1. Swarming tendency and queenlessness

Fig. 1 : swarm cell. They are found mainly along the edges of the combs

1.1 Biological principles The queen is the colony’s only functionally reproductive female. She ensures not only the transmission of genetic heritage, but also social regulation through the continuous production of pheromones. These queen pheromones perform several essential functions: inhibition of ovarian development in workers, inhibition of queen cell construction, stabilisation of social cohesion.

When pheromone production decreases — due to the queen’s ageing or an increase in colony size — the inhibitory signal becomes insufficient. The workers then initiate the construction of queen cells (Fig. 3). This mechanism is not an anomaly, but a natural reproductive process of the colony. Swarming dynamics therefore depend on:

• the age of the queen,
• population density,
• resource availability,
• internal pheromonal balance.

1.2 Swarm cells

Swarm cells are morphologically distinct from worker cells. They are elongated and oriented downward. They develop progressively until capping (Fig. 1). They appear mainly:

• along the edge of the comb,
• in peripheral areas of the brood nest,
• sometimes in drone frames.

The presence of capped swarm cells indicates active preparation for colony division.

1.3 Queenlessness as a breeding mechanism

Queenlessness represents the second biological trigger for queen rearing. In the absence of queen pheromones:

• workers select very young larvae,
• they enlarge the cells,
• they modify feeding by providing exclusively royal jelly.

The differentiated development of a queen does not depend on the initial genetic material, but on the feeding regime and the cell volume. Controlled queenlessness therefore constitutes the technical foundation of directed breeding.

1.4 Implications for the breeder

Queen rearing is based on mastering these two natural mechanisms:

1. inducing or exploiting queenlessness,
2. controlling swarming dynamics.

Without an understanding of these processes, any attempt at breeding remains random.

To learn more :

• Queen cells
• Understanding swarming
• Practical guide : 4.7.4 Management of queenless colonies

2. Queen mating

Fig. 2: queen mating flights

2.1 Mating process After emerging, the young queen makes several mating flights. These flights occur under favourable weather conditions and take place in drone congregation areas. In these areas, males from different colonies concentrate. The queen mates successively with several drones (Fig. 2). This phenomenon of multiple mating (polyandry) is an essential characteristic of honey bee biology.

Polyandry leads to:

• high genetic diversity within the colony,
• the formation of worker sub-families,
• better functional stability of the colony.

These effects do not automatically guarantee superior performance, but they increase the probability of better functional stability of the colony. After mating, sperm is stored in the spermatheca and must be sufficient for the queen’s entire lifespan. The quality and quantity of sperm determine:

• the queen’s longevity,
• the regularity of egg laying,
• the vigour of the colony.

Insufficient or deficient mating can result in irregular egg laying, excessive production of males, or early queen replacement.

2.2 Genetic role of drones

Drones originate from unfertilised eggs. They are haploid and transmit exclusively the genetic heritage of their mother.

Thus:

• each male genetically represents its colony of origin,
• the genetic quality of drone-producing colonies directly influences the next generation.

In a breeding programme, the selection of drone colonies is therefore of equal importance to that of mother colonies. A lack of control over drone origin can compromise the selection efforts achieved on queens.

2.3 Managing mating

Mating can never be fully controlled under natural conditions. However, it can be oriented. Mating stations allow young queens to be isolated and ensure that only drones from selected lines participate in mating. This system makes it possible:

• to stabilise the desired traits,
• to limit the introduction of undesired genetics,
• to create a reliable basis for subsequent evaluation.

The density and quality of drone colonies are decisive to ensure complete mating.

2.4 Biological limits

Even at a mating station, certain parameters escape control:

• weather conditions,
• success of nuptial flights,
• the actual quantity of sperm stored.

Mating remains a biological process subject to variability. The breeder must therefore integrate this uncertainty into the programme and plan a rigorous evaluation of young queens after their introduction.

To learn more :

• Drone rearing
• All about the drone
• Single-drone insemination: an update on this practice

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3. Use of queens

Fig. 3 : introduction cage Fig. 4: nucleus mating hive  Fig. 5: marking the queen

3.1 Introducing young queens Introducing a young queen is a critical step in the breeding process. A genetically promising queen can be lost if introduction conditions are not mastered. The recipient colony must be: sufficiently strong, truly queenless, free of residual queen cells. The queen is generally placed in an introduction cage (Fig. 3). This cage allows gradual acclimatisation. Bees come into contact with the queen through the mesh, which promotes acceptance through the exchange of pheromones and food. Acceptance depends on several factors: duration of prior queenlessness, the colony’s tension state, time of the season, presence or absence of a nectar flow. A poorly prepared introduction can lead to rejection or destruction of the queen.

3.2 Formation of nuclei

Nuclei are used to host mated queens in a controlled environment. The nucleus mating hive generally contains 4 - 6 brood combs (Fig. 4). The presence of open and capped brood stabilises the colony and promotes acceptance. Nuclei serve several functions:

• checking egg-laying quality,
• strategic reserve of queens,
• rapid replacement of failing queens,
• backup overwintering.

A colony that is too weak does not allow a reliable evaluation of the queen. Observed performance depends partly on the strength of the nucleus.

3.3 Marking and traceability

Marking queens is a central element of breeding follow-up (Fig. 5). Each queen receives:

• a numbered disc,
• or a colour marking compliant with the annual international code.

Marking makes it possible:

• to identify origin,
• to verify the queen’s subsequent presence,
• to ensure genealogical traceability.

It is recommended to mark queens before introducing them, notably to avoid any confusion after mating flights. Newly emerged queens are easier to handle. Care must be taken not to obstruct the base of the wings with glue. The queen should only be introduced after a minimum delay of about ten minutes in order to avoid an aggressive reaction linked to the odour of the marking. A queen of unknown origin cannot be integrated into a structured breeding programme.

3.4 Overwintering and delayed validation

The evaluation of a queen cannot be considered definitive before overwintering. A young queen must demonstrate:

• regular egg laying,
• good developmental dynamics,
• an ability to lead the colony towards stable overwintering.

Only in the following spring can one judge:

• her longevity,
• the colony’s stability,
• the overall quality of the offspring.

The use of queens therefore constitutes the link between technical production and genetic validation.

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To learn more :

• How to introduce queens?
• Creating young colonies (nuclei)
• Multiplying a nucleus

4. Heredity

Fig. 6 : Haplodiploidy refers to a form of sex determination in which one sex carries only one set of chromosomes (haploid, drone) and the other sex carries the double set of chromosomes (diploid, queen). In general, the male sex is haploid.

4.1 Haplodiploid system In honey bees, the system of sex determination is haplodiploid (Fig. 6). Queens and workers are diploid: they originate from fertilised eggs and possess two sets of chromosomes. Drones are haploid: they originate from unfertilised eggs and possess only one set of chromosomes. This system has several major consequences: Males transmit to their offspring the genetic heritage received from their mother, in haploid form and without subsequent genetic modification. There is no “father of a male”. Each drone genetically represents the colony from which it originates. Thus, selecting drone-producing colonies is as decisive as selecting mother colonies.

4.2 Within-colony diversity and polyandry

Multiple mating by the queen leads to the formation of several worker sub-families within a single colony. Each sub-family shares:

• the same mother,
• a different father.

This internal genetic diversity contributes to:

• behavioural stability,
• resilience to diseases,
• organisational flexibility.

The variability observed within a colony therefore does not result from a lack of uniformity, but from a biological strategy.

4.3 Heritability

Not all traits are transmitted with the same intensity. Heritability expresses the proportion of variation in a trait that is due to genetic factors, as opposed to environmental influences. A trait with high heritability responds more quickly to selection. Conversely, a trait strongly influenced by the environment requires:

• repeated observation,
• comparable conditions,
• prolonged selection.

Genetic improvement therefore depends on:

• initial variability,
• selection intensity,
• consistency over several generations.

Heritability is not an absolute value attached to a trait. It depends on the population considered and on the environmental conditions in which observations are carried out. A change in breeding conditions can therefore modify the relative share attributable to genetic factors.

4.4 Genetic–environment interaction

The observed phenotype of a colony always results from the interaction between:

• genetic heritage,
• environmental conditions.

A colony that performs well in a favourable environment may not express the same performance in another context. This interaction implies that observed performances must be interpreted in their context. A valid comparison between colonies requires evaluation conditions that are as homogeneous as possible in order to limit the influence of external factors.

Fig. 7 : Microsatellites are segments on chromosomes; they have no influence on characteristics. Individuals, groups of related animals and breeds differ by the length of microsatellites. This makes it possible to control strains and breed membership.

4.5 Microsatellites and line control Microsatellites are chromosomal segments used as genetic markers (Fig. 7). They do not directly determine traits, but make it possible: to identify strains, to verify breed membership, to control line purity. These tools contribute to conserving genetic heritage and managing breeding populations.

4.6 Crossbreeding effects and heterosis

Crosses between genetically distant races can produce a heterosis effect. This effect can result in:

• increased vigour,
• enhanced defensive capacity.

However, these effects can also be accompanied by undesirable behaviours, notably increased aggressiveness. In addition, effects observed in the first crossbred generation may not be maintained with the same intensity in subsequent generations due to genetic recombination. Managing crosses therefore requires caution and control.

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To learn more :

• Introduction to honey bee genetics
• Choosing the queen type (F0 or F1?)
• Epigenetics conducts genetics

5. Selection

Fig. 8 : Selection consists of choosing, within a population, the colonies presenting the desired characteristics

5.1 Foundations of selection Selection consists of choosing, within a population, the colonies presenting the desired characteristics in order to use them for reproduction. It is based on three inseparable elements: a clear definition of objectives, an objective evaluation of performance, control of reproduction. Without mastery of these three parameters, genetic progress remains random. Selection does not aim at individual perfection, but at the progressive improvement of the population.

5.2 Defining criteria

Criteria must be defined before any selection. Among the main criteria are:

• gentleness,
• staying on the comb,
• swarming tendency,
• yield.

Other criteria may be included depending on objectives:

• hygienic behaviour,
• resistance to diseases,
• spring vitality.

Coherent selection requires prioritising criteria. Not all can be improved simultaneously with the same intensity.

5.3 Selecting mother colonies

Mother colonies are chosen among those showing the best overall performance. Evaluation must be carried out:

• over a full season,
• under comparable conditions,
• using a structured scoring system.

An isolated exceptional performance is not sufficient; stability of results is decisive. Queens selected as mothers must demonstrate:

• regular egg laying,
• balanced dynamics,
• overwintering ability.

5.4 Selecting drone-producing colonies

Selection of drone-producing colonies is just as important. Given the haplodiploid system:

• drones transmit their mother’s genetic heritage directly,
• any genetic weakness is transmitted immediately.

In a structured programme, only positively evaluated colonies should produce the drones intended for mating.

5.5 Testing and collective evaluation

Queens resulting from selection are distributed anonymously to testers. This anonymisation makes it possible:

• to avoid evaluation bias,
• to guarantee objectivity.

Performance is observed according to standardised criteria. After the testing period, results are centralised and compared. This process makes it possible:

• to identify superior lines,
• to discard insufficient lines,
• to adjust the selection strategy.

5.6 Progress and limits

Genetic progress is gradual and cumulative. It depends on:

• selection pressure,
• the intensity of culling,
• control of mating,
• consistency over several generations.

Irregular or incoherent selection leads to stagnation, or even regression. Selection thus constitutes the strategic core of directed breeding.

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To learn more :

• Practical guide : 4.7 Evaluation and selection of colonies
• Does selection in beekeeping enable heritability?
• VSH or SMR: varroa resistance traits finally explained

6. Genetic heritage of bees in Europe

Fig. 9 : a bee of the carnica race

6.1 Genetic diversity and racial groups European bees belong to different racial groups derived from distinct evolutionary lineages. This diversity constitutes an important genetic heritage. Within a given race, traits can vary strongly. In addition, directed selection can significantly modify certain characteristics.

Comparisons between races must therefore be interpreted with caution, because:

• environmental conditions influence the expression of traits,
• selected lines may differ from the initial racial type.

Morphological, physiological and behavioural analyses show that carnica bees (Fig. 9) and ligustica are relatively close. Mellifera and caucasica bees belong to other racial groups.

6.2 Mellifera bee (Apis mellifera mellifera)

The mellifera bee, or European black bee, represents a lineage historically adapted to the conditions of Western Europe. Today it is considered threatened worldwide. In Switzerland, its conservation is ensured by specialised organisations. Preserving this race aims at:

• maintaining local genetic diversity,
• adaptation to regional climatic conditions,
• safeguarding a historic beekeeping heritage.

6.3 Carnica bee (Apis mellifera carnica)

Carnica is widely distributed in Central and Eastern Europe. It is almost exclusively bred in Germany and Austria. Certain lines, such as Sklenar, Troisek and Peschetz, originate from structured breeding programmes. The international spread of carnica results largely from its qualities sought in modern beekeeping.

6.4 Caucasica bee (Apis mellifera caucasica)

The Caucasian bee is distinguished in particular by:

• a cubital index below 2.2,
• abundant use of propolis,
• males with a dark to black thoracic coat.

It shows morphological characteristics close to carnica, while belonging to a distinct racial group.

6.5 Crosses and genetic effects

Crosses between genetically distant races can lead to a heterosis effect. This effect can result in:

• increased vigour,
• enhanced defensive capacity.

However, undesirable effects may also appear, notably marked aggressiveness. Managing crosses therefore requires:

• rigorous planning,
• control of mating,
• careful evaluation of offspring.

6.6 Implications for the breeder

Managing genetic heritage does not concern only individual colony performance. It involves:

• conserving adapted lines,
• limiting uncontrolled crosses,
• collective responsibility in maintaining structured races.

Genetic heritage constitutes the basis on which any long-term selection strategy is built.

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To learn more :

• Apis mellifera & other apis
• Defining bee races
• Cryopreservation of drone semen

7. Organisation of queen breeders

Fig. 10 : The breeding pyramid. A few very committed beekeepers select the best possible breeding mothers, mate the young queens in a targeted manner at mating stations A with suitable drones, and submit the resulting mated queens to testing apiaries.

7.1 Breeding as a collective approach Directed breeding can only produce lasting results if it is integrated into a structured organisation. Working in isolation has several limitations: lack of objective comparison, limited control of mating, risk of genetic drift, stagnation of progress. Collective organisation makes it possible to overcome these limits by coordinating: selection objectives, evaluation methods, control of reproduction. Selection then becomes a shared project rather than an individual initiative.

7.2 Common definition of objectives

A breeders’ organisation establishes clear, shared criteria. These criteria may include:

• gentleness,
• behavioural stability,
• low swarming tendency,
• yield,
• resistance to diseases.

Harmonising criteria guarantees comparability of results between operations. Without a common definition, evaluations remain subjective and cannot be accumulated.

7.3 Mating stations and genetic control

Mating stations are a central pillar of the collective system. They make it possible:

• to geographically isolate queens during the mating period,
• to control the origin of drone colonies,
• to avoid undesired crosses.

Maintaining selected drone colonies ensures the genetic coherence of the programme. Managing a station requires:

• rigorous selection of drone-producing colonies,
• logistical coordination,
• collective discipline.

7.4 Structured testing and anonymisation

Collective evaluation relies on a testing system. Queens are distributed anonymously to testers. This anonymisation guarantees:

• objectivity,
• absence of personal influence,
• reliability of scoring.

Data are centralised, compared and analysed. This process makes it possible:

• to identify superior lines,
• to discard insufficient lines,
• to guide future decisions.

7.5 Traceability and responsibility

Traceability is an essential element of the system. Each queen must be traceable to:

• its maternal line,
• its mating station,
• its testing results.

This transparency strengthens:

• the programme’s credibility,
• the quality of selection decisions,
• the conservation of genetic heritage.

Each participating breeder assumes a collective responsibility:

• to respect the established criteria,
• to maintain colony quality,
• to avoid uncontrolled crosses.

7.6 Intergenerational continuity

Genetic progress cannot be observed over a single generation. It requires:

• continuity of objectives,
• methodological consistency,
• sustained cooperation.

Institutional organisation guarantees this stability over time. Directed breeding thus becomes a collective commitment in favour of:

• bee quality,
• behavioural stability,
• adaptation to regional conditions.

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To learn more :

• Breeder instructors
• Practical guide : 4.7 Evaluation and selection of colonies
• Principles and methods of honey bee queen breeding

8. Conclusion

Queen breeding is based on clear biological principles: natural swarming tendency, response to queenlessness, multiple mating, and the particular genetic transmission of bees. These natural mechanisms constitute the basis on which the breeder intervenes in a directed manner.

Understanding heredity, managing mating, and objectively evaluating performance make it possible to transform a spontaneous biological process into a structured selection programme. Genetic progress does not result from an isolated measure, but from coherent and repeated work over several generations.

Conserving Europe’s genetic heritage and maintaining races adapted to local conditions require a collective organisation and close collaboration between breeders. Mating stations, testing and line traceability guarantee the continuity and reliability of breeding work.

Directed breeding thus represents a long-term commitment in favour of high-performing, balanced colonies adapted to current beekeeping requirements. It combines biology, methodological rigour and collective responsibility in the service of bee quality.

 

Source: This summary is inspired by the book « L'apiculture - Une Fascination » , Société Romande d'Apiculture