Reproductive potentials of task-shifting workers in a queenless ant

Abstract Eusocial insects, such as ants and honeybees, are characterized by the sophisticated division of labor among workers. In addition to age polyethism, under fluctuating environmental conditions, division of labor is maintained by task shifting of workers from one task to another if there are insufficient workers performing a certain task. Although several studies show that workers can perform task-shifting in many hymenopteran species, the physiological state of task-shifted workers is largely unknown without a few species. In this study, we examined the relationship between the ovarian development of workers and their task shifting using the queenless ant Diacamma cf. indicum from Japan. Our results showed that most of the nurses maintained their reproductive potential—as evidenced by their well-developed ovaries—even when they had shifted to the foraging task. In contrast, the foragers—whether they had shifted to the nursing task or not—had regressed ovaries. Combined with our previous study, the reproductive potential of workers mediates different effect of task experience on task shifting between nurses and foragers. Furthermore, our study highlights the importance of physiological heterogeneity underlying self-organized systems in insect societies.