Seasonal aspects of life cycles in Calathus melanocephalus and C. micropterus (Coleoptera, Carabidae) in the northern taiga

The seasonal dynamics of the activity and the demographic structure of Calathus melanocephalus and C. micropterus populations were studied in the northern taiga of Arkhangelsk Province. The period of adult activity lasts from early June to mid-or late September with the maximum surface activity observed in the middle of summer. In C. melanocephalus, mature individuals are recorded from early June to early September, and in C. micropterus, during the entire season. The data on seasonal changes of the demographic structure of the population demonstrate that in the northern taiga, these species probably possess a biennial life cycle with summer reproduction. The geographical variability of the demographic structure of populations and of life cycles of two species of the genus Calathus was demonstrated. Northwards from the south, the period of activity decreases and the period of reproduction increases and shifts from autumn to the middle of summer. A hypothesis was formulated, according to which in the species studied the annual life cycle in the central part of the range is replaced by the biennial cycle in the north.