Worker Pheromones

Bee worker pheromones play a critical role in hive organization and productivity. Worker bees rely heavily on pheromones to communicate and coordinate their hive’s activities. These chemical signals act as a cohesive force, enabling bees to divide and execute tasks efficiently.

The hive’s social organization is highly intricate, with each bee assuming a specific role in the collective effort. For instance, some bees serve as nurse bees, caring for the young, while others function as foragers, traveling up to three miles in search of nectar and pollen.

The use of pheromones is key to this highly efficient system, allowing bees to navigate their environment and work in tandem to ensure their colony’s survival. In this guide, we’ll explore the different types of bee worker pheromones and their functions, giving you a better understanding of how these tiny insects work together to create such highly organized and efficient hives.

Introduction to Bee Worker Pheromones

Bee worker pheromones are chemical signals produced by worker bees to communicate with other members of the hive. Their role in hive organization and productivity is helping to ensure that tasks are divided and completed efficiently.

The honey bee pheromonal system relies heavily on caste-specific gland secretions. While some glands are exclusive to either queen or worker bees, most glands like the mandibular, Dufour’s, tarsal, and Koschevnikov glands are present in both, although the functions differ depending on the cast.

The ability of certain glands to change their function is connected to two ways of determining the roles of bees within the colony. It separates queens from workers, and divides workers into different specialized tasks. This process (polyethism) is very important for the efficiency and survival of the colony.

For example, wax and hypopharyngeal glands are active in young bees for building and feeding activities, while sting alarm pheromone production increases in guard bees. The hypopharyngeal gland, also called the called the brood food gland, secretes royal jelly. Furthermore, gland secretion is not rigidly caste-specific, it adapts to the changing needs of the colony. These findings highlight the complex nature of the honey bee caste system and the importance of gland secretion in maintaining colony functionality.

The Role of Queen Mandibular Pheromone

The queen mandibular pheromone (QMP) is one of the most important bee worker pheromones. Produced by the queen bee, it regulates the behavior of worker bees in the hive. QMP helps to suppress the development of ovaries in worker bees, ensuring that they focus on other tasks such as caring for the brood and collecting food. It also helps to prevent the development of new queen bees, maintaining the hierarchy and stability of the hive. Without QMP, the hive would quickly become disorganized and unproductive.

The Function of Worker Pheromones – Brood Recognition

The brood pheromone is another important bee worker pheromone. It is produced by the brood, or the developing bees in the hive. Brood pheromone helps to stimulate the production of worker bees and also influences their behavior. It can signal to worker bees that there is a need for more food, or that the hive needs more workers.

It also signals to worker bees that the brood is still developing in the hive, which helps to limit the development of worker bee ovaries. Brood pheromone can help to regulate the development of new queen bees, ensuring that the hive remains stable and productive. Overall, the function of brood pheromone is to help maintain the health and productivity of the hive.

To maintain the social structure of the hive, the queen secretes a queen substance pheromone, which helps workers differentiate between eggs laid by the queen and those laid by other workers. The presence of this pheromone also serves to prevent other workers from laying eggs in the same cell as the queen’s egg. This ensures that the queen’s offspring receive the proper care and attention needed to thrive in the hive.

Worker Pheromones Nest-mate Recognition: The Cuticular Hydrocarbons

Social insects like honey bees can recognize and distinguish their own colony members (called nest-mates) from outsiders that belong to different colonies (called non-nestmates). This happens because of unique chemical signals on their bodies. Nest-mates have a similar chemical profile, while non-nestmates have different ones. This triggers a defensive response.

These signals are partly inherited and influenced by the environment, such as the material where the nest is made. Cuticular hydrocarbons, specifically alkenes and alkanes, are the crucial compounds that help bees recognize each other. In studies, bees learned to identify alkenes better than alkanes. Also, exposure to queen pheromones changed the chemical signals and affected the recognition process. Nest-mate recognition is vital for the colony’s defense against parasites, predators, and intruders, contributing to colony cohesion and organization.

Alarm Pheromones and Their Importance

Alarm pheromones are another type of bee worker pheromone that plays a critical role in hive communication and defense. A threatened or injured bee releases an alarm pheromone that signals to other bees that there is danger nearby. This pheromone can cause other bees to become more aggressive and defensive, helping to protect the hive from predators or other threats.

Workers display this behavior and have different roles: guards and defenders. Guard bees patrol the entrance of the hive and inspect bees that land there, while defender bees respond to danger by stinging and pursuing the source of disturbance.

Alarm pheromones are also released by bees during stinging and also from stings left in the victim. They activate other bees to attack the source of danger. Two main groups of substances have been identified. Both capable of evoking a defensive response: The sting apparatus alarm pheromones, with isopentyl acetate as the main component, and the mandibular gland alarm pheromone, with the single-component 2-heptanone. Many studies suggest that these substances have different functional values, even though both can deter intruders at the hive entrance.

Sting Apparatus

When honey bees feel threatened, they release a chemical called an alarm pheromone. This chemical is made up of over 40 different compounds, with one called isopentyl acetate (IPA) being the most important. IPA alerts other bees to danger and helps to defend the hive.

Another compound called (Z)-11-eicosenol helps to prolong the effects of IPA. Africanized honey bees have been found to have higher levels of these compounds, making them more aggressive in defending their hive. In fact, they have been known to attack more often than other honey bees.

Worker honey bees produce a substance called 2-heptanone (2HPT) in their mandibular glands. It is not as effective as IPA in alarming bees and inducing stinging, even though it can trigger guard bees near the hive. The levels of 2HPT in workers are not significantly different between aggressive and docile colonies or Africanized and European honey bees.

2HPT acts as an anesthetic for small arthropods like wax moth larva and Varroa mites, which get paralyzed after being bitten by a honey bee. Its main function is likely associated with foraging, as the levels of 2HPT in workers increase with age and are higher in foragers than guard bees. 2HPT may act as a repellent forage-marking pheromone that helps honey bee foragers discard recently visited flowers.

Regulation of Worker Reproduction: The Mandibular Gland Pheromones

Worker pheromones produced in the mandibular gland affect the reproductive development of worker bees. Some researcher believe that the mandibular gland works in unison with the Dufour’s gland to regulate worker reproduction.

In colonies with a queen, the pheromones are suppressed by the queen’s own pheromones. In queenless colonies, these pheromones are crucial in regulating which workers can lay eggs (false queens). The chemical composition of the pheromones produced by false queens is different from that produced by other workers. It has higher levels of certain chemicals that play a role in egg-laying.

The false queens produce pheromones that prevent other workers from developing ovaries. Researchers believe that the mandibular glands contain a substance that acts like QMP and inhibits behavioral development.

The mandibular gland pheromones have another function beyond regulating worker production, although it is one of their most important function. These mandibular worker pheromones have a strong-smelling chemical called 2-heptanone. This chemical is used as an alarm pheromone to signal danger to other bees. When a worker bee becomes a forager, it produces this compound to alert the rest of the colony to potential threats.

Regulation of Worker Activity: Ethyl Oleate

Workers in a beehive control their own tasks. The queen is only an auxiliary factor in driving behavioral development. Young workers who receive substances from foraging bees start foraging sooner. But substances from younger, non-foraging bees delay foraging.

Ethyl oleate is a chemical that delays foraging. It comes from foraging bees and is found on their bodies. It is made in the honey crop from fermented nectar and passed among workers who are close. If many foragers are present, the chemical stops young bees from developing into foragers. This allows young bees to focus on tasks inside the beehive. When foragers are lost or grow old, the chemical fails and young bees can become foragers. Ethyl oleate is also a component in the pheromone blend of queens and brood, which makes it a colony pheromone.

The Nasonov Gland

Worker Pheromones for Orientation and Recruitment

The Nasonov gland is exclusive to worker honeybees. It is located between the sixth and seventh tergites and releases a pheromone composed of seven volatile compounds. The purpose of this pheromone is to attract and orientate members of the colony towards the hive entrance, foraging sources, and during swarm clustering.

The Nasonov pheromone is also released during young workers’ first orientation flights and to select young larvae for queen rearing. Recent studies reveal the Nasonov pheromone’s role in queen rearing, indicating that cells with a higher amount of pheromone are more likely to develop into queen cups.

To release the pheromone, the worker bee flexes the tip of her abdomen downward to free the secretion. During this process, the bee elevates her abdomen and fans her wings to spread the pheromone. This makes it easy to spot worker bees secreting the Nasonov pheromone.

Swarm Clustering Worker Pheromone

Swarm clustering is the process by which bees stick together in a group. The Nasonov gland secretion of the worker bees helps keep the bees together. When a swarm leaves the hive, they find a temporary spot to settle. The first bees to arrive at the spot rub their Nasonov gland on the surface to call the rest of the bees to join them.

The scout bees look for a suitable spot to establish a new nest. When a spot is found, they communicate the location to other bees by the waggle dance before returning to the new location to release Nasonov pheromone, which directs the swarm to the nest entrance. The Nasonov gland contains several components, including geraniol, (E)-citral, and nerolic acid.

Foraging Worker Pheromone

The Nasonov gland helps recruit worker bees to foraging locations, however, the exact mechanism remains unclear. Foragers use this gland to signal nestmates to follow them to profitable food sources, but they don’t always expose the gland when visiting flowers.

Research shows that the gland is mainly used to attract workers to water sources, or to locate nectar sources when the reward is high or the colony needs to store more nectar. When bees find high-sugar rewards, they expose their Nasonov gland for longer periods of time.

Tarsal Glands (Footprint Worker Pheromone)

Worker bees use their tarsal glands to secrete a so-called footprint worker pheromone that marks the hive entrance and food sources. The pheromone is deposited by landing workers and enhances the effect of the Nasonov pheromone, which attracts bees from a distance.

Waggle-dancing bees release four cuticular hydrocarbons from their abdomens. When dispersed into a hive, these pheromones play an important role in worker recruitment . Another pheromone, 2-heptanone, is secreted by workers’ mandibular glands and acts as a repellent for forage marking.