Post-Reproductive Lifespan in Honey Bee Workers with Varying Life Expectancies

This study specifically examines the post-reproductive lifespan and ovarian activation in honeybee workers (Apis mellifera) with differing life expectancies. Drawing on the "grandmother hypothesis", which postulates that older females enhance the survival and reproductive success of their descendants, we aimed to determine if similar patterns exist in eusocial insects. We conducted an experiment with newly emerged honeybee workers, dividing them into two groups: an untreated control group and an injured group with shortened lifespans due to thorax puncturing. The workers were monitored in an experimental apiary, and observations regarding ovarian development and hypopharyngeal gland size were recorded at various age intervals. Our results demonstrated a significant difference in lifespan between the control and injured bees, with injured individuals living notably shorter lives. The size of the hypopharyngeal gland, crucial for brood food production, varied significantly with respect to age and treatment, suggesting that physical injuries adversely affected physiological development. More intriguingly, our findings indicated that older honeybee workers displayed reduced ovarian activation, implying a potential reproductive cessation. This phenomenon can be interpreted as a form of menopause, which represents a strategic shift in energy investment from personal reproduction toward contributing to the colony as older individuals age.