Correlation of Royal Jelly composition with swarming tendency in Honey Bees (Apis mellifera): A Review

Honey bees are eusocial insects which respond to warm weather, abundant food source by increasing their population through swarming to ensure the survival of the colony. To maintain a superior colony a queen must have a nutrient-rich diet and high egg production. Royal jelly is a high-quality food which has numerous beneficial properties required for proper growth, development, survival of the queen. Factors like congestion, lack of adequate queen pheromone, abnormal queen pheromone, pathogenic infections, exposure to pesticides influence the queen quality which further promotes non-reproductive swarming behaviour. Worker bees analyse the queen condition to prepare for supersedure or emergency queen rearing. This review paper highlights the influence of royal jelly composition on the queen quality, the impact of queen quality on swarming tendency, correlation between royal jelly composition and swarming tendency.

The Behavioral Toxicity of Insect Growth Disruptors on Apis mellifera Queen Care

As social insects, honey bees (Apis mellifera) rely on the coordinated performance of various behaviors to ensure that the needs of the colony are met. One of the most critical of these behaviors is the feeding and care of egg laying honey bee queens by non-fecund female worker attendants. These behaviors are crucial to honey bee reproduction and are known to be elicited by the queen’s pheromone blend. The degree to which workers respond to this blend can vary depending on their physiological status, but little is known regarding the impacts of developmental exposure to agrochemicals on this behavior. This work investigated how exposing workers during larval development to chronic sublethal doses of insect growth disruptors affected their development time, weight, longevity, and queen pheromone responsiveness as adult worker honey bees. Exposure to the juvenile hormone analog pyriproxyfen consistently shortened the duration of pupation, and pyriproxyfen and diflubenzuron inconsistently reduced the survivorship of adult bees. Finally, pyriproxyfen and methoxyfenozide treated bees were found to be less responsive to queen pheromone relative to other treatment groups. Here, we describe these results and discuss their possible physiological underpinnings as well as their potential impacts on honey bee reproduction and colony performance.

Bumble bee queen pheromones are context-dependent

Queen pheromones have long been studied as a major factor regulating reproductive division of labor in social insects. Hitherto, only a handful of queen pheromones were identified and their effects on workers have mostly been studied in isolation from the social context in which they operate. Our study examined the importance of behavioral and social context for the perception of queen semiochemicals by bumble bee workers. Our results indicate that a mature queen’s cuticular semiochemicals are capable of inhibiting worker reproduction only when accompanied by the queen’s visual presence and the offspring she produces, thus, when presented in realistic context. Queen’s chemistry, queen’s visual presence and presence of offspring all act to regulate worker reproduction, but none of these elements produces an inhibitory effect on its own. Our findings highlight the necessity to reconsider what constitutes a queen pheromone and suggest a new approach to the study of chemical ecology in social insects.

Bumble bee queen pheromones are context-dependent

Queen pheromones have long been studied as a major factor regulating reproductive division of labor in social insects. Hitherto, only a handful of queen pheromones were identified and their effects on workers have mostly been studied in isolation from the social context in which they operate. Our study examined the importance of behavioral and social context for the perception of queen semiochemicals by bumble bee workers. Our results indicate that a mature queen’s semiochemicals are capable of inhibiting worker reproduction only when accompanied by the queen’s visual presence and the offspring she produces, thus, when presented in realistic context. Queen’s chemistry, queen’s visual presence and presence of offspring all act in synergy to regulate worker reproduction, but none of these elements produces an inhibitory effect on its own. Our findings highlight the necessity to reconsider what constitutes a queen pheromone and suggest a new approach to the study of chemical ecology in social insects.

Hormonal modulation of reproduction and fertility signaling in polistine wasps

In social insects, it has been suggested that reproduction and the production of particular fertility-linked cuticular hydrocarbons (CHC) may be under shared juvenile hormone (JH) control, and this could have been key in predisposing such cues to later evolve into full-fledged queen pheromone signals. However, to date, only few studies have experimentally tested this “hormonal pleiotropy” hypothesis. Here, we formally test this hypothesis using data from four species of Polistine wasps, Polistes dominula, Polistes satan, Mischocyttarus metathoracicus, and Mischocyttarus cassununga, and experimental treatments with JH using the JH analogue methoprene and the anti-JH precocene. In line with reproduction being under JH control, our results show that across these four species, precocene significantly decreased ovary development when compared with both the acetone solvent-only control and the methoprene treatment. Consistent with the hormonal pleiotropy hypothesis, these effects on reproduction were further matched by subtle shifts in the CHC profiles, with univariate analyses showing that in P. dominula and P. satan the abundance of particular linear alkanes and mono-methylated alkanes were affected by ovary development and our hormonal treatments. The results indicate that in primitively eusocial wasps, and particularly in Polistes, reproduction and the production of some CHC cues are under joint JH control. We suggest that pleiotropic links between reproduction and the production of such hydrocarbon cues have been key enablers for the origin of true fertility and queen signals in more derived, advanced eusocial insects.

Regulation of dietary intake of protein and lipid by nurse-age adult worker honeybees

Essential macronutrients are critical to the fitness and survival of animals. Many studies have shown that animals regulate the amount of protein and carbohydrate they eat for optimal performance. Regulation of dietary fat is important but less often studied. Honeybees collect and consume floral pollen to obtain protein and fat but how they achieve the optimal balance of these two macronutrients is presently unknown. Here, using chemically defined diets composed of essential amino acids and lipids (lecithin), we show that adult worker honeybees actively regulate their intake of lipids around optimal values relative to protein in diet. We found that broodless, nurse-age worker honeybees consume foods to achieve a ratio between 1:2 and 1:3 (essential amino acids:lipid) or ∼1.25:1 protein:fat. Bees fed diets relatively high in fat gained abdominal fat and had enlarged hypopharyngeal glands. In most cases, eating diets high in fat did not result in increased mortality. Importantly, we also discovered that the total quantity of food the bees ate increased when they were given a choice of two diets relatively high in fat, implying that dietary fat influences bee nutritional state in a way that in turn, influences behaviour. We speculate that dietary fat plays a critical role in maintaining workers in the nurse-like behavioural state independently of the influence of queen pheromone.

Queen pheromone modulates the expression of epigenetic modifier genes in the brain of honeybee workers

Pheromones are used by many insects to mediate social interactions. In the highly eusocial honeybee ( Apis mellifera ), queen mandibular pheromone (QMP) is involved in the regulation of the reproductive and other behaviour of workers. The molecular mechanisms by which QMP acts are largely unknown. Here, we investigate how genes responsible for epigenetic modifications to DNA, RNA and histones respond to the presence of QMP in the environment. We show that several of these genes are upregulated in the honeybee brain when workers are exposed to artificial QMP. We propose that pheromonal communication systems, such as those used by social insects, evolved to respond to environmental signals by making use of existing epigenomic machineries.

Identification of a queen pheromone mediating the rearing of adult sexuals in the pharaoh ant Monomorium pharaonis

The division of labour between reproductive queens and mostly sterile workers is among the defining characteristics of social insects. Queen-produced chemical signals advertising her presence and fertility status, i.e. queen pheromones, are normally used to assert the queen's reproductive dominance in the colony. Most queen pheromones identified to date are chemicals that stop the daughter workers from reproducing. Nevertheless, it has long been suggested that queen pheromones could also regulate reproduction in different ways. In some multiple-queen ants with obligately sterile workers, for example—such as fire ants and pharaoh ants—queen pheromones are thought to regulate reproduction by inhibiting the rearing of new sexuals. Here, we identify the first such queen pheromone in the pharaoh ant Monomorium pharaonis and demonstrate its mode of action via bioassays with the pure biosynthesized compound. In particular, we show that the monocyclic diterpene neocembrene, which in different Monomorium species is produced solely by fertile, egg-laying queens, strongly inhibits the rearing of new sexuals (queens and males) and also exerts a weakly attractive ‘queen retinue’ effect on the workers. This is the first time that a queen pheromone with such a dual function has been identified in a social insect species with obligately sterile workers.