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With the development of artificial intelligence, numerous researchers are attracted to study new heuristic algorithms and improve traditional algorithms. Artificial bee colony (ABC) algorithm is a swarm intelligence optimization algorithm inspired by the foraging behavior of honeybees, which is one of the most widely applied methods to solve optimization problems. However, the traditional ABC has some shortcomings such as under-exploitation and slow convergence, etc. In this study, a novel variant of ABC named chaotic and neighborhood search-based ABC algorithm (CNSABC) is proposed. The CNSABC contains three improved mechanisms, including Bernoulli chaotic mapping with mutual exclusion mechanism, neighborhood search mechanism with compression factor, and sustained bees. In detail, Bernoulli chaotic mapping with mutual exclusion mechanism is introduced to enhance the diversity and the exploration ability. To enhance the convergence efficiency and exploitation capability of the algorithm, the neighborhood search mechanism with compression factor and sustained bees are presented. Subsequently, a series of experiments are conducted to verify the effectiveness of the three presented mechanisms and the superiority of the proposed CNSABC, the results demonstrate that the proposed CNSABC has better convergence efficiency and search ability. Finally, the CNSABC is applied to solve two engineering optimization problems, experimental results show that CNSABC can produce satisfactory solutions. [ABSTRACT FROM AUTHOR]

Honeybees are highly social insects with a rich behavioral repertoire and are a versatile model for neurobiological research. Their gut microbiota comprises a limited number of host-restricted bacterial phylotypes that are important for honeybee health. However, it remains unclear how specific gut members affect honeybee behaviors. Here, we find that antibiotic exposure disturbs the gut community and influences honeybee phenotypes under field conditions. Using laboratory-generated gnotobiotic bees, we show that a normal gut microbiota is required for olfactory learning and memory abilities. Brain transcriptomic profiling reveals distinct brain gene expression patterns between microbiota-free and conventional bees. Subsequent metabolomic analyses of both hemolymph and gut samples show that the microbiota mainly regulates tryptophan metabolism. Our results indicate that host-specific Lactobacillus strains promote memory behavior by transforming tryptophan to indole derivatives that activate the host aryl hydrocarbon receptor. Our findings highlight the contributions of specific gut members to honeybee neurological processes, thus providing a promising model to understand host-microbe interactions. Eusocial honeybee is a versatile model for neurobiological research. Here, the authors established a link between honeybee gut Lactobacillus in bee learning and memory ability via indole derivatives that activate host's aryl hydrocarbon receptor. [ABSTRACT FROM AUTHOR]

The artificial bee colony (ABC) is a population-based optimization algorithm that mimics the foraging behavior of honeybees. Here, we focus on the parameter setting that ensures the ABC algorithm stability. Therefore, this paper introduces a matrix-iterative model, taking into account the coupling within bees. Moreover, the model considered the difference between update modes, i.e., synchronous or sequential. The necessary conditions for absolute stability were derived under the quasi-deterministic assumption. We further investigated the criteria for first and second-order stochastic stability. These criteria report on the ranges for setting the uniform distributions of the ABC algorithm. Finally, some supporting simulations were carried out on CEC 2017 benchmark functions in different search space dimensions (10, 30, and 50) and on twenty real-world problems (CEC 2011). Six considered ABC variants tested the derived and state-of-the-art criteria in different update modes. Moreover, ABC algorithms were compared with some state-of-the-art metaheuristics (Particle Swarm Optimization, Gravitational Search Algorithm, and Grey Wolf Optimizer). The overall results show that stochastic stability proffers ABC competitiveness. The two update modes may alter the ABC performance only slightly or drastically, depending on the problem, with no evidence on the supremacy of one of them. [ABSTRACT FROM AUTHOR]

The bounded diameter minimum spanning tree (BD-MST) problem seeks a spanning tree (T) of minimum weight on a given connected, undirected and edge-weighted graph subject to the diameter of T does not exceed D ≥ 2 , where D is a given positive integer. The BD-MST problem is N P -hard problem and finds many real-world applications. In this paper, we propose an artificial bee colony (ABC) algorithm for the BD-MST problem. ABC algorithm is a swarm-based metaheuristic technique based on the intelligent foraging behavior of honeybees. The proposed ABC algorithm employs permutation encoding. To exploit this encoding structure, two neighborhood strategies that help ABC algorithm in faster convergence towards finding high quality solutions are applied. On a set of Euclidean and non-Euclidean benchmark instances for various diameter bounds, the proposed approach has been compared with state-of-the-art approaches. Computational results demonstrate the effectiveness of the proposed approach to the other extant approaches in the literature. [ABSTRACT FROM AUTHOR]

Hygienic behavior is a social defense mechanism against parasites and pathogens in honeybees. We studied the genetic basis of hygienic behavior in African-derived Apis mellifera by performing RNA sequencing on brains of individual honeybee workers observed performing hygienic behavior, in order to identify expression changes linked with this behavior. We also used the transcriptome data to search for single nucleotide polymorphism (SNP) variation in genes previously associated with the trait in other A. mellifera populations. The analysis revealed 49 differentially expressed genes (DEG), most of them upregulated during hygienic acts. One DEG, Apidaecin, also showed SNP variation across samples, providing a promising candidate gene for both expression-based and heritable variation in hygienic behavior. We also identified 27 additional SNPs in the coding regions of five candidate genes previously linked with honeybee hygienic behavior. These results provide a useful starting place to analyze the genetic basis of hygienic behavior in African-derived honeybees. [ABSTRACT FROM AUTHOR]

Apis mellifera is an important provider of ecosystem services, and during flight and foraging behaviour is exposed to environmental pollutants including airborne particulate matter (PM). While exposure to insecticides, antibiotics, and herbicides may compromise bee health through alterations of the gut microbial community, no data are available on the impacts of PM on the bee microbiota. Here we tested the effects of ultrapure Titanium dioxide (TiO2) submicrometric PM (i.e., PM1, less than 1 µm in diameter) on the gut microbiota of adult bees. TiO2 PM1 is widely used as a filler and whitening agent in a range of manufactured objects, and ultrapure TiO2 PM1 is also a common food additive, even if it has been classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen in Group 2B. Due to its ubiquitous use, honey bees may be severely exposed to TiO2 ingestion through contaminated honey and pollen. Here, we demonstrated that acute and chronic oral administration of ultrapure TiO2 PM1 to adult bees alters the bee microbial community; therefore, airborne PM may represent a further risk factor for the honey bee health, promoting sublethal effects against the gut microbiota. [ABSTRACT FROM AUTHOR]

Honey bee queens undergo dramatic behavioral (e.g., reduced sexual receptivity), physiological (e.g., ovary activation, ovulation, and modulation of pheromone production) and transcriptional changes after they complete mating. To elucidate how queen post-mating changes are influenced by seminal fluid, the non-spermatozoa-containing component of semen, we injected queens with semen or seminal fluid alone. We assessed queen sexual receptivity (as measured by likelihood to take mating flights), ovary activation, worker retinue response (which is influenced by queen pheromone production), and transcriptional changes in queen abdominal fat body and brain tissues. Injection with either seminal fluid or semen resulted in decreased sexual receptivity, increased attractiveness of queens to workers, and altered expression of several genes that are also regulated by natural mating in queens. The post-mating and transcriptional changes of queens receiving seminal fluid were not significantly different from queens injected with semen, suggesting that components in seminal fluid, such as seminal fluid proteins, are largely responsible for stimulating post-mating changes in queens. [ABSTRACT FROM AUTHOR]

The honeybee is one of several eusocial species with a complex set of anatomical, physiological, and behavioural traits that are correlated with foraging preferences. Sensory sensitivity to sucrose is associated with the foraging preferences of workers, with individuals that are less sensitive to sugar preferring to forage for nectar and those that are highly sensitive to sucrose preferring to forage for pollen. In this study, we test this hypothesis by comparing the sucrose responsiveness of genetically similar normal and rebel honeybee workers, which present different foraging preferences. We found that rebels, which prefer to forage for nectar and have a higher reproductive potential than normal workers, are characterised by sucrose sensitivity that is lower than that of normal workers. Moreover, we show that in both rebel and normal workers, sensitivity to sugar in nectar is lower in workers when their ovaries contain more ovarioles. The results confirm the prediction that bees present a foraging preference depending on their response thresholds to sucrose in solution. However, compared with previous studies, our investigation does not support the assumption that reproductive workers are more sensitive to sucrose concentrations in nectar. [ABSTRACT FROM AUTHOR]

The primer and releaser effects of dominant honey bee workers' tergal gland pheromones are not known under queenless conditions. The Cape honey bee, Apis mellifera capensis, is the ideal model to investigate such question since workers normally reproductively dominate workers of all other subspecies. We determined the effects that short- and long-term exposure to pheromone blends from dominant A. m. capensis workers had on subordinate workers of A. m. scutellata. Three putative pheromonal blends, 1 (palmitic acid, oleic acid, n-heneicosene and n-tricosene), 2 (ethyl palmitate, ethyl oleate and ethyl stearate) and 3 (mixture of blends 1 + 2), were tested. All the three putative pheromonal blends elicited releaser effects in the form of retinue formation and primer effects by suppressing ovarian activation in workers. The resultant effects indicated that these pheromonal blends appear to play a role in establishing dominance among workers and hence regulating opportunities to reproduce. [ABSTRACT FROM AUTHOR]

Hygienic behaviour (HB) in honeybees reflects social immunity against diseases and parasites. Young bees showing HB detect, uncap, and remove infested brood from a colony. We developed a new variant of freeze-killed brood (FKB*) test to optimise the duration of the HB test, the costs, and safety for the operator. In 2016, we performed a comparison between traditional FKB and FKB* on 25 unselected and unrelated colonies in the apiary of the University of Milano. To estimate repeatability and heritability, in 2017 and 2018, FKB* was used to phenotype, respectively, 56 and 95 colonies twice, in the context of a breeding programme. FKB* took less time and required a smaller amount of liquid nitrogen. The two methods showed a correlation between colony effects of 0.93, indicating that they measure the same trait. For single records, the phenotypic correlation between both methods was 0.64. Estimated heritability and repeatability for single records HB were 0.23 and 0.24, respectively, whilst heritability for the average HB value of two records was 0.37. [ABSTRACT FROM AUTHOR]

The parasitic mite Varroa destructor is a major threat to the European honey bee Apis mellifera. Beekeepers apply the miticide thymol directly within the hives to kill this parasitic mite. Thymol is repellent to bees and causes them to ventilate the hive, yet its impact on bee hygienic behaviours that prevent the spread of diseases has never been studied. We measured the efficiency of colonies at removing dead adult bees, uncapping dead pupal cells and removing dead brood in two miticide-free Australian environments where the mite is absent. Thymol increased the uncapping and removal of dead brood by 24 to 36% after 48 h at both locations but had no effect on the removal of dead adult bees. The increased removal of brood could enhance the effect of thymol on V. destructor, especially if bees preferentially remove cells infected with the mite. [ABSTRACT FROM AUTHOR]

In social insects, the tuning of activity levels among different worker task groups, which constitutes a fundamental basis of colony organization, relies on the exchange of reliable information on the activity level of individuals. The underlying stimuli, however, have remained largely unexplored so far. In the present study, we describe low-frequency thoracic vibrations generated by honey bee workers (Apis mellifera) within the colony, whose velocity amplitudes and main frequency components significantly increased with the level of an individual's activity. The characteristics of these vibrations segregated three main activity level-groups: foragers, active hive bees, and inactive hive bees. Nectar foragers, moreover, modulated their low-frequency vibrations during trophallactic food unloading to nestmates according to the quality of the collected food. Owing to their clear association with the activity level of an individual and their potential perceptibility during direct contacts, these low-frequency thoracic vibrations are candidate stimuli for providing unambiguous local information on the motivational status of honey bee workers. [ABSTRACT FROM AUTHOR]

Previous experience in a natural environment with a stimulus has lasting influences on honey bee behavior, as demonstrated in laboratory studies of appetitive conditioning. However, it is unknown whether the same holds true for studies of aversive conditioning. Aversive conditioning is important for insects such as honey bees to survive environmental risks. Previous experience in natural settings may lead to maladaptive behavioral patterns in bees exposed to new risks. This study presents the first examination of the effect of a visual stimulus presented in a naturalistic setting on aversive conditioning, using the shuttle box choice chamber paradigm. The present study examines both the effect of the visual stimuli, as well as differences present between the Apis mellifera subspecies of mellifera and ligustica. Results support the presence of behavioral biases based on the visual stimulus presented prior to the experimental sessions. [ABSTRACT FROM AUTHOR]

Parasites often modify host foraging behavior, for example, by spurring changes to nutrient intake ratios or triggering self-medication. The gut parasite, Nosema ceranae, increases energy needs of the European or Western honey bee (Apis mellifera), but little is known about how infection affects foraging behavior. We used a combination of experiments and observations of caged and free-flying individual bees and hives to determine how N. ceranae affects honey bee foraging behavior. In an experiment with caged bees, we found that infected bees with access to a high-quality pollen were more likely to survive than infected bees with access to a lower quality pollen or no pollen. Non-infected bees showed no difference in survival with pollen quality. We then tested free-flying bees in an arena of artificial flowers and found that pollen foraging bees chose pollen commensurate with their infection status; twice as many infected bees selected the higher quality pollen than the lower quality pollen, while healthy bees showed no preference between pollen types. However, healthy and infected bees visited sucrose and pollen flowers in the same proportions. Among hive-level observations, we found no significant correlations between N. ceranae infection intensity in the hive and the proportion of bees returning with pollen. Our results indicate that N. ceranae-infected bees benefit from increased pollen quality and will selectively forage for higher quality while foraging for pollen, but infection status does not lead to increased pollen foraging at either the individual or hive levels. [ABSTRACT FROM AUTHOR]

Varroa-specific hygienic behavior is a hereditary trait of honey bee (Apis mellifera), which supports resistance to Varroa destructor. This study investigated the response of Apis mellifera scutellata to Varroa-infested worker brood cells in Kenya, East Africa. Uncapping, removal of the brood, and disappearance of the introduced mite were recorded in a total of 690 cells into which live mites were introduced. We recorded a high proportion of untouched cells in controls (median, 80%) compared to manipulated cells in which mites had been introduced (median, 12.5%) with a significant difference (GLMM, p < 0.001). Mites were removed and cells were recapped in about 26% of the artificially infested brood cells. When ten, eight, and five mites were singly introduced in closely neighboring brood cells, hygienic bees were more responsive in the high mite density regime of eight and ten mites, an indication of a possibility that chemicals play a role in identification of Varroa-infested brood cells. [ABSTRACT FROM AUTHOR]

The removal of Varroa destructor was assessed in Russian honey bee (RHB) colonies with known levels of Varroa Sensitive Hygienic (VSH) and brood removal activities. The expression of grooming behaviour using individual bees was also measured using three groups of RHB displaying different VSH levels: low hygiene (RHB-LH, < 35% VSH), medium hygiene (RHB-MH, 35-70%) and high hygiene (RHB-HH, > 70%). Italian colonies (5.43-71.62% VSH) served as control. Our results demonstrated, for the first time, significant relationships between two hygienic responses (VSH activity measured as percent change in infestation and the actual brood removal of Varroa-infested donor comb) and two measurements of mite fall (trapped old mites/trapped mites or O/T and trapped young mites/trapped mites or Y/T). However, these relationships were only observed in RHB colonies. In addition, the RHB colonies that displayed the highest levels of hygiene (RHB-HH) also groomed longer in response to the presence of a V. destructor mite based on individual bee assays. The positive regressions between the two hygienic measurements and O/T and their negative regressions with Y/T suggest that the removal of infested brood prevented successful mite reproduction, ultimately suppressing V. destructor infestations in the RHB colonies. In addition, it is demonstrated that RHB resistance to V. destructor rests on both an increased hygienic response and the removal of phoretic mites, released by hygienic behaviour, through grooming. Both resistance traits are reflected in the O/T and Y/T ratios found in trapped mites from RHB colonies. None of the measurements involving mite injuries were associated with any measurements of hygiene and colony infestations. [ABSTRACT FROM AUTHOR]

Circulating hemocytes are responsible for defensive and healing mechanisms in the honey bee, Apis mellifera. Parasitism by the mite Varroa destructor and injection of V. destructor homogenate in buffer, but not buffer injection, showed similar reductions in total hemocyte concentrations in both Africanized and European adult honey bees. This indicated that compounds in V. destructor homogenate can have similar effects as V. destructor parasitism and that the response is not solely due to wounding. Samples from honey bees with different hemocyte concentrations were compared for the expression patterns of hemolectin (AmHml), prophenol oxidase (AmPpo), and class C scavenger receptor (AmSRC-C). Of the genes tested, only the expression of AmPpo correlated well with hemocyte counts for all the treatments, indicating that melanization is associated with those responses. Thus, the expression of AmPpo might be a suitable biomarker for hemocyte counts as part of cellular defenses against injection of buffer or mite compounds and V. destructor parasitism and perhaps other conditions involving healing and immunity. [ABSTRACT FROM AUTHOR]

How complex is the memory structure that honeybees use to navigate? Recently, an insect-inspired parsimonious spiking neural network model was proposed that enabled simulated ground-moving agents to follow learned routes. We adapted this model to flying insects and evaluate the route following performance in three different worlds with gradually decreasing object density. In addition, we propose an extension to the model to enable the model to associate sensory input with a behavioral context, such as foraging or homing. The spiking neural network model makes use of a sparse stimulus representation in the mushroom body and reward-based synaptic plasticity at its output synapses. In our experiments, simulated bees were able to navigate correctly even when panoramic cues were missing. The context extension we propose enabled agents to successfully discriminate partly overlapping routes. The structure of the visual environment, however, crucially determines the success rate. We find that the model fails more often in visually rich environments due to the overlap of features represented by the Kenyon cell layer. Reducing the landmark density improves the agents route following performance. In very sparse environments, we find that extended landmarks, such as roads or field edges, may help the agent stay on its route, but often act as strong distractors yielding poor route following performance. We conclude that the presented model is valid for simple route following tasks and may represent one component of insect navigation. Additional components might still be necessary for guidance and action selection while navigating along different memorized routes in complex natural environments. [ABSTRACT FROM AUTHOR]

The circadian clock is an advantageous adaptive system that enables organisms to predict and anticipate the daily environmental changes. The circadian rhythms are generated molecularly through the expression of clock genes, based on autoregulatory feedback loops. Honeybees are an excellent model to investigate how the circadian rhythms are modulated accordingly to the social context, behavioral plasticity, and task-related activities. Here, we show how the clock genes behave during the daily cycles in adult worker heads of Apis mellifera. Our results point to the clock genes period and cryptochrome as essential regulators of the circadian rhythms associated to the behavioral maturation in this social insect. We also identified putative miRNA-target and protein-protein interactions involving honeybee clock genes, indicating regulatory networks behind the adjustment of the molecular clock. [ABSTRACT FROM AUTHOR]

Waggle-dancing honeybee foragers emit four hydrocarbons that have been shown to stimulate colony foraging by reactivating experienced foragers and increasing the number of recruitment dances. These hydrocarbons, the alkanes tricosane and pentacosane, and the alkenes (Z)-9-tricosene and (Z)-9-pentacosene, are part of the array of social insects cuticular lipids which have been well studied in the context of nestmate recognition. This study seeks to determine which of the dance hydrocarbons produce the behavioral responses of forager bees by using a binary choice behavioral assay for attraction or repulsion to the volatile phase of the dance compounds. We found no significant deviation from random choice for single dance compounds and pairs of compounds, but bees were significantly attracted to a mixture of the three compounds (Z)-9-tricosene, tricosane, and pentacosane. These results suggest synergy among the waggle-dance hydrocarbons, which was unexpected based on previous research where, in the context of nestmate recognition, alkenes have been shown to play a key role in eliciting behavioral responses. Synergy among the waggle-dance hydrocarbons may provide specificity that facilitates adaptive, context-specific behavioral responses to this subset of cuticular hydrocarbons. [ABSTRACT FROM AUTHOR]

Honey bees, Apis mellifera, exploit the geomagnetic field for orientation during foraging and for alignment of their combs within hives. We tested the hypothesis that honey bees sense the polarity of magnetic fields. We created an engineered magnetic anomaly in which the magnetic field generally either converged toward a sugar reward in a watch glass, or away from it. After bees in behavioral field studies had learned to associate this anomaly with a sugar water reward, we subjected them to two experiments performed in random order. In both experiments, we presented bees with two identical sugar water rewards, one of which was randomly marked by a magnetic field anomaly. During the control experiment, the polarity of the magnetic field anomaly was maintained the same as it was during the training session. During the treatment experiment, it was reversed. We predicted that bees would not respond to the altered anomaly if they were sensitive to the polarity of the magnetic field. Our findings that bees continued to respond to the magnetic anomaly when its polarity was in its unaltered state, but did not respond to it when its polarity was reversed, support the hypothesis that honey bees possess a polarity-sensitive magnetoreceptor. [ABSTRACT FROM AUTHOR]

Wild honey bee colonies-both truly wild (in trees and buildings) and simulated wild (in small hives)-were studied to determine their life-history traits, to see if these traits have changed now that these colonies are infested with Varroa destructor. Most colonies (97%) survive summers, but only 23% of founder (first-year) colonies and 84% of established colonies survive winters. Established colonies have a mean lifespan of 5-6 years and most (87%) have a queen turnover (probably by swarming) each summer. A population model shows that these life-history traits produce a stable population of colonies. Remarkably, the suite of colony life-history traits found in the 2010s (with V. destructor) matches that found in the 1970s (without V. destructor). It seems likely that the wild colonies living near Ithaca, NY, possess defenses against V. destructor that are not costly. [ABSTRACT FROM AUTHOR]

Highly aggressive Africanized honeybees (AHB) invaded Puerto Rico (PR) in 1994, displacing gentle European honeybees (EHB) in many locations. Gentle AHB (gAHB), unknown anywhere else in the world, subsequently evolved on the island within a few generations. Here we sequence whole genomes from gAHB and EHB populations, as well as a North American AHB population, a likely source of the founder AHB on PR. We show that gAHB retains high levels of genetic diversity after evolution of gentle behaviour, despite selection on standing variation. We observe multiple genomic loci with significant signatures of selection. Rapid evolution during colonization of novel habitats can generate major changes to characteristics such as morphological or colouration traits, usually controlled by one or more major genetic loci. Here we describe a soft selective sweep, acting at multiple loci across the genome, that occurred during, and may have mediated, the rapid evolution of a behavioural trait. [ABSTRACT FROM AUTHOR]

Fighting and aggression are important tasks for self-preservation in animals. In honey bees, virgin queens fight against each other for survival in a monogynous colony. Because the virgin queens have higher levels of dopamine (DA) in the brain than do mated queens with low aggressiveness, DA may promote fighting and aggression behaviours of virgin queens. In the present study, we investigated the effect of DA on the fighting and stinging response of honey bee virgin queens. We injected two concentrations (10 M and 10 M) of DA and the DA receptor blocker flupenthixol into the abdomen of one-day-old virgin queens and observed fighting and stinging responses. DA injection did not affect fighting and stinging. Injections of 10 M flupenthixol decreased the winning rate significantly, whereas 10 M flupenthixol increased the winning rate, indicating the opposite effects on fighting responses depending on the degrees of blockade of DA signalling. In terms of the stinging response, 10 M flupenthixol-injected virgin queens stung significantly more often than control and 10 M flupenthixol-injected virgin queens. These results suggest an involvement of DA signalling in the regulation of fighting and aggression in virgin queens, although a blockade of DA does not always inhibit these behaviours. [ABSTRACT FROM AUTHOR]

Internal temperatures of honey bee hives kept at different sites in North Dakota were monitored before and during winter to evaluate the effects of treatment, in the form of exposure to commercial pollination, and location on colony health. In October, hives exposed to commercial pollination during the summer had fewer adult bees and less brood than hives kept near natural forage, as well as lower average temperatures throughout winter. Within-day temperature variability was higher among hives exposed to commercial agriculture than for those kept near natural forage, indicating reduced temperature control. Fungicides, insecticides, varroacides, and an herbicide were detected in bee bread and wax samples; no major differences were observed either in the diversity or in the concentrations of agrochemicals with the exception of chlorpyrifos at one site. Varroa and Nosema densities were low overall. Data from the same site used in successive years showed significantly more brood the first year, as well as lower temperature variability; high levels of chlorpyrifos were detected in bee bread of colonies in the second year. Colony average temperature and temperature variability were informative with respect to colony phenology and post-winter status. [ABSTRACT FROM AUTHOR]

There has been a long-standing interest in developing approaches to maximize honey production by Kenyan beekeepers. Since honey bees in Kenya are passively managed, the main decision beekeepers make is which hive type to use: traditional Log hives, Langstroth hives, and Kenyan top-bar hives. We found Langstroth hives to be the most attractive to migrating swarms, followed by Log hives, while Kenyan top-bar hives were the least preferred. Pathogen and parasite loads correlated only with colony age and absconding rates were associated only with colony size and weight. We recommend additional studies to understand the factors that drive swarm attraction to hive bodies and highlight practical concerns about Kenyan top-bar hives that need to be addressed to improve their utility to beekeepers. Also, placing apiaries in areas with floral resources may reduce absconding rates; however, periodic breaks in brood production may serve as a mechanism to reduce parasite and pathogen loads. [ABSTRACT FROM AUTHOR]

Nest drifting is often observed in honeybees ( Apis mellifera) and can be detrimental to neighbouring colonies because it has the potential to increase disease transmission. However, the characteristics of drifting behaviour over a honeybee's lifetime and the influence of parasitism on this phenomenon have been insufficiently investigated. Using optical bee counters, we tracked the drifting behaviour of workers that were either infected with the parasite Nosema ceranae or uninfected. Approximately 10 % of the tracked bees drifted into a foreign colony. The drifting prevalence was influenced by the colony's location in space but not by N. ceranae parasitism. However, the number and duration of drifts changed over the lifetime of the bees and the season, and parasitism had an effect on drifters, with Nosema-infected bees performing more but shorter drifts. This phenomenon was more pronounced in old bees (+62 and −15 % for the number and duration of drifts, respectively) and could potentially be explained by the energetic stress induced by the parasite. In conclusion, combining a detailed analysis of drifting behaviour with the actual risk of newly established disease in colonies will benefit our knowledge of bee epidemiology. [ABSTRACT FROM AUTHOR]

Recruitment-related behaviours such as waggle dances enable honey bee foragers to inform their nestmates about the location of important resources. However, it is still not known how the information contained in a dance performed in the darkness of the nest is transferred to followers. Although, there are findings indicating that dancing honey bees produce airborne sounds which may convey the information, there has only been indirect evidence that moving wings are the source of these airborne sounds. In this study, honey bee dances were recorded using a high-speed camera in order to directly observe and precisely measure the frequency of wing beats and abdomen wags of dancers. Dancing bees moved their wings for 40.4% of the duration of a waggle run and for only 8.1% of the duration of a circle run. The episodes of wing movements consisted of one to five wing beats and were separated by intervals of motionless wings. The mean frequency of wing beats was 167.0 Hz and significantly differed depending on the number of wing beats in one episode ( p < 0.001) and the position of the wings ( p = 0.007). The mean frequency of abdomen wags was 14.6 Hz. The mean number of followers was 7.9 and significantly more of them gathered around the abdomens of dancers than around their heads and thoraxes ( p = 0.001). The results of this study support the assumption that moving wings are the source of airborne sounds emitted during honey bee dances. [ABSTRACT FROM AUTHOR]

Honey bees ( Apis mellifera) are prone to judge an ambiguous stimulus negatively if they had been agitated through shaking which simulates a predator attack. Such a cognitive bias has been suggested to reflect an internal emotional state analogous to humans who judge more pessimistically when they do not feel well. In order to test cognitive bias experimentally, an animal is conditioned to respond to two different stimuli, where one is punished while the other is rewarded. Subsequently a third, ambiguous stimulus is presented and it is measured whether the subject responds as if it expects a reward or a punishment. Generally, it is assumed that negative experiences lower future expectations, rendering the animals more pessimistic. Here we tested whether a most likely negatively experienced formic acid treatment against the parasitic mite Varroa destructor also affects future expectations of honey bees. We applied an olfactory learning paradigm (i.e., conditioned proboscis extension response) using two odorants and blends of these odorants as the ambiguous stimuli. Unlike agitating honey bees, exposure to formic acid did not significantly change the response to the ambiguous stimuli in comparison with untreated bees. Overall evidence suggests that the commonest treatment against one of the most harmful bee pests has no detrimental effects on cognitive bias in honey bees. [ABSTRACT FROM AUTHOR]

Heritabilities and genetic correlations were estimated for honey yield and behavioural traits in Austrian honey bees using data on nearly 15,000 colonies of the bee breeders association Biene Österreich collected between 1995 and 2014. The statistical models used distinguished between the genetic effect of workers and that of the queen of the colony. Heritability estimates for worker effect were larger than those for queen effect. Genetic correlations between both effects were negative. Heritability estimates for the sum of both effects (i.e. selection criterion) were 0.27, 0.37, 0.38 and 0.06 for honey yield, gentleness, calmness and swarming behaviour, respectively, indicating that meaningful genetic improvement is possible. Genetic correlations between these traits were generally small to medium, with large standard errors, with the exception of the high genetic correlation between gentleness and calmness. The models we present here can be used to estimate breeding values in honey bees. [ABSTRACT FROM AUTHOR]

Workers of open-nesting honey bee species form a bee curtain to cover the comb and protect it against adverse environmental conditions and predators. We studied different aspects of structural and temporal dynamics of the bee curtain in Apis florea. First, in the course of daily observations, we discovered massed flight activity (MFA) of A. florea colonies similar to that previously described for A. dorsata. The MFAs started with the opening of gaps in the curtain and appearance of chains of bees shortly before the massed take off. Second, monitoring the worker movement patterns in the outer layer indicated a constant turnover of bees in the curtain. Finally, introduction of marked 1-day-old workers showed that workers joined the curtain at a very young age. First flight activity appeared around day 20, but the majority of workers started to fly after day 47, which is twice the age at which A. mellifera workers start to forage. [ABSTRACT FROM AUTHOR]

The honeybee, Apis mellifera, undergoes complete metamorphosis before transitioning to the adult stage. The newly emerged individual and the red-eye pupa stage are well defined and easily recognizable in the time life cycle honeybee and, therefore, very useful for studying physiological and developmental factors. We analyzed in detail the hemolymph proteome of newly emerged honeybee worker using 2D-E-MS/MS (pI 3-10 and 4-7). The comparison of identical hemolymph volumes (20 μL per 2D-E) for newly emerged bee and red-eye pupa revealed a dramatic decrease in the number of spots (qualitative changes) and overall protein quantity during the non-feeding stage. The results increase our knowledge about honeybee metamorphosis during the non-feeding period and clarify previous findings regarding particular proteins. The results will be useful for future comparative physiological, developmental, and host-pathogen studies on individual or population level. [ABSTRACT FROM AUTHOR]

European honey bees were introduced to Fernando de Noronha Island in 1984 already infested by Varroa destructor, and since then they have survived without any control measures. In 2012, adult and brood infestation rates were measured and compared to historical records. There was no significant difference in mite levels between the values obtained in 1996 (14 mites/100 adult bees) and 2012 (16.5 mites/100 bees). The percentage of mites that reproduced in worker brood cells also was not significantly different from the data obtained in 1996. The frequency of hygienic behavior was similar to data obtained for resistant African-derived honey bees. Average fecundity decreased slightly between 1996 and 2012, but remained high. From our data, we conclude that those bees have maintained stable infestation levels for at least 16 years. Infestation rates remain high, at rates that would be fatal to honey bees in most regions of the world, but there is no Varroa-related colony mortality on the island. [ABSTRACT FROM AUTHOR]

Honeybees are essential components to modern agriculture and economy. However, a continuous increase in cases of colony losses and colony depopulation are being reported worldwide. This critical situation has put the fragile equilibrium between bees and plants on the edge. As a consequence, several scientists have begun to focus their lines of research on this issue. Most researchers agree that there is no single explanation for the observed colony losses. Instead, these losses result from a synergistic interaction between different stressors. South America is not the exception; several cases of colony losses and colony depopulation were reported by beekeepers throughout the continent, yet no accurate data has been published to date. Therefore, this article attempts to analyze the past and present situation of honeybee health in South America, specifically in Argentina, Chile, Uruguay, Brazil, and Venezuela. Furthermore, it is intended to serve as a comparison to future colony losses, as well as to provide guidance for future hypothesis-driven research on the causes of colony mortality. We evaluate the impact of the main parasites and pathogens affecting honeybee colonies and discuss the role of each with respect to reported honeybee losses. We also contemplate the main challenges that each nation must confront with regards to honeybee health. [ABSTRACT FROM AUTHOR]

The honey bee time memory enables foragers to return to a profitable food source in anticipation of the time of day at which they previously collected food from that source. The time memory thus allows foragers to quickly resume exploiting a source after interruption, at the appropriate time of day, without the costs associated with having to rediscover it. A portion of a foraging group (the persistent foragers) will reconnoiter a previously profitable source and may do so for several days. The remaining bees (the reticent foragers) await confirmation of availability before revisiting the source. Recent work has shown that both persistent and reticent bees make extracurricular flights to alternative sources when one food source ceases being productive. Little else, however, is known about reticent foragers. In the present study, we determined that reticent bees congregate near the hive entrance in anticipation of the learned foraging time as do persistent foragers. We then confirmed that the food-anticipatory clustering takes place on the waggle dance floor, as suspected, but also found differences in the number of days that persistent and reticent foragers continue clustering. Finally, we found that persistent foragers had significantly more rewards per day at the source than did reticent foragers, supporting the hypothesis that experience at a food source influences a forager's decision to become either persistent or reticent. Our findings demonstrate that persistence and reticence are not immutable characteristics of foragers themselves but rather strategies they employ toward different food sources. Significance statement: Much has been learned in recent years about the honey bee time memory and foraging behavior. Receiving scant attention, however, is the phenomenon of forager bees gathering near the hive entrance, anticipating the time of day when previously productive food sources become available. We show that both persistent and reticent bees (foragers that do and do not investigate the source, respectively) congregate on the waggle dance floor at the appropriate time of day, but, in the absence of food at the source, persistent bees continue to show this behavior a day or two longer than reticent bees do. We also show that experience with the source influences the decision to become persistent or reticent. Our results reveal how foraging experience influences the individual bee's decision making, thereby providing insights into how foragers are reallocated efficiently among different resources in the environment. [ABSTRACT FROM AUTHOR]

In the honeybee swarm nest-site selection process, individual bees gather information about available candidate sites and communicate the information to other bees. The swarm makes an agreement for a candidate site when the number of bees that supports the site reaches a threshold. This threshold is usually referred to as the quorum threshold and it is shown by many studies as a key parameter that is a compromise between the accuracy and speed of decisions. In the present work, we use a model of the honeybee Apis mellifera nest-site selection process to study how the quorum threshold and discovery time of candidate sites have major impact on two unfavorable situations in selecting a nest site: decision deadlock and decision split. We show that cross-inhibitory stop-signaling, delivered among bees supporting different sites, enables swarms to avoid the decision split problem in addition to avoiding the decision deadlock problem that has been previously proposed. We also show that stop-signaling improves decision speed, but compromises decision accuracy in swarms using high quorum thresholds by causing the swarms to be trapped in local optima (e.g., choosing a sub-optimal option that is encountered first). On the other hand, we demonstrate that stop-signaling can reduce split decisions without compromising decision accuracy in swarms using low quorum thresholds when it is compared to the accuracy of swarms using the same threshold values but not exhibiting stop-signaling. Based on our simulations, we suggest that swarms using low quorum thresholds (as well as swarms with large population sizes) would benefit more from exhibiting the stop-signaling activity than not exhibiting it. [ABSTRACT FROM AUTHOR]

Division of labor (DOL) in the social insects is one of nature's most derived examples of phenotypic plasticity. Here, we explore the regulatory genomics of DOL in honey bees using RNA-Seq between nurses and foragers for eight tissues. We begin to test the hypothesis that caste-specific gene expression may be controlled in a manner analogous to how sex-specific gene expression is controlled. Specifically, we look for candidate master caste regulators that could play a role in controlling caste-specific gene expression analogous to the role played by double sex in sex-specific gene expression. We make significant first steps towards testing this hypothesis by showing that only a small number of regulatory genes show widespread differential expression across many tissues and are thus candidates for genes that could coordinate widespread patterns of gene expression in response to endocrine signals responsive to social needs. Two strong candidates are kruppel homolog-1 and double sex. Double sex, in particular, has previously been associated with sex linked phenotypic plasticity in other insects and is a promising candidate for future work. In addition to testing this primary hypothesis, we also show that the control of DOL has a complex genetic basis such that the same regulatory genes are used repeatedly in different tissues at the same caste transition in an independent manner. We further show that most regulatory genes only show differential expression in a single tissue. Overall, this study suggests candidate genes for the key regulators of social behavior in honey bees. [ABSTRACT FROM AUTHOR]

In comparison to other insects, like honeybees, bumblebees are very effective pollinators. Even though landing is a crucial part of pollination, little is known about how bumblebees orchestrate the final, critical moments of landing. Here, we use high-speed recordings to capture the fine details of the landing behaviour of free-flying bumblebees ( Bombus terrestris), while landing on a flat platform with different orientations. We find that the bees have a fairly constant body and head orientation at the moment of leg extension, irrespective of platform tilt. At the same moment in time, the distance to the platform is held constant at around 8 mm (with the exception of low platform tilts). The orientation of the antennae and the first appendage that touches the platform vary between platform orientations, while the duration of the hover phase does not. Overall, the final moments of landing in bumblebees and their close relatives, the honeybees, are similar. However, the distance to the platform at the moment of leg extension and the duration of the hover phase are different in bumblebees and honeybees, suggesting that they are primarily adapted to land on surfaces with different orientations. [ABSTRACT FROM AUTHOR]

Octopamine- and dopamine-based neuromodulatory systems play a critical role in learning and learning-related behaviour in insects. To further our understanding of these systems and resulting phenotypes, we quantified DNA sequence variations at six loci coding octopamine-and dopamine-receptors and their association with aversive and appetitive learning traits in a population of honeybees. We identified 79 polymorphic sequence markers (mostly SNPs and a few insertions/deletions) located within or close to six candidate genes. Intriguingly, we found that levels of sequence variation in the protein-coding regions studied were low, indicating that sequence variation in the coding regions of receptor genes critical to learning and memory is strongly selected against. Non-coding and upstream regions of the same genes, however, were less conserved and sequence variations in these regions were weakly associated with between-individual differences in learning-related traits. While these associations do not directly imply a specific molecular mechanism, they suggest that the cross-talk between dopamine and octopamine signalling pathways may influence olfactory learning and memory in the honeybee. [ABSTRACT FROM AUTHOR]

The larval pheromone ( E)-β-ocimene (EBO) inhibits worker ovary development and accelerates the behavioral transition from nursing to foraging in the honey bee, Apis mellifera. Because EBO diffuses throughout the hive, it has been hypothesized that honey bee workers can use it to indirectly assess brood abundance. Here, we evaluate this hypothesis by testing whether EBO plays a role in the regulation of worker foraging activity. We exposed paired colonies to a pulse of either synthetic β-ocimene or paraffin oil control and recorded the subsequent number of pollen and non-pollen foragers returning to the colony. Exposure to synthetic β-ocimene moderately but significantly increased overall foraging activity, but not pollen foraging. For pollen foraging, the effect of pheromone treatment was the greatest directly after pheromone exposure. [ABSTRACT FROM AUTHOR]

Honey bees were displaced several 100 m from their hive to an unfamiliar site and provisioned with honey. After feeding, almost two-thirds of the bees flew home to their hive within a 50 min observation time. About half of these returning, bees signalled the direction of the release site in waggle dances thus demonstrating that the dance can be guided entirely by information gathered on a single homeward trip. The likely reason for the bees' enthusiastic dancing on their initial return from this new site was the highly rewarding honeycomb that they were given there. The attractive nature of the site is confirmed by many of these bees revisiting the site and continuing to forage there. [ABSTRACT FROM AUTHOR]

The decision-making behavior of individuals is limited by a lack of information and a limited capacity to process information. When seeking locations to construct a hive, the honeybee Apis mellifera collectively succeeds at overcoming these individual limitations and, thus, arrives at (nearly) optimal decisions. This article examines the behaviors and coordination mechanisms that have reinforced this trait in the course of evolution. We consider what lessons might be learned concerning human behavior and how better decisions can be made. [ABSTRACT FROM AUTHOR]

In the honey bee ( Apis mellifera), social organization is primarily mediated by pheromones. Queen-produced 9-oxo-2-decenoic acid (9-ODA) functions as both a social and sex pheromone, eliciting attraction in both female workers and male drones, but also affecting other critical aspects of worker physiology and behavior. These effects are also maturation related, as younger workers and sexually mature drones are most receptive to 9-ODA. While changes in the peripheral nervous system drive sex-related differences in sensitivity to 9-ODA, the mechanisms driving maturation-related shifts in receptivity to 9-ODA remain unknown. Here, we investigate the hypothesis that changes at the peripheral nervous system may be mediating plastic responses to 9-ODA by characterizing expression levels of AmOR11 (the olfactory receptor tuned to 9-ODA) and electrophysiological responses to 9-ODA. We find that receptor expression correlates significantly with behavioral receptivity to 9-ODA, with nurses and sexually mature drones exhibiting higher levels of expression than foragers and immature drones, respectively. Electrophysiological responses to 9-ODA were not found to correlate with behavioral receptivity or receptor expression, however. Thus, while receptor expression at the periphery exhibits a level of plasticity that correlates with behavior, the mechanisms driving maturation-dependent responsiveness to 9-ODA appear to function primarily in the central nervous system. [ABSTRACT FROM AUTHOR]

The analytical approach to navigation studies aims to identify elementary sensory motor processes that guide an animal to a remote site. This approach will be used here to characterize components of navigation in a flying insect, the honeybee. However, navigation studies need to go beyond an analysis of behavioral routines to come up with a synthesis. We will defend the concept of an active memory structure guiding navigation in bees that is best described as a mental or cognitive map. In our opinion, spatial/temporal relations of landmarks are stored in a mental map in such a way that behavioral routines such as expectation and planning, as indicated by shortcutting, are possible. We view the mental map of animals including the honeybee as an 'action memory of spatial relations' rather than as a sensory representation as we humans experience it by introspection. Two components characterize the mental map, the relational representation of landmarks and the meaning of locations to the animal. As yet, there is little data to suggest that bees assign meaning to the experienced locations. To explore this possibility, further studies will be needed, whereby honeybees provide a unique model to address this question. [ABSTRACT FROM AUTHOR]

Information on the effect of hypoxia on the behavior and physiological state of the honeybee was compiled and systematized. It was shown that, in the course of colonization of temperate and cold climate zones by the honeybee, natural selection favored the acquisition of an effective mechanism of thermoregulation and high tolerance to hypoxia. It was noted that bees can develop under conditions when the CO concentration exceeds the content of this gas in the surface layer of the Earth by more than three orders of magnitude; however, this leads to deviations in the morphometric traits from the norm. At the adult stage, anesthesia with carbon dioxide was found to reduce the body weight and the water content in it. It was shown that the effect of anesthesia in adult bees increases with temperature and that hypoxia in adult bees and queens accelerates their senescence and reduces viability. [ABSTRACT FROM AUTHOR]

Identification of honey bee ( Apis mellifera) subspecies is important for their protection. It is also used by queen breeders to maintain some breeding lines. In this study, we compared three methods of subspecies identification based on the following: 17 microsatellite loci, COI-COII mitotypes and geometric morphometrics of forewing venation. The methods were used to classify colonies and workers from a mixed population of A. m. mellifera and A. m. carnica. There was highly significant correlation between results obtained using the three methods. More than three quarters of colonies were classified to the same subspecies by all three methods. The agreement was highest between microsatellites and morphometrics. More than 90 % of colonies were classified to the same subspecies by the two methods. There was also relatively high agreement (75 %) between microsatellites and morphometrics when workers were classified as pure subspecies or hybrids. In particular, one pure subspecies was never misclassified as other pure subspecies. The results presented here show that morphometrics can be used for detection of hybrids between A. m. mellifera and A. m. carnica. [ABSTRACT FROM AUTHOR]

Older larvae of honeybee drones are fed with a diet containing pollen. It is not known how pollen deprivation during the larval development of drones might affect their reproductive quality. This study investigated ejaculation ability and semen quality in drones reared in colonies with limited (LP) and unlimited (ULP) access to pollen. Access to pollen was limited by pollen traps. Drone brood rearing was not instantly abandoned in colonies with limited access to pollen. Colonies from the LP group reared drones with smaller mass, which ejaculated in fewer numbers and released smaller amounts of semen. The LP and ULP groups did not differ in semen quality as judged by the concentration, number, and viability of spermatozoa in ejaculate. It was found that access to pollen during larval development directly affects the reproductive quality of drones. [ABSTRACT FROM AUTHOR]

Although the honey bee queen and worker have identical genomes, they exhibit morphological, behavioral, and reproductive differences. Queen larvae (QL) and worker larvae (WL) have different gene and protein expression profiles and different DNA methylation profiles. MicroRNAs (miRNAs) play an important role in regulating gene expression and cell biological processes. To examine the roles of miRNAs in caste differentiation, we analyzed small RNA profiles in 4-day-old QL and WL ( Apis mellifera). The results demonstrated that the small RNAs with a length of 22 nt showed significant difference between the two castes. By comparison with mirBase 19.0, we identified 61 known miRNAs in QL and WL; 17, 24 and 20 of these miRNAs were respectively up-regulated, equally expressed, and down-regulated in QL compared with WL. These differentially expressed miRNAs were involved in many signaling pathways related to caste differentiation. [ABSTRACT FROM AUTHOR]

The aim of the present study was: to compare thermoregulatory behaviour of single honeybee workers and groups of 3-15 bees over their annual activity period and to check out whether the annual fluctuations of ambient temperature selection are correlated with phases of the colony development. Thermal behaviour of both single workers and groups of bees was recorded, using a video camera, in a thermal gradient system. Thermal preferences of the insects were tested seasonally in spring (May/June), summer (July/August) and autumn (September-November). Both single bees and small groups of bees changed their thermal behaviour in daily cycle. The season of the year had distinct effect on temperature preferences of both single honeybee workers or small groups of bees. In single honeybee workers the lowest ambient temperatures were preferred in late spring (the swarming phase) while the highest temperatures were selected during the summer (the colony growing phase). There were significant seasonal changes in ambient temperature selected by groups of honeybee workers. Groups of honeybee workers tended to prefer the lowest temperatures in late spring and the highest temperatures were selected during the summer. The day-night differences exhibited by small groups of bees in our experiments are likely to represent behavioural responses of the honeybee colony. In our experiments we proved an influence of the season of the year on the honeybees' thermal behaviour, which might be connected with seasonal shifts of temperature regulated by the honeybee colony. [ABSTRACT FROM AUTHOR]

Honey bee ( Apis mellifera) colonies divide foraging activities between scouts, who search for new sources of food, and non-scouts, who rely on information from waggle dances to find food sources. Molecular analyses of scouts and non-scouts have revealed differences in the expression of numerous genes, including several related to neurotransmitter signaling. Despite this progress, we know almost nothing about cognitive, sensory, or behavioral differences that underlie scouting. We tested three hypotheses related to differences between scouts and non-scouts. First, we tested whether scouts and non-scouts differ in their reversal-learning abilities and found that scouts showed a significantly faster reversal in their response to an odor that was punished and then rewarded. The results also suggested an interaction between the effects of foraging role (scout or non-scout) and seasonal effects on reversal-learning abilities. Second, we tested whether scouts and non-scouts show differences in responsiveness to sucrose rewards and found no difference. Third, we hypothesized that scouts have more foraging experience than do non-scouts. We tested this by comparing wing damage and found that non-scouts showed greater wing damage in the early summer but not the late summer. Together, these three results contribute to our understanding of the underpinnings of scouting behavior. [ABSTRACT FROM AUTHOR]