[Some demographic datas from Ixodes ricinus Linné: vector of a virus strain of central european encephalitis in Alsace (author's transl)].

This work shows the montly variation in the density and stage composition of the population of the tick Ixodes Ricinus in the Rhine forest. Some factors influencing this variation are analysed. These include the locality of egg-laying and of down localisation and the main climatic variables. We also try to link these ecological data with the strains of Central European Encephalitis virus isolated from this arthropod.