A comparison of the biology and karyotypes of Zodarion germanicum and Zodarion rubidum (Araneae, Zodariidae) which occur in central Europe was carried out. Surprisingly, these species were found to differ in a number of characters such as pattern of activity, reproduction and karyotypes. Zodarion germanicum was observed to be diurnal, whereas Z. rubidum is nocturnal. Courtship and mating were markedly longer and more complex in Z. germanicum than in Z. rubidum. Females of Z. germanicum produced only one or two successive egg sacs including 17 eggs on average which they would guard, while females of Z. rubidum produced up to 5 egg sacs each having 4 eggs that they abandoned. The two species differ from each other also in number of chromosomes and the sex chromosome system. Results suggest these species belong to distant evolutionary lineages within the genus Zodarion.