Honey bee queens mate in dramatic midair encounters with multiple males, and the act kills the drones involved. That single sentence captures the core answer, but bee reproduction is stranger and more varied than most people realize. The sex of a bee is determined not by sex chromosomes but by whether an egg is fertilized at all, workers actively police each other’s attempts to reproduce, and at least one subspecies has figured out how to produce daughters without mating. The mechanics deserve a closer look.
The Mating Flight
A virgin honey bee queen mates during one or a few flights early in her life, and she never mates again. Males, called drones, gather each day at specific aerial locations known as drone congregation areas. Research tracking flight times across different regions found that drones in New Zealand’s Waikato region fly to these areas between roughly 2:00 and 5:00 p.m., with peak activity around 4:00 p.m., though globally most drone flight periods begin after noon.1New Zealand Journal of Zoology. Global variation in honey bee (Apis mellifera) mating flight times The timing varies by latitude and climate, but the basic pattern is the same everywhere: drones wait, and a queen flies into the swarm.
When a drone catches a queen in flight, mating is fast and violent. The drone’s reproductive organ, called the endophallus, is stored internally and must evert outward under pressure. This eversion happens in two stages. At first, a constriction in the organ stops the process partway through. Only when internal pressure builds sufficiently do the walls of a narrow duct open, allowing the bulb to pass through and complete the eversion, which forces semen out with considerable force.2Apidologie. Why the eversion of the endophallus of honey bee drone stops at the partly everted stage and significance of this That forceful ejection matters because queens mate with many drones in succession, and each male’s sperm needs to reach deep inside the queen’s reproductive tract. The eversion rips the drone’s abdomen open, and he dies almost immediately. A piece of his genitalia, often called the mating sign, stays lodged in the queen until the next drone removes it.
A queen typically mates with a dozen or more drones across her mating flights. Once she returns to the hive for the last time, she will spend the rest of her life, potentially several years, laying eggs fertilized by sperm she collected during those few flights.
How an Egg’s Fertilization Decides Its Sex
In most animals, sex depends on chromosomes inherited from both parents. Bees work differently. They use a system called haplodiploidy: females develop from fertilized eggs and carry two sets of chromosomes, while males develop from unfertilized eggs and carry only one set.3PubMed Central. Sex mosaics in the honeybee: how haplodiploidy makes possible the evolution of novel forms of reproduction in social Hymenoptera This means that a queen can choose whether to fertilize an egg as she lays it. When she lays an egg in a smaller worker cell, she releases sperm from her storage organ and the egg develops into a female worker or, under the right conditions, a new queen. When she lays an egg in the larger drone cell, she withholds sperm and the egg develops into a male.
A further layer of genetic control involves a gene called the complementary sex determiner, or csd. For a fertilized egg to develop normally as a female, it needs two different versions of this gene, one from each parent. If a fertilized egg happens to receive two identical copies, which can occur when the queen’s mate is too closely related, the result is a diploid drone, a male that developed from a fertilized egg. These diploid drones are typically eaten by workers shortly after hatching because they are reproductively useless to the colony.4Apidologie. Non-lethal genotyping of honey bee queens and drones prior to artificial insemination for targeted mating This is one reason genetic diversity matters so much in bee populations: too little diversity at the csd gene means more eggs are wasted on inviable males.
Storing Sperm for Years
Once a queen returns from her mating flights, the sperm she collected migrates into a specialized organ called the spermatheca. This small, spherical structure keeps sperm alive and functional for the queen’s entire reproductive life. How the spermatheca pulls this off has been a subject of serious research. Proteomic analysis of the fluid inside the spermatheca has identified over a hundred proteins that the queen contributes, many of which are enzymes involved in energy metabolism and antioxidant defense.5PubMed Central. Insights into female sperm storage from the spermathecal fluid proteome of the honeybee Apis mellifera Keeping sperm alive for years requires both a steady energy supply and protection against oxidative damage, and the spermathecal fluid is specifically tuned for both.
Gene expression studies have added detail to this picture. After mating, the queen’s spermatheca upregulates trehalose transporters, sugar-shuttling molecules that help fuel the organ’s energy demands and keep sperm oxygenated and viable long-term.6PLOS ONE. Transcriptomic analysis of the honey bee (Apis mellifera) queen spermathecae reveals genes that may be involved in sperm storage after mating The spermathecal fluid is, in effect, a carefully maintained life-support system. A queen who mates successfully in her first week of life can lay fertilized eggs for three to five years without ever mating again.
Why Queens Mate With So Many Males
Mating with a single drone would be simpler and safer, so the fact that queens routinely mate with a dozen or more has puzzled biologists. The leading explanation is that genetic diversity within the colony improves its resilience. Research has shown that colony fitness increases at queen mating frequencies higher than the point where overall genetic diversity levels off, suggesting that extreme polyandry does more than just diversify the workforce.7Behavioral Ecology and Sociobiology. Colony fitness increases in the honey bee at queen mating frequencies higher than genetic diversity asymptote Two proposed mechanisms help explain this: mating with many males optimizes the mix of genotypes for common tasks like foraging and nursing, and it also increases the chance of capturing rare allele combinations that protect against specific threats, such as Varroa mite resistance. Colonies headed by queens that mated with more drones had fewer mites when the colony carried Varroa-sensitive hygiene genetics, a benefit that only emerged at high mating numbers.
From the drones’ perspective, the calculus is completely different. A drone exists solely to mate. He does no work in the hive, produces no wax, collects no nectar. His entire contribution to the colony is genetic, and he dies in the act of delivering it. Colonies produce drones seasonally and expel any survivors before winter.
How the Colony Keeps Workers From Reproducing
Worker honey bees are female and possess ovaries, so in principle they could lay eggs. In practice, this almost never happens in a healthy colony with a queen. Two overlapping systems of suppression are at work. The queen produces a pheromone blend called queen mandibular pheromone, and young larvae produce their own chemical signal. Experiments have shown that both the queen’s pheromone and the larval pheromone significantly suppress worker ovary development, and the larval pheromone is actually more effective at doing so than the queen’s own signal.8PubMed Central. Queen and young larval pheromones impact nursing and reproductive physiology of honey bee (Apis mellifera) workers As long as the queen is present and healthy brood is being reared, the chemical environment of the hive keeps workers’ reproductive systems shut down.
Even when a worker does manage to activate her ovaries and lay an egg, a second enforcement mechanism kicks in. Because workers are unmated, they can only produce unfertilized (male) eggs. Other workers detect these eggs and eat them, a behavior called worker policing. Queens mark their eggs with a chemical signal, and worker-laid eggs lack this marker, making them identifiable and targeted for destruction.9Behavioral Ecology. Egg marking pheromones of anarchistic worker honeybees (Apis mellifera) Experiments have confirmed strong discrimination by workers against worker-laid male eggs.10Nature. Worker policing in the honeybee Between pheromonal suppression and active policing, worker reproduction is effectively shut down in queenright colonies.
Reproduction Without Mating
There is one notable exception to the rule that female bees need sperm to produce daughters. The Cape honey bee, a subspecies found in the southern tip of South Africa, has workers that can lay eggs that develop into females without fertilization. This ability, called thelytokous parthenogenesis, arises from an unusual form of cell division in which two of the mother’s own genetic contributions fuse back together, restoring the double chromosome set needed for female development.11PubMed. A Single Gene Causes Thelytokous Parthenogenesis, the Defining Feature of the Cape Honeybee Apis mellifera capensis Researchers have traced this trait to a single gene, making it one of the clearest examples of a major reproductive shift controlled by minimal genetic change.
This ability creates problems when Cape bees encounter other subspecies. Cape workers can invade a foreign colony, activate their ovaries, and lay female eggs that the host colony raises as its own. The parasitic Cape workers effectively hijack the reproductive machinery of the host hive, sometimes leading to its collapse. It is a vivid illustration of how reproductive conflict, normally held in check by pheromones and policing, can become destabilizing when the usual rules break down.
Beyond Honey Bees
Honey bees get most of the attention, but they represent a tiny fraction of the roughly 20,000 known bee species. The majority of bees are solitary, meaning each female builds her own nest, provisions it with pollen and nectar, lays eggs, and leaves. There is no queen, no worker caste, no colony. Mating in these species looks very different. A broad overview of bee mating systems found that most female bees outside the highly polyandrous honey bees appear to mate only once, though genetic confirmation of this is limited for most species.12Apidologie. Male mating behaviour and mating systems of bees: an overview Males of solitary species often patrol flowers, nest entrances, or specific landmarks looking for females, and competition can be fierce, sometimes involving physical combat or scramble competition.
Bumblebees occupy a middle ground. They are social, with queens and workers, but their colonies are annual rather than perennial. A bumblebee queen mates in autumn, hibernates through winter, and founds a new colony alone in spring. The presence of her first workers dramatically changes her reproductive physiology: queens with workers have elevated juvenile hormone levels, lay eggs far sooner, and experience much lower mortality.13PubMed Central. An organizing feature of bumble bee life history: worker emergence promotes queen reproduction and survival in young nests In one study, no queens died while in the presence of workers, while solitary queens suffered substantially higher mortality. The colony’s social structure does not just organize labor; it actively sustains the queen’s reproductive capacity.
Stingless bees, another large group of social bees found in tropical regions, have their own reproductive peculiarities. In some species, mating involves a traumatic process in which the male leaves a mating plug that creates a permanent melanized scar on the queen’s abdomen. Research on multiple stingless bee species found that some queens are effectively locked into lifelong monogamy by these mating plugs, while others manage to remate despite the scarring.14PubMed Central. Queens remate despite traumatic mating in stingless bees Controlled mating experiments with the stingless bee Tetragonula carbonaria showed that even when a male successfully deposited a mating plug, only about 30% of queens actually had sperm in their spermathecae afterward, suggesting the queen may need to actively cooperate for sperm transfer to succeed.15Insectes Sociaux. Virgin queen behaviour and controlled mating in the stingless bee Tetragonula carbonaria (Meliponini)
Sexually Transmitted Infections in the Hive
Bees have sexually transmitted diseases. The fungal pathogen Nosema apis is widespread in honey bee populations and can be transmitted from drones to queens during mating. Drones are highly susceptible to Nosema infections, but their seminal fluid mounts an impressive defense. Proteomic analysis found that infected drones significantly altered the composition of their seminal fluid, with over a hundred proteins changing in abundance. The largest group of proteins that shifted were immune-related, including chitinases, enzymes previously suspected to have antifungal activity against Nosema.16PubMed. Infections with the Sexually Transmitted Pathogen Nosema apis Trigger an Immune Response in the Seminal Fluid of Honey Bees (Apis mellifera)
Further experiments revealed that seminal fluid attacks Nosema spores in two distinct ways. The protein fraction induces spores to germinate prematurely outside cells, which disrupts the parasite’s life cycle and renders it harmless. The non-protein fraction, meanwhile, directly kills intact spores.17PubMed Central. Seminal fluid of honeybees contains multiple mechanisms to combat infections of the sexually transmitted pathogen Nosema apis In other words, the drone’s ejaculate comes equipped with its own antimicrobial toolkit. This makes evolutionary sense: if a drone’s sperm transmits a fatal disease to the queen, his genetic legacy dies with her colony. Selection has favored males whose seminal fluid can clean itself before delivery.
When Reproduction Goes Wrong
Bee reproduction is vulnerable to environmental contamination. Drones reared in beeswax contaminated with pesticides show reduced sperm viability compared to those reared in clean wax. The effect is especially pronounced with miticides, the chemicals beekeepers use to treat Varroa mite infestations.18PubMed Central. Exposure to pesticides during development negatively affects honey bee (Apis mellifera) drone sperm viability Because a queen mates only once in her life, the quality of the drones she encounters during those flights has outsized consequences. If the drones in a region carry low-viability sperm due to pesticide exposure, queens may end up with a smaller or less functional sperm supply, which shortens their productive lifespan and weakens the colony over time. The irony of miticides impairing drone fertility is not lost on beekeepers: a treatment meant to save the colony from one threat can quietly undermine its reproductive future.
Instrumental Insemination
Beekeepers and researchers sometimes bypass natural mating entirely using instrumental insemination, a technique that allows precise control over which drones contribute genetics to a queen. The process involves collecting semen from selected drones by manually triggering partial eversion of the endophallus, then gathering roughly 8 to 12 microliters of semen from multiple drones into a syringe. The queen is anesthetized with carbon dioxide, which both immobilizes her and triggers hormonal changes that promote egg-laying, and semen is injected directly into her oviduct.19Journal of King Saud University – Science. Instrumental insemination: A nontraditional technique to produce superior quality honey bee (Apis mellifera) queens Sperm migration into the spermatheca takes about 40 hours after insemination.
The technique is finicky. Drones must be used within half an hour of collection because cooling quickly renders them unusable. Not every drone produces usable semen, so operators need a large surplus of mature males on hand. Contamination is a constant concern; drones often defecate during the process, and if the queen defecates during insemination, she is discarded. Despite these challenges, instrumental insemination is invaluable for breeding programs aimed at selecting for traits like disease resistance, gentleness, or honey production. It is the only reliable way to ensure a queen is mated exclusively with genetically known males, something that is impossible to guarantee during open mating flights where any drone from any colony within range can participate.
Haplodiploidy and the Evolution of Social Living
The unusual sex-determination system that governs bee reproduction has long been proposed as a key driver behind the evolution of their social lifestyle. The idea, first suggested by W.D. Hamilton in the 1960s, is that haplodiploidy inflates the genetic relatedness between sisters. Under this system, full sisters share three-quarters of their genes, more than they would share with their own offspring. This should theoretically make it worthwhile for workers to forgo their own reproduction and instead help their mother produce more sisters. It was an elegant explanation, and it dominated textbooks for decades.
More recent modeling work has cooled enthusiasm for this idea. A kin-selection analysis of the specific biological scenarios through which haplodiploidy could promote social behavior found that the effects are weak and unlikely to persist. Worker control of sex allocation may promote cooperation slightly, but the effect is short-lived, and worker reproduction actually tends to inhibit rather than promote helping behavior.20PubMed. Haplodiploidy and the evolution of eusociality: worker revolution Several biologically realistic factors, including the fact that workers are unmated and that sex-allocation control is likely spread across many genes, further erode the effect. The current consensus leans toward haplodiploidy being, at best, a minor contributor to the evolution of eusociality rather than the primary explanation. Ecological pressures, shared nesting, and progressive provisioning of young are now considered at least as important.