Pheromones are chemical signals released by an animal that influence the behavior or physiology of other animals of the same species. Bees, like many social insects, rely heavily on these chemical messages for nearly every aspect of their lives, from development and reproduction to defense and orientation. This intricate system of chemical communication allows individual bees to coordinate their actions, ensuring the survival of their complex colony structure. These chemical cues facilitate communication between all bee castes: queens, workers, and drones, as well as between adult bees and their developing young.
Types of Bee Pheromones
Bee pheromones are categorized into two types: primer pheromones and releaser pheromones. Primer pheromones elicit long-term physiological changes, affecting development and behavior. Releaser pheromones, in contrast, trigger immediate behavioral responses. A single pheromone can sometimes exhibit both primer and releaser functions.
The queen bee produces several pheromones, with Queen Mandibular Pheromone (QMP) being the most studied. QMP is a complex blend of compounds secreted from the queen’s mandibular glands. Worker bees also produce a variety of pheromones from different glands. Examples include alarm pheromone, released from the Koschevnikov gland, and Nasanov pheromone, secreted from an abdominal gland.
Developing brood emit brood pheromones, which are blends of fatty-acid esters that vary with the brood’s age. Drones also produce pheromones.
Pheromones in Colony Organization
Queen Mandibular Pheromone (QMP) plays a role in maintaining social order within a bee colony. It suppresses the development of ovaries in worker bees, ensuring that only the queen reproduces. This pheromone also influences worker behavior by attracting a retinue of attendants who feed and groom the queen, distributing QMP throughout the hive through physical contact and food sharing. The presence of adequate QMP signals a healthy queen to the colony, which can inhibit the construction of new queen cells, thereby discouraging swarming.
Brood pheromones, emitted by developing young, are also important in colony organization. These chemical signals inform nurse bees about the presence, age, and nutritional needs of the developing young. Brood pheromones stimulate the activity of nurse bees’ hypopharyngeal glands, which produce royal jelly for larval feeding, and also encourage foragers to collect pollen for brood food. The collective signal from the brood helps to inhibit worker ovary development, reinforcing the reproductive division of labor.
Alarm pheromones are important for hive defense. When a threat is detected, guard bees release these volatile compounds, notably isopentyl acetate (IPA), which has a characteristic banana-like scent. This chemical signal alerts other bees, recruiting them to join the defensive effort and triggering aggressive behaviors such as stinging. The release of alarm pheromone primes the colony for a coordinated response, increasing their likelihood of attacking intruders.
Pheromones in Foraging and Reproduction
Nasanov pheromone is a worker-produced chemical blend that plays a role in orientation and recruitment outside the hive. Bees release this pheromone by raising their abdomens and fanning their wings, dispersing a scent that helps orient returning foragers back to the colony entrance. It is also used to mark profitable foraging sites, guiding other bees to food or water sources. During swarming, Nasanov pheromone helps keep the migrating swarm cohesive and guides bees to new nest locations.
Alarm pheromones also function in external contexts, beyond immediate hive defense. These pheromones, released when a bee perceives danger, can warn foraging bees about unsafe food sources or areas with predators. This allows foragers to make informed decisions, choosing alternative, safer foraging sites. The scent of alarm pheromone can deter other bees from visiting a dangerous location, helping to coordinate avoidance for the colony’s foraging force.
Reproduction in bees involves queen and drone pheromones. Virgin queen bees release pheromones, primarily from their mandibular glands, that attract drones during mating flights. These pheromones guide drones to specific aerial locations known as drone congregation areas (DCAs), which can contain thousands of drones from various colonies. While queen pheromones attract drones to these areas, drones themselves may also produce aggregation pheromones to help form and maintain these congregation sites.
Pheromones and Human Interaction
Understanding bee pheromones has practical applications in beekeeping, enabling more effective colony management. Beekeepers utilize synthetic queen pheromone substitutes to influence hive behavior, such as preventing swarming by mimicking the presence of a strong, healthy queen. These synthetic pheromones can also be used to attract and capture swarms, redirecting them into empty hives or swarm-catching boxes, preventing their loss. Additionally, knowledge of queen pheromones assists in uniting weak colonies or introducing new queens.
Synthetic Nasanov pheromone lures, which contain compounds like citral and geraniol, are employed by beekeepers to attract swarms to unoccupied hives, aiding in colony establishment. Beekeepers also employ smoke during hive inspections to mask the bees’ alarm pheromone, reducing defensive behavior and making handling safer. The distinctive banana-like scent of alarm pheromone, largely due to isopentyl acetate, is recognized by beekeepers as a signal of heightened defensive readiness.
Pheromone research extends to broader conservation and pest management efforts. Scientists study bee pheromones to understand bee health, social behavior, and their responses to environmental changes. This research can inform strategies for attracting beneficial insects, such as pollinators or natural enemies of agricultural pests, to specific areas. Synthetic insect pheromones are also being explored for targeted pest control, including monitoring pest populations using pheromone traps or disrupting mating cycles to reduce pest reproduction, offering environmentally sound alternatives to traditional pesticides.