Pheromone Communication in Honey Bee Colonies
How honey bees run their colony almost entirely on chemical signals, from queen mandibular pheromone and brood pheromone to alarm signals and Nasonov recruitment scent.
A Colony Run Largely on Chemistry
Vision and the waggle dance get most of the popular attention, but the great majority of coordination inside a honey bee colony happens through pheromones — chemical signals detected primarily by receptors on the antennae and passed between bees through direct contact, trophallaxis (mouth-to-mouth food exchange), and simple diffusion through the crowded, still air of the hive. A honey bee colony produces dozens of distinct chemical signals from multiple glands, and disruption of these signals is often a far better explanation for observed colony behaviour than beekeepers realise: a colony that becomes suddenly agitated, or fails to notice queenlessness for days, or begins laying worker eggs, is very often responding to a shift in its pheromone environment rather than to any single dramatic event.
Because pheromones work through smell and contact rather than sight, and diffuse relatively slowly compared with visual signals, colony-wide pheromone communication tends to operate over minutes to days — appropriate for regulating steady-state processes like caste development, ovary suppression and swarming preparation, in contrast to the faster visual and vibrational signalling used for moment-to-moment recruitment.
Queen Mandibular Pheromone and Colony Cohesion
The single most studied bee pheromone is queen mandibular pheromone (QMP), a blend of several fatty acid components produced in the queen's mandibular glands and spread through the colony as workers groom and feed her, then pass it onward through trophallaxis and contact with other workers. QMP suppresses worker ovary development, preventing most workers from laying their own eggs, and signals the queen's presence and general health to the colony; it also plays a role in attracting a retinue of attendant workers who groom and feed the queen directly, which is itself the main mechanism by which QMP gets distributed through the hive.
When a queen dies or her QMP output declines with age, the change in pheromone signal — rather than any 'awareness' of the queen's physical absence — is what triggers the colony to begin building emergency queen cells from existing young larvae. This is also why a queen removed for even a short period is often noticeably 'missed' by the colony within hours: QMP dissipates and its suppressive effect on worker ovaries starts to fade quickly once the source is gone, and if queenlessness persists for more than one to two weeks without recognised eggs or larvae to raise a replacement from, an increasing proportion of workers begin developing active ovaries and can start laying unfertilised, drone-producing eggs.
Alarm Pheromones and Defensive Response
When a worker stings, or a guard bee detects a threat, isopentyl acetate and related compounds released from the sting apparatus's Koschevnikov gland act as an alarm pheromone with a distinctive banana-like odour that beekeepers sometimes notice directly around an agitated hive. This alarm signal recruits nearby bees to investigate and, if the threat persists, to sting as well, which is why a single sting near a hive entrance can rapidly escalate into a more general defensive response and why experienced beekeepers use smoke deliberately to mask alarm pheromone and disrupt this recruitment cascade during inspections.
A second alarm signal, released from the mandibular glands and associated more with head-on threat detection and biting than stinging, complements the sting-gland alarm pheromone, giving the colony layered defensive signalling depending on the nature and location of a perceived threat. Colonies vary considerably in how strongly and how quickly they mount an alarm-pheromone cascade, which is part of the underlying physiological basis for the temperament differences beekeepers observe and select against when breeding for gentler stock.
Nasonov Pheromone and Recruitment Signals
Nasonov pheromone, released from an exposed gland at the tip of a worker's abdomen and fanned into the air with the wings, is a citrus-scented orientation and recruitment signal used to mark a location — most visibly when a swarm has settled and scout bees fan Nasonov pheromone to guide the rest of the swarm cluster to converge on the chosen spot, or when foragers mark a good water or nectar source to help nestmates locate it. Beekeepers exploit this deliberately: a swarm being coaxed into a new hive or box is often seen fanning Nasonov scent at the entrance once enough bees have gone in and begun to recognise it as the new colony location, helping stragglers find their way in.
Nasonov signalling works over relatively short range compared with the symbolic, distance-and-direction information encoded in the waggle dance, functioning more as a 'home beacon' or local marker than as a means of communicating information about distant, unseen locations — the two systems are complementary rather than redundant, dance communication getting a forager to roughly the right area and Nasonov-type scent marking helping pinpoint the final few metres.
Brood Pheromone and the Division of Labour
Developing larvae produce their own pheromone blend, broadly termed brood pheromone, which influences several aspects of colony organisation independent of anything the queen produces. Brood pheromone stimulates foraging activity in proportion to the amount of brood present, helps regulate the age at which workers transition from in-hive tasks to foraging (a process called behavioural or temporal polyethism), and appears to contribute to suppressing worker ovary activation alongside queen pheromone, meaning that even a queenless colony with plenty of young brood present tends to remain more stable and cohesive for longer than one that is both queenless and broodless.
This is one reason the standard emergency response to sudden, unexplained queenlessness — giving the colony a frame of open brood from another hive — works on two levels simultaneously: it gives workers the young larvae needed to raise emergency queen cells, and the brood pheromone itself helps hold the workforce together and suppress laying-worker development during the vulnerable weeks before a new queen is mated and established.
Practical Implications for Beekeepers
Recognising that so much of colony behaviour is chemically mediated changes how several routine beekeeping observations should be interpreted. A colony that seems unusually calm and cohesive typically has a strong, healthy queen producing ample QMP and plenty of brood; one that becomes noticeably more defensive, or shows a spike in queen cell building, may be responding to a decline in queen pheromone output well before any visible sign of queen failure appears on inspection. Smoke works during inspections in large part by masking alarm pheromone signalling and triggering a feeding response that distracts and calms bees, rather than through any purely physical effect.
Understanding brood pheromone's stabilising role also explains standard emergency management practice: giving a suspected queenless colony a test frame of eggs and young larvae from another hive is diagnostic (if they draw queen cells, the colony genuinely lacks a queen) and therapeutically stabilising at the same time, buying valuable weeks of cohesion through brood pheromone while a new queen is reared or introduced.
Frequently Asked Questions
What is queen mandibular pheromone and why does it matter?
Queen mandibular pheromone (QMP) is a blend of chemicals produced by the queen and spread through the colony via her attendant workers, and it suppresses worker ovary development while signalling her presence and condition. A decline or disappearance of QMP, more than any direct awareness of the queen's physical absence, is what triggers a colony to begin rearing emergency replacement queens.
Why does smoke calm bees during a hive inspection?
Smoke works largely by masking the alarm pheromone released by guard or disturbed bees, disrupting the chemical signal that would otherwise recruit nearby bees into a defensive response, and it also triggers a feeding response that distracts bees from investigating the disturbance.
What is the banana smell sometimes noticed near an agitated hive?
That smell is isopentyl acetate, the principal component of honey bee alarm pheromone released from the sting apparatus when a bee stings or perceives a threat, and its distinctive banana-like odour recruits nearby bees to investigate and potentially join a defensive response.
How does brood help stabilise a queenless colony?
Young brood produces its own pheromone signal that helps suppress worker ovary activation and supports general colony cohesion, independent of the queen. This is why giving a queenless colony a frame of eggs and young larvae both tests whether they will draw emergency queen cells and helps hold the workforce together while a new queen is reared.
What is Nasonov pheromone used for?
Nasonov pheromone is a citrus-scented signal fanned from a gland at the tip of a worker's abdomen, used as a short-range orientation and recruitment marker — most visibly when scout bees fan it to guide a settled swarm toward a chosen new nest site, or when it helps stragglers locate the entrance of a colony recently moved into a new hive.