In large apiaries, bees from different hives will inevitably intermingle on their quest for pollen from time to time. Some drifter bees might even wander from one hive to another in search of a new home. Because hives have limited space and resources, it’s up to guard bees to determine who gets in and who gets turned away at the door.
So how do the guard bees decide who belongs in the hive and who doesn’t?
Recently, a team of scientists at the University of Queensland in Brisbane, Australia conducted extensive research to get a better idea of how guard bees operate. They found that guard bees use scent receptors to analyze the chemical profiles of newcomers to the hive. When the chemical profile is similar to that of the existing bees in the hive, the visiting bees are more likely to be allowed inside. Otherwise, they may be rejected by the guards. These scent inspections can take up to 30 seconds to complete.
Guard bees are more likely to let new bees into the hive when there’s a surplus of food. When food is scarce, the guard bees will prevent new bees from entering the hive. In total, the scientists estimate that guard bees let about 30 percent of drifter bees into their hives.
The guard bees are also extremely adept at identifying attacking wasps and robber bees that steel honey from hives. The robber bees are identified based on their speed and flight patterns, and are typically intercepted and stung by guard bees before they ever reach the hive. The guards almost never mistake wasps for friendly honey bees.
Fortunately for the rest of the colony, these guard bees are remarkably good at determining which bees pose a threat to the hive, and which are just friendly travelers stopping by for a visit.