The timing of the release of bumblebees of the genus Bombus (Hymenoptera: Apidae) from the state of winter diapause in the Leningrad province

Abstract

Important for bumblebees of the genus Bombus (Hymenoptera: Apidae), as anthophilic insects with a prolonged family life period, is the formation of such a phenological calendar that allows bumblebees of various species and inhabitants of various ecotopes to adapt to the trophic use of plants growing there. The analysis of long-term series of phenological observations showed that the earliest fixed date of departure of bumblebees for the Leningrad province during the observation period from 1925 to 2023 was April 3 (Tosnensky district), the latest was May 26 (Podporozhsky district). The average departure dates was in the range from April 22 to May 11. The latest departures at the observation points were recorded in the period from May 5 to May 26. The interval between the earliest and the latest departure time of bumblebees at different observation points varied from 14 to 40 days. The average value of this interval was 29.67 days. A high and average level of dependence of the timing of the release of bumblebees from the winter diapause is shown for the latitudinal characteristic (boreal) of the habitat, the influence of the longitude characteristic (continentality) of the habitat has for the most part a weak level of influence on the timing of the departure of overwintered female bumblebees. The average level of dependence on longitude is marked only by the average departure time (r = 0.529, p = 0.615). The dependence of the departure time on the altitude of the terrain above sea level has not been revealed.