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

## TL;DR

This study explores how aging honeybee workers shift energy from reproduction to colony work, similar to the 'grandmother hypothesis' in humans.

## Contribution

The study provides empirical evidence of menopause-like behavior in honeybees, linking it to energy reallocation in aging workers.

## Key findings

- Injured bees had significantly shorter lifespans compared to the control group.
- Older bees showed reduced ovarian activation, suggesting a menopause-like shift.
- Hypopharyngeal gland size varied with age and injury, indicating altered physiological development.

## Abstract

This study investigates the post-reproductive lifespan and ovarian activation in honeybee workers (Apis mellifera) with different life expectancies, based on the “grandmother hypothesis”. We divided newly emerged bees into a control group and an injured group with shortened lifespans due to thorax puncturing. Observations of ovarian development and hypopharyngeal gland size were recorded. The results showed that injured bees had significantly shorter lifespans, and gland size varied with age and treatment, indicating injuries affected development. Notably, older bees exhibited reduced ovarian activation, suggesting a form of menopause, where energy shifts from reproduction to colony contribution as they age.

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.