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

Pair bonding, defined as an exclusive relationship between two adults in the same species, often involves the selective exclusion of rivals and is widely recognized in the social behaviors of vertebrates. However, pair bonding has not been documented in invertebrates, despite their diverse social systems. Here, we show that pairs of the wood-feeding cockroach Salganea taiwanensis display selective aggression after their unique mutual wing-eating ritual: both sexes repelled intruders of either sex but never attacked or replaced their mate. This behaviour indicates mate exclusivity, fulfilling the defining criterion of pair bonding. Our findings provide the first behavioural evidence for pair bonding within mating pairs in invertebrates, enhancing our understanding of social systems in animals. This strict social and sexual commitment between post-mated S. taiwanensis, indicating recognition of mates, provides a new model for the cognitive ecology of mating in invertebrates.