Regulation of reproductive and behavioral plasticity in social insects.

Eusocial insects organize colony life through division of labor, with specialized adult phenotypes arising from a shared genotype. Reproductive individuals primarily invest in egg production, whereas non-reproductive workers perform context-dependent tasks such as brood care, nest maintenance, foraging, and defense. Unlike their solitary ancestors, which perform a broad range of tasks throughout adulthood, eusocial insects partition these functions among distinct individuals. Yet this behavioral organization remains plastic. We conceptualize adult role reorganization as a tilting Waddington-style landscape, in which social and environmental cues reshape the barriers between behavioral states and promote transitions across alternative roles. This raises a key question: how did eusociality reconfigure adult plasticity such that conserved regulatory modules now produce tighter caste constraint and greater colony-level specialization? We approach this question by focusing on two major forms of adult plasticity: plasticity within non-reproductive castes, including demand-driven and reversible task switching, and plasticity at the reproductive boundary, including worker-to-egg-layer transitions and the mechanisms that reopen reproductive states.