Honey bees engage in a form of cannibalism, though it is not driven by aggression or indiscriminate predation. The behavior, which primarily involves the consumption of eggs, larvae, or pupae, is a calculated, collective strategy for colony survival and hygiene. This selective consumption is a social defense mechanism and resource management tool, ensuring the hive can adapt to environmental stress or eliminate disease threats.
Cannibalism Driven by Starvation
A major trigger for cannibalism is a sudden shortage of incoming pollen, the colony’s primary source of protein. During a nectar dearth or prolonged bad weather that prevents foraging, nurse bees consume the youngest brood to recycle nutrients back into the colony’s reserves. This necessary survival mechanism allows the adult population and the queen to sustain themselves. Workers typically consume eggs and larvae less than three days old, as these have had the least amount of colony resources invested in them.
Recycling this protein helps nurse bees continue producing the glandular secretions needed to feed the queen and older larvae. This action reduces the colony’s overall food demand while providing a protein supply to maintain the adult workforce. By sacrificing the youngest, the colony concentrates dwindling resources on the older brood, who are closer to emerging, and on the queen, whose survival is paramount.
Culling for Colony Health
Cannibalism also serves as a form of social immunity known as hygienic behavior. Specialized nurse bees actively inspect and remove diseased, dead, or infested brood from their cells. This behavior prevents the transmission of pathogens, such as American foulbrood, or manages parasitic threats like the Varroa mite.
The process begins when a worker detects a chemical cue, often an odor, emitted by the compromised larva or pupa. The hygienic worker uncaps the cell and physically removes the contents, either consuming them or carrying them out of the hive. Removing the infected brood reduces the pathogen load and prevents the disease from spreading to healthy developing bees. Colonies that exhibit high levels of this selective culling are better equipped to resist disease.
Seasonal Removal of Drones
A third context for bee cannibalism involves the adult male bees, or drones, and occurs seasonally as a resource conservation strategy. Drones are non-productive members of the colony, consuming significant amounts of honey and pollen but contributing only to mating. In late summer and early autumn, when foraging ends and the colony prepares for winter, workers begin to evict the drones.
Workers stop feeding the drones, effectively starving them, and physically prevent them from re-entering the hive. Since drones are larger and cannot feed themselves, they quickly weaken and die outside the colony. This ensures stored food is reserved exclusively for the overwintering queen and worker bees. Workers may also consume drone brood before it emerges to conserve resources and eliminate future consumers.
How the Hive Handles Dead Adults
The handling of dead adult bees is different from brood consumption and rarely involves cannibalism. The death of an adult bee inside the hive triggers a disposal process called necrophoresis, carried out by specialized “undertaker bees.” These workers are responsible for maintaining hive cleanliness to prevent the buildup of pathogens.
The undertaker bee identifies a dead nestmate by a change in its chemical signature, including a reduction in cuticular hydrocarbons and the presence of oleic acid. Once the corpse is confirmed, the worker grasps it with its mandibles and carries it away from the nest entrance, often flying a distance before dropping it. The primary goal is disposal, not consumption, which contrasts with the selective consumption of brood for nutrient recycling or disease control.