Caste dimorphism in necrophoric behaviour of Oecophylla smaragdina (Fabricius): Implications for colony hygiene and disease management.

Social immunity in eusocial insects involves collective behavioural mechanisms that reduce pathogen transmission within colonies. In ants, necrophoric behaviour plays an important role in colony hygiene; however, the relationship between caste-specific morphology, sensory structures, and hygienic performance remains poorly understood in Oecophylla smaragdina. This study investigated caste differences in necrophoric behaviour, morphometric traits, and antennal sensilla morphology in major and minor workers of O. smaragdina using behavioural assays, morphometric analysis, and scanning electron microscopy (SEM). Linear mixed-effects model analysis revealed significant caste-dependent differences in corpse detection latency, colony included as a random effect. Minor workers detected corpses significantly faster than major workers across all five colonies, exhibiting mean detection latencies of 40.20 ± 13.32 s to 50.60 ± 9.13 s, compared to 122.40 ± 14.03 s to 143.80 ± 17.78 s in major workers. Morphometric analyses showed that major workers possessed significantly larger body dimensions than minor workers across all measured traits. SEM examination revealed distinct caste-specific variation in antennal and mandibular structures. Minor workers exhibited higher total antennal sensillar counts (117) compared to major workers (94), whereas sensilla in majors appeared comparatively larger. These findings suggest that sensory and morphological specialization may contribute to caste-specific hygienic roles and division of labour in O. smaragdina.