S. Mahunka szerk.: Folia Entomologica Hungarica 46/2. (Budapest, 1985)
and Querco-Fagetum on lime, limestone and volcanic substrates in areas with lower annual precipitation than 700 mm (mountains of Bakony, Mecsek, Vértes, Gerecse, Pilis, Börzsöny in Hungary and Burda, Povazsky' Inovec, Tribec? in Slovakia). Similarly, it was not registered in forest - free alluvial plains of rivers despite of their secondary reafforestation by poplar groves. In humid areas with a higher annual total of precipitation and on alluvial terraces with a permanent moisture survives this species also in bushy groves and in wet habitats with Phragmites, Typha, Carex sp. out of forests (lowlands along the Danube and Tisza rivers), but in meso- and xerophilous hedges and fencerows (Roso - Prunetum and similar ones) surrounded by agricultural lands In lowland and hilly region - scapes despite the occurrence of it's hosts, e.g. C. glareolus. Megabothris (Megabothris) walkeri (Rothschild, 1902) Taxonomy: Monotypic species. General distribution: Boreal Mesoeuropean, European part of Mesic Mediterranean, SW parts of Siberian sector of Palaearctis. Hosts: Arvicolidae - Microtus oeconomus mehelyi, M. agrestis and Clethrionomys glareolus. Distribution in the Carpathian Basin (Fig. 2): Hungary: 4640/1713 Kisbalaton (SZABÓ, 1966, 1973); 4640/1713 Kisbalaton, Diássziget 23-26.03.1982 12 §, 13 9 leg. J. KOVÁCIK, F. MÉSZÁROS, A. STOLLMANN (Our unpublished data). Czechoslovakia: 4757/1735 Gabcikovo; 4752/1747 Calovo; 4750/1742 Cilizská Radvan (ROSICKY, 1957); 4748/1748 Cicov (CYPRICH et al. 1984); 47 50/1736 Topolbvec (Our unpublished data). Austria: 4 7 52/1641 Neusiedlersee, N-shore; 4757/1651 Neusiedl (SMIT, 1967; PEUS 1969). Microtus oeconomus is known from 4 sites in the Pannonian lowland (SZUNYOGHY, 1954; TOPÄL, 1963; TAST, 1982) in depressions with native wetlands. Megabothris walkeri was registered in three areas within that region (the environs of lake Neusiedl, Balaton and Zitny ostrov - Cereal island) while the fourth region Ágasegyháza - Orgovány (between the Danube and Tisza rivers) was not investigated as to Siphonaptera and, according to recent information, habitats are disappearing due to meliorations. The mountain inhabiting populations of M. walkeri (related to Microtus agrestis ) that are numerous in regions belonging to Hercynicum and the Alps (ROSICKY^ 1957; PEUS, 1972; SMIT, 1966) do not occur in the Carpathians. An exeption is the northern part of Slovakia, Orava, harbouring the most of Sphagnetum peat-bogs (DUDICH, 1982). It means, populations of M. walkeri are occupying very detached territories, surrounded originally by alluvial woodland (transferred to the cultural steppes mostly at present time). Due to a very common scale of host organisms, there was - and still is - certain co-existence of M.wal keri and M. turbidus . We have evaluated material of fleas obtained in three regions within the Carpathian Basin (e.g. Kisbalaton - SZABO, 1969; 1973; own finds from the Danubian lowland and the Orava region) from sites of common (syntopical and synoxenous) occurrence of both Megabothris species. The first one, M. walkeri was registered 25 times from hosts: M. oeconomus mehelyi, M. agrestis , C. glareolus and N. fodiens . The second one was registered 23 times from hosts: M. oeconomus méhelyi, M. agrestis , M. arvalis , C. glareolus, A. terrestris , A. flavicollis , A. sylvatlcus , A. agrárius , M. minutus, S. araneus . An idioxenous occurrence (both species on the same specimen of host mammal investigated) was recorded only once. We suppose, the distribution of apparently sympatric species is determined by an apparent segregation of ecological niches. The critical stages of ontogenesis, e.g., larvae of both species are inhabitants of different habitats nests (habitats of 2. rate). Their occurrence would be considered as microallopatric, therefore. Nosopsyllus (Nosopsyllus) fasciatus (Bosc, 1800) Taxonomy: Monotypic species. General distribution: Cosmopolitan. Hosts: 28 species of host organisms are known from the Carpathian Basin belonging to insectivores, rodents and carnivores. Major hosts are species of the genera Rattus. Apodemus and Mus musculus . Distribution in the Carpathian Basin (Fig. 3):
