Caste‐Associated Social Context Modulates Behavioural Interactions With Insecticide‐Exposed Individuals in Nasutitermes corniger (Termitidae: Nasutitermitinae)

Termites are eusocial insects that maintain cohesion and exchange information through frequent physical interactions among nestmates. This social organisation underlies the principle of horizontal insecticide transfer, which is widely exploited as a termite control strategy. However, despite extensive laboratory evidence supporting its effectiveness, the specific behaviours mediating interactions between intoxicated and healthy individuals remain poorly understood. Here, we evaluate how caste‐associated social context shapes behavioural interactions between healthy nestmates and a single imidacloprid‐exposed individual in Nasutitermes corniger (Termitidae: Nasutitermitinae). We compared two biologically relevant social scenarios: worker groups interacting with an exposed worker and mixed worker–soldier groups interacting with an exposed soldier. We quantified alarm‐ and prophylaxis‐related behaviours and subsequently assessed group mortality. Our results show that antennation responses depended on the interaction between insecticide treatment and caste‐associated social context. Vibratory behaviour was more frequent in worker‐only groups, whereas trophallaxis was more frequent in mixed worker–soldier groups, independently of insecticide exposure. Grooming increased independently in mixed groups and following insecticide exposure. Mortality analyses did not provide evidence that the introduction of a single exposed individual consistently altered group‐level mortality risk. Overall, our findings indicate that termite responses to intoxicated nestmates depend on caste‐associated social context, probably reflecting both caste‐specific interaction patterns and the morphological dependence of soldiers on workers.