Vegetation on the southern slopes of the Tribec and Hronský Inovec mountains.

The detailed investigation of a natural focus of arbovirus infection involves the study of all the factors that affect the circulation of the virus in nature, including the type of vegetation in the focus. In a contribution to the study of the circulation of the tick-borne encephalitis virus in the Tribeć and Hronský Inovec Mountains region of Czechoslovakia, the author has characterized the different types of vegetation found within the region. These include thermophilic and mesophilic oak-forest communities on loess and communities of acid oak forests on gneiss. The most favourable biotope for the circulation of Ixodes ticks, which are the principal vectors of the virus, is provided by the margins of these natural forests and their supplementary shrub communities.