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Simple Summary: Explanations for the evolution of menopause in humans and other animals concern the indirect fitness benefits that older females can receive by caring for the offspring of their children and grandchildren. Knowledge about the post-reproductive lifespan is still incomplete and until recently was documented only in nonhuman primates, a few species of toothed whales, and guppies, though it has also been documented in insects for gall-forming aphids and parthenogenetic ants. In our paper, we provide evidence that menopause also exists in honeybee societies. Honeybee workers are usually sterile. Nevertheless, the absence of a queen and her pheromones in a nest stimulates workers to activate their ovaries and lay unfertilized eggs that develop into males. However, even in queenless colonies, some workers do not activate their ovaries. In this study, we show that physiologically older workers have less activated ovaries than physiologically younger individuals, indicating that the possibility of workers' reproduction decreases with workers' physiological age. This may happen because bees require a minimum of two weeks to activate their ovaries, meaning physiologically older workers can die before producing their own eggs. Thus, investing energy in helping relatives care for their offspring rather than channelling that energy into one's own reproduction can positively influence workers' fitness. The post-reproductive lifespan is an evolutionary enigma because the cessation of reproduction in animals seems contrary to the maximization of Darwinian fitness. Several theories aim to explain the evolution of menopause, one of which suggests that females of a certain age receive more fitness benefits via indirect selection (kin selection) than they would directly from continuing reproduction. Post-reproductive lifespans are not very common in nature but have been described in humans, nonhuman primates, a few species of toothed whales, guppies, and in some insect societies consisting of clonal colony members, such as aphid and ant societies. Here, we provide evidence that menopause also exists in honeybee societies. Our study shows that workers with a short life expectancy (older and/or injured workers) invest fewer resources and less time in their own reproduction than workers with a long life expectancy (younger and/or uninjured workers), even if their colony is hopelessly queenless. These results are consistent with the kin selection explanation for the evolution of menopause and help us understand the net effects of relatedness and social cooperation in animals. [ABSTRACT FROM AUTHOR]

Worker honeybees may reproduce in either their own or foreign colonies; the latter situation is termed intraspecific reproductive parasitism (IRP). In this study, we compared the tendency for IRP between normal honeybee workers, which are characterized by a relatively low reproductive potential, and "rebel workers", a recently discovered subcaste of honeybee workers characterized by a high reproductive potential that develops when the colony is without a queen. We expected that the high reproductive potential of the rebel workers would influence their reproductive strategy and that these individuals would drift to other colonies to lay eggs more often than normal workers. The results confirm our expectations and show that rebel workers are more likely than normal workers to drift to foreign colonies. The rebel workers also preferred to drift to queenless colonies than to queenright colonies, while the normal workers did not show this preference. This study indicates that rebel workers have a tendency for IRP, which may be responsible for the maintenance of the rebel worker strategy in bee populations. In this article we find that new subcaste of honeybee workers can be intraspecific parasites. These individuals drift to other colonies and activated their ovaries. [ABSTRACT FROM AUTHOR]

Under the age-related division of labour of a honeybee colony, workers participate first in safe inside-nest tasks and then switch to risky outside-nest foraging. However, honeybees show great plasticity during behavioural development: their hive-to-field transition can be accelerated, delayed or even reversed in response to changes in colony conditions or environmental factors. After nursing bees are removed from a colony, younger foragers are more likely to revert to nursing than older ones. The ‘division of labour by division of risk’ hypothesis predicts that it is not the workers'' age but their life expectancy that influences whether or not foragers return to inside-nest activity. We tested this prediction by dividing same-age honeybee workers into three groups after they started foraging. Workers in the control group were not treated. The life expectancy of the other two groups was shortened with carbon dioxide anaesthesia or by injury. In a cage experiment we showed that control bees had a longer expected life span than anaesthetized and injured workers, while in a field experiment the control workers, with a longer expected life span, proved more likely to revert to nursing than anaesthetized and injured workers of the same age. Behavioural reversion was accompanied by ovary development and hypertrophy of the hypopharyngeal glands. These results support the tested hypothesis that the division of labour in eusocial insects is a consequence of differences in expected worker life span and differences in the risks associated with inside-nest and outside-nest tasks. [Copyright &y& Elsevier]

Social insects, especially honeybees, have received much attention in comparative gerontology because of their peculiar and flexible ageing patterns that differ across genetically similar individuals. The longevity of honeybee individuals varies and depends on patterns of gene expression during development; females developing into reproductive individuals (queens) live longer than facultatively sterile workers. Here, we show that rebel workers, which develop under queenless conditions after swarming and have high reproductive potential, live approximately 4 days longer in hives and approximately 3 days longer in cages than individuals that develop in queenright colonies and have lower reproductive potential; this difference in longevity occurs in both free-flying and caged workers. Moreover, we show that both rebel and normal workers live longer when their ovaries contain more ovarioles. Longer-living rebel workers can benefit the colony because they can fill the generation gap that emerges between workers after queen exchange during swarming. Our findings provide novel evidence that the fecundity of workers in a social insect colony impacts their intrinsic longevity. [ABSTRACT FROM AUTHOR]