Pheromones – Communication without Sound
By: Ed Erwin
Beekeepers know that pheromones are the key to controlling all activities of the bees in the beehive. The word pheromone comes from the ancient Greek word phero, which means "to bear" and hormone. Pheromones of the honey bee are a variety of chemical substance mixtures in varying percentages produced by the individual bee. The array of chemical compounds are released by 15 different glands located in different parts of the body. Each chemical pheromone is different and when excreted or secreted, they trigger responses from other bees.
These discharges are either a releaser pheromone, which have a short-term effect with almost immediate behavioral response from the receiving bee, or a primer pheromone with long term effects which change the physiology and behavior of the recipient.
Pheromones are initially produced in a liquid form and transmitted to the other bees in the liquid form or as a vapor. Depending on the pheromone, they are either produced as volatile or non-volatile. The chemical messages are received principally on the bee’s 170 odor receptors (chemoreceptors) located on the antenna and other body parts, such as the feet.
The honey bee pheromone communication is one of the most complex and effective among insects. The worker honey bee is known to transmit over eight, which include: Alarm, Brood recognition, Drone, Dufour's gland, Egg marking, Footprint, Forager, Nasonov, and a few others. The queen honey bee produces a few of her own pheromones which include the Queen mandibular and Queen retinue.
Pheromones are the key factor in the way the queen, workers and drones communicate and coordinate the complex activities within the hive. They are important to all types of activities including foraging for resources, wax foundation construction, defending the hive, new queen development and swarming. Some of the key pheromones:
When a honey bee stings another animal, it releases alarm pheromones which signal other bees to become defensive and attack the sting location. Two main alarm pheromones have been identified in honey bee workers.
The Koschevnikov gland is located near the sting shaft and releases an alarm pheromone when a bee stings. This pheromone is made up of over forty highly volatile chemical compounds. When released, this pheromone attracts other bees to the sting location and all the bees begin defending the colony. The alarm pheromone smells like bananas.
The other alarm pheromone is released by the mandibular glands located on the head and can be a highly volatile substance. When honey bees are in their foraging stage (older worker honey bees) the mandibular glands produce an alarm pheromone. When the worker bees are younger and performing nursing tasks, they produce a nutritional secretion called royal jelly from the mandibular gland, which along with pollen and honey is fed to worker bee larvae. If a larvae is fed only royal jelly the larvae will develop into a queen.
Smoke can mask the bees’ alarm pheromone.
Brood Recognition Pheromone
When the bee colony is raising larvae and pupae, they emit a brood recognition pheromone from their larval salivary glands. This pheromone acts both as a primer and releaser. Brood cannot survive without the constant care and feeding of nurse bees. This pheromone also helps nurse bees differentiate between female worker bee and drone larvae and pupae development. When it is time for the developing pupae to develop a cocoon, the silk for the cocoon is produced from the salivary glands. This pheromone also hinders worker bee’s ovarian development and prevents worker bees from bearing offspring.
In the spring the queen begins the production of drone (male) bees from unfertilized eggs whose purpose is to mate with virgin queens from other hives. Drone bees produce and emit a pheromone from their mandibular gland to attract other drones to the drone congregation area (DCA) to mate with virgin queens. It is also believed the virgin queens follow this pheromone scent when locating the drone congregation area. The drones are generally concentrated in areas between 100 to 770 feet in diameter and 50 to 130 feet above the ground.
Egg Marking and Dufour’s pheromone
The queen produces the egg marking pheromone that has several chemical compounds unique to the queen. Because both the queen and workers can lay eggs, these compounds allow workers to recognize eggs not deposited by the queen. Subsequently they will destroy the eggs without the marking pheromone. It is believed that the egg marking pheromone is associated with the Dufour’s gland. The Dufour’s gland opens into the dorsal vaginal wall and is named after the French naturalist Léon Marie Dufour. This pheromone is composed of 24 different alkaline chemicals and lets the workers know when the colony is “queenright” or if the colony is queenless.
Also known as the footprint pheromone and trail pheromone, the tarsal pheromone is an oily, colorless, chemical secretion, with a low volatility. It is deposited by queens, workers, and drones as they walk on surfaces. The pheromone glands are located on the 5th tarsomere of all six legs. Queens secrete 12 compounds, workers 11 and drones 1. This attractive odor affects the behavior of other workers, particularly in locating the hive entrance, nectar, and other food sources. When bees are standing at the entrance of the hive with their abdomens raised and fanning their wings, they are helping returning foraging bees in orientation and location of the hive. As the queen walks on the comb, she deposits her tarsal pheromone which inhibits queen cell construction and therefore less motivation for the bees to swarm.
The queen honey bee controls the main colony functions by means of a complex chemical blend of pheromones produced by different glands known as “queen signal”. This signal is a primer pheromone causing behavioral modifications in the worker bees and establishes social hierarchy and preserves the queen’s dominance in producing offspring for the hive. The queen signal is consistent and if it decreases, or is absent, the worker bees will begin feeding larvae royal jelly within 24 hours in order to produce a new queen for the hive.
Amazingly, the communication within the hive is conducted by the emittance and receipt of pheromones – all done in the dark.