The Role of Pheromones

Have you ever wondered how a queen bee manages to organize her colony? The answer is queen pheromones, the most advanced form of communication in social insects. Pheromones are chemical substances bees secrete from their exocrine glands. When released into the environment they change the behavior and physiology of fellow bees.

They play a crucial role in honey bee colonies because they facilitate communication among different castes. This includes communication between queen-workers, workers-workers, queen-drones, as well as with the brood. By emitting and sensing these chemical substances, bees can regulate the behavior and development of their colony. It helps them to work together effectively and maintain colony health and productivity.

Pheromones are typically directed towards members of the same colony. However, there are a few exceptions where they may target others. The broad range of activities that pheromones influence within the colony include development, reproduction, foraging, defense, and overall integration.

Introduction to Bee Pheromones

Bees communicate and coordinate their activities within the colony using chemical signals called bee pheromones. They produce these signals in various glands in their bodies (see diagram).

Once released into the air or onto surfaces, the pheromone is detected by other bees. By using pheromones, bees can efficiently organize and carry out their tasks. Understanding the functions of these chemical signals provides valuable insights into the behavior and biology of bees.

Types

Honey bees have two types of pheromones: primer and releaser pheromones. Primer pheromones evoke complex and long-lasting physiological responses in the receiver. They act at a deeper level, which leads to developmental and behavioral changes. In contrast, releaser pheromones have a weaker effect. They operate at a surface level, and evoke only temporary and simple behavioral responses in the receiver.

Pheromones are categorized according to their function. These include sexual attraction, gathering, dispersal, alarm, aggregation, trail, recruitment, territorial and recognition. Social insects utilize primer pheromones to maintain harmony and stability within the colony.

In honey bees, the queen and brood mainly release primer pheromones, worker bees generally emit releaser pheromones. The development of primer pheromones is critical to social insects as these signals play a vital role in their social structure and homeostasis.

How do Bees detect Pheromones?

Queen, drone, worker bees, and laying worker bees secrete chemical messengers that trigger specific responses in other bees. These messengers take on the form of volatile or non-volatile liquids and are transmitted either through direct contact as a liquid or as vapor. The bee’s antenna and body parts are responsible for receiving these chemical messages.

These messengers contain an array of unique chemicals that play different roles. For example, queen bees emit a pheromone that prevents worker bees from laying eggs, ensuring their reproductive dominance. They also secrete a pheromone that helps attract drones for mating purposes. On the other hand, worker bees produce a chemical that signals to others that a particular task needs to be completed.

Antennae

Bees use their antennae to detect pheromones through a series of sensory structures called sensilla. These structures contain nerve cells that are stimulated when a pheromone molecule binds to specific receptor sites. The antennae of bees are covered in thousands of these sensilla, allowing them to detect even very low concentrations of pheromones.

The exact mechanisms by which this process works are still not fully understood, but it is believed that the shape and electrical charge of the pheromone molecules play a critical role in their detection. Once a pheromone is detected, the bee’s behavior and physiological responses are altered in specific ways that help the colony function more effectively, such as by signaling the presence of a queen, or the need for more workers.

Body

Bees use not only their antennae but also other parts of their body to detect pheromones. The incoming pheromone molecules, such as queen mandibular pheromones (QMPs), bind to specific receptor cells in the bee’s antenna, as well as on their mouthparts, legs, wings, and even the reproductive organs.

Once the pheromone molecules are detected, they activate sensory neurons and trigger nerve impulses, which are then transmitted to the bee’s brain. This process prompts a range of behavioral changes in the bee, including foraging, feeding, brood rearing, and mating.

Can Bees detect Human Scent?

When fear arises in humans or animals, their bodies release fear pheromones, which can be detected by bees. The bees that detect these pheromones immediately communicate the threat to their nearby hive mates. In response, the hive instinctively defends its territory to maintain the safety and security of its community.

This chemical communication between bees is just one example of the remarkable social and survival mechanisms that exist within this highly organized insect society.

How long do bee pheromones last?

The duration of bee pheromones can vary, depending on the specific pheromone and the environmental conditions. For example, the queen bee’s pheromone can last for several days or even up to a few weeks. Worker bee alarm pheromones dissipate more quickly because the bees use them in response to immediate threats.

For example, guard bees release a chemical called sting alarm pheromone (SAP) to signal foragers to defend the hive. Isopentyl acetate, the primary component of SAP, mimics this effect and is dependent on dosage. The response to this pheromone lasts for up to 24 hours.

The longevity of pheromones can also be affected by factors such as temperature, humidity, and airflow in the hive. Ultimately, the duration and effectiveness of pheromones depend on their intended purpose and the overall health and functioning of the bee colony.

How far do bee pheromones travel?

The range of bee pheromone detection can vary depending on the specific pheromone and the surrounding conditions. Some bee pheromones, like the queen mandibular pheromones (QMPs) and alarm pheromones can travel several feet within the hive and other bees still detect them.

For example, QMPs can spread throughout the hive and aid in the coordination and organization of workers. Additionally, some bee pheromones can be detected by other bees even outside of the hive. This allows workers to locate flowers and navigate back to the hive. The exact range of pheromone detection is dependent on a variety of factors, including the particular pheromone, concentration, airflow in the environment, and the bee’s physiological state.

When queen bees and drones are ready to mate, they release pheromones that help them locate each other. The queen releases a pheromone called 9-oxodecenoic acid (9-ODA), which attracts drones in the surrounding area. This pheromone can travel up to two miles and remains effective for several days.

Similarly, the drones release a pheromone called (Z)-11-eicosen-1-ol (E-11), which helps the queen detect their presence and location. This pheromone can also travel several miles and remains effective for up to a week. The strength and effectiveness of these pheromones are essential in ensuring the successful mating of queens and drones and the overall health of the bee colony.

 

Can humans smell bee pheromones?

Bees rely on smells to locate their hive or new home after swarming. The pheromone they use for this purpose has a distinct lemony fragrance to humans. In the event of danger, when a bee stings, it emits an odor called an alarm pheromone that smells like bananas.

This signals other bees to come to the hive’s defense. If the alarm pheromone remains on clothing, it can continue to attract bees. It is therefore advisable to wash any stung clothing before wearing it again. Overall, the use of pheromones is a crucial aspect of bee communication and plays a significant role in their survival.

Does killing a bee release pheromones?

When bees sting or are sick or injured, they release an alert pheromone that signals danger to its fellow bees. The bees also use this pheromone to mark and identify flowers they have already visited for nectar.

This chemical plays a crucial role as it acts as a signal to either repel or attract. Plus, it mobilizes bees into definite action towards a certain direction.

Do Sick Bees release Pheromones?

Research to understand how pheromones and social communication of bees change when infected with the N. ceranae fungus showed that infected bees had significantly higher concentrations of an alert pheromone. Bees produce this chemical if they detect a threat by large invaders like humans or larger mammals. The bees also use this pheromone to mark and identify flowers they have already visited for nectar.

The pheromone serves as a call to action, either to repel or attract. In the case of N. ceranae infestations, the pheromone either stimulates bees to care for their sick hive mates, or remove and kill them. It needs further research to determine  the specific cause behind the chemical’s production in the impacted beehives.