[The correlation of light and hygrothermal factors in the determination of the morphogenetic diapause of the larvae and nymphs of the taiga tick in the northwestern spurs of the eastern Sayan].

In the taiga of the region in question at the latitude 56 degrees N the photoperiod regimens of 25 June and 21 July determine 50% diapause in engorged larvae and nymphs of Ixodes persulcatus. The durations of the day time on these dates are 17 h 34 min and 16 h 45 min respectively. Seasonal fluctuations of temperature and precipitation in May-June are the main reasons for the modification of the critical photoperiod. In some years the critical dates for larvae and nymphs vary under these factors within the limits 11-28 July and 19 June-6 July respectively. The critical durations of the day time for these date limits are 16 h 20 min-17 h 12 min and 17 h 23 min-17 h 37 min respectively.