Honey Bee Pheromones
Together with the honey bee dance, honey bee pheromones represent one of the most advanced ways of
communication among social insects.
The composite organization of the honey bee society, which consists of three adult castes (queen, worker, and
male) and non-self-sufficient brood, provides for many coordinated activities and developmental processes and
thus needs a similar elaborate way of communication among the colony members. Pheromones are the key
factor in generating and maintaining this complexity, assuring a broad plasticity of functions that allow the
colony to deal with unforeseen events or changing environmental conditions.
The honey bee society cannot function without effective communication. Most honey bee communication
occurs by smell and taste. The intricate system of chemical messengers are termed hormones and
pheromones. Pheromones are chemical substances secreted by an animal’s exocrine glands that elicit a
behavioral or physiological response by another animal of the same species. In honey bees the targets of
pheromonal messages are usually members of the same colony, but there are some exceptions in which the
target can be a member of another colony
Pheromones are involved in almost every aspect of the honey bee colony life: development and reproduction
(including queen mating and swarming), foraging, defense, orientation, and in general the whole integration of
colony activities, from foundation to decline. Pheromones allow communication among all the honey bee castes:
queen–workers, workers–workers, queen–drones, and between adult bees and brood.
In honey bees, as in other animals, there are two types of pheromones: primer pheromones and
releaser pheromones. Primer pheromones act at a physiological level, triggering complex and
long-term responses in the receiver and generating both developmental and behavioral changes. Releaser
pheromones have a weaker effect, generating a simple and transitory response that influences the receiver
only at the behavioral level.
In the following paragraphs the main honey bee pheromones are described, based on the honey bee caste to
which they belong and the glands responsible for their production. In the first part of the chapter the effect (or
the effects) exerted by each pheromone on the receivers and on the bee colony will be illustrated, while the
neurophysiologic and molecular mechanisms of the response to the chemicals will be discussed later.
Releaser and primer effects of the queen signal, which regulates colony functions and development.
Stimulating effects are indicated as “+” and inhibiting effects as “–.”
The honey bee queen represents the main regulating factor of the colony functions. This regulation is largely
achieved by means of pheromones, which are produced by different glands and emitted as a complex
chemical blend, known as the “queen signal.”
The queen signal acts principally as a primer pheromone, inducing several physiological and behavioral
modifications in the worker bees of the colony that result in maintenance of colony homeostasis through
establishment of social hierarchy and preservation of the queen’s reproductive supremacy. More specifically,
the effects of the queen signal are maintenance of worker cohesion, suppression of queen rearing, inhibition of
worker reproduction, and stimulation of worker activities: cleaning, building, guarding, foraging, and brood
It is known that when the queen is old or sick (low pheromonal signal) or it dies (no
pheromonal signal), workers are driven to rear new queens from young brood within 12–24 hours; the removal
of the queen in absence of young brood soon leads to the decline of the colony: the workers stop performing
their activities and start to lay unfertilized eggs that develop into male adults (drones); the colony becomes
disorganized, unfit, dirty, susceptible to diseases and prey of predators; it rapidly depopulates and goes toward
a certain death.
In addition to its primer effect, the queen signal exerts an attractive releaser effect: it calls workers around the
queen in a retinue group, which is stimulated to feed and groom her; in young premating queens it acts as
attractant for drones during the mating flights; during swarming it keeps the swarm together.
When the queen is stationary on the comb she is surrounded by a circle of workers known as “court” or
“retinue” that face toward her and feed, palpate, and lick her. Usually the retinue is composed of eight or 10
workers. QMP secretion, which represents the main constituent of the queen signal and its components are
accountable for the formation of the retinue.
The attention paid by retinue workers increases when the virgin
queen becomes mated and lays eggs, and then decreases as she grows old. The degree of attractiveness of
the queen is null at 0–1 day old, medium from 2 to 4 days old, and high from 5 days to 18 months old. Mating is
a crucial factor for the development of the chemical signal of the queen and its attractive effect on workers.
QMP also suppresses both queen supersedure and swarming by its dispersal throughout the colony
Alarm pheromones are widely distributed in social insects. Honey bees have two different alarm pheromones,
one from each end of the body. The mandibular glands of workers produce 2-heptanone and one of the glands
of the sting produces isopentyl acetate. The sting pheromone is better known and is the major alarm chemical.
The chemical released when a bee stings, isopentyl acetate, is absent in newly emerged workers whereas bees
15+ days of age have one to five mg. There are several other components of the gland such as acetates and
alcohols and they may work in conjunction with isopentyl acetate. Actual stinging or defensive behavior is
correlated with isopentyl acetate. Defensive behaviors range from alerting to flying (buzzing); if disturbance
persists stinging is the last response. Bees display a faster reaction time and more concentrated defensiveness
upon perception of the alarm pheromone. Generally, bees will respond to alarm pheromone only at or near the
colony, not in the field. Smoke in some way masks the pheromone.
The second alarm pheromone, 2-heptanone, is produced in worker mandibular glands. It, like isopentyl acetate,
is absent in newly emerged workers but is present by foraging age. Bees respond to 2-heptanone at the nest
entrance similarly as they do to isopentyl acetate, but it is not nearly as effective in producing a response,
requiring 20 to 70 times as much compound before bees respond. Queen and drones lack 2-heptanone.
Workers have a scent (Nasonov) gland at the tip of the abdomen. The gland emits a mixture of seven terpenoids
which serve primarily in orientation. To release the chemical mixture the workers stand high on the hind legs
with the abdomen elevated and tilt the last abdominal segment downward while fanning the wings. Bees use the
scent to help sisters locate home, food, and water sources. It acts with queen substance in a pheromone concert
to keep the bees of the swarm together.
Honey bees have a trail pheromone that includes chemicals released from their lowest leg segment, which serve
as orientation pheromones. Brood, drones, and beeswax comb emit pheromones . the former helps to maintain
queen dominance as it is responsible for retarding worker reproductive organ development. The mixture of
pheromones plus the distinctive queen signature pheromone, mix with food odors to give each bee colony a
distinctive hive odor. Hive odor is not a specific pheromone but does impart a chemical identity to each social