Karyotypes ofPipistrellus Pipistrellus(Schreber 1774) andP. Nathusii(Keyserling and Blasius 1839) (Chiroptera: Vespertilionidae)

SUMMARYExamination was made of the chromosomes of Common Pipistrelle and Nathusius' Pipistrelle originating from the Bialowieza Primeval Forest (52°42'N, 23°51'E). Identical 2N=44 and NFa=50 were found in both specics. The karyotypes of the species examined differ only in respect of the dimensions of one pair of marker chromosomes. The possibility of the evolution of the chromosome formula in different geographical cytotypes of P pipistrellus is discussed.