Myotis oxygnathu s, due to technical causes. The fundamentally slight differences between the two species in this regard is hardly appreciable and might safely be left out of account.In this population, the period between sunset and departure lasted between 56 and 63 minutes at the end of July, 1957 (Table l), hence it deviates from that observed at the Pisznice Cave. In a clear weather on 20 June, the bats began their exit 4 minutes earlier than on the next evening under an overcast sky t Therefore it was found again that contrarily to the behaviour of Rhlnolophus euryal e, this species is not influenced at all. by the light conditions at the close of the day. At the beginning of July, 1953, the time elapsed after sunset until the commencement of the departure was 42 minutes, and this no more differed from the situation at the Pisznice Cave. These differences therefore imply that a consideration of the seasonal changes is not sufficient in itself, but the comparison of observations made in diverse years is also indispensable. KOLB's (8) results also show deviations between the data of two years. Also, at the explanation of the differences between the Héviz and Pisznice data on should not leave the fact out of consideration that, in the mixed population of the Pisznice Cave, the earlier activity of the Rh. euryale specimens may have a stimulating effect on the M yoti s individuals. In studying the Héviz population, I might yet add
