Honey Bee Pheromones: 50+ Chemical Signals

The waggle dance gets all the attention. Karl von Frisch won the Nobel Prize for decoding it. It's in every biology textbook. It's the answer to "how do bees communicate?" in every pub quiz on earth.

But the dance is only half the language. The other half is chemistry - and it's considerably stranger.

A honey bee colony runs on pheromones the way a city runs on electricity: invisibly, constantly, and catastrophically when the supply cuts out. At least fifteen separate glands distributed across the bee's body produce more than fifty identified chemical compounds that regulate everything from reproduction to defense to corpse removal. The queen alone produces a cocktail so pharmacologically potent that it suppresses ovary development in 50,000 workers, blocks certain types of learning in young bees' brains, and rewrites epigenetic markers in neurons. And she does it by sitting there and letting retinue workers lick it off her face.

Colin Butler at Rothamsted Research coined the term "queen substance" in a 1954 Bee World article, which, given what the substance actually does, might be the greatest understatement in the history of entomology.

The Queen's Pharmaceutical Operation

Queen mandibular pheromone - QMP - is produced in glands on either side of the queen's head. The primary blend contains five compounds: 9-oxo-2-decenoic acid (9-ODA, roughly 200 micrograms per queen), cis- and trans-9-hydroxydec-2-enoic acid (9-HDA, about 80 micrograms), methyl p-hydroxybenzoate (HOB, roughly 20 micrograms), and 4-hydroxy-3-methoxyphenylethanol (HVA, about 2 micrograms). A queen produces approximately 500 micrograms of QMP daily.

Four additional retinue compounds were discovered later: coniferyl alcohol, methyl oleate, hexadecane-1-ol, and linoleic acid. None trigger retinue behavior alone - they only function in combination with the primary five. Nine components total. Each one useless by itself. The whole thing, together, runs the colony.

Butler worked with James Simpson and Robert Callow on the discovery and synthesis. Brother Adam - the Benedictine monk who spent seventy years breeding bees - supplied Butler with surplus queens because 1950s analytical techniques required vast numbers of queens for pheromone extraction. Butler even patented synthetic queen substance, hoping it could control swarming. It couldn't. The chemistry was right. The delivery mechanism was wrong. You can synthesize the molecule. You can't synthesize a queen.

What QMP does to a colony reads less like biology and more like science fiction. It suppresses worker ovary development - chemical birth control for tens of thousands of bees. It prevents workers from building queen cells, which prevents swarming. It attracts the retinue - the eight to twelve workers who constantly groom and feed the queen, and who serve as the distribution network for the pheromone itself. Workers antennate and lick QMP from the queen's body, then spread it through trophallaxis (food sharing) and physical contact. The signal propagates through the colony like a rumor through a newsroom.

And 9-ODA specifically attracts drones during mating flights, at approximately ten meters altitude, which is how a queen finds mates in an open sky and also why drone congregation areas form where they do.

The Part Where It Gets Strange

In 2007, a paper published in Science demonstrated that QMP blocks aversive learning in young worker bees. Young workers exposed to queen pheromone cannot learn to associate a stimulus with a negative outcome. They can still learn positive associations - appetitive learning remains intact. But fear conditioning? Gone.

Read that again. The queen produces a chemical that makes young bees unable to learn to be afraid of things. She selectively disables fear while leaving the ability to learn rewards untouched.

The mechanism runs through dopamine. QMP modulates brain dopamine function in workers - dopamine levels, dopamine receptor gene expression, and cellular responses to the amine are all affected. Cage experiments showed that QMP transiently regulated expression of several hundred genes and chronically regulated expression of 19. Eleven of fifteen genes related to epigenetic processes were upregulated in worker brains exposed to QMP. The queen isn't just affecting behavior. She's rewriting gene expression patterns at the epigenetic level.

A 2024 study in the Journal of Experimental Biology found that early-life exposure to QMP creates persistent transcriptional changes in the brains of honey bee foragers. Workers exposed to QMP as young adults carry altered gene expression into their foraging careers, weeks later. The exposure window closes, but the effects don't.

Keith N. Slessor at Simon Fraser University co-developed synthetic QMP. Mark L. Winston, also at SFU, collaborated with Slessor and Yves Le Conte of INRA France to demonstrate that bee chemical signals have, as they described it, "a syntax deeper in complexity and richer in nuance than previously thought." Syntax. They used a linguistics term. For insect chemistry.

Bananas Mean 'Attack Here'

The alarm pheromone is released from two sources: the mandibular glands and the Koschevnikov gland, which is associated with the sting apparatus. When a bee stings, it releases isopentyl acetate - IPA - at the sting site. Other bees detect it, produce their own alarm pheromone, and the colony escalates into full defensive mode. One sting begets dozens. It's a chemical cascade.

More than forty chemical compounds make up the alarm pheromone blend - IPA, butyl acetate, 1-hexanol, n-butanol, 1-octanol, hexyl acetate, octyl acetate, n-pentyl acetate, 2-nonanol, and 2-heptanone from the mandibular glands, among others. But IPA is the primary signal. And IPA smells like bananas.

Not "sort of like" bananas. Not "reminiscent of" bananas. Isopentyl acetate is the exact compound that gives bananas their characteristic smell. Bananas contain it. Alarm pheromone contains it. They are the same molecule. This is why beekeepers are warned not to eat bananas near hives - the scent mimics the chemical signal that means "an enemy is here, sting this spot." A beekeeper who smells like bananas has, from the colony's perspective, already been stung.

Africanized honey bees produce twice as much IPA as European honey bees, with higher levels of nine of twelve alarm pheromone components. They respond with greater intensity, in greater numbers, and continue responding for longer. Their lower threshold of pheromone response partly explains the more aggressive colony defense that gives them their reputation.

In 1995, P. Kirk Visscher, Richard S. Vetter, and Gene E. Robinson used electroantennography - hooking electrodes to bee antennae - to prove that smoke doesn't "calm" bees at all. It temporarily overwhelms their olfactory system, preventing the alarm cascade from propagating. The bees aren't calmer. They just can't smell the emergency.

The Babies Are in Charge

E-beta-ocimene is a volatile brood pheromone produced by young larvae - newly hatched to three days old, producing the highest quantity relative to body weight. It is, functionally, a hunger signal. Starving larvae produce more of it. Adding synthetic E-beta-ocimene to empty cells increased worker visits to those cells. Adding it to larvae increased the visitation rate further.

But E-beta-ocimene does something else that rewrites the assumed hierarchy of the colony. It inhibits worker ovary development more effectively than QMP does.

Three-day-old larvae - blind, legless, floating in royal jelly - suppress worker reproduction better than the queen. The babies outperform the monarch at the one job everyone assumes is the monarch's most important function. The larvae are also capable of pushing adult workers to start foraging earlier in life - effectively manipulating adult career decisions through chemistry.

Yves Le Conte and colleagues identified the broader brood pheromone blend - a complex mixture of fatty acid esters exuded by larval salivary glands. It functions as both a primer pheromone (long-term physiological effects) and a releaser pheromone (immediate behavioral triggers). Le Conte, with Leam Sreng, Jerome Trouiller, and Serge Henri Poitou, patented artificial brood pheromone in 1996.

The hierarchy, it turns out, is not what the org chart suggests. The queen is running a pharmaceutical operation. The larvae are running a more effective one. And the workers, whose brains are being rewritten by both, are the ones actually making all the decisions about foraging, building, defending, and everything else.

The Forager Pheromone Is Brewed From Fermented Nectar

In 2004, Leoncini and colleagues identified ethyl oleate as the pheromone that regulates the transition from in-hive work to foraging. The compound is found in high concentrations on the bodies of adult forager bees. It's transmitted through trophallaxis - foragers pass it along with the nectar they share.

When enough foragers are present, ethyl oleate delays younger bees from transitioning to foraging. When foragers are lost - to predation, pesticides, or bad weather - ethyl oleate concentrations drop, and younger bees mature into foragers faster. The colony has a self-regulating labor ratio between in-hive workers and foragers, and no individual bee makes the decision. The pheromone makes it.

The production mechanism is the detail that stops you in your tracks. Ethyl oleate is produced in the epithelium of the honey crop through transformation of ethanol derived from fermented nectar. The bees are brewing their own communication chemicals from their food. Fermented nectar becomes ethanol becomes ethyl oleate becomes a workforce planning signal. The career management system is powered by alcohol.

How Bees Detect Death

Oleic acid is a conserved necromone - a death chemical - found across arthropod taxa, not unique to bees. In honey bee colonies, hygienic removal of dead brood requires two odorants working together: E-beta-ocimene (the same larval hunger signal) flags workers' attention, and oleic acid provides the actual death cue. Neither works as reliably alone. Together, they trigger the hygienic behavior that keeps colonies clean.

The dual-signal system means E-beta-ocimene has two completely different meanings depending on context. Coming from live larvae, it means "feed me." Associated with dead brood, it means "remove this." Same chemical. Different meaning. Bee chemical communication has homonyms.

Approximately 10% of workers aged two to three weeks specialize as undertakers - bees dedicated to removing corpses from the hive. They're specialists in a workforce that doesn't have job titles.

And here's a detail that makes biologists simultaneously excited and philosophical: Western and Eastern honey bees detect death differently. Apis mellifera - the Western honey bee - smells death directly through oleic acid. Apis cerana - the Eastern honey bee - instead monitors levels of heptacosane and nonacosane, cuticular hydrocarbons associated with living bees. When these drop below "alive" levels (within about thirty minutes of death), the corpse gets removed. Western bees detect the presence of death. Eastern bees detect the absence of life. Same outcome. Different philosophical approaches.

The Nasonov Signal: 'Over Here'

When a forager returns to the hive and raises her abdomen while fanning her wings, she's exposing the Nasonov gland on the dorsal surface of the seventh abdominal segment. The gland releases a blend of seven volatile compounds - geraniol, nerolic acid, geranic acid, (E)-citral, (Z)-citral, (E,E)-farnesol, and nerol - that create an airborne scent plume pointing toward the hive entrance.

The Nasonov pheromone serves as a beacon. It orients returning foragers. During swarming, scouts release it at new nest sites to guide the swarm to the exact entrance. It's the GPS of bee navigation - a chemical broadcast that says "home is here."

Synthetic Nasonov blends - typically citral and geraniol in a 2:1 ratio - attract swarms to artificial nest cavities in field tests. Commercial products like Swarm Commander use all-natural food-grade floral terpenes to mimic the signal. The chemistry is simple enough to synthesize. The context in which bees produce and respond to it is not.

When the Chemistry Breaks Down

The pheromone system is robust until it isn't. Neonicotinoid pesticides target nicotinic acetylcholine receptors - the same receptors that process pheromone signals. Thiacloprid exposure causes faster signal degeneration in antennae responding to both QMP and 2-heptanone (the mandibular alarm pheromone). Bees exposed to neonicotinoids can't properly detect queen pheromone or alarm signals. The result is poor brood care, reproductive dysregulation, and colony disorganization.

The cascade compounds. Neonicotinoid exposure reduces expression of dorsal-1A, a critical immune transcription factor, suppressing the Toll pathway. This leads to higher deformed wing virus replication and increased mortality. Combined pesticide exposure - neonicotinoid plus fungicide - produces a 2.93-fold increase in mortality plus increased varroa mite infestation.

The pheromone system doesn't break in isolation. When it breaks, everything that depends on it breaks too. Brood care. Disease resistance. Workforce regulation. Colony cohesion. The chemical infrastructure that holds fifty thousand individuals together as a functioning superorganism starts dissolving, and the colony follows it down.

The Queen's Distress Signal

In 2025, a paper published in Proceedings of the National Academy of Sciences revealed something that reframes the entire relationship between queen health and colony survival.

Queens experimentally challenged with deformed wing virus B and black queen cell virus showed a reduction in methyl oleate production - one of the nine retinue pheromone compounds. Virus infection shrinks the queen's ovaries, which changes her pheromone output. Workers detect the shift and begin rearing replacement queens - the process called supersedure.

The colony can smell its queen's illness before any visible symptoms appear. The pheromone change precedes the physical decline. It's an early warning system built into the chemistry itself.

In initial field trials, colonies supplemented with synthetic methyl oleate were far less likely to begin rearing replacement queens than colonies given blends without it. The synthetic supplement stabilized the "queen is healthy" signal even when the queen was not.

The implications for colony management are immediate. If methyl oleate can serve as a diagnostic biomarker for queen health, beekeepers could detect failing queens before colony performance declines. If synthetic supplementation can stabilize colonies during critical periods - almond pollination, peak honey production - it could reduce the supersedure events that currently disrupt colony productivity at the worst possible moments.

The queen's body is broadcasting its own health status, in real time, through chemistry. The workers are listening. They've always been listening. Science just started eavesdropping.

Fifty Compounds and Counting

Fifteen glands. More than fifty identified compounds. Primer pheromones that change physiology over days. Releaser pheromones that trigger behavior in seconds. Context-dependent signals where the same molecule means different things in different situations. A pharmaceutical operation run by a queen, a more effective one run by larvae, a workforce planning system powered by fermented nectar, and a death-detection mechanism that differs between species based on philosophical approach.

The waggle dance is remarkable. It won a Nobel Prize. But the chemical language that operates alongside it - invisible, continuous, older than any dance - is the deeper system. It regulates reproduction, defense, labor allocation, hygiene, navigation, and queen succession without any individual bee understanding what it's doing. The signals flow. The colony responds. The chemistry holds fifty thousand lives together through compounds measured in micrograms.

Colin Butler called it "queen substance." He had found a molecule. What he had actually found was a government.