Abstract

Comparison of lateralization in social and non-social bees tests the hypothesis that population-level,
directional asymmetry has evolved as an adjunct to social behaviour. Previous research has supported
this hypothesis: directional bias of antennal use in responding to odours and learning to associate
odours with a food reward is absent in species that feed individually, such as mason bees, whereas
it is clearly present in eusocial honeybees and stingless bees. Here we report that, when mason bees
engage in agonistic interactions, a species-typical interactive behaviour, they do exhibit a directional
bias according to which antenna is available to be used. Aggression was significantly higher in dyads
using only their left antennae (LL) than it was in those using only their right antennae (RR). This
asymmetry was found in both males and females but it was stronger in females. LL dyads of a male and
a female spent significantly more time together than did other dyadic combinations. No asymmetry
was present in non-aggressive contacts, latency to first contact or body wiping. Hence, population-level
lateralization is present only for social interactions common and frequent in the species’ natural
behaviour. This leads to a refinement of the hypothesis linking directional lateralization to social
behaviour.