[The activity of Dermacentor reticulatus Fabr. (Ixodidae) ticks in nature]

The experimental population-based ecological parameters most closely associated with the age of ticks, including activity, were assessed in the D. reticulatus imago (Moscow Province). The activity rise of ticks in autumn is twice as low as that in spring, with their inactivity in summer. There are some seasonal variations in the ratio of males to females. Evidence has been first provided for the maximum duration (more than 2.5 years, about 1%) of active life till the third spring when the coloured imagoes are let free. Most new-generation individuals have been found to be inactive in autumn. There is a high repeated activity in ticks by seasons: as many as half of the spring individuals (48%) in autumn and more than a third (37%) in spring to come. The repeatedly active individuals whose age is less than a year are most among those in the autumn peak. The summer inactivity of hungry imagoes represents ticks' stable behavioral adaptation, by increasing their active life. This condition is regarded as a component of the "activation diapause" phenomenon.