Exclusive aggression against intruders in cockroach mating pairs following mutual wing-eating

Abstract Pair bonding is often described as a selective association between two conspecific adults that involves the exclusion of rivals. While extensively studied in vertebrates, experimental evidence for partner-specific behavioural selectivity in invertebrates remains extremely limited. Among invertebrates, the wood-feeding cockroach Salganea taiwanensis has been proposed as a particularly strong candidate for exhibiting pair-associated social behaviour based on its unique mating ecology. Here, we show that mating pairs of S. taiwanensis exhibit exclusive rejection of potential alternative mates following pair formation through their unique mating behaviour: mutual wing-eating. After pairing through this ritual, both males and females consistently repelled intruders of either sex while never attacking or replacing their established partner. This indicates that immediately following mutual wing-eating, individuals do not accept alternative mate candidates. This study provides the first experimental demonstration of selective aggression as a behavioural component of selective social association in an invertebrate. This finding establishes S. taiwanensis as a promising invertebrate model system for investigating the cognitive ecology of mating and advances our understanding of the evolution of social systems across animals.