Hidden role plasticity of the reproductive caste in a morphologically differentiated termite society

Reproductive division of labor is the defining characteristic of eusocial insects, separating germline‐like reproductives from soma‐like workers. While most studies have focused on worker sterility, it is generally assumed that developing reproductives invest only in maturation, not in colony labor. Here we show that nymphs (pre‐alates) in a highly structured termite society can contribute to colony labor under natural conditions. During a rare colony emigration event of a marching termite, Longipeditermes longipes , we observed developed nymphs carrying brood items to the new nest. In ~ 8 h of field observation, ~ 155 000 termites emigrated with ~ 35 000 brood and ~ 30 000 food items transported, and nymphs participated exclusively in brood transportation. The traffic flow of nymphs was positively correlated with brood‐carrying workers but negatively correlated with soldiers. Movement patterns were not different between brood‐carrying and non‐carrying nymphs, suggesting that nymphs express nursing worker‐like behavior at minimum costs, consistent with the theoretical prediction of task allocations. These results reveal that caste flexibility exists even in highly canalized societies and emerges under ecological stress.