High levels of tolerance between nestmates and non-nestmates in the primitively eusocial sweat bee Halictus scabiosae (Rossi) in Turkey (Hymenoptera: Halictidae)

Abstract

Eusocial sweat bees with variable intra-colony relatedness due to multiple foundresses and/or worker drifting may express high levels of tolerance among non-nestmates. We used circle-tube arenas to test hypotheses related to this phenomenon in Halictus scabiosae (Rossi), an obligately eusocial species with frequent inter-nest worker drifting. We conducted experiments in mid-July with bees from a nest aggregation found on the Uludağ University campus, near the city of Bursa, in the Republic of Turkey. We recorded high frequencies of tolerant behaviors in both nestmate and non-nestmate trials. Among tolerant behaviors, mutual passing was more common in pairs of nestmates while non-aggressive contacts were more common in non-nestmate pairs. Moderate levels of aggression were frequent, particularly in nestmate trials, and avoidance was more common in non-nestmate pairs. Except for the moderate levels of aggression, our results are similar to those on Lasioglossum malachurum Kirby, another obligately eusocial species with strong tolerance for conspecifics and with nests that often include a mixture of related and unrelated workers. Thus, our observations support the hypothesis that reduced intra-colony relatedness, resulting from multiple foundresses and/or drifting among conspecific colonies of eusocial sweat bees, is correlated with high levels of tolerance among nestmates.