[Development of ixodid ticks in the northern limits of their geographic range in Amur Province].

In the northern part of the Amur district the life cycle of I. persulcatus and H. concinna lasts three, four and five years while that of D. silvarum--one year. The distribution of I. persulcatus and H. concinna further to the north is limited by an unsufficient heat for the development of eggs while for D. silvarum heat is not enough to complete its life cycle within a year.