Clarence Collison
Queen Pheromones
Honey bee queens produce a sophisticated array of chemical signals
Honey bee queens produce a sophisticated array of chemical signals (pheromones) that influence both the behavior and physiology of their nest mates (Beggs et al. 2007). Well known impacts of the queen’s pheromones include formation of the queen’s retinue, inhibiting ovary development in workers, inhibiting the production of queen cells and attraction of drones during her mating flight(s). However, there are several other less known effects associated with the queen’s pheromones.
Queen mandibular pheromone (QMP) is a chemical blend that primes bees to perform several colony-related tasks. Beggs et al. (2007) found that QMP has profound effects on dopamine pathways in the brain, pathways that play a central role in behavioral regulation and motor control. In young worker bees, dopamine levels, levels of dopamine receptor gene expression and cellular responses to this amine are all affected by QMP. They identified homovanilly alcohol (a chemical component of QMP) as a key contributor to these effects and provided evidence linking QMP-induced changes in the brain to changes at a behavioral level.
Small colonies containing 600 workers were trained to collect syrup from counter-feeders in screened flight cages. Foraging activity was recorded for two days while all colonies had caged queens. Some queens were then replaced by porous plastic blocks containing queen extract, synthetic 9-oxodec-trans-2-enoic (9-oxodecenoic) acid, or alcohol. Foraging activity was recorded for three more days. Bees from colonies receiving only alcohol flew fewer trips and carried less syrup than those from colonies that received 9-oxodecenoic acid or that retained their queens. Bees receiving extract visited the feeder about as many times as those with alcohol but carried significantly greater quantities of syrup. Death losses were greatest in colonies that received alcohol and least in those that retained their queen. Field experiments using colonies of about 10,000 workers confirmed the cage results and indicated that pollen foraging is not controlled primarily by queen pheromones as is nectar foraging. In both field and cage experiments, synthetic 9-oxodecenoic acid, at sufficiently high dosage, was an effective substitute for a queen in stimulating nectar foraging (Jaycox 1970).
Higo et al. (1992) investigated the effects of synthetic queen mandibular gland pheromone on colony foraging and brood rearing. Colonies newly established in the Spring showed a significant, dose-dependent increase in the number of foragers gathering pollen, and individual pollen foragers returned to the nest with larger pollen loads. These two effects combined resulted in a doubling of the amount of pollen brought into colonies by foraging bees. Brood rearing also increased, but not significantly. In contrast, large, established colonies showed no effects at their Summer population peak. They concluded that queen mandibular pheromone can significantly affect foraging, but its effects depend on colony conditions and environmental factors.
Synthetic queen mandibular gland pheromone (QMP) was applied to honey bee colonies to test two hypotheses: (i) QMP acts like a primer pheromone in the regulation of age-related division of labor, and (ii) this primer effect, if present, varies in three strains of workers that show genetically-based differences in their retinue attraction response to QMP (a pheromone releaser effect). Strains of workers that were high, or low in their response to QMP in a laboratory bioassay, as well as unselected ‘wild-type’ workers, were fostered in queenright colonies with or without supplemental QMP. Effects of QMP on foraging ontogeny and juvenile hormone III (JH) blood titers in worker honey bees were measured. Bees in QMP-supplemented colonies showed significant delays in foraging ontogeny, and foraging activity was reduced. They also had significantly lower JH titers, although the titer curves were somewhat atypical. There were no differences in foraging ontogeny or JH titers among the three strains. It was concluded that (i) QMP can delay the ontogeny of foraging by some mechanism that suppresses JH production, (ii) this QMP primer response is independent of the retinue releaser response, and (iii) QMP can play an important role in regulating division of labor (Pankiw et al. 1998).
Honey bee workers develop from fertilized eggs, but those reared in a queenless colony develop into ‘rebel’ workers, which are more queen-like than typical workers. Rebels develop after an old queen leaves with a swarm and before a new queen hatches. It was hypothesized that larval food lacking queen mandibular pheromones trigger the rebel phenotype. Larvae reared under queenright or queenless conditions were additionally fed with water or a drop of macerated queen mandibular glands. After following development of the bees and subjecting them to dissection, they found that those reared with a queen or fed the macerated glands under queenless conditions developed into typical workers. Only those workers reared without a queen and without macerated glands added to their food developed into rebels; these rebels had more ovarioles, smaller hypopharyngeal glands, and larger mandibular and Dufour’s glands than did typical workers. This is the first evidence that larval perception of the presence or absence of queen pheromones causes an alternative development strategy (Woyciechowski et al. 2017).
Honey bee queen attendants disperse queen pheromones to supplement pheromone dispersal by direct queen-worker contacts. With time they lose their dispersal function exponentially due mainly to volatilization of queen pheromones carried on their bodies. The elimination of those airborne pheromones together with the air while ventilating the hive is balanced by pheromone release by the queen. This equilibrium results in a certain level of queen pheromones in the broodnest. The change of the pheromone level (for example, due to loss of the colony of its queen) can serve as a signal to alter the behavior of the workers and the state of the colony (Juška et al. 1981).
Worker-laid and queen-laid male eggs were transferred into combs of empty drone cells in four honey bee (Apis mellifera ligustica) colonies. Worker-laid eggs treated with an ethanol extract of queen Dufour’s gland were removed by workers (worker policing) at a significantly lower rate than either untreated or ethanol-treated worker-laid eggs, but this effect was less when 1:10 dilution was used and it disappeared at a 1:100 dilution. Worker-laid eggs that had been touched to an area of a queen at the base of the sting and between the sting sheaths (‘sting-wipe’ treatment) were also removed at a significantly lower rate than untreated worker-laid control eggs. In all trials, the removal rate of worker-laid eggs exceeded that of queen-laid eggs. Queen-laid eggs treated with the polar solvents methanol and ethanol were removed more rapidly than those treated with the less-polar hexane and methylene chloride, but it was not possible to determine if this was because methanol and ethanol were more effective at removing a possible pheromone or because they caused more damage to the eggs. The results support a hypothesis that recognition of worker-laid eggs during worker policing is via a queen-produced egg-marking pheromone (Ratnieks 1995).
The influence of the queen and her pheromonal signal on comb construction was examined. Four treatments were tested with newly hived packages of bees containing: 1) a mated queen, 2) a virgin queen, 3) no queen but with a dispenser containing synthetic queen mandibular pheromone (QMP), and 4) no queen and no pheromone. After 10 days, the comb produced by each colony was removed, comb measurements made, bees from the comb-building area collected, the size of the scales on the wax mirrors of the collected bees ranked on a scale of zero to four and the queens removed and analyzed for QMP components. Queenless workers built substantially less comb and the comb they did build had significantly larger, drone-sized cells than for the other three treatments, indicating that both cell size and the quantity of comb built are mediated through the queen, particularly QMP. The observations of wax scale size suggested that QMP influenced comb building behavior rather than wax scale production. These results support the idea that queenless honey bees can adopt a strategy of constructing drone-sized cells in order to increase reproductive fitness through male production following queen loss (Ledoux et al. 2001).
Queen pheromones ensure that the queen successfully accompanies swarming workers to their new nest site. The area spanned by a migrating swarm of bees is vast: flying swarms of 11,000 bees can occupy a space that is eight to 12 meters long, six to eight meters wide, and three to four meters high (Beekman et al. 2006). The presence of a queen in an airborne swarm improves the moving swarm’s cohesion—swarm clusters that liftoff without a queen are much more dispersed, spanning a diameter of up to 60 meters (Morse 1963). Furthermore, if the queen is prevented from accompanying the flying workers, workers will return to the last place that they clustered with her (Avitabile et al. 1975) or move to her new location if she is placed nearby (Simpson 1963; Morse 1963), thereby ensuring that the queen remains with the swarm to establish the new nest. Some components of queen pheromone play a clear role in informing swarms of the presence of their queen. When queens are prevented from lifting off with swarms but some workers are marked with 9-ODA, workers will relocate to their new nest site without returning for their abandoned queens (Avitabile et al. 1975). Swarms will also cluster stably around a lure impregnated with 9-ODA and/or 9-HDA (Butler et al. 1964; Butler and Simpson 1967; Winston et al. 1982). However, while 9- ODA, 9-HDA, and QMP are attractive to workers from queenless swarms, whole-queen extracts or live queens are significantly more attractive (Boch et al. 1975; Winston et al. 1989). Thus, additional queen-produced compounds may be involved in swarm cohesion, attraction and migration (Grozinger et al. 2014).
Bahreini and Currie (2015) studied the effects of honey bees with different grooming ability and queen pheromone status on mortality rates of Varroa mites, mite damage, and mortality rates of honey bees. Twenty-four small queenless colonies containing either stock selected for high rates of mite removal (n = 12) or unselected stock (n = 12) were maintained under constant darkness at 5°C (41° F.) Colonies were randomly assigned to be treated with one of three queen pheromone status treatments: (1) caged, mated queen, (2) a synthetic queen mandibular pheromone lure (QMP), (3) queenless with no queen substitute. The results showed overall mite mortality rate was greater in stock selected for grooming than in unselected stock. There was a short-term transitory increase in bee mortality rates in selected stock when compared to unselected stock. The presence of queen pheromone from either caged, mated queens or QMP enhanced mite removal from clusters of bees relative to queenless colonies over short periods of time and increased the variation in mite mortality over time relative to colonies without queen pheromone, but did not affect the proportion of damaged mites. The effects of source of bees on mite damage varied with time but damage to mites was not reliably related to mite mortality.
References
Avitabile, A., R.A. Morse and R. Boch 1975. Swarming honey bees guided by pheromones. Ann. Entomol. Soc. Amer. 68: 1079-1082.
Bahreini, R. and R.W. Currie 2015. The effect of queen pheromone status on Varroa mite removal from honey bee colonies with different grooming ability. Exp. Appl. Acarol. 66: 383-397.
Beekman, M., R.L. Fathke and T.D. Seeley 2006. How does an informed minority of scouts guide a honeybee swarm as it flies to a new home? Anim. Behav. 71: 161-171.
Beggs, K.T., K.A. Glendining, N.M. Marechal, V. Vergoz, I. Nakamura, K.N. Slessor, and A.R. Mercer 2007. Queen pheromone modulates brain dopamine function in worker honey bees. Proc. Natl. Acad. Sci. USA 104: 2460-2464.
Boch, R., D.A. Shearer and J.C. Young 1975. Honey bee pheromones: field tests of natural and artificial queen substance. J. Chem. Ecol. 1: 133-148.
Butler, C.G. and J. Simpson 1967. Pheromones of the queen honeybee (Apis mellifera L.) which enable her workers to follow her when swarming. Proc. R. Entomol. Soc. A 42: 149-154.
Butler, C.G., R.K. Callow and J.R. Chapman 1964. 9-hydroxydec-trans-2-enoic acid, a pheromone stabilizing honeybee swarms. Nature 201: 733.
Grozinger, C., J. Richards and H. Mattila 2014. From molecules to societies: mechanisms regulating swarming behavior in honey bees (Apis spp.). Apidologie 45: 327-346.
Higo, H.A., S.J. Colley, M.L. Winston and K.N. Slessor 1992. Effects of honey bee (Apis mellifera L.) queen mandibular gland pheromone on foraging and brood rearing. Can. Entomol. 124: 409-418.
Jaycox, E.R. 1970. Honey bee queen pheromones and worker foraging behavior. Ann. Entomol. Soc. Amer. 63: 222-228.
Juška, A., T.D. Seeley, and H.H.W. Velthuis 1981. How honeybee queen attendants become ordinary workers. J. Insect Physiol. 27: 515-519.
Ledoux, M.N., M.L. Winston, H. Higo, C.I. Keeling, K.N. Slessor and Y. Le Conte 2001. Queen and pheromonal factors influencing comb construction by simulated honey bee (Apis mellifera L.) swarms. Insectes Soc. 48: 14-20.
Morse, R.A. 1963. Swarm orientation in honeybees. Science 141: 357-358.
Pankiw, T., Z.-Y. Huang, M.L. Winston and G.E. Robinson 1998. Queen mandibular gland pheromone influences worker honey bee (Apis mellifera L.) foraging ontogeny and juvenile hormone titers. J. Insect Physiol. 44: 685-692.
Ratnieks, F.L.W. 1995. Evidence for a queen-produced egg-marking pheromone and its use in worker policing in the honey bee. J. Apic. Res. 34:31-37.
Simpson, J. 1963. Queen perception by honeybee swarms. Nature 199: 94-95.
Winston, M.L., K.N. Slessor, M.J. Smirle and A.A. Kandil 1982. The influence of a queen-produced substance, 9HDA, on swarm clustering behavior in the honeybee Apis mellifera L., J. Chem. Ecol. 8: 1283-1288.
Winston, M.L., K.N. Slessor, L.G. Willis, K. Naumann, H.A. Higo, M.H. Wyborn and L.A. Kaminski 1989. The influence of queen mandibular pheromones on worker attraction to swarm clusters and inhibition of queen rearing in the honey bee (Apis mellifera L.). Insectes Soc. 36: 15-27.
Woyciechowski, M., K. Kuszewska, J. Pitorak and J. Kierat 2017. Honeybee worker larvae perceive queen pheromones in their food. Apidologie 48: 144-149.
Clarence Collison is an Emeritus Professor of Entomology and Department Head Emeritus of Entomology and Plant Pathology at Mississippi State University, Mississippi State, MS.
