5.1. PHEROMONES OF THE HONEY BEE COLONY

Together with the honey bee dance, honey bee pheromones represent one of the most advanced ways of communication among social insects.

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 (Free 1987).

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.

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 (Trhlin and Rajchard 2011; Winston 1987).

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.

Most of the pheromones known in insects are of the releaser type; they are classified into several categories based on their function (e.g., sexual, aggregation, dispersal, alarm, recruitment, trail, territorial, recognition) (Ali and Morgan 1990). Primer pheromones are especially developed in social insects, where they represent the major driving force in the evolution of social harmony and in maintaining colony homeostasis (Le Conte and Hefetz 2008). Among honey bee pheromones, the queen signal and the brood pheromones (described in detail below) are principally primer pheromones (having also some releaser functions), while most worker pheromones are to be considered releaser pheromones.

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 in the second part of the chapter.

5.1.1. Queen Pheromones

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 feeding (Figure 5.1). 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.

FIGURE 5.1

Releaser and primer effects of the queen signal, which regulates colony functions and development. Stimulating effects are indicated as “+” and inhibiting effects as “–.” (Adapted from Winston, M.L. (1987) The Biology (more...)

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.

5.1.1.1. Main Component of the Queen Signal: The Queen Mandibular Pheromone

The queen mandibular pheromone (QMP) is by far the most studied and well-known chemical signal in the honey bee society. Its first identification dates back to 1960, when (E)-9-oxodec-2-enoic-acid, more simply known as 9-ODA, was detected as the substance secreted by the queen mandibular glands (Barbier and Lederer 1960; Callow and Johnston 1960). The secreting organs are a pair of saclike glands located inside the head above the base of the mandible (Figure 5.2). The glands open through a short duct at the base of the mandible and their secretion runs along a deeper channel surrounded by hairs (Billen 1994).

FIGURE 5.2

Exocrine glands of the honey bee queen. The pheromone-producing glands that concur to the formation of the queen signal are highlighted in bold. (Adapted from Goodman, L. (2003) Form and Function in the Honey Bee. Cardiff, UK: IBRA.)

In 1988, Slessor et al. discovered four other compounds secreted by the mandibular glands that act synergistically with 9-ODA: the two enantiomers of 9-hydroxydec-2-enoic acid (9-HDA), methyl p-hydroxybenzoate (HOB) and 4-hydroxy-3-methoxy-phenylethanol (homovanillyl alcohol [HVA]). The five components together were more active than any of the single substances, alone or in combination, in forming the retinue of worker bees (see Section 5.1.1.1.1). It was concluded that these five chemicals together form the base of QMP secretion, which represents the main constituent of the queen signal.

Several authors analyzed the evolution of QMP components during queen aging, from emergence until the full dominant status. Generally, the amount of volatiles was found to increase with age, but the findings concerning the different compounds and their relative amounts were inconsistent among authors, as illustrated by the studies described below.

Engels et al. (1997) identified three different ontogenetic patterns of QMP in queens: (1) virgin premating queens presented a weak signal, with oleic acid (OLA) as the main component, (2) mating queens intensified the signal, mainly consisting of 9-ODA along with OLA and small amounts of 9-HDA, and (3) postmating dominant queens exhibited a strong signal with high concentrations of 9-ODA combined with medium proportions of 9-HDA, less OLA, and small amounts of oxygenated aromates. The authors suggested that these oxygenated aromates, especially HOB and the late appearing HVA, could be the typical signal of old egg-laying and dominant queens.

Plettner et al. (1997) compared the quantities of the QMP components between 6-day-old virgins and 1-year-old mated egg-laying queens of several species; they found that mated Apis mellifera queens had significantly higher levels of 9-ODA, 9-HDA, HOB, and HVA, while an opposite trend was found for 10-HDA and 10-HDAA, which are typical components of worker mandibular glands (see Section 5.1.2.1) and are produced in higher amounts by virgin queens.

Slessor et al. (1990), who compared virgin with mated queens of different ages, found slightly different results, with levels of 9-ODA almost constant in the different groups, 9-HDA levels higher in mated than in virgin queens, and HOB and HVA levels higher in the oldest mated queens compared to the virgin and the young mated ones. In all cases pheromone levels were highest in mature, mated, laying queens.

On the contrary, Rhodes et al. (2007), comparing 7-day-old virgin and mated queens, found that the former had higher levels of 9-HDA, 9-ODA, and 10-HDA than the latter. In a similar comparison, Richards et al. (2007) found that the quantities of 9-ODA, 9-HDA, and HVA were all significantly lower in mated queens compared to virgins, although the extract of mated queens’ mandibular glands was more attractive towards workers than the one of virgin queens.

Finally, Strauss et al. (2008), analyzing the mandibular gland compounds of virgin, drone-laying, and mated queens, found similar amounts of 9-ODA in the three groups and increasing amounts of all the other components (9-HDA, 10-HDA, 10-HDAA, and HVA) except HOB, from virgin to mated queens. The constant level of 9-ODA, which corresponds to a higher relative proportion in the virgin queen, suggests that 9-ODA plays a greater role in drone attraction of virgin queens than of retinue attraction in mated queens; on the contrary, 9-HDA, 10-HDA, 10-HDAA, and HVA are positively correlated with the reproductive potential and the ovarian activation of the queen (Strauss et al. 2008).

These contradictory results suggest that the role of single QMP components in queen signal is not fully understood and that there could be additional unknown compounds in mated queens’ mandibular glands that synergize with 9-ODA and 9-HDA in the attractive function.

5.1.1.1.1. Attracting the Workers: The Retinue

The first functions of QMP to be discovered were due to its attractant properties toward the workers: the formation of the queen retinue and the constitution and maintenance of the swarm cluster (Kaminsky et al. 1990; Winston et al. 1989).

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. Several studies demonstrated that QMP and its components are accountable for the formation of the retinue (Free 1987), and this is supported by the fact that worker attraction towards the queen could be related to the modifications in the QMP pattern. 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 (De Hazan et al. 1989). Richards et al. (2007) tested the mandibular gland extracts of virgin and inseminated queens on worker retinue responses and found that gland extracts of the inseminated queens were more attractive than those of the virgin queens, and those of queens inseminated with more than one drone were more attractive than those of queens inseminated with a single drone. This suggests that mating is a crucial factor for the development of the chemical signal of the queen and its attractive effect on workers.

In 2003, Keeling et al. identified four additional compounds produced by the queen that act synergistically with QMP in attracting workers to form the retinue group: coniferyl alcohol (CA), methyl oleate (MO), hexadecane-1-ol (PA), and linoleic acid (LA); the first is secreted by the mandibular glands, while the others are produced in different parts of the queen’s body. These substances were inactive alone, but in combination with QMP they were found to greatly increase activity of the queen’s retinue. Furthermore, in a recent study, Maisonnasse et al. (2010a) showed that queens artificially deprived of mandibular glands can still attract workers in the retinue, suggesting that QMP was not the only pheromone able to attract workers and that in its absence other substances can take its role.

5.1.1.1.2. Attracting the Workers: The Swarm

Swarming is the way in which the colony reproduces itself; workers rear new queens and the first emerging one will kill the others, and after mating will become the new colony regnant, while the old queen drives the swarm toward a new nest. The presence of the queen is essential to keep the swarming bee cluster together: if the queen dies or is unable to fly, the swarm soon returns to the parental hive. The queen’s attractiveness towards the swarm cluster is triggered by means of pheromonal signals, mainly the QMP. In 1989, Winston et al. compared the effects of the queen, the mandibular gland extracts, and the five-component-blend on the swarming and thus demonstrated that the component blend and the gland extract showed comparable effects, while the queen alone always had the strongest attractiveness. This suggested, as with induction of retinue behavior, that other extra mandibular components could be involved in formation of the swarm cluster.

5.1.1.1.3. Attracting the Drones: QMP as a Sexual Pheromone

Soon after its discovery it became clear that the QMP is used by virgin queens to attract drones during mating flights (Gary 1962); more specifically, by using queen dummies 9-ODA was clearly shown to attract drones (Gary and Marston 1971).

In further experiments, different combinations of 9-HDA, 10-HDA, and HOB were also found to increase the number of drones making contact with the queen dummy; 9-HDA and 10-HDA in particular seemed to be responsible for the increased mating contacts, although they were active only at short range, contrary to 9-ODA, which also acted at a higher distance (Brockmann et al. 2006; Loper et al. 1996). Comparing QMP components in virgin and mated queens it emerges that 10-HDA is more represented in the former while it is highly reduced in quantity in the latter (Plettner et al. 1997). The fact that 10-HDA is produced in large amounts by virgin queens suggests its role as a sex pheromone in mating behavior.

An increase in the frequency of mating behavior was observed also when tergal gland extracts were added to 9-ODA (Renner and Vierling 1977). This suggests that several glandular sources could cooperate in increasing the effectiveness of the pheromonal stimulus, leading to a stronger response and a more complete performance of the mating behavior sequence.

Thus, the relative contribution of different components of QMP and other glands on the sex pheromone blend is not yet completely clear.

5.1.1.1.4. Unique Queen: Suppression of Queen Rearing and Swarming

Many insect societies are monogynous, which means that a single queen is present in each colony. In small and primitive social species the maintenance of queen dominance is achieved by fight and physical competition among females; in contrast, in large monogynous colonies a physical dominance is not possible and a more efficient system has evolved for the maintenance of queen dominance that is based on pheromonal signals.

As previously stated, the removal of the queen from a colony of A. mellifera results in worker bees building special cells (queen cups) for rearing new queens (Winston 1992), but the precise way in which this happens is still in part unclear.

The rearing of new queens in a colony has two main scopes: reproduction of the colony through swarming and replacement of the queen when it is old or weak (this phenomenon is known as supersedure) or if it dies for some apicultural or pathological reason. QMP suppresses both queen supersedure and swarming by its dispersal throughout the colony (Winston et al. 1989). Several studies were addressed to elucidate the mechanisms of dispersal of QMP inside the colony and its transfer among workers. In 1991 Naumann et al. identified the group of retinue workers as the first actors in transferring queen pheromones toward the other workers and self-grooming as the means by which the pheromone is translocated from the mouthparts and the head to the abdomen of the workers (Naumann 1991). The distribution of QMP seems to be influenced by the size of the colony, since in populous colonies workers at the periphery gain a lower amount of pheromone than in unpopulous nests (Naumann et al. 1993). This explains why populous colonies swarm: the pheromone signal “the queen is present” tends to decline when the colony grows because pheromone dispersal is reduced and workers thus perceive a lower amount of pheromone, and the result is colony reproduction through queen rearing and colony swarming. When the queen dies or is removed, the pheromone signal disappears completely and workers are stimulated to rear new queens.

The role of QMP in the suppression of initiating queen rearing was confirmed by several studies that showed that administration of synthetic QMP to queenless colonies (i.e. colonies without a queen) suppresses the production of queen cups (Pettis et al. 1995) if the administration occurs within 24 hours from queen loss; in fact if synthetic QMP is applied 4 days after queen loss no effect is observed, indicating that QMP inhibits the initiation of queen-rearing but not the maintenance of established cells (Melathopolous et al. 1996).

5.1.1.1.5. Unique Mother: Suppression of Worker Reproduction

One of the main features of the honey bee society is the presence of two female castes (queen and workers) among which the queen is the only reproductive one. Workers are anatomically equipped with ovaries (which contain a lower number of ovarioles compared to queens) but development of the oocytes is inhibited by presence of the queen. If the queen is absent (and the colony and its workers are termed “queenless” as opposite to “queenright”), the workers’ ovaries can become active and workers can thus lay eggs (Butler and Fairey 1963; de Groot and Voogd 1954; Jay 1968; Velthuis et al. 1990). However, they can only produce haploid unfertilized eggs that give rise to male offspring, since they have not mated and do not have a spermatheca. A further confirmation of the inhibiting role of queen presence on ovarian development is provided by the findings of Malka et al. (2007), who showed that queenless egg-laying workers reintroduced into queenright colonies showed a clear regression in ovary development, whereas this did not happen if they were reintroduced into queenless colonies. This indicates that ovarian regression was not due to the change of colony but to the presence of a queen and her signals.

The specific role of QMP in the suppression of worker reproduction has been hotly debated for a long time. The first hypothesized mechanism for inhibition of ovarian development is that QMP acts by lowering the titer of juvenile hormone (JH) in workers and that this low titer corresponds to a low level of ovarian development and vice versa, as demonstrated in other social insects (Hartfelder 2000; Robinson and Vargo 1997). However, different studies exploring this hypothesis in honey bees gave contrasting results. First, the correlation between JH level and ovarian development in adult hemolymph is not confirmed (Robinson et al. 1991, 1992a). Furthermore, the administration of synthetic QMP alone was able to lower the titer of JH but not able to suppress the development of worker ovaries and egg-laying (Kaatz et al. 1992; Willis et al. 1990).

Disregarding the involvement of JH, the work of Hoover et al. (2003) clearly demonstrated that synthetic QMP alone is active in suppressing ovary development in workers and that its effect is comparable to that of the whole queen extract, thus excluding the involvement of other queen-produced substances. The components of queen pheromone identified by Keeling et al. in 2003 failed in suppressing ovary development and did not improve the efficacy of QMP when applied in combination, suggesting that they play a role in retinue behavior but not in workers’ ovary development.

More recently Katzav-Gozansky et al. (2006) observed that QMP alone or in combination with the secretion of Dufour’s gland inhibited ovarian development, with the combination of the two pheromones being the most effective treatment, but always less effective than the presence of a live queen, redrawing attention to the hypothesis of a queen multisignal in the regulation of worker reproduction.

It thus appears that the regulation of worker ovary development is probably an even more complex process, involving both queen and brood signals, since two components of the brood pheromone, ethyl palmitate and methyl linoleate, also play a role in suppressing worker ovary development (Mohammedi et al. 1998). Possibly the queen regulation alone becomes essential when no brood is present in the colony, such as during interruption of egg-laying due to environmental conditions (in winter or in summer in southern climates).

5.1.1.1.6. Regulation of Worker Activity and Behavioral Development

In highly advanced insect societies there is a typical organization of the infertile caste that determines an age-dependent division of labor, called temporal polyethism, in which workers progress from tasks performed inside the nest (cleaning, building, feeding) during the first 2–3 weeks of life, to those performed outside it (ventilating, guarding, foraging) in the last 1–3 weeks (Robinson 1992). This behavioral progress seems to be driven by endogenous factors, as it is linked to the amount of JH in worker hemolymph, which increases with the increasing age (Huang et al. 1991). Nevertheless, the task allocation of each worker cohort (group of workers of the same age) can be modulated by environmental factors that modify the requirements of the colony: a loss of older workers (e.g., forager bees that die in the field) can result in faster development of young bees into foragers, while a lack of young bees (e.g., for a natural or artificial interruption of queen egg-laying) can result in a slower behavioral development or a reverse from foragers to nest bees (Huang and Robinson 1992; Robinson et al. 1992b).

This plasticity in worker task allocation is at least partly regulated by QMP, via suppression of JH titers in workers; in colonies supplemented with synthetic QMP workers showed a reduced level of JH associated with a delay in behavioral development and a reduction of foraging activity (Pankiw et al. 1998). This mechanism could have an adaptive significance, such that the presence of the queen prevents workers from developing too rapidly into foragers, thus preserving a stock of young workers in case of loss of foragers due to adverse environmental causes (Winston and Slessor 1998).

Nevertheless, it is likely that the regulation of worker behavioral development is primarily modulated by the workers themselves, since the artificial alteration of worker demography is effective in changing age polyethism development even with constant presence of the queen (Huang and Robinson 1996; Robinson and Huang 1998). It is more likely that QMP acts as an auxiliary inhibitor on the workers’ division of labor rather than as a primary motor; this modulating role can be exerted by the queen’s strict contact with nurse bees in the nest, which determines an augmented inhibiting effect on the behavioral development of this group of bees.

The influence of QMP has been demonstrated on the activity of single workers, such as comb building. In the presence either of a mated queen or of artificial QMP, workers are stimulated to produce a higher amount of wax for the comb than in the presence of a virgin queen or in queen absence. In the latter case, furthermore, workers tend to produce male cells, demonstrating that the presence of the mated queen or QMP inhibits the production of male brood (Ledoux et al. 2001). A small difference was observed in the effects produced by presence of a mated queen and application of synthetic QMP, suggesting that QMP is not the only queen pheromone that influences comb building. Among the QMP components, HVA and HOB seem to play a major role in comb building, confirmed by the fact that virgin queens produce very low amounts of this component in their mandibular glands and do not stimulate comb building (Ledoux et al. 2001).

QMP also has an effect on stimulating foraging behavior and brood rearing. Higo et al. (1992) observed that in newly established spring colonies treated with synthetic QMP the number of foragers and the weight of pollen loads increased. Brood rearing also increased, but not significantly. In contrast, no effects were observed on large established colonies at their summer population peak, suggesting that QMP affects foraging, but its effect is influenced by colony conditions and environmental factors.

The defensive behavior is one of the best known features of a honey bee colony and consists in recognition of predators, alerting nestmates, and enacting antipredator behavior (from threat postures to buzzing and finally stinging). The defensive behavior will be illustrated more in detail in the description of the alarm pheromones but we mention it here because the presence of the queen seems to be important for its regulation, since it was observed that queenless colonies exhibit an increased aggressive behavior compared to queenright ones, and that synthetic QMP decreases stinging response in caged honey bees (Kolmes and Njehu 1990). The effect of QMP on the colony’s defensive behavior was recently confirmed by Gervan et al. (2005), who showed that the administration of synthetic QMP significantly reduces defensive behavior in both queenright and queenless colonies, with a decrease in the number of bees that respond to a simulated danger and a slight reduction of sting reaction, and by Vergoz et al. (2007) who found that QMP blocks aversive learning in young workers.

5.1.1.2. Beyond the QMP: Other Queen Pheromones

Mandibular glands are not the only source of chemicals with a role in social cohesion and colony homeostasis. For many years researchers presumed that QMP alone could account for the regulation of all colony functions. Later on, other pheromone sources were discovered that were in agreement with a multicomponent nature of the queen signal. Already in 1970, Velthuis already found that queens from which mandibular glands were removed were still able to exert some regulatory functions on workers (retinue behavior, inhibition of queen cup construction, suppression of worker ovary development). But it was not until 2010 that Maisonnasse et al. confirmed these results, showing that demandibulated queens retain their full regulatory role on the above mentioned functions (Maisonnasse et al. 2010a). The authors discovered that the levels of QMP components were similar in demandibulated and control queens, with the exception of 9-ODA, which was not detected in the former. This suggests that only 9-ODA is uniquely produced and stored in the mandibular glands, while the other substances (HOB and 9-HDA) appear to have another source of production in the queen’s body. 9-ODA has always been considered the main substance acting on retinue behavior but this is conserved in demandibulated queens, suggesting that other queen substances have the potential to substitute 9-ODA in evoking this behavior.

Alternative sources of the queen signal have been identified in the tergal, tarsal, Dufour’s, and Koschevnikov glands (Figure 5.2). Their secretions can either cooperate with QMP in the composition of the queen signal or be responsible for a single or few specific regulatory functions.

5.1.1.2.1. QMP Assistants: Tergal Gland Pheromones

Tergal glands, also known as Renner and Bumann glands, are located underneath the abdominal tergites and their ducts open through the cuticle in the tergites’ posterior edge region (Renner and Baumann 1964). In queens, numerous big gland cells occur, mainly in tergites III to V, whereas workers only have very few and considerably reduced cells (Billen et al. 1986).

The role of tergal glands as the source of pheromones with a supporting function to QMP has been postulated by several authors, in particular in African honey bee races (Velthuis 1970, 1985). De Hazan et al. (1989) found that the exocrine secretions of both mandibular and tergal glands in A. mellifera contribute to the attraction of worker bees, although the first to a greater extent than the second. On the contrary Moritz and Crewe (1991) in A. m. capensis (a honey bee race that occurs in the Cape province of South Africa) found that tergal and mandibular secretions contribute equally to the total pheromone blend. According to Wossler and Crewe (1999a) the major compound of the tergal gland secretion in workers and virgin and mated queens (studied in A. m. capensis and A. m. scutellata) is (Z)-9-octadecenoic acid, while Espelie et al. (1990) had found that the major components in virgin honey bee queens of 3–10 days old were decyl decanoate and longer chain-length esters of decanoic acid.

Just like the QMP, the tergal gland secretion shows both primer and releaser properties. In A. m. scutellata Wossler and Crewe (1999b) showed that queen mandibular gland secretions were more effective than tergal gland secretions in formation of the retinue, but the two secretions together were even more efficient, indicating a releaser function of queen tergal gland pheromone in evoking the worker retinue behavior. On the other hand, the tergal gland extracts of virgin queens of both A. m. capensis and A. m. scutellata showed a significant effect in the inhibition of ovarian development in their own workers, indicating that the secretions from the tergal glands can also operate as primer pheromone (Wossler and Crewe 1999c). Furthermore, in A. m. capensis the secretions of the queen tergal glands are used by workers as kin recognition signals (Moritz and Crewe 1988).

In A. m. ligustica the glandular production was suggested to be a specific signal of the mated queen, since the production of tergal gland alkenes is stimulated by natural mating and not by instrumental insemination (Smith et al. 1993).

5.1.1.2.2. Footprint Pheromone: Tarsal Gland Pheromones

The tarsal glands (Arnhart 1923) are present in queens, workers, and drones and consist of a unicellular layer of glandular epithelium located in the sixth tarsomere of each of the six legs. The secretory products accumulate in a saclike reservoir inside the tarsus, which communicates with the exterior at the level of an articular slit located between the fifth tarsomere and the arolium (Lensky et al. 1985); these secretions are oily, colorless substances that are extruded through openings when the bee is walking, from which comes the name footprint pheromones. It is assumed that the secrete of tarsal glands can serve different purposes in the three bee castes, since some differences in the chemical composition in queens, workers, and males were observed (Lensky et al. 1984).

Lensky and Slabezki (1981) observed that tarsal gland secretions deposited by the mated queen on the comb inhibit queen cup construction by workers; this hypothesis is supported by the observation that in overcrowded colonies the queens’ movements are restricted to the central parts of the comb, thus they are almost absent from the bottom edges of the combs where queen cups are usually built. A blend of the mandibular and tarsal pheromones is able to inhibit this behavior, giving an example of coregulation by these two pheromones.

5.1.1.2.3. Fertility Signal: Dufour’s Gland Pheromones

Dufour’s gland, first described in honey bees by Dufour in 1841, is a tubular gland associated with the sting apparatus together with the venom, sting sheath, and Koschevnikov glands (Figure 5.3). It opens into the dorsal vaginal wall (Billen 1987) close to the setosa membrane, a hairy region of cuticle that surrounds the entire sting bulb and acts as a platform for pheromone release (Lensky et al. 1995; Martin et al. 2005). The peculiar position of Dufour’s gland suggested different possible functions for its secretions, linked mainly to reproduction and egg-laying in queens (production of an egg coating or egg marking) and to defense in workers (production of a sting lubricant, neutralization of the remains of the acid secretion in the sting).

FIGURE 5.3

Pheromone-producing glands and organs and their main products in the honey bee worker, and their effect in the different worker activities. Stimulating effects are indicated as “+” and inhibiting effects as “–.” (more...)

One of the main explored theories is the role of Dufour’s gland secretion as a caste-specific egg-marking pheromone applied by the queen during deposition, which could allow the workers to distinguish between queen-laid or worker-laid eggs (Ratnieks 1988; Ratnieks and Visscher 1989). Egg recognition is fundamental to the mechanism of worker policing, by which workers kill eggs laid by fellow workers but leave queen-laid eggs (a small percentage of workers lays eggs even in presence of the queen) (Ratnieks 1993). The existence of an egg-discriminatory pheromone was postulated by Ratnieks in 1988, and in subsequent experiments he found evidence that the Dufour’s gland secretion could be a source for this pheromone (Ratnieks 1995). However, in later studies it was found that neither the glandular secretion nor its ester or hydrocarbon constituents were able to protect worker-born eggs from policing; in fact, treated worker eggs were removed significantly faster than queen eggs, and at the same rate as nontreated worker eggs (Katzav-Gozansky et al. 2001; Martin et al. 2002). These results lead to the rejection of the hypothesis that the Dufour’s gland secretion serves as an egg-marking pheromone.

An alternative hypothesis for the role of the Dufour’s gland secretions is a fertility signal. This is supported by the caste-specific composition of its secretions: in workers they consist of a series of long-chain hydrocarbons, whereas in queens there is in addition a series of waxlike esters; these queen-specific esters are tightly correlated with ovarian development (Katzav-Gozansky et al. 1997, 2000). Queenless workers, which are likely to become egg layers, produce a queenlike secretion with an augmented level of the ester fraction that is correlated with worker ovarian development (Dor et al. 2005; Katzav-Gozansky et al. 2003). In workers of A. m. capensis, which are known to be social parasites, this mimicry of queen secretion profile by egg-laying workers is even more developed (Sole et al. 2002).

The Dufour’s gland secretion seems to act similarly to the QMP in attracting workers, which form a retinue around the scented source. Bioassays reveal that the active constituents are the queen-specific esters rather than the hydrocarbons. The queenlike glandular secretions of egg-laying workers are also attractive to nestmates, although to a lesser degree than those of the queen, while the secretions of non-egg-laying workers are totally inactive (Katzav-Gozansky et al. 2002, 2003). Moreover, workers were more attracted to Dufour’s gland extract from inseminated queens compared with virgins and to multidrone inseminated queens compared with single-drone inseminated ones, confirming the relation between Dufour’s gland secretions and reproductive potential (Richard et al. 2011).

Finally, as previously stated, the combination of QMP and Dufour’s gland secretions was effective in inhibiting ovarian development in workers, although neither was as effective as the presence of the queen (Katzav-Gozansky et al. 2006).

All this evidence suggests that Dufour’s gland secretion is a component of the queen signal, both in its releaser effects, as revealed by the stimulation of retinue behavior, and in its primer effects, correlated with reproductive dominance and fertility, through the inhibition of ovarian development. The specific roles of the Dufour’s gland secretion and QMP in regulating the physiological development and the behavior of workers still have to be elucidated.

5.1.1.2.4. Aging of the Queen Signal: Koschevnikov Gland Pheromones

The Koschevnikov gland is located near the sting shaft (Figure 5.3) and is composed of glandular units, each consisting of a secretory cell and a duct cell connected to the epidermis. Secretions are emitted onto the entire surface of the setosa membrane (Grandperrin and Cassier 1983), where they are released together with the alarm pheromones originating from the glandular part of the sting sheaths.

In honey bee workers the gland produces an alarm pheromone that is released when a bee stings (see Section 5.1.2.5.1, worker alarm pheromones). In queens the gland seems to play a different role, concurring to the already described queen signal. This is supported also by a caste-specific chemical composition of its extracts: 28 compounds including acids, alcohols, alkanes, and alkenes were found in queen Koschevnikov glands, which are not present in worker alarm pheromone (Lensky et al. 1991). Other studies highlighted that topical treatment of worker bees with extracts of queen Koschevnikov glands induced aggressive reaction by other workers, the so-called “balling behavior,” which is usually generated by a high-concentration QMP treatment (Pettis et al. 1998).

The gland starts degenerating after the queen is 1 year of age and this contributes to the loss of signal in old queens (Grandperrin and Cassier 1983).

5.1.4. Brood Pheromones

Larvae of A. mellifera produce a complex mixture of compounds that act both as primer and releaser pheromones, regulating worker development and colony growth. This brood pheromone (BP) is a blend of 10 fatty-acid esters: methyl palmitate, methyl oleate, methyl stearate, methyl linoleate, methyl linolenate, ethyl palmitate, ethyl oleate, ethyl stearate, ethyl linoleate, and ethyl linolenate (Le Conte et al. 1990). All together these compounds form the brood primer pheromone, but each component, alone or in combination, shows one or more releaser effects on adult bees (Le Conte et al. 2001).

5.1.4.1. Regulation of Brood Development and Care

BP is secreted by larval salivary glands, which are better known in honey bee larvae for their function in the silk secretion necessary for the construction of the pupal cocoon. The epithelial cells of the larval salivary glands secrete the fatty acids into the lumen of the glands, which act as a reservoir of the ester components of BP (Le Conte et al. 2006). The production of the different pheromone constituents varies in function of caste and larval age (Le Conte et al. 1994/1995) and this modulation of the signal is functional to guarantee the proper response to the needs of any larval age and caste by receiver nurse bees. For instance, methyl linolenate, methyl linoleate, methyl oleate, and methyl palmitate, which are produced in large quantities by the larvae during the cell capping, were found to induce the worker bees to cap the cells (Le Conte et al. 1994). Methyl palmitate and ethyl oleate increase the activity of the workers’ hypopharyngeal glands, which produce proteinaceous material (royal jelly) that is fed by nurse bees to young larvae (Mohammedi et al. 1996).

During queen rearing, methyl stearate increases the acceptance of the queen cups, methyl linoleate enhances the production and administration of royal jelly, and methyl palmitate increases the weight of the queen larvae (Le Conte et al. 1995).

Several studies demonstrated that colonies treated with BP rear more brood and more adults than controls, thus regulating colony growth. The BP treatment lead to an increased brood area and an augmented number of bees; the amount of protein consumption was augmented, as well as the amount of extractable protein from hypopharyngeal glands, indicating an enriched nutritional environment (Pankiw et al. 2008). Moreover, the queen in BP-treated colonies was fed longer, was more active, and laid more eggs; the workers spent more time cleaning cells and rearing the brood, resulting in a larger brood area in BP-treated colonies compared nontreated colonies (Pankiw et al. 2004; Sagili and Pankiw 2009).

5.1.4.2. Regulation of Worker Reproduction

Beside its releaser effects on workers linked to larval development, BP components act as primer pheromones regulating, in synergy with QMP, worker ovarian development. In particular, ethyl palmitate and methyl linolenate were found to act as worker ovary development inhibitors (Mohammedi et al. 1998), probably lowering worker JH titers, since the administration of high doses of BP resulted in lower JH levels in both laboratory and field experiments (Le Conte et al. 2001). This is consistent with JH inhibitory effect on behavioral development: JH titers and rates of JH biosynthesis are low in nurse bees and high in foragers, and JH treatments cause precocious foraging (Robinson 1992a; Robinson and Vargo 1997). Moreover, BP shunts vitellogenin transport to the hypopharyngeal gland rather than to the ovaries, thus redirecting worker metabolism from reproduction to brood care (Le Conte and Hefetz 2008).

All the above described BP components are nonvolatile substances and their distribution is probably mediated by worker to worker contact. Recently a new highly volatile pheromone, E-β-ocimene, has been identified in honey bee larvae (Maisonnasse et al. 2009); it belongs to the terpene family and has an aerial transmission, being easily dispersed within the colony. Compared to BP, E-β-ocimene has a prevalent effect in the regulation of adult worker physiology and development. In particular it exerts two main effects: inhibition of worker ovaries and modulation of worker behavioral maturation (Maisonnasse et al. 2010b). It seems that BP and E-β-ocimene act in a synergistic manner to repress the activation of the workers’ ovaries; this influence also has a consequence on brood care, since reproductive workers do not work as hard as sterile workers, showing a reduction in both larval care and foraging tasks.

5.1.4.3. Regulation of Worker Behavioral Development

In addition to the effects on larval development, BP induces an increase in colony growth also through a modulation of worker behavioral development. The treatment of colonies with BP caused an increased number of pollen foragers and augmented the weight of pollen load they transport (Pankiw et al. 2004). Pollen intake is also modulated by BP by altering the ratio of pollen to nonpollen foragers. Treatment with BP significantly decreased pollen forager turnaround time in the hive, increasing the ratio of pollen to non-pollen foragers entering the colony (Pankiw 2007).

Later studies demonstrated that BP acts in a dose-dependent manner in altering the demographics of colony foraging behavior: a low amount decreases the foraging age, resulting in a higher proportion of pollen foragers compared to nurse bees; high doses slow down the development of young bees from nest to foraging duties, so the foraging age increases, resulting in a lengthened nursing phase (Le Conte et al. 2001; Sagili et al. 2011). Moreover, pollen foragers exposed to a low amount of BP return to the nest with larger pollen loads compared to those treated with a higher amount (Sagili et al. 2011). This dose-dependent action is functional to the regulation of worker tasks on the basis of brood presence and age, as will be described.

As for worker ovarian development, E-β-ocimene cooperates with BP in the regulation of worker activity; in particular E-β-ocimene induces an earlier worker development toward foraging tasks, thereby optimizing food collection. Maisonnasse et al. (2010b) tried to explain how these two pheromones act synergically in maintaining colony homeostasis through the retention of a proper nurse/forager ratio and the inhibition of worker reproduction. It is known that in presence of brood, workers initiate foraging earlier compared to broodless colonies (Amdam et al. 2009; Tsuruda and Page 2009), thus assuring adequate food collection; however, an overabundance of foragers could lead to a lack of and a decline in brood care. Conversely, too many nurses cause a decrease in food collection and storage in the colony and a subsequent decline in brood nourishment. BP and E-β-ocimene are able to control this equilibrium since young and old larvae emit different types and quantities of these two pheromones: young larvae emit principally E-β-ocimene, while BP is produced in a growing amount during larval growth, reaching the highest concentrations during the capping stage.

In this way the young larvae, which have lower nursing needs, promote foraging and pollen collection by emitting a low quantity of BP and a large amount of E-β-ocimene, whereas old larvae, which have higher nursing needs, delay foraging and promote an increased brood care by producing a high quantity of BP, which also stimulates the development of worker hypopharyngeal glands and brood care tasks like cleaning, nourishment, and cell capping (Figure 5.4). Thus, young and old larvae play opposite roles in the behavioral maturation of worker bees according to their specific needs: young larvae promote foraging and old larvae promote brood care (Maisonnasse et al. 2010b).

FIGURE 5.4

Effect of brood pheromones on the regulation of worker behavioral and sexual development. Large arrows indicate effect of the pheromones on development; small black arrows indicate effect of the pheromones on activities. In the lower part of the figure: (more...)

It is clear that worker behavioral development, which leads to the typical honey bee age polyethism, is a complex and flexible process, involving more than one stimulus. The combined effect of queen signals, worker pheromones (ethyl oleate), and brood pheromones results in a plastic modulation of worker activity that is able to adapt worker response to the needs of the colony, which vary depending on colony developmental stage and environmental factors (Castillo et al. 2012).

5.2. NEUROPHYSIOLOGY OF CHEMICAL COMMUNICATION: PHEROMONE PROCESSING IN THE BEE BRAIN

The study of honey bee pheromones started in the 1960s and since then many advancements have been made in the knowledge of composition of pheromone blends, their glandular origin, and their colony target. But while we knew the effects of many of these pheromones, for a long time we could only speculate as to the neuronal mechanisms that mediate between pheromone and function. Only recently, with the development of molecular and genetic tools, some progress has been achieved in this direction. Thus, we are just starting to gain some awareness of the neurophysiological pathways of pheromone reception and processing in the bee brain, and only a few mechanisms have been entirely elucidated.

As previously reported, releaser and primer pheromones exert different effects on the receiver, the former being immediate and transitory and the latter delayed and long-termed. This difference suggests that two different mechanisms may exist by which pheromones influence the receiver: a direct effect on neural transmission for releaser pheromones against an effect on physiological processes (e.g., hormonal, metabolic, or genetic changes) for primer pheromones.

A common question regarding queen primer pheromones is their mode of action in regulating worker reproduction and behavioral development: is it by means of a controlling mechanism (queen pheromone as a suppressive agent) or a signaling one (queen pheromone as an “honest” signal) (Strauss et al. 2008)? In the “control” hypothesis the queen pheromones manipulate workers coercively by inhibiting their ovarian and behavioral development. In the signal hypothesis, also called the cooperation hypothesis, queen pheromones simply act to signal to workers the queen presence and its egg-laying potential, rather than to manipulate worker behavior and/or physiology. In the presence of a strong and healthy queen, workers refrain themselves from reproducing and prevent nestmate workers from reproducing (worker policing) in order to maximize colony fitness. When workers perceive a decline in the fecundity of the queen, they can activate their ovaries to produce their own male offspring (Keller and Nonacs 1993; Kocher and Grozinger 2011; Le Conte and Hefetz 2008; Strauss et al. 2008).

Both hypotheses make sense from an evolutionary point of view, and several authors tried to collect evidence to support one or the other theory, but without giving a definite and unquestionable response. Both theories could explain the richness and variety of queen pheromones, whose components increase with increasing level of sociality, such as both theories could support the variability of response given by different workers to the colony pheromones (Kocher and Grozinger 2011; Strauss et al. 2008). In either case, the way the pheromone is detected and processed in the brain of different receiver workers seems to play a crucial role in the regulation mechanism.

Different pheromones use different ways of transmission from the producer to the receiver. Volatile substances, such as the alarm and Nasonov pheromones produced by the workers, and the components of the QMP that attract drones for mating and workers for swarm clusters, use a dispersal mechanism; footprint pheromones, BP, and most components of QMP are transmitted primarily by contact, and the same is true for the esters produced in other queen glands (e.g., tergal and Dufour’s), which are delivered as an integral part of the queen signal together with QMP; for this reason some authors have named them “passenger pheromones” (Keeling and Slessor 2005; Slessor et al. 2005).

Whatever the way of transmission of the pheromone, the reception process starts in the receiver olfactory system.

5.2.1. Reception of the Pheromonal Signal

5.2.1.1. Olfactory Receptor Neurons

In insects, the peripheral odour detection starts in the peripheral chemosensory system with the detection of the chemical signal by olfactory receptor neurons (ORNs), which express specific olfactory receptors (ORs). ORs are seven-transmembrane domain proteins coupled to G proteins; following the binding with odorant molecules cellular transduction cascades are activated, implicating the production of cAMP, leading to depolarization and action potentials.

These receptors are located mainly in the antennae, where they are organized in olfactory sensilla of various shapes; the poreplate sensilla are the most frequent sensilla in the honey bee antennae (Figure 5.5). A poreplate sensillum is formed by an oval-shaped thin cuticular plate with numerous minute pores and is innervated by 5 to 35 ORNs with their corresponding ORs. Each poreplate contains the whole range of ORs and thus represents a whole miniature system (Brockmann and Brueckner 1995; Sandoz 2011).

FIGURE 5.5

Schematic representation of the reception pathway for general odors and social pheromones in the worker honey bee (left) and for sexual pheromones in the honey bee drone (right) from the antenna poreplate sensilla to the antennal lobe, and the following (more...)

Odorant molecules reach the dendrites of ORNs by diffusing through an extracellular fluid, called sensillum lymph, filling the sensillum cavity. In this fluid, odorant binding proteins (OBPs) transport the odorants to the ORNs (Sandoz 2011). While OBPs bind general odorants, a specific class of OBPs, the PBPs (pheromone binding proteins) are specialized in binding sexual pheromones and are present mainly in male insect sensilla (Laughlin et al. 2008; Leal 2005). OBPs and PBPs play an essential role in the detection of general odors and pheromonal molecules and in their transduction, passing the molecules to the sensory neuron membrane protein, which then delivers it to the olfactory receptor (Pesenti et al. 2008, 2009). Another class of soluble chemosensory proteins (CSPs), which shares no sequence homology with either PBPs or general OBPs, has been described in honey bees (Danty et al. 1998). However, in honey bees only 21 genes coding for OPBs and six coding for CSPs have been found in the genome, so that the relative importance of these molecules in the process of odor perception is still unclear (Forêt and Maleska 2006). The results of a recent study using a proteomic approach show that 12 of the 21 OBPs and 2 of the 6 CSPs predicted in the honey bee genome are present in the foragers’ antennae (Dani et al. 2010) and some OBPs are found to be more highly expressed in the mandibular glands of different honey bee castes, suggesting their involvement also in solubilization and release of semiochemicals (Iovinella et al. 2011). Three main subclasses of OBPs are defined in honey bees on the basis of antennal specific proteins (ASPs), namely ASP1, ASP2, and ASP3 (Danty et al. 1997, 1998). ASP1 is thought to be associated with QMP because of its higher abundance in drone sensilla and the ability to bind 9-ODA and 9-HDA, the most active components of the queen pheromone blend, while ASP2 and ASP3 bind general odorants (Danty et al. 1999). One of the CSPs, called ASP3c, specifically binds brood pheromone components and not general odorants or other pheromones (Briand et al. 2002).

The wide range of pheromones described in honey bees, together with the great number of environmental odors they encounter, suggests a highly developed olfactory system that must be able to discriminate a large number of volatile substances. Indeed, the sequencing of the honey bee genome allowed the identification of an exceptionally high number of OR types (160–170), compared to the already known ORs of Drosophila melanogaster (62 ORs) and Anopheles gambiae (79 ORs) (Robertson and Wanner 2006). This high number is evidently linked to the extraordinary olfactory abilities of honey bees, whose social life requires the perception of several pheromone blends as well as kin recognition signals and numerous floral odors.

It is presumable that different ORs are differentially expressed according to caste and function; indeed, among the identified antennal ORs, the AmOR11, which is upregulated in drones, was recently demonstrated in male antennae to specifically detect 9-ODA and to respond to all the main QMP components (Wanner et al. 2007). On the contrary, a number of other receptors (OR63, OR81, OR109, OR150, OR151, OR152) are more highly expressed in worker bees than in drones and are probably linked to floral odorant reception, being differentially expressed in bees which live in different environments and thus experience diverse floral scents (Reinhard and Claudianos 2013).

5.2.1.2. Antennal Lobes and the Glomeruli

The ORNs project their axons to a specific area of the deutocerebrum called antennal lobe, which is organized in densely packed nervous structures termed glomeruli (Figure 5.5). The axons of several ORNs converge to the glomeruli through four sensory tracts (T1–T4), which define four subpopulations of glomeruli, two containing about 70 glomeruli each (T1 and T3) and two with seven glomeruli each (T2 and T4). The ORNs of an individual poreplate project to all four glomerular subpopulations and are therefore distributed across the whole antennal lobes (Brockmann and Brueckner 1995; Flanagan and Mercer 1989; Kelber et al. 2006).

The arrangement and number of glomeruli are largely species-specific and vary from about 32 in the mosquito Aedes aegypti to more than 1000 in locusts and social wasps. In honey bees the workers possess 166 glomeruli and the drones 103. The latter also have four large glomerular complexes exclusively committed to processing sexual pheromones, probably with a functional specialization for a specific pheromone substance in each of the four complexes (Arnold et al. 1985).

It has to be noted that the number of glomeruli in the honey bee antennal lobe is almost equal to the number of ORN types expressing a given OR in the antennae, supporting the hypothesis of a linear relationship one-receptor/one-neuron/one-glomerulus.

Within the glomeruli the ORN axons synapse with two other kinds of neurons: the local neurones and the projection neurones (Figure 5.5). The former are mainly GABAergic neurons with an inhibitory output, while the latter are cholinergic neurons that show either excitatory or inhibitory responses to odors. The local neurons can be classified into two main types: the homogeneous local neurons, which innervate most if not all glomeruli in a uniform manner, and the heterogeneous local neurons, which innervate only a small subset of glomeruli with one dominant glomerulus that is densely innervated and a few others with very sparse processes (Flanagan and Mercer 1989; Sandoz 2011). The function of local interneurons is to interconnect the glomeruli and modulate the signal coming from ORs.

Projection neurons leave the antennal lobe via a variable number of pathways called antennocerebral tracts, connecting it with different areas of the protocerebrum, mostly the calyces of the mushroom bodies and the lateral protocerebrum (Hansson and Anton 2000; Kay and Stopfer 2006). Projection neurons can also be classified into two types: uniglomerular projection neurons branch in a single glomerulus within the antennal lobe and project to the mushroom body or the lateral horn through two major antennocerebral tracts, while multiglomerular projection neurons branch in most glomeruli and their axons follow three lesser antennocerebral tracts leading to other areas of the protocerebrum surrounding the α-lobe of the mushroom body or extending toward the lateral horn (Sandoz 2011, 2013).

5.2.1.3. Pheromone Processing in the Glomeruli

Within the glomeruli the olfactory signal undergoes an important integration and encoding before being transmitted to the higher centers. Glomeruli are the anatomical and functional units of the antennal lobes and constitute sites of synaptic interaction between different neuron types. The activity patterns of antennal lobes in response to odors was studied in the honey bee by optical imaging techniques (Galizia et al. 1997, 1998). Axons of ORNs expressing the same odorant receptor or with similar odor specificities converge onto the same glomerulus. Considering that a single type of molecule interacts with a number of different ORNs, which activate a similar number of glomeruli, an odor blend is represented by the activation of a variable number of glomeruli, resulting in a spatial representation of the odor within the antennal lobe (Galizia et al. 1999; Joerges et al. 1997; Sachse and Galizia 2003; Sachse et al. 1999). This representation is variable in time and depends on the olfactory experience; therefore, odorants are represented in the antennal lobe as changing spatiotemporal patterns of glomerular activity (Sandoz et al. 2003). The early olfactory learning during young adulthood enhances glomerular activity and modifies the spatiotemporal response patterns; these changes affect neural activity until the time when bees initiate foraging activities (Arenas et al. 2009; Galizia and Vetter 2005).

Social (nonsexual) pheromones, like citral and geraniol (components of the Nasonov gland), IPA (the major component of the alarm pheromone associated with the sting apparatus), and the worker mandibular gland pheromone 2-heptanone, are coded in the antennal lobe as “general” odors since they elicit activity in the same brain region as environmental odors (Galizia et al. 1999; Joerges et al. 1997; Sachse et al. 1999). IPA elicits strong responses in several glomeruli that also exhibit strong responses to orange, clove oil, limonene, and several plant extracts (Galizia and Menzel 2001). Nevertheless, Sandoz et al. (2001) found that IPA and 2-heptanone, which share an alarm role but have a different chemical structure and source, induce a reciprocal generalization in olfactory conditioning tests, suggesting that a similarity in the neural representation of odor could rely not only on the chemical structure but also on their functional value (Sandoz et al. 2001).

Wang et al. (2008) investigated the neural activity elicited by eight components of the sting pheromone, compared with the whole bee sting apparatus, at the level of the antennal lobes of honey bee workers. They found that the sting preparation evokes a clearly distinct glomerular pattern compared to those of individual pheromone components (e.g., IPA-activated glomeruli in the medial part of the antennal lobes), whereas the stings activated the lateral dorsal part. It seems that the sting apparatus pheromone is processed in a similar way to general odors, since the main determinant of glomerular activation is its chemical structure rather than its pheromonal value. However, in contrast to the elemental strategy used for processing nonpheromonal mixtures, where the neural representation of mixtures of two to four nonpheromonal odors could be linearly predicted based on the neural representation of each component (Deisig et al. 2006), pheromonal blends do not follow such a linear representation, revealing more complex strategies for the processing of pheromonal mixtures in the honey bee antennal lobe (Wang et al. 2008).

5.2.1.4. Sexual Communication: Drone Reception of QMP in Macroglomerular Complexes

Male insects, including honey bee drones, have a specialized olfactory subsystem to detect female sexual pheromones even at long distances. This subsystem is characterized by a large number of ORs and ORNs sensitive to the components of the female pheromones. Their axons converge to hypertrophied glomerular subunits called macroglomerular complexes that are located in the antennal lobes. In honey bees the sexual dimorphism of the reception system is evident (Figure 5.5); compared with worker bees, drones have larger antennae, with a flagellum surface twice as large as that of the workers, and about seven times as many poreplate sensilla (around 18,000 versus 2700) and ORNs (around 340,000 versus 65,000) (Esslen and Kaissling 1976). In addition, the female antennal lobe is composed of isomorphic glomeruli (about 160 in workers and 150 in queens), whereas in drones there is a reduced number of these “ordinary” isomorphic glomeruli (about 100) but there are four voluminous macroglomeruli (Arnold et al. 1985).

The sexual dimorphism of the reception system corresponds to different neuronal strategies to detect and respond to the pheromone signals. Electroantennographic studies showed that while worker antennae have a very similar response to the various QMP components, suggesting that there is no antennal specialization with regard to the number of sensory neurons, in contrast, drone antennae showed marked responses to 9-ODA and to synthetic QMP compared to the other QMP components. This high antennal response is characteristic of sexual pheromones that elicit a long-distance reaction and is attributed to a much higher number of sensory neurons in the male antennae (Brockmann et al. 1998).

These results confirm that worker antennae have a kind of generalized antennal tuning with no significant differences in the number of sensory neurons for individual mandibular pheromone components, while drone antennae are specialized in the perception of one component of the mandibular pheromone, 9-ODA. This scenario is in accordance with the above described differential morphology in the olfactory system between workers and drones, and confirmed by the finding that drones of the more primitive honey bee species, Apis florea, have only 1200 poreplate sensilla per antenna and only two macroglomeruli in their antennal lobes, corresponding to a minor complexity of the sex pheromone mixture in this species compared to A. mellifera (Brockmann and Bruchner 2001).

Wanner et al. (2007) identified four candidate sex pheromone ORs from the honey bee genome based on their higher expression in drone antennae compared to worker antennae. This number coincides with the number of macroglomeruli in the drone antennal lobe, but only one of them, the already cited AmOr11, specifically responds to 9-ODA, while the other three could not be linked to any queen pheromone component.

Further analysis of drone antennal lobes led to the discovery that the ventral part carries only ordinary glomeruli while the dorsal part shows two of the four macroglomeruli, one located dorsomedially (MG1) and the other on the dorso-lateral side (MG2). Optical imaging of the antennal lobe showed that floral odors and blend mixtures induced focal responses on the ventromedial side of the antennal lobe, a region rich in ordinary glomeruli. In contrast MG2 is clearly and specifically devoted to the reception of the QMP main component 9-ODA, which does not induce signals in regions other than MG2. Among the other QMP components, HOB and HVA induced activity mostly in two ordinary glomeruli in the center of the frontal region, which showed responses also to floral odorants 1-hexanol, limonene, clove oil, and orange oil blends, while 9-HDA and 10-HDA induced only very low and diffuse signals in ordinary glomeruli that could not be measured (Sandoz 2006, 2007). The fact that HVA and HOB are detected in drones by the general olfactory system and not by the pheromonal subsystem can be explained by their different pheromonal role: in fact they are produced mainly by mated queens and not (or very little) by virgin queens, suggesting that they are used for the induction of workers’ retinue behavior and not for drone attraction by virgin queens (Plettner et al. 1997). The role of 9-HDA and 10-HDA as sex attractants remains unclear.

The different organization of the olfactory system between workers and drones reflects their diverse role in the honey bee society: drones exhibit a clear olfactory specialization for the sexual pheromone 9-ODA consistent with their exclusive reproductive role in the hive, while workers show a broader range and less specific response for both pheromonal and nonpheromonal odors consistent with the use of these different signals in different behavioral contexts (Sandoz et al. 2007).

5.2.1.5. Pheromone Processing in Higher Centers

Processed olfactory information leaves the antennal lobe by the projection neurons, towards higher-order brain centers, especially the mushroom bodies and the lateral horn (Figure 5.5).

Olfactory inputs project to a specific area of the mushroom bodies, the Kenyon cells, which form two cup-shaped regions called calyces in each brain hemisphere. The calyces are anatomically and functionally subdivided into the lip, the collar, and the basal ring. The lip region and the inner half of the basal ring receive olfactory input, whereas the collar and outer half of the basal ring receive visual input. The axons of Kenyon cells project in bundles into the midbrain, forming the peduncle and the vertical and horizontal lobes, also called α and β lobes (Strausfeld 2002).

The mushroom bodies receive not only olfactory and visual signals, but also mechanosensory and gustatory inputs. They play an important role in the process of associative learning of olfactory stimuli but also act as a multisensory integration center with a feedback and modulatory function (Mercer and Erber 1983). They are also involved in higher nervous functions, such as learning, memory, and cognitive processes.

In contrast, the processing of olfactory stimuli in the lateral horn are still mostly unknown, including the topography of neurons leaving the lateral horn and the descending pathways involved in behavioral output. In Drosophila this region is divided in two main subregions that separately process pheromones and fruit odors (Jefferis et al. 2007); since the honey bee’s lateral horn shows a specific compartmentalization with at least four subcompartments, an organization similar to that of Drosophila could exist in the honey bee, with a specific pheromone processing region in the lateral horn.

Given that no dedicated glomeruli have been found in workers for the processing of pheromones, Sandoz et al. (2007) hypothesized that specific recognition of pheromones, especially the social ones, may take place at higher processing levels downstream from the antennal lobes. It is conceivable that particular Kenyon cells could recognize specific combinations of activated projection neurons, which would indicate that the detected stimulus is a pheromone.

5.3. CONCLUDING REMARKS

If one compares the very high number of pheromonal substances identified in the honey bee colony with the relative scarcity of uncovered physiological mechanisms subtending pheromonal effects, it clearly emerges that there is still much study required to fully understand the pathways from pheromone production to pheromonal output.

Pheromone processing starts in the peripheral sensory system where the chemical signal is transduced, and partially elaborated in the glomeruli of the antennal lobes (Figure 5.6).

FIGURE 5.6

Schematic representation of the pheromone processing pathway from its reception to its behavioral and physiological effects. Pheromones are transduced by the antennal odorant reception neurons (ORNs) and processed in the antennal lobes, respectively, (more...)

The pheromonal signal is probably elaborated in the mushroom bodies and in the lateral horn during its transmission from the neuronal fibers leaving the antennal lobes to the central nervous system. At this level, the outcome of the signal is modulated by biogenic amines, which act as neurotransmitters and neuromodulators in several neuronal functions, and whose fibers are well represented in these two neuropils. The precise role of biogenic amines in the transmission of pheromonal signals has not been clearly elucidated, but it is quite certain that they are involved in the process of worker behavioral development, which is triggered by the queen pheromones. This is confirmed by the fact that one component of QMP, HVA, which shares a similar chemical structure with DA, is able to skip the reception step in antennal lobes and directly affect worker behavior by modulating DA neuronal pathway and DA levels in the brain (Figure 5.6).

The recent advances in genomics have strongly contributed to understanding the mechanisms that regulate pheromone communication by showing a direct correlation between pheromonal signal and expression of genes involved in worker behavior. This was shown in particular for two primer pheromones, QMP and BP, but also for a releaser one, the sting alarm pheromone, thus questioning the old distinction between primer and releaser pheromones, at least for their operating mechanism (Figure 5.6).

In 1998, Winston and Slessor, in their article “Honey bee primer pheromones and colony organization: gaps in our knowledge,” stated that “we know a considerable amount about the functions in which these pheromones are active, but the modes of action, physiological effects and precise chemical nature of specific pheromonal activities remain as subjects for future research”. Today, after 15 years of research, we can say that several of these gaps have been filled, but still our understanding of neuronal and molecular mechanisms in pheromone processing is represented by separate pieces of an extremely more complex puzzle. A complete comprehension of the mechanism of pheromone communication in honey bees needs to put all the pieces together in an organic and all-inclusive picture that is able to display the complex routes and the multiple connections of this sophisticated chemical communication system.

REFERENCES

• Alaux C, Robinson G.E. Alarm pheromone induces immediate–Early gene expression and slow behavioral response in honey bees. J Chem Ecol. 2007;33:1346–50. [PubMed: 17505874]
• Alaux C, Le Conte Y, Adams H.A, Rodriguez-Zas S, Grozinger C.M, Sinha S, Robinson G.E. Regulation of brain gene expression in honey bees by brood pheromone. Gene Brain Behav. 2009;8:309–19. [PubMed: 19220482]
• Ali M.F, Morgan E.D. Chemical communication in insect communities: A guide to insect pheromones with special emphasis on social insects. Biol Rev Camb Philos. 1990;65(3):227–47.
• Al-Kahtani S.N, Bienefeld K. The Nasonov gland pheromone is involved in recruiting honey bee workers for individual larvae to be reared as queens. J Insect Behav. 2012;25:392–400.
• Allan S.A, Slessor K.N, Winston M.L, King G.G.S. The influence of age and task specialization on the production and perception of honey bee pheromones. J Insect Physiol. 1987;33:917–22.
• Amdam G.V, Aase A.L.T.O, Seehuus S.C, Norberg K, Hartfelder K, Fondrk M.K. Social reversal of immunosenescence in honey bee workers. Exp Gerontol. 2005;40:939–47. [PMC free article: PMC2409152] [PubMed: 16169181]
• Amdam G.V, Norberg K, Hagen A, Omholt S.W. Social exploitation of vitellogenin. Proc Natl Acad Sci U S A. 2003;100:1799–802. [PMC free article: PMC149913] [PubMed: 12566563]
• Amdam G.V, Rueppell O, Fondrk M.K, Page R.E, Nelson C.M. The nurse’s load: Early-life exposure to brood-rearing affects behavior and lifespan in honey bees (Apis mellifera). Exp Gerontol. 2009;44:467–71. [PMC free article: PMC3798062] [PubMed: 19264121]
• Amdam G.V, Simões Z.L.P, Hagen A, Norberg K, Schrøder K, Mikkelsen O, Kirkwood T.B.L, Omholt S.W. Hormonal control of the yolk precursor vitellogenin regulates immune function and longevity in honey bees. Exp Gerontol. 2004;39:767–73. [PubMed: 15130671]
• Arechavaleta-Velasco M.E, Hunt G.J. Genotypic variation in the expression of guarding behavior and the role of guards in the defensive response of honey bee colonies. Apidologie. 2003;34:439–47.
• Arenas A, Giurfa M, Farina W.M, Sandoz J.-C. Early olfactory experience modifies neural activity in the antennal lobe of a social insect at the adult stage. Eur J Neurosci. 2009;30:1498–508. [PubMed: 19821839]
• Arnhart L. Das krallenglied der honigbiene. Arch Bienenk. 1923;5:37–86.
• Arnold G, Masson C, Budharugsa S. Comparative study of the antennal lobes and their afferent pathways in the worker bee and the drone (Apis mellifera). Cell Tissue Res. 1985;242:593–605.
• Balderrama N, Nuñez J, Guerrieri F, Giurfa M. Different functions of two alarm substances in the honey bee. J Comp Physiol A. 2002;188:485–91. [PubMed: 12122467]
• Barbier J, Lederer E. Structure chimique de la substance royale de la reine d’abeille (Apis mellifera L.). C R Acad Sci Ser III Sci Vie. 1960;251:1131–35.
• Barron A.B, Robinson G.E. Selective modulation of task performance by octopamine in honey bee (Apis mellifera) division of labour. J Comp Physiol A. 2005;191:659–68. [PubMed: 15889261]
• Barron A.B, Schulz D.J, Robinson G.E. Octopamine modulates responsiveness to foraging-related stimuli in honey bees (Apis mellifera). J Comp Physiol A. 2002;188:603–10. [PubMed: 12355236]
• Beggs K.T, Mercer A.R. Dopamine receptor activation by honey bee queen pheromone. Curr Biol. 2009;19:1206–9. [PubMed: 19523830]
• Beggs K.T, Glendining K.A, Marechal N.M, Vergoz V, Nakamura I, Slessor K.N, Mercer A.R. Queen pheromone modulates brain dopamine function in worker honey bees. Proc Natl Acad Sci U S A. 2007;104:2460–64. [PMC free article: PMC1892986] [PubMed: 17287354]
• Ben-Shahar Y, Dudek N.L, Robinson G.E. Phenotypic deconstruction reveals involvement of manganese transporter malvolio in honey bee division of labor. J Exp Biol. 2004;207:3281–88. [PubMed: 15326204]
• Bicker G. Biogenic amines in the brain of the honey bee: Cellular distribution, development, and behavioral functions. Microsc Res Techniq. 1999;44(2–3):166–78. [PubMed: 10084823]
• Billen J.P.J. New structural aspects of the Dufour’s and venom glands in social insects. Naturwissenschaften. 1987;74:340–41.
• Billen J.P.J. Morphology of exocrine glands in social insects: An update 100 years after Ch. Janet. In: Lenoir A, Arnold G, Lepage M, editors. In: Les Insectes Sociaux. Paris: Publication Université de Paris Nord; 1994.
• Billen J.P.J, Morgan E.D. Pheromones communication in social insects: Sources and secretions. In: Vander Meer R.K, Breed M.D, Espelie K.E, Winston M.L, editors. In: Pheromone Communication in Social Insects: Ants, Wasps, Bees, and Termites. Boulder, CO: Westview Press; 1998. pp. 3–33.
• Billen J.P.J, Dumortier K.T.M, Velthuis H.H.W. Plasticity of honey bee castes: Occurrence of tergal glands in workers. Naturwissenschaften. 1986;73:332–33.
• Bloch G, Grozinger C.M. Social molecular pathways and the evolution of bee societies. Philos T Roy Soc B. 2011;366:2155–70. [PMC free article: PMC3130366] [PubMed: 21690132]
• Blum M.S, Fales H.M, Tucker K.W, Collins A.M. Chemistry of the sting apparatus of the worker honey bee. J Apicult Res. 1978;17:218–21.
• Boch R, Shearer D.A. Iso-pentyl acetate in stings of honey bees of different ages. J Apicult Res. 1966;5:65–70.
• Boch R, Shearer D.A. 2-heptanone and 10-hydroxy-trans-dec-2-enoic acid in the mandibular glands of worker honey bees of different ages. Z Vergl Physiol. 1967;54:1–11.
• Boch R, Shearer D.A, Petrasovits A. Efficacies of two alarm substances of the honey bee. J Insect Physiol. 1970;16:17–24. [PubMed: 5417706]
• Boch R, Shearer D.A, Stone B.C. Identification of iso-amyl acetate as an active component in the sting pheromone of the honey bees. Nature. 1962;195:1018–20. [PubMed: 13870346]
• Breed M.D. Recognition pheromones of the honey bee. Bioscience. 1998;48:463–70.
• Breed M.D, Guzman-Novoa E, Hunt G.J. Defensive behavior of honey bees: Organization, genetics, and comparisons with other bees. Annu Rev Entomol. 2004a;49:271–98. [PubMed: 14651465]
• Breed M.D, Leger E.A, Pearce A.N, Wang Y.J. Comb effects on the ontogeny of honey bee nestmate recognition. Anim Behav. 1998;55:13–20. [PubMed: 9480667]
• Breed M.D, Perry S, Bjostad L.B. Testing the blank slate hypothesis: Why honey bee colonies accept young bees. Insect Soc. 2004b;51:12–16.
• Breed M.D, Robinson G.E, Page R.E. Division of labor during honey bee colony defense. Behav Ecol Sociobiol. 1990;27:395–401.
• Breed M.D, Smith T.A, Torres A. Role of guard honey bees (Hymenoptera: Apidae) in nestmate discrimination and replacement of removed guards. Ann Entomol Soc Am. 1992;85:633–37.
• Briand L, Swasdipan N, Nespoulous C, Bézirard V, Blon F, Huet J.-C, Ebert P, Pernollet J.-C. Characterization of a chemosensory protein (ASP3c) from honey bee (Apis mellifera L.) as a brood pheromone carrier. Eur J Biochem. 2002;269:4586–96. [PubMed: 12230571]
• Brockmann A, Brueckner D. Projection pattern of poreplate sensory neurones in honey bee worker, Apis mellifera L. (Hymenoptera: Apidae). Int J Insect Morphol. 1995;24(4):405–11.
• Brockmann A, Brueckner D. Structural differences in the drone olfactory system of two phylogenetically distant Apis species, A. florea and A. mellifera. Naturwissenschaften. 2001;88:78–81. [PubMed: 11320892]
• Brockmann A, Brückner D, Crewe R. The EAG response spectra of workers and drones to queen honey bee mandibular gland components: The evolution of a social signal. Naturwissenschaften. 1998;85:283–85.
• Brockmann A, Dietz D, Spaethe J, Tautz J. Beyond 9-ODA: Sex pheromone communication in the European honey bee Apis mellifera L. J Chem Ecol. 2006;32(3):657–67. [PubMed: 16586035]
• Brown S.M, Napper R.M, Mercer A.R. Foraging experience, glomerulus volume, and synapse number: A stereological study of the honey bee antennal lobe. J Neurobiol. 2004;60(1):40–50. [PubMed: 15188271]
• Butler C.G, Fairey E.M. The role of the queen in preventing oogenesis in worker honey bees. J Apicult Res. 1963;2:14–18.
• Calderone N.W, Page R.E. Genotype variability in age polyethism and task specialization in the honey bee, Apis mellifera (Hymenoptera: Apidae). Behav Ecol Sociobiol. 1988;22:17–25.
• Callow R.K, Johnston N.C. The chemical constitution and synthesis of queen substance of honey bees (Apis mellifera). Bee World. 1960;41:152–53.
• Carcaud J, Roussel E, Giurfa M, Sandoz J.-C. Odour aversion after olfactory conditioning of the sting extension reflex in honey bees. J Exp Biol. 2009;212:620–26. [PubMed: 19218512]
• Cassier P, Lensky Y. The Nassanov gland of the workers of the honey bee (Apis mellifera L.): Ultrastructure and behavioural function of the terpenoid and protein component. J Insect Physiol. 1994;40:577–84.
• Cassier P, Tel-Zur D, Lensky Y. The sting sheaths of honey bee workers (Apis mellifera L.): Structure and alarm pheromone secretion. J Insect Physiol. 1994;40:23–32.
• Castillo C, Chen H, Graves C, Maisonnasse A, Le Conte Y, Plettner E. Biosynthesis of ethyl oleate, a primer pheromone, in the honey bee (Apis mellifera L.). Insect Biochem Molec. 2012;42:404–16. [PubMed: 22406167]
• Chaline N, Sandoz J.-C, Martin S.J, Ratnieks F.L.V, Jones G.R. Learning and discrimination of individual cuticular hydrocarbons by honey bees (Apis mellifera). Chem Senses. 2005;30:327–35. [PubMed: 15788713]
• Collins A.M. Effect of age on the response to alarm pheromones by caged honey bees. Ann Entomol Soc Am. 1980;73:307–9.
• Collins A.M, Blum M.S. Bioassay of compounds derived from the honey bee sting. J Chem Ecol. 1982;8(2):463–70. [PubMed: 24414957]
• Collins A.M, Rinderer T.E, Daly H.V, Harbo J.R, Pesante D. Alarm pheromone production by two honey bee (Apis mellifera) types. J Chem Ecol. 1989;15:1747–56. [PubMed: 24272178]
• Collins A.M, Rinderer T.E, Harbo J.R, Bolten A.B. Colony defense by Africanized and European honey bees. Science. 1982;218:72–74. [PubMed: 17776713]
• Contessi A. Le api: Biologia, allevamento, prodotti. Bologna, Italy: Edagricole; 2004.
• Crane E. Bees and Beekeeping: Science, Practice and World Resources. Ithaca, NY: Cornell University Press; 1990.
• Crewe R.M, Velthuis H.H.W. False queens: A consequence of mandibular gland signals in worker honey bees. Naturwissenschaften. 1980;67:467–69.
• Dani F.R, Iovinella I, Felicioli A, Niccolini A, Calvello M.A, Carucci M.G, Qiao H, Pieraccini G, Turillazzi S, Moneti G, Pelosi P. Mapping the expression of soluble olfactory proteins in the honey bee. J Proteome Res. 2010;9:1822–33. [PubMed: 20155982]
• Dani F.R, Jones G.R, Corsi S, Beard R, Pradella D, Turillazzi S. Nestmate recognition cues in the honey bee: Differential importance of cuticular alkanes and alkenes. Chem Senses. 2005;30:477–89. [PubMed: 15917370]
• Danty E, Arnold G, Huet J.-C, Huet D, Masson C, Pernollet J.-C. Separation, characterization and sexual heterogeneity of multiple putative odorant-binding proteins in the honey bee Apis mellifera L. (Hymenoptera: Apidea). Chem Senses. 1998;23:83–91. [PubMed: 9530973]
• Danty E, Briand L, Michard-Vanhée C, Perez V, Arnold G, Gaudemer O, Huet D, Huet J.-C, Ouali C, Masson C, Pernollet J.-C. Cloning and expression of a queen pheromone-binding protein in the honey bee: An olfactory-specific, developmentally regulated protein. J Neurosci. 1999;19:7468–75. [PMC free article: PMC6782524] [PubMed: 10460253]
• Danty E, Michard-Vanhée C, Huet J.-C, Genecque E, Pernollet J.-C, Masson C. Biochemical characterization, molecular cloning and localization of a putative odorant-binding protein in the honey bee Apis mellifera L. (Hymenoptera: Apidea). FEBS Lett. 1997;414:595–98. [PubMed: 9323043]
• de Groot A.P, Voogd S. On the ovary development in queenless worker bees (Apis mellifera L.). Experientia. 1954;10:384–85. [PubMed: 13210347]
• De Hazan M, Lensky Y, Cassier P. Effect of queen honey bee (Apis mellifera) ageing on her attractiveness to workers. Comp Biochem Physiol. 1989;93A:777–83.
• De Jong R, Pham-Delègue M.H. Electroantennogram responses related to olfactory conditioning in the honey bee (Apis mellifera ligustica). J Insect Physiol. 1991;37:319–24.
• Deisig N, Giurfa M, Lachnit H, Sandoz J.-C. Neural representation of olfactory mixtures in the honey bee antennal lobe. Eur J Neurosci. 2006;24:1161–74. [PubMed: 16930442]
• Dombroski T, Simões Z, Bitondi M. Dietary dopamine causes ovary activation in queenless Apis mellifera workers. Apidologie. 2003;34:281–89.
• Dor R, Katzav-Gozansky T, Hefetz A. Dufour’s gland pheromone as a reliable fertility signal among honey bee (Apis mellifera) workers. Behav Ecol Sociobiol. 2005;58:270–76.
• Downs S.G, Ratnieks F.L.W. Recognition of conspecifics by honey bee guards (Apis mellifera) uses non-heritable cues applied in the adult stage. Anim Behav. 1999;58:643–48. [PubMed: 10479380]
• Downs S.G, Ratnieks F.L, Badcock N, Mynott A. Honey bee guards do not use food derived odours to recognise non-nestmates: A test of the odour convergence hypothesis. Behav Ecol. 2001;12:47–50.
• Downs S.G, Ratnieks F.L, Jefferies S.L, Rigby H.E. The role of floral oils in the nestmate recognition system of honey bees (Apis mellifera L.). Apidologie. 2000;31:357–65.
• Engels W, Rosenkranz P, Adler A, Taghizadeh T, Lübke G, Francke W. Mandibular gland volatiles and their ontogenetic patterns in queen honey bees, Apis mellifera carnica. J Insect Physiol. 1997;43(4):307–13. [PubMed: 12769892]
• Espelie K.E, Butz V.M, Dietz A. Decyl decanoate: a major component of the tergite glands of honey bee queens (Apis mellifera L.). J Apicult Res. 1990;29:15–19.
• Esslen J, Kaissling K.E. Zahl und verteilung antennaler sensillen bei der honigbiene (Apis mellifera L.). Zoomorphologie. 1976;83:227–51.
• Fan Y, Richard F.-J, Rouf N, Grozinger C.M. Effects of queen mandibular pheromone on nestmate recognition in worker honey bees, Apis mellifera. Anim Behav. 2010;79:649–56.
• Farooqui T, Robinson K, Vaessin H, Smith B.H. Modulation of early olfactory processing by an octopaminergic reinforcement pathway in the honey bee. J Neurosci. 2003;23:5370–80. [PMC free article: PMC6741157] [PubMed: 12832563]
• Farris S.M, Robinson G.E, Fahrbach S.E. Experience- and age-related outgrowth of intrinsic neurons in the mushroom bodies of the adult worker honey bee. J Neurosci. 2001;21(16):6395–404. [PMC free article: PMC6763189] [PubMed: 11487663]
• Ferguson A.W, Free J.B. Factors determining the release of Nasonov pheromone by honey bees at the hive entrance. Physiol Entomol. 1981;6(1):15–19.
• Fernandez P.C, Gil M, Farina W.M. Reward rate and forager activation in honey bees: Recruiting mechanisms and temporal distribution of arrivals. Behav Ecol Sociobiol. 2003;54:80–87.
• Fischer P, Grozinger C.M. Pheromonal regulation of starvation resistance in honey bee workers (Apis mellifera). Naturwissenschaften. 2008;95:723–29. [PubMed: 18414825]
• Flanagan D, Mercer A.R. An atlas and 3-D reconstruction of the antenna1 lobes in the worker honey bee, Apis mellifera L. (Hymenoptera: Apidae). Int J Insect Morphol. 1989;18:145–59.
• Fluri P, Luscher M, Wille H, Gerig L. Changes in the weight of the pharyngeal gland and haemolymph titres of juvenile hormone, protein and vitellogenin in worker honey bees. J Insect Physiol. 1982;28:61–68.
• Forêt S, Maleska R. Function and evolution of a gene family encoding odorant binding-like proteins in a social insect, the honey bee (Apis mellifera). Genome Res. 2006;16:1404–13. [PMC free article: PMC1626642] [PubMed: 17065610]
• Francis B.R, Blanton W.E, Littlefield J.L, Nunamaker R.A. Hydrocarbons of the cuticle and hemolymph of the adult honey bee (Hymenoptera: Apidae). Ann Entomol Soc Am. 1989;82(4):486–94.
• Free J.B. The food of adult drone honey bees (Apis mellifera). J Anim Behav. 1957;5:7–11.
• Free J.B. Pheromones of Social Bees. London: Chapman and Hall; 1987.
• Free J.B, Simpson J. The alerting pheromones of the honey bee. Z Vergl Physiol. 1968;61:361–65.
• Free J.B, Ferguson A.W, Pickett J.A. Evaluation of the various components of the Nasonov pheromone used by clustering honey bees. Physiol Entomol. 1981a;6(3):263–68.
• Free J.B, Pickett J.A, Ferguson A.W, Smith M.C. Synthetic pheromones to attract honey bee (Apismellifera) swarms. J Agr Sci. 1981b;97:427–31.
• Free J.B, Ferguson A.W, Simpkins J.R, Al Sa’ad B.N. Effect of honey bee Nasonov and alarm pheromone components on behaviour at the nest entrance. J Apicult Res. 1983;22(4):214–23.
• Frilli F, Barbattini R, Milani N. L’ape: Forme e funzioni. Bologna, Italy: Calderini, Edagricole; 2001.
• Frumhoff P.C, Baker J. A genetic component to division of labour within honey bee colonies. Nature. 1988;33:358–61.
• Galizia C.G, Menzel R. The role of glomeruli in the neural representation of odours: Results from optical recording studies. J Insect Physiol. 2001;47:115–30. [PubMed: 11064019]
• Galizia C.G, Vetter R. Optical methods for analyzing odor-evoked activity in the insect brain. In: Christensen T.A, editor. In: Advances in Insect Sensory Neuroscience. Boca Raton, FL: CRC Press; 2005. pp. 349–92.
• Galizia C.G, Joerges J, Kuttner A, Faber T, Menzel R. A semi-in-vivo preparation for optical recording of the insect brain. J Neurosci Meth. 1997;76:61–69. [PubMed: 9334940]
• Galizia C.G, Nägler K, Hölldobler B, Menzel R. Odour coding is bilaterally symmetrical in the antennal lobes of honey bees (Apis mellifera). Eur J Neurosci. 1998;10:2964–74. [PubMed: 9758166]
• Galizia C.G, Sachse S, Rappert A, Menzel R. The glomerular code for odor representation is species-specific in the honey bee Apis mellifera. Nat Neurosci. 1999;2:473–78. [PubMed: 10321253]
• Gary N.E. Chemical mating attractants in the queen honey bee. Science. 1962;136:773–74. [PubMed: 17752107]
• Gary N.E, Marston J. Mating behavior of drone honey bees with queen models (Apis mellifera L.). Anim Behav. 1971;19:299–304.
• Gauthier M, Grünewald B. Neurotransmitter systems in the honey bee brain: Functions in learning and memory. In: Galizia C.G, Eisenhardt D, Giurfa M, editors. In: Honeybee Neurobiology and Behavior. A Tribute to Randolf Menzel. Dordrecht, Netherlands: Springer; 2013. pp. 155–69.
• Gervan N, Winston M, Higo H, Hoover S. The effects of honey bee (Apis mellifera) queen mandibular pheromone on colony defensive behaviour. J Apicult Res. 2005;44:175–79.
• Giurfa M. The repellent scent mark of the honey bee Apis mellifera ligustica and its role as communication cue during foraging. Insect Soc. 1993;40:59–67.
• Giurfa M. Behavioral and neural analysis of associative learning in the honey bee: A taste from the magic well. J Comp Physiol A. 2007;193:801–24. [PubMed: 17639413]
• Goodman L. Form and Function in the Honey Bee. Cardiff, UK: IBRA; 2003.
• Grandperrin D, Cassier P. Anatomy and ultrastructure of the Koschewnikow’s gland of the honey bee, Apis mellifera L. (Hymenoptera: Apidae). Int J Insect Morphol. 1983;12(1):25–42.
• Grozinger C, Robinson G. Endocrine modulation of a pheromone-responsive gene in the honey bee brain. J Comp Physiol A. 2007;193(4):461–70. [PubMed: 17192826]
• Grozinger C.M, Fischer P, Hampton J.E. Uncoupling primer and releaser responses to pheromone in honey bees. Naturwissenschaften. 2007;94(5):375–79. [PubMed: 17187255]
• Grozinger C.M, Sharabash N.M, Whitfield C.W, Robinson G.E. Pheromone-mediated gene expression in the honey bee brain. Proc Natl Acad Sci U S A. 2003;100(2):14519–25. [PMC free article: PMC304112] [PubMed: 14573707]
• Hammer M. An identified neurone mediates the unconditioned stimulus in associative olfactory learning in honey bees. Nature. 1993;366:59–63. [PubMed: 24308080]
• Hammer M, Menzel R. Multiple sites of associative odor learning as revealed by local brain microinjections of octopamine in honey bees. Learn Mem. 1998;5:146–56. [PMC free article: PMC311245] [PubMed: 10454379]
• Hansson B.S, Anton S. Function and morphology of the antennal lobe: New developments. Annu Rev Entomol. 2000;45:203–31. [PubMed: 10761576]
• Harris J, Woodring J. Effects of dietary precursors to biogenic amines on the behavioural response from groups of caged worker honey bees (Apis mellifera) to the alarm pheromone component isopentyl acetate. Physiol Entomol. 1999;24:285–91.
• Hartfelder K. Insect juvenile hormone: From “status quo” to high society. Braz J Med Biol Res. 2000;33(2):157–77. [PubMed: 10657056]
• Higo H.A, Colley S.J, Winston M.L, Slessor K.N. Effects of honey bee (Apis mellifera) queen mandibular gland pheromone on foraging and brood rearing. Can Entomol. 1992;124:409–18.
• Insights into social insects from the genome of the honey bee Apis mellifera. Nature. 2006;443:931–49. Honey Bee Genome Sequencing Consortium. [PMC free article: PMC2048586] [PubMed: 17073008]
• Hoover S.E.R, Keeling C.I, Winston M.L, Slessor K.N. The effect of queen pheromones on worker honey bee ovary development. Naturwissenschaften. 2003;90:477–80. [PubMed: 14564409]
• Hoover S.E.R, Winston M.L, Oldroyd B.P. Retinue attraction and ovary activation: Responses of wild type and anarchistic honey bees (Apis mellifera) to queen and brood pheromones. Behav Ecol Sociobiol. 2005;59:278–84.
• Huang Z.-Y, Robinson G.E. Honey bee colony integration: Worker-worker interactions mediate hormonally regulated plasticity in division of labor. Proc Natl Acad Sci U S A. 1992;89:11726–29. [PMC free article: PMC50629] [PubMed: 1465390]
• Huang Z.-Y, Robinson G.E. Regulation of honey bee division of labor by colony age demography. Behav Ecol Sociobiol. 1996;39:147–58.
• Huang Z.-Y, Plettner E, Robinson G.E. Effect of social environment and mandibular gland removal on division of labor in worker honey bees. J Comp Physiol A. 1998;183:143–52. [PubMed: 9693990]
• Huang Z.-Y, Robinson G.E, Tobe S.S, Yagi K.J, Strambi C, Strambi A, Stay B. Hormonal regulation of behavioural development in the honey bee is based on changes in the rate of juvenile hormone biosynthesis. J Insect Physiol. 1991;37:733–41.
• Humphries M.A, Mustard J.A, Hunter S.J, Mercer A, Ward V, Ebert P.R. Invertebrate D2 type dopamine receptor exhibits age-based plasticity of expression in the mushroom bodies of the honey bee brain. J Neurobiol. 2003;55:315–30. [PubMed: 12717701]
• Hunt G.J. Flight and fight: A comparative view of the neurophysiology and genetics of honey bee defensive behavior. J Insect Physiol. 2007;53:399–410. [PMC free article: PMC2606975] [PubMed: 17379239]
• Hunt G.J, Wood K.V, Guzmán-Novoa E, Lee H.D, Rothwell A.P, Bonham C.C. Discovery of 3-methyl-2-buten-1-yl acetate, a new alarm component in the sting apparatus of Africanized honey bees. J Chem Ecol. 2003;29:451–61. [PubMed: 12737269]
• Iovinella I, Dani F.R, Niccolini A, Sagona S, Michelucci E, Gazzano A, Turillazzi S, Felicioli A, Pelosi P. Differential expression of odorant-binding proteins in the mandibular glands of the honey bee according to caste and age. J Proteome Res. 2011;10:3439–49. [PubMed: 21707107]
• Jay S.C. Factors influencing ovary development of worker honey bees under natural conditions. Can J Zool. 1968;46:345–47.
• Jefferis G.S, Potter C.J, Chan A.M, Marin E.C, Rohlfing T, Maurer C.R Jr, Luo L. Comprehensive maps of Drosophila higher olfactory centers: Spatially segregated fruit and pheromone representation. Cell. 2007;128:1187–203. [PMC free article: PMC1885945] [PubMed: 17382886]
• Joerges J, Küttner A, Galizia C.G, Menzel R. Representations of odours and odour mixtures visualized in the honey bee brain. Nature. 1997;387:285–88.
• Kaatz H.H, Eichmueller S, Kreissl S. Stimulatory effect of octopamine on juvenile hormone biosynthesis in honey bees (Apis mellifera): Physiological and immunocytochemical evidence. J Insect Physiol. 1994;40:865–72.
• Kaatz H.H, Hildebrandt H, Engels W. Primer effect of queen pheromone on juvenile hormone biosynthesis in adult worker bees. J Comp Physiol. 1992;162:588–92.
• Kaminski L.-A, Slessor K.N, Winston M.L, Hay N.W, Borden J.H. Honey bee response to queen mandibular pheromone in laboratory bioassays. J Chem Ecol. 1990;16:841–50. [PubMed: 24263599]
• Katzav-Gozansky T. The evolution of honey bee multiple queen-pheromones–A consequence of a queen-worker arm race? Braz J Morphol Sci. 2006;23(3–4):287–94.
• Katzav-Gozansky T, Boulay R, Soroker V, Hefetz A. Queen-signal modulation of worker pheromonal composition in honey bees. Proc R Soc Lond B Bio. 2004;271:2065–69. [PMC free article: PMC1691821] [PubMed: 15451697]
• Katzav-Gozansky T, Boulay R, Soroker V, Hefetz A. Queen pheromones affecting the production of queen-like secretion in workers. J Comp Physiol A. 2006;192:737–42. [PubMed: 16482439]
• Katzav-Gozansky T, Soroker V, Hefetz A. Plasticity in caste related exocrine secretion biosynthesis in the honey bee (Apis mellifera). J Insect Physiol. 2000;46:993–98. [PubMed: 10802112]
• Katzav-Gozansky T, Soroker V, Hefetz A. Honey bees Dufour’s gland: Idiosyncrasy of a new queen signal. Apidologie. 2002;33:525–37.
• Katzav-Gozansky T, Soroker V, Hefetz A. Honey bee egglaying workers mimic a queen signal. Insect Soc. 2003;50:20–23.
• Katzav-Gozansky T, Soroker V, Hefetz A, Cojocaru M, Erdmann D.H, Francke W. Plasticity of caste-specific Dufour’s gland secretion in the honey bee (Apis mellifera L.). Naturwissenschaften. 1997;84:238–41.
• Katzav-Gozansky T, Soroker V, Ibarra F, Francke W, Hefetz A. Dufour’s gland secretion of the queen honey bee (Apis mellifera): An egg discriminator pheromone or a queen signal? Behav Ecol Sociobiol. 2001;51:76–86.
• Kay L.M, Stopfer M. Information processing in the olfactory systems of insects and vertebrates. Sem Cell Devel Biol. 2006;17(4):433–42. [PubMed: 16766212]
• Keeling C.I, Slessor K.N. A scientific note on aliphatic esters in queen honey bees. Apidologie. 2005;36:559–60.
• Keeling C.I, Slessor K.N, Higo H.A, Winston M.L. New components of the honey bee (Apis mellifera L.) queen retinue pheromone. Proc Natl Acad Sci U S A. 2003;100:4486–91. [PMC free article: PMC153582] [PubMed: 12676987]
• Kelber C, Roessler W, Kleineidam C.J. Multiple olfactory receptor neurons and their axonal projections in the antennal lobe of the honey bee Apis mellifera. J Comp Neurol. 2006;496:395–405. [PubMed: 16566001]
• Keller L, Nonacs P. The role of queen pheromones in social insects: Queen control or queen signal? Anim Behav. 1993;45:787–94.
• Kirchner W.H, Gadagkar R. Discrimination of nestmate workers and drones in honey bees. Insect Soc. 1994;41(3):335–38.
• Kocher S.D, Grozinger C.M. Cooperation, conflict, and the evolution of queen pheromones. J Chem Ecol. 2011;37:1263–75. [PubMed: 22083225]
• Kokay I.C, Ebert P.R, Kirchhof B.S, Mercer A.R. Distribution of dopamine receptors and dopamine receptor homologs in the brain of the honey bee, Apis mellifera L. Microsc Res Technol. 1999;44:179–89. [PubMed: 10084824]
• Kolmes S.A, Njehu N. Effect of queen mandibular pheromones on Apis mellifera worker stinging behavior (Hymenoptera: Apidae). J New York Entomol S. 1990;98(4):495–98.
• Kreissl S, Eichmüller S, Bicker G, Rapus J, Eckert M. Octopamine-like immunoreactivity in the brain and subesophageal ganglion of the honey bee. J Comp Neurol. 1994;348(4):583–95. [PubMed: 7530730]
• Kurshan P.T, Hamilton I.S, Mustard J.A, Mercer A.R. Developmental changes in expression patterns of two dopamine receptor genes in mushroom bodies of the honey bee, Apis mellifera. J Comp Neurol. 2003;466:91–103. [PubMed: 14515242]
• Laughlin J.D, Ha T.S, Jones D.N, Smith D.P. Activation of pheromone-sensitive neurons is mediated by conformational activation of pheromone binding protein. Cell. 2008;133:1255–65. [PMC free article: PMC4397981] [PubMed: 18585358]
• Le Conte Y, Hefetz A. Primer pheromones in social Hymenoptera. Annu Rev Entomol. 2008;53:523–42. [PubMed: 17877458]
• Le Conte Y, Arnold G, Trouiller J, Masson C. Identification of a brood pheromone in honey bees. Naturwissenschaften. 1990;77:334–36.
• Le Conte Y, Becard J.M, Costagliola G, de Vaublanc G, El Maataoui D.C, Plettner E, Slessor K.N. Larval salivary glands are a source of primer and releaser pheromone in honey bee (Apis mellifera L.). Naturwissenschaften. 2006;93:237–41. [PubMed: 16541233]
• Le Conte Y, Mohammedi A, Robinson G.E. Primer effects of a brood pheromone on honey bee behavioural development. Proc R Soc Lond B Bio. 2001;268:163–68. [PMC free article: PMC1088586] [PubMed: 11209886]
• Le Conte Y, Sreng L, Poitout S.H. Brood pheromone can modulate the feeding behavior of Apis mellifera workers (Hymenoptera: Apidae). J Econ Entomol. 1995;88:798–804.
• Le Conte Y, Sreng L, Trouiller J. The recognition of larvae by worker honey bees. Naturwissenschaften. 1994;81:462–65.
• Le Conte Y, Sreng L, Sacher N, Trouiller J, Dusticier G, Poitout S.H. Chemical recognition of queen cells by honey bee workers Apis mellifera (Hymenoptera: Apidae). Chemoecology. 1994/1995;5/6:6–12.
• Leal W.S. Pheromone reception. Top Curr Chem. 2005;240:1–36.
• Ledoux M.N, Winston M.L, Higo H, Keeling C.I, Slessor K.N, Le Conte Y. Queen and pheromonal factors influencing comb construction by simulated honey bee (Apis mellifera L.) swarms. Insect Soc. 2001;48(1):14–20.
• Lensky Y, Cassier P. The alarm pheromones of queen and worker honey bees. Bee World. 1995;76:119–29.
• Lensky Y, Slabezki Y. The inhibiting effect of the queen bee (Apis mellifera L.) foot-print pheromone on the construction of swarming queen cups. J Insect Physiol. 1981;27(5):313–23.
• Lensky Y, Cassier P, Finkel A, Delorme-Joulie C, Levinsohn M. The fine structure of the tarsal glands of the honey bee Apis mellifera L. (Hymenoptera). Cell Tissue Res. 1985;240:153–58.
• Lensky Y, Cassier P, Finkel A, Teeslshee A, Shelensinger R, Delorme-Joulie C, Levinsohn N. Le glandes tarsales de l’abeille mellifique (Apis mellifera L.): Reines, ouvriéres et faux bourdons (Hymenoptera, Apidae). II. Role biologique. Ann Sci Nat Zool Biol Anim. 1984;6:167–75.
• Lensky Y, Cassier P, Rosa S, Grandperrin D. Induction of balling in worker honey bees (Apis mellifera L.) by “stress” pheromone from Koschewnikow glands of queen bees: Behavioural, structural and chemical study. Comp Biochem Physiol. 1991;100A:585–94.
• Lensky Y, Cassier P, Tel-Zur D. The setaceous membrane of honey bee (Apis mellifera L.) workers’ sting apparatus: Structure and alarm pheromone distribution. J Insect Physiol. 1995;41:589–95.
• Leoncini I, Le Conte Y, Costagliola G, Plettner E, Toth A.L, Wang M, Huang Z, Bécard J, Crauser D, Slessor K.N, Robinson G.E. Regulation of behavioral maturation by a primer pheromone produced by adult worker honey bees. Proc Natl Acad Sci U S A. 2004;101:17559–64. [PMC free article: PMC536028] [PubMed: 15572455]
• Lipínski Z. The calming properties of the honey bee queen, young brood and older bees. J Apic Sci. 2006;50(1):63–70.
• Loper G.M, Taylor O.R Jr, Foster L.J, Kochansky J. Relative attractiveness of queen mandibular pheromone components to honey bee (Apis mellifera L.) drones. J Apic Res. 1996;35:122–23.
• Maisonnasse A, Alaux C, Beslay D, Crauser D, Gines C, Plettner E, Le Conte Y. New insights into honey bee (Apis mellifera) pheromone communication. Is the queen mandibular pheromone alone in colony regulation? Front Zool. 2010a;7:18–25. [PMC free article: PMC2897789] [PubMed: 20565874]
• Maisonnasse A, Lenoir J.C, Beslay D, Crauser D, Le Conte Y. E-β-ocimene, a volatile brood pheromone involved in social regulation in the honey bee colony (Apis mellifera). PLoS ONE. 2010b;5(10):e13531. [PMC free article: PMC2958837] [PubMed: 21042405]
• Maisonnasse A, Lenoir J.C, Costagliola G, Beslay D, Choteau F, Crauser D, Becard J.M, Plettner E, Le Conte Y. A scientific note on E-β-ocimene, a new volatile primer pheromone that inhibits worker ovary development in honey bees. Apidologie. 2009;40:562–64.
• Makert G.R, Paxton R.J, Hartfelder K. Ovariole number—A predictor of differential reproductive success among worker subfamilies in queenless honey bee (Apis mellifera L.) colonies. Behav Ecol Sociobiol. 2006;60:815–25.
• Maleszka J, Barron A, Helliwell P, Maleszka R. Effect of age, behaviour and social environment on honey bee brain plasticity. J Comp Physiol A. 2009;195(8):733–40. [PubMed: 19434412]
• Malka O, Shnieor S, Hefetz A, Katzav-Gozansky T. Reversible royalty in worker honey bees (Apis mellifera) under the queen influence. Behav Ecol Sociobiol. 2007;61:465–73.
• Malka O, Shnieor S, Katzav-Gozansky T, Hefetz A. Aggressive reproductive competition among hopelessly queenless honey bee workers triggered by pheromone signalling. Naturwissenschaften. 2008;95:553–59. [PubMed: 18320158]
• Martin S.J, Dils V, Billen J. Morphology of the Dufour gland within the honey bee sting gland complex. Apidologie. 2005;36:543–46.
• Martin S.J, Jones G.R, Châline N, Middleton H, Ratnieks F.L.W. Reassessing the role of the honey bee (Apis mellifera) Dufour’s glands in egg marking. Naturwissenschaften. 2002;89:528–32. [PubMed: 12451458]
• Masson C, Arnold G. Ontogeny, maturation and plasticity of the olfactory system in the worker bee. J Insect Physiol. 1984;30:7–14.
• McQuillan H.J, Barron A.B, Mercer A.R. Age- and behaviour-related changes in the expression of biogenic amine receptor genes in the antennae of honey bees (Apis mellifera). J Comp Physiol A. 2012;198:753–61. [PubMed: 22930400]
• Melathopoulos A.P, Winston M.L, Pettis J.S, Pankiw T. Effect of queen mandibular pheromone on initiation and maintenance of queen cells in the honey bee (Apis mellifera L.). Can Entomol. 1996;128:263–72.
• Menzel R, Heyne A, Kinzel C, Gerber B, Fiala A. Pharmacological dissociation between the reinforcing, sensitizing, and response-releasing functions of reward in honey bee classical conditioning. Behav Neurosci. 1999;113:744–54. [PubMed: 10495082]
• Mercer A. Biogenic amines and the bee brain. In: Menzel R, Mercer A, editors. Neurobiology and Behaviour of Honey bees. Berlin: Springer-Verlag; 1987. pp. 245–52.
• Mercer A.R, Erber J. The effects of amines on evoked potentials recorded in the mushroom bodies of the bee brain. J Comp Physiol. 1983;151:469–76.
• Mercer A.R, Menzel R. The effects of biogenic amines on conditioned and unconditioned responses to olfactory stimuli in the honey bee, Apis mellifera. J Comp Physiol. 1982;145:363–68.
• Millor J, Pham-Delègue M, Deneubourg J.L, Camazine S. Self-organized defensive behavior in honey bees. Proc Natl Acad Sci U S A. 1999;96:12611–15. [PMC free article: PMC23012] [PubMed: 10535970]
• Mohammedi A, Crauser D, Paris A, Le Conte Y. Effect of a brood pheromone on honey bee hypopharyngeal glands. C R Acad Sci. 1996;319:769–72. [PubMed: 8952879]
• Mohammedi A, Paris A, Crauser D, Le Conte Y. Effect of aliphatic esters on ovary development of queenless bees (Apis mellifera L.). Naturwissenschaften. 1998;85:455–58.
• Morgan S.M, Butz Huryn V.M, Downes S.R, Mercer A.R. The effects of queenlessness on the maturation of the honey bee olfactory system. Behav Brain Res. 1998;91(1–2):115–26. [PubMed: 9578445]
• Moritz R.F.A, Crewe R.M. Chemical signals of queens in kin recognition of honey bees, Apis mellifera L. J Comp Physiol A. 1988;164:83–89.
• Moritz R.F.A, Crewe R.M. The volatile emission of honey bee queens (Apis mellifera L.). Apidologie. 1991;22:205–12.
• Moritz R.F.A, Crewe R.M, Hepburn H.R. Queen avoidance and mandibular gland secretion of honey bee workers (Apis mellifera L.). Insectes Soc. 2002;49:86–91.
• Moritz R.F.A, Simon U.E, Crewe R.M. Pheromonal contest between honey bee workers (Apis mellifera capensis). Naturwissenschaften. 2000;87:395–97. [PubMed: 11091962]
• Muenz T.S, Maisonnasse A, Plettner E, Le Conte Y, Rössler W. Sensory reception of the primer pheromone ethyl oleate. Naturwissenschaften. 2012;99:421–25. [PubMed: 22426740]
• Mustard J.A, Blenau W, Hamilton I.S, Ward V.K, Ebert P.R, Mercer A.R. Analysis of two D1-like dopamine receptors from the honey bee, Apis mellifera, reveals agonist-independent activity. Mol Brain Res. 2003;113:67–77. [PubMed: 12750008]
• Naumann K. Grooming behaviors and the translocation of queen mandibular gland pheromone on worker honey bees (Apis mellifera L.). Apidologie. 1991;22:523–31.
• Naumann K, Winston M.L, Slessor K.N. Movement of honey bee (Apis mellifera L.) queen mandibular gland pheromone in populous and unpopulous colonies. J Insect Behav. 1993;6:211–23.
• Naumann K, Winston M.L, Slessor K.N, Prestwich G.D, Webster F.X. The production and transfer of honey bee (Apis mellifera L) queen mandibular gland pheromone. Behav Ecol Sociobiol. 1991;29:321–32.
• Nelson C.M, Ihle K, Amdam G.V, Fondrk M.K, Page R.E. The gene vitellogenin has multiple coordinating effects on social organization. PLoS Biol. 2007;5:673–77. [PMC free article: PMC1808115] [PubMed: 17341131]
• Nuñez J.A, Almeida L, Balderrama N, Giurfa M. Alarm pheromone induces stress analgesia via an opioid system in the honey bee. Physiol Behav. 1998;63:75–80. [PubMed: 9402618]
• Nuñez J.A, Maldonado H, Miralto A, Balderrama N. The stinging response of the honey bee: Effects of morphine, naloxone and some opioid peptides. Pharm Biochem Behav. 1983;19:921–24. [PubMed: 6657718]
• Onions G.W. South African “fertile” worker bees. Agric J S Afr. 1912;7:44–46.
• Page R.E Jr, Metcalf R.A, Metcalf R.L, Erickson E.H Jr, Lampman R.L. Extractable hydrocarbons and kin recognition in honey bee (Apis mellifera L.). J Chem Ecol. 1991;17(4):745–56. [PubMed: 24258919]
• Pankiw T. Worker honey bee pheromone regulation of foraging ontogeny. Naturwissenschaften. 2004a;91:178–81. [PubMed: 15085275]
• Pankiw T. Cued in: Honey bee pheromones as information flow and collective decision-making. Apidologie. 2004b;35:217–26.
• Pankiw T. Brood pheromone regulates foraging activity of honey bees (Hymenoptera: Apidae). J Econ Entomol. 2004c;97:748–51. [PubMed: 15279247]
• Pankiw T. Brood pheromone modulation of pollen forager turnaround time in the honey bee (Apis mellifera L.). J Insect Behav. 2007;20:173–80.
• Pankiw T, Page R.E. Brood pheromone modulates honey bee (Apis mellifera L.) sucrose response thresholds. Behav Ecol Sociobiol. 2001;49:206–13.
• Pankiw T, Huang Z, Winston M.L, Robinson G.E. Queen mandibular gland pheromone influences worker honey bee (Apis mellifera L.) foraging ontogeny and juvenile hormone titers. J Insect Physiol. 1998;44(7–8):685–92. [PubMed: 12769952]
• Pankiw T, Roman R, Sagili R.R, Metz B.N. Brood pheromone effects on colony protein supplement consumption and growth in the honey bee (Hymenoptera: Apidae) in a subtropical winter climate. J Econ Entomol. 2008;101(6):1749–55. [PubMed: 19133452]
• Pankiw T, Roman R, Sagili R.R, Zhu-Salzman K. Pheromone-modulated behavioral suites infiuence colony growth in the honey bee (Apis mellifera). Naturwissenschaften. 2004;91:575–78. [PubMed: 15452700]
• Pankiw T, Winston M.L, Slessor K.N. Variation in worker response to honey bee (Apis mellifera L.) queen mandibular pheromone. J Insect Behav. 1994;7:1–15.
• Pankiw T, Winston M.L, Slessor K.N. Queen attendance behavior of worker honey bees (Apis mellifera L.) that are high and low responding to queen mandibular pheromone. Insect Soc. 1995;41:371–78.
• Papachristoforou A, Kagiava A, Papaefthimiou C, Termentzi A, Fokialakis N, Skaltsounis A.-L, Watkins M, Arnold G, Theophilidis G. The bite of the honey bee: 2-Heptanone secreted from honey bee mandibles during a bite acts as a local anaesthetic in insects and mammals. PLoS ONE. 2012;7(10):e47432. [PMC free article: PMC3472974] [PubMed: 23091624]
• Pesenti M.E, Spinelli S, Bezirard V, Briand L, Pernollet J.-C, Tegoni M, Cambillau C. Structural basis of the honey bee PBP pheromone and pH-induced conformational change. J Mol Biol. 2008;380:158–69. [PubMed: 18508083]
• Pesenti M.E, Spinelli S, Bezirard V, Briand L, Pernollet J.-C, Campanacci V, Tegoni M, Cambillau C. Queen bee pheromone binding protein pH-Induced domain swapping favors pheromone release. J Mol Biol. 2009;390:981–90. [PubMed: 19481550]
• Pettis J.S, Westcott L.C, Winston M.L. Balling behaviour in the honey bee in response to exogenous queen mandibular gland pheromone. J Apicult Res. 1998;37(2):125–31.
• Pettis J.S, Winston M.L, Slessor K.N. Behaviour of queen and worker honey bees (Hymenoptera: Apidae) in response to exogenous queen mandibular gland pheromone. Ann Entomol Soc Am. 1995;88(4):580–88.
• Pflumm W, Wilhelm K. Olfactory feedback in the scent-marking behaviour of foraging honey bees at the food source? Physiol Entomol. 1982;7:203–7.
• Pham-Delègue M.H, Trouiller J, Bakchine E, Roger B, Masson C. Age dependency of worker bee response to queen pheromone in a four-armed olfactometer. Insect Soc. 1991;38:283–92.
• Pham-Delègue M.H, Trouiller J, Caillaud C.M, Roger B, Masson C. Effect of queen pheromone on worker bees of different ages: Behavioral and electrophysiological responses. Apidologie. 1993;24:267–81.
• Pickett J.A, Williams I.H, Martin A.P. (Z)-11-Eicosen-1-ol, an important new pheromonal component from the sting of the honey bee, Apis mellifera L. (Hymenoptera, Apidae). J Chem Ecol. 1982;8(1):163–75. [PubMed: 24414592]
• Pickett J.A, Williams I.H, Martin A.P, Smith M.C. Nasonov pheromone of the honey bee Apis mellifera L. (Hymenoptera:Apidae). I. Chemical characterization. J Chem Ecol. 1980;6:425–34.
• Plettner E, Otis G.W, Wimalaratne P.D.C, Winston M.L, Slessor K.N, Pankiw T, Punchihewa P.W.K. Species- and caste-determined mandibular gland signals in honey bees (Apis). J Chem Ecol. 1997;23:363–77.
• Plettner E, Slessor K.N, Winston M.L, Oliver J.E. Caste-selective pheromone biosynthesis in honey bees. Science. 1996;271:1851–53.
• Plettner E, Slessor K.N, Winston M.L, Robinson G.E, Page R.E. Mandibular gland components and ovarian development as measures of caste differentiation in the honey bee (Apis mellifera L.). J Insect Physiol. 1993;39:235–40.
• Plettner E, Sutherland G.R.J, Slessor K.N, Winston M.L. Why not be a queen? Regioselectivity in mandibular secretions of honey bee castes. J Chem Ecol. 1995;21:1017–29. [PubMed: 24234416]
• Ratnieks F.L.W. Reproductive harmony via mutual policing by workers in eusocial Hymenoptera. Am Nat. 1988;132:217–36.
• Ratnieks F.L.W. Egg-laying, egg-removal, and ovary development by workers in queenright honey bee colonies. Behav Ecol Sociobiol. 1993;32:191–98.
• Ratnieks F.L.W. Evidence for a queen-produced egg-marking pheromone and its use in worker policing in the honey bee. J Apic Res. 1995;34:31–37.
• Ratnieks F.L.W, Visscher P.K. Worker policing in honey bees. Nature. 1989;342:796–97.
• Rehder V, Bicker G, Hammer M. Serotonin-immunoreactive neurons in the antennal lobes and suboesophageal ganglion of the honey-bee. Cell Tissue Res. 1987;247:59–96.
• Reinhard J, Claudianos C. Molecular insights into honey bee brain plasticity. In: Galizia C.G, Eisenhardt D, Giurfa M, editors. Honey bee Neurobiology and Behavior. A Tribute to Randolf Menzel. Dordrecht: Springer; 2013. pp. 359–72.
• Renner M, Baumann M. Über Komplexe von subepidermalen Drüsenzellen (Duftdrüsen?) der Bienenkönigin. Naturwissenschaften. 1964;3:68–69.
• Renner M, Vierling G. Die Rolle des Taschendruesenpheromons beim Hochzeitsflug der Bienenkoenigin. (The secretion of the tergite glands and the attractiveness of the queen honey bee to drones in the mating flight). Behav Ecol Sociobiol. 1977;2:329–38.
• Rhodes J.W, Lacey M.J, Harden S. Changes with age in queen honey bee (Apis mellifera) head chemical constituents (Hymenoptera: Apidae). Sociobiology. 2007;50:11–22.
• Richard F.-J, Schal C, Tarpy D.R, Grozinger C.M. Effects of instrumental insemination and insemination quantity on Dufour’s gland chemical profiles and vitellogenin expression in honey bee queens (Apis mellifera). J Chem Ecol. 2011;37:1027–36. [PubMed: 21786084]
• Richard F.-J, Tarpy D.R, Grozinger C.M. Effects of insemination quantity on honey bee queen physiology. PLoS ONE. 2007;2(10):e980. [PMC free article: PMC1989138] [PubMed: 17912357]
• Robertson H.M, Wanner K.W. The chemoreceptor superfamily in the honey bee, Apis mellifera: Expansion of the odorant, but not gustatory, receptor family. Genome Res. 2006;16:1395–403. [PMC free article: PMC1626641] [PubMed: 17065611]
• Robinson G.E. Hormonal regulation of age polyethism in the honey bee, Apis mellifera. In: Menzel R, Mercer A, editors. Neurobiology and Behaviour of Honey bees. Berlin: Springer-Verlag; 1987a. pp. 266–79.
• Robinson G.E. Modulation of alarm pheromone perception in the honey bee: Evidence for division of labor based on hormonally regulated response thresholds. J Comp Physiol A. 1987b;160:613–19.
• Robinson G.E. Regulation of division of labor in insect societies. A Rev Entomol. 1992;37:637–65. [PubMed: 1539941]
• Robinson G.E, Huang Z.-Y. Colony integration in honey bees: Genetic, endocrine and social control of division of labor. Apidologie. 1998;29:159–70.
• Robinson G.E, Page R.E. Genetic determination of guarding and undertaking in honey bee colonies. Nature. 1988;333:356–58.
• Robinson G.E, Page R.E. Genetic determination of nectar foraging, pollen foraging and nestsite scouting in honey bee colonies. Behav Ecol Sociobiol. 1989;24:317–23.
• Robinson G.E, Vargo E.L. Juvenile hormone in adult eusocial Hymenoptera: Gonadotropin and behavioral pacemaker. Arch Insect Biochem Physiol. 1997;35:559–83. [PubMed: 9210289]
• Robinson G.E, Grozinger C.M, Whitfield C.W. Sociogenomics: social life in molecular terms. Nat Rev Genet. 2005;6(4):257–70. [PubMed: 15761469]
• Robinson G.E, Page R.E, Strambi C, Strambi A. Colony integration in honey bee: Mechanism of behavioural reverse. Ethology. 1992b;90(4):336–48.
• Robinson G.E, Strambi C, Strambi A, Feldlaufer M.F. Comparison of juvenile hormone and ecdysteroid haemolymph titres in adult worker and queen honey bees (Apis mellifera). J Insect Physiol. 1991;37(12):929–35.
• Robinson G.E, Strambi C, Strambi A, Huang Z.-Y. Reproduction in worker honey bees is associated with low juvenile hormone titers and rates of biosynthesis. Gen Comp Endocr. 1992a;87:471–80. [PubMed: 1426950]
• Sachse S, Galizia C.G. The coding of odour-intensity in the honey bee antennal lobe: Local computation optimizes odour representation. Eur J Neurosci. 2003;18:2119–32. [PubMed: 14622173]
• Sachse S, Rappert A, Galizia C.G. The spatial representation of chemical structures in the AL of honey bees: Steps towards the olfactory code. Eur J Neurosci. 1999;11:3970–82. [PubMed: 10583486]
• Sagili R.R, Pankiw T. Effects of brood pheromone modulated brood rearing behaviors on honey bee (Apis mellifera L.) colony growth. J Insect Behav. 2009;22:339–49. [PMC free article: PMC2705719] [PubMed: 19587803]
• Sagili R.R, Pankiw T, Metz B.N. Division of labor associated with brood rearing in the honey bee: How does it translate to colony fitness? PLoS ONE. 2011;6(2):e16785. [PMC free article: PMC3035648] [PubMed: 21347428]
• Sakagami S.F. The false queen: fourth adjustive response in dequeened colonies. Behaviour. 1958;8:280–96.
• Sakamoto H.C, Soares A.E.E, Lopes J.N.C. Relationship between 2-heptanone and some biological and environmental variables in Apis mellifera L. J Apicult Res. 1990a;29(4):194–98.
• Sakamoto H.C, Soares A.E.E, Lopes J.N.C. A comparison of 2-heptanone production in Africanised and European strains of the honey bee, Apis mellifera L. J Apicult Res. 1990b;29(4):199–205.
• Sandoz J.-C. Odour-evoked responses to queen pheromone components and to plant odours using optical imaging in the antennal lobe of the honey bee drone Apis mellifera L. J Exp Biol. 2006;209:3587–98. [PubMed: 16943499]
• Sandoz J.-C. Behavioral and neurophysiological study of olfactory perception and learning in honey bees. Front Syst Neurosci. 2011;5:98. [PMC free article: PMC3233682] [PubMed: 22163215]
• Sandoz J.-C. Olfaction in honey bees: From molecules to behavior. In: Galizia C.G, Eisenhardt D, Giurfa M, editors. Honey bee Neurobiology and Behavior. A Tribute to Randolf Menzel. Dordrecht: Springer; 2013. pp. 235–52.
• Sandoz J.-C, Deisig N, de Brito Sanchez M.G, Giurfa M. Understanding the logics of pheromone processing in the honey bee brain: From labeled-lines to across-fiber patterns. Front Behav Neurosci. 2007;1:5. [PMC free article: PMC2525855] [PubMed: 18958187]
• Sandoz J.-C, Galizia C.G, Menzel R. Side-specific olfactory conditioning leads to more specific odor representation between sides but not within sides in the honey bee antennal lobes. Neuroscience. 2003;120:1137–48. [PubMed: 12927218]
• Sandoz J.-C, Pham-Delègue M.H, Renou M, Wadhams L.J. Asymmetrical generalisation between pheromonal and floral odours in appetitive olfactory conditioning of the honey bee (Apis mellifera L.). J Comp Physiol A. 2001;187:559–68. [PubMed: 11730303]
• Sasaki K, Nagao T. Distribution and levels of dopamine and its metabolites in brains of reproductive workers in honey bees. J Insect Physiol. 2001;47:1205–16. [PubMed: 12770199]
• Schaefer S, Rehder V. Dopamine-like immunoreactivity in the brain and suboesophageal ganglion of the honey bee. J Comp Neurol. 1989;280:43–58. [PubMed: 2918095]
• Schmidt J.O. Attraction of reproductive honey bee swarms to artificial nests by Nasonov pheromone. J Chem Ecol. 1994;20:1053–56. [PubMed: 24242302]
• Schmidt J.O. Attractant or pheromone: The case of Nasonov secretion and honey bee swarms. J Chem Ecol. 1999;25:2051–56.
• Schröter U, Malun D, Menzel R. Innervation pattern of suboesophageal ventral unpaired median neurones in the honey bee brain. Cell Tissue Res. 2006;327:647–67. [PubMed: 17093927]
• Schuermann F.W, Klemm N. Serotonin-immunoreactive neurons in the brain of the honey bee. J Comp Neurol. 1984;225:570–80. [PubMed: 6376546]
• Schuermann F.W, Elekes K, Geffard M. Dopamine-like immunoreactivity in the bee brain. Cell Tissue Res. 1989;256:399–410.
• Schulz D.J, Robinson G.E. Biogenic amines and division of labor in honey bee colonies: Behaviorally related changes in the antennal lobes and age related changes in the mushroom bodies. J Comp Physiol A. 1999;184:481–88. [PubMed: 10377981]
• Schulz D.J, Robinson G.E. Octopamine influences division of labor in honey bee colonies. J Comp Physiol A. 2001;187:53–61. [PubMed: 11318378]
• Schulz D.J, Barron A.B, Robinson G.E. A role for octopamine in honey bee division of labor. Brain Behav Evolut. 2002a;60:350–59. [PubMed: 12563167]
• Schulz D.J, Sullivan J.P, Robinson G.E. Juvenile hormone and octopamine in the regulation of division of labour in honey bee colonies. Horm Behav. 2002b;42:222–31. [PubMed: 12367575]
• Seehuus S.C, Norberg K, Gimsa U, Krekling T, Amdam G.V. Reproductive protein protects sterile honey bee workers from oxidative stress. Proc Natl Acad Sci U S A. 2006;103:962–67. [PMC free article: PMC1347965] [PubMed: 16418279]
• Seeley T. Honey bee Democracy. Princeton, NJ: Princeton University Press; 2010.
• Shearer D.A, Boch R. 2-Heptanone in the mandibular gland secretion of the honey bee. Nature. 1965;206:530.
• Simon U.E, Moritz R.F, Crewe R.M. The ontogenetic pattern of mandibular gland components in queenless worker bees (Apis mellifera capensis Esch.). J Insect Physiol. 2001;47(7):735–38. [PubMed: 11356420]
• Slessor K.N, Kaminski L.A, King G.G.S, Borden J.H, Winston M.L. Semiochemical basis for retinue response to queen honey bees. Nature. 1988;332:354–56.
• Slessor K.N, Kaminski L.A, King G.G.S, Winston M.L. Semiochemicals of the honey bee queen mandibular glands. J Chem Ecol. 1990;16:851–60. [PubMed: 24263600]
• Slessor K.N, Winston M.L, Le Conte Y. Pheromone communication in the honey bee (Apis mellifera L.). J Chem Ecol. 2005;31(11):2731–45. [PubMed: 16273438]
• Smedal B, Brynem M, Kreibich C.D, Amdam G.V. Brood pheromone suppresses physiology of extreme longevity in honey bees (Apis mellifera). J Exp Biol. 2009;212:3795–801. [PubMed: 19915120]
• Smith R.K, Spivak M, Taylor O.R Jr, Bennett C, Smith M.L. Maturation of tergal gland alkene profiles in European honey bee queens, Apis mellifera L. J Chem Ecol. 1993;19:133–42. [PubMed: 24248518]
• Sole C.L, Kryger P, Hefetz A, Katzav-Gozansky T, Crewe R.M. Mimicry of queen Dufour’s gland secretions by workers of Apis mellifera scutellata and A. m. capensis. Naturwissenschaften. 2002;89:561–64. [PubMed: 12536278]
• Southwick E.E, Moritz R.F.A. Metabolic response to alarm pheromone in honey bees. J Insect Physiol. 1985;31:389–92.
• Strausfeld N.J. Organization of the honey bee mushroom body: Representation of the calyx within the vertical and gamma lobes. J Comp Neurol. 2002;450:4–33. [PubMed: 12124764]
• Strauss K, Scharpenberg H, Crewe R.M, Glahn F, Foth H, Moritz R.F.A. The role of the queen mandibular gland pheromone in honey bees (Apis mellifera): Honest signal or suppressive agent? Behav Ecol Sociobiol. 2008;62:1523–31.
• Sullivan J.P, Fahrbach S.E, Harrison J.F, Capaldi E.A, Fewell J.H, Robinson G.E. Juvenile hormone and division of labor in honey bee colonies: Effects of allatectomy on flight behavior and metabolism. J Exp Biol. 2003;206:2287–96. [PubMed: 12771177]
• Tan K, Yang M, Wang Z, Radloff S.E, Pirk C.W.W. The pheromones of laying workers in two honey bee sister species: Apis cerana and Apis mellifera. J Comp Physiol A. 2012;198:319–23. [PubMed: 22252612]
• Taylor D.J, Robinson G.E, Logan B.J, Laverty R, Mercer A.R. Changes in brain amine levels associated with the morphological and behavioural development of the worker honey bee. J Comp Physiol A. 1992;170:715–21. [PubMed: 1432851]
• Thom C, Gilley D.C, Hooper J, Esch H.E. The scent of the waggle dance. PLoS Biol. 2012;5(9):e228. [PMC free article: PMC1994260] [PubMed: 17713987]
• Toth A.L, Robinson G.E. Worker nutrition and division of labour in honey bees. Anim Behav. 2005;69(2):427–35.
• Toth A.L, Kantarovich S, Meisel A.F, Robinson G.E. Nutritional status influences socially regulated foraging ontogeny in honey bees. J Exp Biol. 2005;208:4641–49. [PubMed: 16326945]
• Trhlin M, Rajchard J. Chemical communication in the honey bee (Apis mellifera L.): A review. Vet Med-Czech. 2011;56(6):265–73.
• Tsuruda J.M, Page R.E. The effects of young brood on the foraging behavior of two strains of honey bees (Apis mellifera). Behav Ecol Sociobiol. 2009;64:161–67. [PMC free article: PMC2779344] [PubMed: 19946650]
• Urlacher E, Francés B, Giurfa M, Devaud J.M. An alarm pheromone modulates appetitive olfactory learning in the honey bee (Apis mellifera). Front Behav Neurosci. 2010;4:157. [PMC free article: PMC2936933] [PubMed: 20838475]
• Vallet A, Cassier P, Lensky Y. Ontogeny of the fine structure of the mandibular glands of the honey bee (Apis mellifera L.) workers and the pheromonal activity of 2-heptanone. J Insect Physiol. 1991;37:789–804.
• Velthuis H.H.W. Queen substances from the abdomen of the honey bee queen. Z Vergl Physiol. 1970;70:210–22.
• Velthuis H.H.W. The honey bee queen and the social organization of her colony. In: Hölldobler B, Lindauer M, editors. Experimental Behavioural Ecology and Sociobiology: In Memoriam Karl von Frisch. Stuttgart, Germany: Gustav Fischer Verlag; 1985. pp. 1886–1982.pp. 343–57.
• Velthuis H.H.W, Ruttner F, Crewe R.M. Differentiation in reproductive physiology and behaviour during the development of laying worker honey bees. In: Engels W, editor. Social Insects. Berlin: Springer-Verlag; 1990. pp. 231–43.
• Vergoz V, McQuillan H.J, Geddes L.H, Pullar K, Nicholson B.J, Paulin M.G, Mercer A.R. Peripheral modulation of worker bee responses to queen mandibular pheromone. Proc Natl Acad Sci U S A. 2009;106:20930–35. [PMC free article: PMC2791564] [PubMed: 19934051]
• Vergoz V, Roussel E, Sandoz J.-C, Giurfa M. Aversive learning in honey bees revealed by the olfactory conditioning of the sting extension reflex. PLoS ONE. 2007a;2:e288. [PMC free article: PMC1810431] [PubMed: 17372627]
• Vergoz V, Schreurs H.A, Mercer A.R. Queen pheromone blocks aversive learning in young worker bees. Science. 2007b;317:384–86. [PubMed: 17641204]
• Wagener-Hulme C, Schulz D.J, Kuehn J.C, Robinson G.E. Biogenic amines and division of labor in honey bee colonies. J Comp Physiol A. 1999;184:471–79. [PubMed: 10377980]
• Wager B.R, Breed M.D. Does honey bee sting alarm pheromone give orientation information to defensive bees? Ann Entomol Soc Am. 2000;93:1329–32.
• Wakonig G, Eveleigh L, Arnoldj G, Crailsheim K. Cuticular hydrocarbon profiles reveal age-related changes in honey bee drones (Apis mellifera carnica). J Apicult Res. 2000;39(3–4):137–41.
• Wang S, Sato K, Giurfa M, Zhang S. Processing of sting pheromone and its components in the antennal lobe of the worker honey bee. J Insect Physiol. 2008;54:833–41. [PubMed: 18455180]
• Wanner K.W, Nichols A.S, Walden K.K, Brockmann A, Luetje C.W, Robertson H.M. A honey bee odorant receptor for the queen substance 9-oxo-2-decenoic acid. Proc Natl Acad Sci U S A. 2007;104:14383–88. [PMC free article: PMC1964862] [PubMed: 17761794]
• Whitfield C.W, Ben-Shahar Y, Brillet C, Leoncini I, Crauser D, Le Conte Y, Rodrigues-Zas S, Robinson G.E. Genomic dissection of behavioral maturation in the honey bee. Proc Natl Acad Sci U S A. 2006;103:16068–75. [PMC free article: PMC1622924] [PubMed: 17065327]
• Whitfield C.W, Cziko A.M, Robinson G.E. Gene expression profiles in the brain predict behavior in individual honey bees. Science. 2003;302:296–99. [PubMed: 14551438]
• Williams I.H, Martin A.P, Pickett J.A. The Nasonov pheromone of the honey bee Apis mellifera L. (Hymenoptera, Apidae). II. Bioassay of the components using foragers. J Chem Ecol. 1981;7(2):225–37. [PubMed: 24420468]
• Willis L.G, Winston M.L, Slessor K.N. Queen honey bee mandibular pheromone does not affect worker ovary development. Can Entomol. 1990;122:1093–99.
• Winston M.L. The Biology of the Honey Bee. Cambridge, MA: Harvard University Press; 1987.
• Winston M.L. Semiochemicals and insect sociality. In: Roitberg B.D, Isman M.B, editors. Insect Chemical Ecology: An Evolutionary Approach. New York: Routledge, Chapman & Hall; 1992. pp. 315–33.
• Winston M.L, Slessor K.N. Honey bee primer pheromones and colony organization: Gaps in our knowledge. Apidologie. 1998;29:81–95.
• Winston M.L, Slessor K.N, Willis L.G, Naumann K, Higo H.A, Wyborn M.H, Kaminski L.-A. The influence of queen mandibular pheromones on worker attraction to swarm clusters and inhibition of queen rearing in the honey bee (Apis mellifera L.). Insect Soc. 1989;36:15–27.
• Wossler T.C, Crewe R.M. Mass spectral identification of the tergal gland secretions of female castes of two African honey bee races (Apis mellifera). J Apicult Res. 1999a;38(3–4):137–48.
• Wossler T.C, Crewe R.M. The releaser effects of the tergal gland secretion of queens honey bees (Apis mellifera L.). J Insect Behav. 1999b;12(3):343–51.
• Wossler T.C, Crewe R.M. Honey bee queen tergal gland secretion affects ovarian development in caged workers. Apidologie. 1999c;30:311–20.