Caste theory hypothesizes that division of labor in insect colonies is the result of selection for worker task specialization, leading to efficient colony operations and enhanced fitness.  Temporal polyethism is a critical concept in caste theory, but the role of worker age in division of labor has been controversial.  The caste discretization model of temporal polyethism developed using the ant Pheidole dentata hypothesizes that minor workers shift between non-overlapping task sets beginning with brood care and culminating in foraging (Wilson 1976). This model assumes that callow minors are specialist nurses.  Seid and Traniello (2006) found that minor workers begin their labor as nurses but add new tasks to their existing repertoire as they age. Minors develop their complete task repertoire (which includes nursing and foraging) roughly 20 days post-eclosion.  We examined the ability of young minor workers (Age Class 1 [AC1, 1-2 days old]) to attend to brood by comparing their brood-care behavior to that of older minors (Age Class 4 [AC4, 18-20 days old]) in monoclass subcolonies.  AC1 minor workers approached brood and performed brood care at significantly lower frequencies than AC4 minor workers. Our results indicate that AC1 minors appear to be less responsive to brood than AC4 minors.  Collateral neuroanatomical and histological studies suggest that AC1 minor workers may be developmentally immature and unable to efficiently perform brood care or other tasks.  

Seid, M. and Traniello, J.F.A. 2006.  Age-related repertoire expansion and division of labor in Pheidole dentata (Hymenoptera:Formicidae): a new perspective on temporal polyethism and behavioral plasticity in ants. Behav. Ecol. Sociobiol., in press.

Wilson, E.O. 1976. Behavioral discretization and number of castes in an ant species. Behav. Ecol. Sociobiol. 1: 141-154.