An ant colony is organized entirely around its queen, the sole reproductive member in many species. She is responsible for producing all workers, soldiers, and future reproductives throughout her long lifespan. Her control is not exercised through physical command but through a continuous release of pheromones, chemical signals that govern the behavior, development, and fertility of the worker caste. The queen’s presence and fertility maintain the colony’s social order, suppressing worker reproduction and directing labor. Her death, whether natural or forced, is the single most disruptive event an ant colony can experience.
The Queen’s Natural Mortality
The remarkable longevity of a queen ant provides foundational stability for her colony. Some species, like the carpenter ant, live for up to 20 years, far exceeding the lifespans of their worker offspring. This extended lifespan is thought to be due to differences in metabolic pathways compared to workers, decoupling the typical trade-off between reproduction and aging. Despite this resilience, the queen is not immortal, and her life will eventually end due to natural causes.
Senescence, or biological aging, is the most common end for a queen who successfully establishes a mature colony. Her reproductive capacity inevitably declines over time, a process the colony often senses. Other non-violent ends include disease, introduced by foraging workers, or accidents. During the vulnerable founding stage, a queen is susceptible to external predation or environmental collapse before her first generation of workers can protect her.
Active Worker Regicide
While a queen is typically revered and constantly attended to by her workers, the colony will, under specific circumstances, actively turn on and kill its monarch. This violent overthrow is not an emotional response but a strategic, collective action aimed at increasing the colony’s fitness. The primary trigger for regicide is a perceived decline in the queen’s reproductive output or the failure of her chemical control.
Workers closely monitor the queen’s health and fertility by sensing the pheromones she produces. A significant drop in the concentration or composition of these chemical signals, often due to old age or injury, serves as an alarm that her dominance is fading. When the queen’s egg-laying rate falls below the threshold necessary to maintain colony growth, workers may eliminate her to redirect resources toward a successor.
In some cases, workers will engage in “social immunity,” preemptively killing a queen who shows signs of infection or disease. This action prevents the pathogen from spreading throughout the colony, sacrificing the queen for the health of the superorganism. The physical act of regicide often involves workers surrounding the queen, biting or stinging her in a coordinated attack known as “balling,” which rapidly leads to her death.
Queen Replacement Mechanisms
Distinct from the active aggression of regicide is a more passive, yet ultimately fatal, process known as supersedure. This strategy is employed by colonies that sense a queen’s decline and proactively raise a new reproductive female before the old one is infertile. The workers feed select larvae an enriched diet, triggering their development into new queens.
During this transition, the old queen’s fate is often sealed by neglect rather than violence. Workers gradually reduce the care and food provided to the failing queen, effectively starving her while diverting resources and attention to the developing successors. This passive demise ensures the colony maintains a continuous supply of eggs, avoiding the reproductive gap a sudden, unplanned death would cause.
In species like the Indian jumping ant (Harpegnathos saltator), a unique form of replacement occurs where a new queen is not produced from the brood. Instead, a few workers transition into reproductive individuals called gamergates, who physically duel to establish a new reproductive hierarchy. The winners of these ritualized matches gain the ability to lay eggs and experience a significant increase in lifespan, effectively becoming a pseudoqueen and maintaining the colony’s fertility.
Colony Survival After Queen Death
The fate of an ant colony following the death of its queen is dependent on the species’ reproductive strategy. In monogyne species, where only a single queen is tolerated, removing the reproductive center initiates a rapid breakdown of social structure. The loss of the queen’s pheromones causes immediate behavioral chaos, as the primary organizing signal is gone, disrupting foraging, brood care, and nest maintenance.
Since no new workers are produced, the colony is on an irreversible path toward demographic collapse, as the existing workers die of old age. Some worker ants may begin to lay unfertilized eggs, a process known as arrhenotoky, in a final effort to pass on the colony’s genes. These unfertilized eggs develop only into males. This reproductive burst produces winged males to mate with queens from other colonies, ensuring a final genetic legacy before the colony dies out. Polygynous species, which maintain multiple queens, are far more resilient; the death of one queen shifts the reproductive burden to the surviving co-queens, allowing the colony to continue functioning with minimal disruption.