THE IMPACT OF FIRES ON THE QUANTITY AND SOCIAL BEHAVIOR OF HALICTUS QUADRICINCTUS (F.) IN EASTERN EUROPEAN FOREST-STEPPE (VORONEZH REGION) (HYMENOPTERA, HALICTIDAE)
Changes in the population and social behavior of Halictus quadricinctus as a consequence of exogenous disturbances in the Eastern European forest-steppe are analyzed (Voronezh Region, Usman Forest). During the 16 years of observations (1994–2010) the number of H. quadricinctus nests remained stable. As a result of the fire in 2010, the number of nests in 2011 decreased by 30 times. The sharp decline in the number of nests has significantly affected the social behavior of the investigated species. In one of the remaining nests after the fire a new form of social behavior – eusociality first was detected. Eusociality has not been registered previously in H. quadricinctus. According to our observations in the nests of eusocial colonies H. quadricinctus caste determination took place at the imaginal development stage: paired females wintered and became the foundress, not paired ones became workers. We have done preliminary conclusion about the formation of eusocial behavior of H. quadricinctus only in isolated nests that are not included in the aggregation that has adaptive value.