Asymmetry of mating behaviour affects copulation success in two stored-product beetles

Lateralization (i.e. left–right asymmetries in the brain and behaviour) has been documented in all vertebrate classes, while evidences for invertebrates are limited. To the best of our knowledge, there is no information about behavioural asymmetries in the order Coleoptera. In this research, we investigated the lateralization of mating traits in two major pests of stored products: the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), and the confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae). Both T. confusum and S. oryzae males showed population-level left-biased copulation approaches of potential mates. Interestingly, T. confusum and S. oryzae males performing left-biased copulation attempts achieved higher mating success over right-biased males. Furthermore, S. oryzae males periodically exhibited a typical head wagging behaviour, which consists of waving the rostrum laterally across the female thorax and then resting the rostrum on the mid thorax. This behaviour was right-biased, even in the majority of males that previously showed left-biased copulation attempts. The quantification of mating displays could allow comparisons with other strains, in order to evaluate the impact of a given host or of the rearing methods on the mating traits of S. oryzae and T. confusum. Overall, this is the first report of lateralization of mating traits in Coleoptera. Furthermore, this research adds basic knowledge to the reproductive behaviour of S. oryzae and T. confusum.