Individual Honeybees Research Articles

꿀벌 외부 기생성 응애류 방제용 살비제의 양봉꿀벌에 대한 실내 독성평가

Two species of the mite, Varroa destructor and Tropilaelaps mercedesae, are the main ectoparasites of the honey bee, Apis mellifera, in South Korea. Mite infection deteriorates individual honey bee health and further reduces population size of the bee colonies, thereby destructing the colonies. The chemical acaricides including fluvalinate, coumaphos, amitraz and cymiazole hydrochloride are used along with the natural chemical substances to control mite species. Recently, several beekeepers have complained of honey bee damage from the cymiazole hydrochloride treatment. To evaluate the toxicity of cymiazole hydrochloride we treated it to the honey bee workers according to the recommended method and dosage. Amitraz and coumaphos, which are the main acaricides for mite control, were used as comparison groups. 48 hours after treatment, cymizaole hydrochloride, amitraz and coumaphos showed mortalities of 22.2±1.9%, 3.3±5.8% and 1.1±3.3%, respectively.

Acute toxicity of microplastic fibers to honeybees and effects on foraging behavior

Microplastics (MPs) are considered emerging and persistent pollutants, although most of the research has been conducted on marine environments. Declines in honeybee populations have been reported globally, and recently, microplastic pollution has been considered a possible cause of this. Thus, we aimed to determine acute toxicity of polyester fibers and their effects on foraging behavior in honeybees. To test this, we conducted an oral acute toxicity bioassay, testing the effect of MPs on individual honeybees, and we studied the foraging behavior of honeybees when exposed to food and water containing MPs. We observed no mortality in honeybees fed with sucrose solution containing 100 mg MP/L after 24 and 48 h. Upon bee dissection of the digestive tract, we found 1.27 ± 1.5 fibers per bee, showing a mean (±SE) of 0.92 (±1.14) and 0.32 (±0.70) in their gut and crop respectively. The length of these microfibers ranged between 0.05 and 1.24 mm with a mean (±SE) of 0.42 (±0.25) mm. Although we did not find any preference or avoidance of MPs when presented in sucrose solutions and water; bees consumed MP-free solutions faster than solutions with 10 and 100 mg MPs/L. This might be due to changes in the viscosity of the solutions containing plastic and has implications for the impact of microplastic pollution on insects. Results suggest that MPS do not pose a threat to honeybees in the short term, based on the lack of acute mortality. However, bee foraging behavior does not prevent them from ingesting MPs present in water or resources which potentially might cause lethal long-term effects of MPs.

HONEYBEE VIRUSES PRESENCE IN SERBIAN APIARIES: A REVIEW

The honey bee Apis mellifera is an important beneficial insect recognized by production of honeybee products, having an important role in agricultural production through pollination, and play an equally crucial role in conserving the biodiversity in many natural ecosystems. According to available literature data, in the last more than 20 years, dramatic honey bee winter colony losses have been reported frequently all over the world that could have a direct influence on human food resources and can affect not only apiculture or agriculture, but also has an anthropological threats. One among many reasons for global bees-decline phenomenon is the influence of many viruses on honeybees’ health. Until today, in total, 36 viruses is detected in honey bees, and for many of them still without known pathogenicity on honeybees’ health. However, it is well known that some of these viruses like Acute Bee Paralysis Virus (ABPV), Chronic Bee Paralysis Virus (CBPV), Deformed Wing Virus (DWV), Black Queen Cell Virus (BQCV), Sacbrood Virus (SBV), Kashmir Bee Virus (KBV), Israeli Acute Paralysis Virus (IAPV), Slow bee paralysis virus (SBPV), Varroa destructor virus (VDV1) and some others has direct or indirect influence on individual honeybee or on whole honeybees colony health. In this paper the review of existing literature data on the presence, prevalence and characterization of honeybee viruses detected in honeybee colonies and apiaries from different regions in Serbia from first detection of their presence in 1986 till nowadays is presented and discussed.

The effect of a novel dietary supplement based on fishery industry waste hydrolysate, essential fatty acids and phytochemicals on honey bee nuclei development

In the late winter or early spring, beekeepers stimulate the colonies to increase the population of bees using different dietary supplements, principally based on carbohydrates and proteins. Honey bees require multiple sources of nectar and pollen to obtain balanced nutrition, so the formulation of effective supplements requires the identification and testing of candidate components, especially at the colony level. In this study, we evaluated the effectiveness of a nutritional supplement (SUP) composed of two important phytochemicals that have been reported to improve honey bee health (abscisic acid (ABA) and p-coumaric acid (CUM)) combined with fish protein hydrolyzate (FPH), and essential omega fatty acids (Ω3/6) in nuclei colonies. We first evaluated the toxicity of SUP compared with the control (sugar syrup) in laboratory bioassays during 96 hours. Then, we tested the effect on the amount of brood, honey, and pollen in bee hives nuclei supplemented with SUP for thirty days. In addition, we quantified and compared the concentration of total proteins in individual honey bees collected at the beginning and at the end of the experiment. The results obtained show that SUP is palatable, nontoxic to Apis mellifera, and significantly increases the amount of open brood and pollen reserves of bee nuclei compared with nuclei feed with sugar syrup. No significant differences were observed, between nuclei feed with SUP and control nuclei, in the amount of honey reserves and total proteins of individual bees. Here, we show the value of a nutritional supplement that combines essential nutritional components and phytochemicals to improve important parameters associated with colony fitness. We expected this nutritional supplement helps beekeepers to develop their colonies in view of the increase of industrial agriculture and the consequent loss of floral resources.

Honey bees as biomonitors – Variability in the elemental composition of individual bees

Homogenized or pooled samples of honey bees are already used for monitoring of metal pollution in the environment for a couple of decades. This is the first study that analyzed the elemental composition of individual honey bees. One apiary with 21 hives was used to test in-hive and between-hive differences at the same location. Highest in-hive variability was observed for Al (14.1x), Li (10.3x), V (10.3x), As (8.9x) and Cd (7.9x). For the elements Cu, K, Mg, Na, P, S and Zn the smallest both in-hive (2.3x, 1.8x, 2.0x, 2.2x, 1.9x, 1.7x, 2.4x respectively) as well as between-hive variability (1.5x, 1.4x, 1.4x, 1.6x, 1.4x, 1.4x and 1.5x respectively) was observed. Nonetheless, between-hive variability was statistically significant for all the analyzed elements. We proved that these differences significantly influence comparison of element concentrations in bees from different locations. One hive from Mesić apiary had significantly lower concentrations of Al (hive 18: 18.6 mg kg−1) and U (hive 1: 0.0013 mg kg−1), while at the same time a different hive from the same apiary showed higher concentration of these elements (Al, hive 14: 125 mg kg−1; U, hive 13: 0.012 mg kg−1) compared to another location (thermal power plant, Al: 97 mg kg−1, U: 0.0044 mg kg−1). Therefore, when using honey bees as biomonitors, we recommend a larger number of hives to be sampled at each location to provide an adequate dataset for reliable interpretation of results. Comparing individual bee elemental concentrations, for Na, Mg, P, S, K, Fe, Cu, and Zn negative correlations were found between dry mass of a bee and concentrations of these elements. These negative correlations could be a consequence of higher honey or nectar content in some of the sampled bees. However, this should also be considered when using honey bees as bioindicators.

Multi-tiered analyses of honey bees that resist or succumb to parasitic mites and viruses

BackgroundVarroa destructor mites, and the numerous viruses they vector to their honey bee hosts, are among the most serious threats to honey bee populations, causing mortality and morbidity to both the individual honey bee and colony, the negative effects of which convey to the pollination services provided by honey bees worldwide. Here we use a combination of targeted assays and deep RNA sequencing to determine host and microbial changes in resistant and susceptible honey bee lineages. We focus on three study sets. The first involves field sampling of sympatric western bees, some derived from resistant stock and some from stock susceptible to mites. The second experiment contrasts three colonies more deeply, two from susceptible stock from the southeastern U.S. and one from mite-resistant bee stock from Eastern Texas. Finally, to decouple the effects of mites from those of the viruses they vector, we experimentally expose honey bees to DWV in the laboratory, measuring viral growth and host responses.ResultsWe find strong differences between resistant and susceptible bees in terms of both viral loads and bee gene expression. Interestingly, lineages of bees with naturally low levels of the mite-vectored Deformed wing virus, also carried lower levels of viruses not vectored by mites. By mapping gene expression results against current ontologies and other studies, we describe the impacts of mite parasitism, as well as viruses on bee health against two genetic backgrounds. We identify numerous genes and processes seen in other studies of stress and disease in honey bee colonies, alongside novel genes and new patterns of expression.ConclusionsWe provide evidence that honey bees surviving in the face of parasitic mites do so through their abilities to resist the presence of devastating viruses vectored by these mites. In all cases, the most divergence between stocks was seen when bees were exposed to live mites or viruses, suggesting that gene activation, rather than constitutive expression, is key for these interactions. By revealing responses to viral infection and mite parasitism in different lineages, our data identify candidate proteins for the evolution of mite tolerance and virus resistance.

Comparative Genomics Reveals Recent Adaptive Evolution in Himalayan Giant Honeybee Apis laboriosa.

The Himalayan giant honeybee, Apis laboriosa, is the largest individual honeybee with major ecological and economic importance in high-latitude environments. However, our understanding of its environmental adaptations is circumscribed by the paucity of genomic data for this species. Here, we provide a draft genome of wild A. laboriosa, along with a comparison to its closely related species, Apis dorsata. The draft genome of A. laboriosa based on the de novo assembly is 226.1 Mbp in length with a scaffold N50 size of 3.34 Mbp, a GC content of 32.2%, a repeat content of 6.86%, and a gene family number of 8,404. Comparative genomics analysis revealed that the genes in A. laboriosa genome have undergone stronger positive selection (2.5 times more genes) and more recent duplication/loss events (6.1 times more events) than those in the A. dorsata genome. Our study implies the potential molecular mechanisms underlying the high-altitude adaptation of A. laboriosa and will catalyze future comparative studies to understand the environmental adaptation of modern honeybees.

Thermal stress induces tissue damage and a broad shift in regenerative signaling pathways in the honey bee digestive tract.

Honey bee colonies in the USA have suffered from increased die-off in the last few years with a complex set of interacting stresses playing a key role. With changing climate, an increase in the frequency of severe weather events, such as heat waves, is anticipated. Understanding how these changes may contribute to stress in honey bees is crucial. Individual honey bees appear to have a high capacity to endure thermal stress. One reason for this high-level endurance is likely their robust heat shock response (HSR), which contributes to thermotolerance at the cellular level. However, less is known about other mechanisms of thermotolerance, especially those operating at the tissue level. To elucidate other determinants of resilience in this species, we used thermal stress coupled with RNAseq and identified broad transcriptional remodeling of a number of key signaling pathways in the honey bee, including those pathways known to be involved in digestive tract regeneration in the fruit fly such as the Hippo and JAK/STAT pathways. We also observed cell death and shedding of epithelial cells, which likely leads to induction of this regenerative transcriptional program. We found that thermal stress affects many of these pathways in other tissues, suggesting a shared program of damage response. This study provides important foundational characterization of the tissue damage response program in this key pollinating species. In addition, our data suggest that a robust regeneration program may also be a critical contributor to thermotolerance at the tissue level, a possibility which warrants further exploration in this and other species.

Physiological and Immunological Status of Adult Honeybees (Apis mellifera) Fed Sugar Syrup Supplemented with Pentadecapeptide BPC 157.

Simple SummaryAdministration of BPC 157 induces positive physiological changes in honeybees. Those changes include few biochemical and immunological parameters in hemolymph and hypopharyngeal gland of newly emerged worker bees in laboratory-controlled conditions and increased enzymatic activity in the digestive system of young honeybees in apiary. Changes in proteolytic enzyme activity are particularly visible in the top of the epithelial cells in the mid-guts of honeybees, indicating a connection between oral administration of sucrose diet enriched with BPC 157 and honeybees’ immunity. These cognitions give a firm basis for further studies of BPC 157 use in all aspects of beekeeping.Various factors contribute to a decline in diversity and number of bees. Here, an integrated approach in experimental BPC 157 therapy was implemented, combining laboratory-controlled and field study results. The aim of a study was to assess the effects of BPC 157 additional feeding of newly emerged worker honeybees on few biochemical and immunological parameters in hemolymph (glucose, trehalose, lipids, proteins, vitellogenin, glucose-oxidase (GOX)), and hypopharyngeal gland (HPG), in laboratory-controlled conditions. Additionally, to examine the physiological status of protein digestion, the enzymatic activity of leucine aminopeptidase (LAP) in the mid-guts of worker honeybees was analyzed. It was found that individual honeybees, in hoarding cages, following BPC 157 administration through carbohydrate food, showed positive physiological changes when compared to the control groups. Those results were complemented by strong and visible LAP activity, particularly noticeable in the apical parts of the epithelial cells in the mid-guts of young worker honeybees originated from treated hives, suggesting a link between alternative oral therapy with BPC 157 and honeybees’ immunity.

Assessment and Comparison of Two Different Methods to Extract Nucleic Acids From Individual Honey Bees

AbstractThe honey bee is an excellent model system to study behavioral ecology, behavioral genetics, and sociogenomics. Nucleic acid-based analyses enable a broad scope of research in functional genomics, disease diagnostics, mutant screening, and genetic breeding. Multiple levels of analysis lead to a more comprehensive understanding of the causes of phenotypic variation by integrating genomic variation, transcriptomic profiles, and epigenomic information. One limitation, however, is the sample preparation procedures to obtain high quality DNA and RNA simultaneously, particularly from small amounts of material, such as tissues of individual bees. We demonstrate that it is feasible to perform dual extractions of DNA and RNA from a single individual bee and compare the quality and quantity of the extracted nucleic acids using two different types of methods. There was a greater total yield of DNA and RNA from ethanol-based extractions with minimal differences in overall concentration in ng/uL. We describe here the first validated method for dual extraction of DNA and RNA specifically from individual honey bees (Apis mellifera).

The mite Varroa destructor lowers the stinging response threshold of honey bees (Apis mellifera)

The ecto-parasitic mite Varroa destructor is an extremely damaging biotic factor of honey bees (Apis mellifera) worldwide. The magnitude of the damage that V. destructor causes to the health of honey bees is well documented, but little is known about how it affects their behavior. For example, it is not known whether parasitism by V. destructor influences the bees’ defensive behavior, and since this behavior has evolutionary and practical implications, its study is of importance. In this research, we used a constant-current stimulator to expose worker bees to a 0.5 mA electric stimulus after being parasitized by Varroa mites to test the hypothesis that V. destructor parasitism affects the stinging response threshold of individual honey bees. Bees exposed to V. destructor parasitism stung significantly faster than control bees in each of three trials (p < 0.05) and thus, it is concluded that the irritation caused by V. destructor reduces the stinging response threshold of honey bees. The implications of these findings are discussed, as well as the need for further studies to understand how V. destructor affects neuronal processes in the honey bee to make them more defensive.

Heritable Cognitive Phenotypes Influence Appetitive Learning but not Extinction in Honey Bees.

Learning and attention allow animals to better navigate complex environments. While foraging, honey bees (Apis mellifera L.) learn several aspects of their foraging environment, such as color and odor of flowers, which likely begins to happen before they evaluate the quality of the food. If bees begin to evaluate quality before they taste food, and then learn the food is depleted, this may create a conflict in what the bee learns and remembers. Individual honey bees differ in their sensitivity to information, thus creating variation in how they learn or do not learn certain environmental stimuli. For example, foraging honey bees exhibit differences in latent inhibition (LI), a learning process through which regular encounter with a stimulus without a consequence such as food can later reduce conditioning to that stimulus. Here, we test whether bees from distinct selected LI genotypes learn differently if reinforced via just antennae or via both antennae + proboscis. We also evaluate whether learned information goes extinct at different rates in these distinct LI genetic lines. We find that high LI bees learned significantly better when they were reinforced both antenna + proboscis, while low LI and control bees learned similarly with the two reinforcement pathways. We also find no differences in the acquisition and extinction of learned information in high LI and low LI bees. Our work provides insight into how underlying cognition may influence how honey bees learn and value information, which may lead to differences in how individuals and colonies make foraging decisions.

The Effect of Artificial Media and Temperature on the Growth and Development of the Honey Bee Brood Pathogen Ascosphaera apis.

Simple SummaryChalkbrood is a worldwide spread honey bee brood disease caused by the fungal pathogen Ascosphaera apis. The disease is commonly treated with fungicides, but due to the accumulation of residues, these fungicides have been banned in many countries, including European Union countries. Since then, control of chalkbrood has been problematic. The disease is fatal to individual honey bee larvae and can cause significant losses in terms of both bee numbers and colony productivity, and can even in some cases lead to colony collapse. Owing to these reasons, in vitro fungus cultivation is necessary to properly understand its pathogenesis as well as life cycle for the possible future development of an efficient and environmentally friendly control method. Therefore, in this study, several artificial media and different temperatures were evaluated to see their impact on the growth and development of A. apis. Furthermore, one of the media was modified by the addition of crushed honey bee brood to simulate natural conditions. This medium was found to be the most suitable for fungus reproductive structure production. In addition, a biological pattern was found explaining the relationships between temperature and the size of the fungal reproductive structures.Ascosphaera apis is a causative agent of chalkbrood, which is one of the most widespread honey bee diseases. In our experiments, the influence of several artificial media and cultivation under different temperatures was evaluated. Concretely, the radial growth of separated mating types was measured, reproductive structures in a Neubauer hemocytometer chamber were counted simultaneously, and the morphometry of spore cysts and spore balls was assessed. The complex set of experiments determined suitable cultivation conditions. A specific pattern between reproductive structure size and temperature was found. The optimal temperature for both mating types was 30 °C. SDA and YGPSA media are suitable for fast mycelial growth. Moreover, the effect of bee brood on fungus growth and development in vitro was investigated by modification of culture medium. The newly modified medium PDA-BB4 was most effective for the production of the reproductive structures. The result suggests that honey bee brood provides necessary nutrients for proper fungus development during in vitro cultivation. As there is no registered therapeutic agent against chalkbrood in most countries, including the European Union, the assessment of A. apis growth and development in different conditions could help to understand fungus pathogenesis and thus control chalkbrood disease.

The Effects of Exposure to Flupyradifurone on Survival, Development, and Foraging Activity of Honey Bees (Apis mellifera L.) under Field Conditions.

Simple SummaryHoney bees play an invaluable role in ecosystem stability and global food security. Recently, much attention has been directed toward the safety of pesticides to bees. Flupyradifurone (FPF) is a new butenolide insecticide and is considered friendly to honey bee fitness according to risk assessment procedures. Although no significant side-effects on bee colony strength parameters at FPF field-realistic concentration, laboratory experiments have demonstrated that FPF has multiple negative effects on the behavior of individual honey bees. The information suggested that FPF is posing potential risks to honey bees. In this study, we found that the survival rate of bees exposed to FPF was statistically significantly reduced, whereas there were no negative effects on larvae development nor foraging activity. In addition, immune- and detoxification-related genes were upregulated in exposed foragers and newly emerged bees, suggesting that more important synergistic and behavioral effects that can affect colony fitness should be explored in the future.Flupyradifurone (FPF) is a novel systemic nAChR agonist that interferes with signal transduction in the central nervous system of sucking pests. Despite claims that FPF is potentially “bee-safe” by risk assessments, laboratory data have suggested that FPF has multiple sub-lethal effects on individual honey bees. Our study aimed to expand the studies to the effects of field-realistic concentration of FPF. We found a statistically significant decrease in the survival rate of honey bees exposed to FPF, whereas there were no significantly negative effects on larvae development durations nor foraging activity. In addition, we found that the exposed foragers showed significantly higher expression of ApidNT, CYP9Q2, CYP9Q3, and AmInR-2 compared to the CK group (control group), but no alteration in the gene expression was observed in larvae. The exposed newly emerged bees showed significantly higher expression of Defensin and ApidNT. These results indicate that the chronic exposure to the field-realistic concentration of FPF has negligible effects, but more important synergistic and behavioral effects that can affect colony fitness should be explored in the future, considering the wide use of FPF on crops pollinated and visited by honey bees.

A computational approach to tracking age-based task frequency distributions of Apis mellifera worker cohorts

We present a model for tracking future task frequency distributions of individual adult worker honey bee (Apis mellifera L.) cohorts in a colony based on the composition of immatures at a specific time period. The user inputs the proportions of brood comb occupied by eggs, larvae, capped brood, or non-brood/empty cells. The model captured an experimental example where a brood comb is inserted into a surrogate colony and the individuals then emerge and express their adult lives. This model has clear application to many other experiments such as sublethal pesticide exposure. The model output is the expected proportion of cohort members engaged in a focal task at any given day post-insertion.

Neonicotinoid-contaminated diet causes behavior changes in forager honey bees (Apis mellifera) that may reduce colony survival during late fall

Neonicotinoid insecticides are often detected in pollen and nectar, which are the main food resources for honey bees. Sub-lethal and chronic exposure to these insecticides may have a prolonged effect on honey bees who are solely dependent on the stored food inside of the hive during cold weather. Our study investigated the effects of sub-lethal concentrations of imidacloprid on late fall forager honey bees’ behavior by accessing their activity levels and walking performance after being fed ad libitum with six different concentrations (2—125 μg/kg) of imidacloprid-dosed syrup for up to 48 h in the laboratory. Numbers of honey bees that walked after being released into a UV light illuminated tunnel decreased significantly as dosages of neonicotinoid in their diet increased. However, their walking speeds were not significantly affected by imidacloprid. The behavioral changes we observed in honey bees chronically exposed to neonicotinoid via diet could negatively affect individual honey bee performance of hive duties and consequently, colony survival during cold weather.

Exposure to low doses of pesticides induces an immune response and the production of nitric oxide in honeybees

Honeybees are essential pollinators of many agricultural crops and wild plants. However, the number of managed bee colonies has declined in some regions of the world over the last few decades, probably caused by a combination of factors including parasites, pathogens and pesticides. Exposure to these diverse biotic and abiotic stressors is likely to trigger immune responses and stress pathways that affect the health of individual honeybees and hence their contribution to colony survival. We therefore investigated the effects of an orally administered bacterial pathogen (Pseudomonas entomophila) and low-dose xenobiotic pesticides on honeybee survival and intestinal immune responses. We observed stressor-dependent effects on the mean lifespan, along with the induction of genes encoding the antimicrobial peptide abaecin and the detoxification factor cytochrome P450 monooxygenase CYP9E2. The pesticides also triggered the immediate induction of a nitric oxide synthase gene followed by the delayed upregulation of catalase, which was not observed in response to the pathogen. Honeybees therefore appear to produce nitric oxide as a specific defense response when exposed to xenobiotic stimuli. The immunity-related and stress-response genes we tested may provide useful stressor-dependent markers for ecotoxicological assessment in honeybee colonies.

You are what you eat: relative importance of diet, gut microbiota and nestmates for honey bee, Apis mellifera, worker health

In eusocial honey bees, Apis mellifera, diet, gut microbiota and nestmates can all contribute to the health of freshly emerged individual workers, but their relative importance for longevity and body weight is currently unknown. Here, we show that diet is most relevant, followed by gut microbiota and the presence of nestmates. Freshly emerged workers were randomly assigned to eight treatments (with or without honey/pollen, protein-substitute lactalbumin, antibiotic tetracycline and nestmates for 24 h) and maintained under standardised laboratory conditions. Longevity and food consumption were measured daily and fresh body weight was assessed at day 7. The data show a significantly better survival and a higher body weight in workers supplied with honey/pollen. Survival was higher in the lactalbumin treatments compared to the ones restricted to sucrose only, but lower compared to those with honey/pollen, highlighting the importance of micronutrients. In contrast, antibiotic treatment had a significant negative effect on longevity and body weight, which may be explained by inactivated gut microbiota and/or toxicity of the antibiotics. There was no positive effect of nestmates, probably due to the short exposure period. In contrast, nestmates showed a negative effect on survival in antibiotic-treated workers, possibly by transmitting pathogens and antibiotic-induced gut dysbiosis. In conclusion, a macro- and micronutrient-rich diet appears to be the key to individual honey bee worker health. Providing an optimal diet and possibly gut microbiota appears to be a promising way to promote managed A. mellifera health.

The effects of crude propolis, its volatiles and ethanolic extracts on the ecto-parasitic mite, Varroa destructor and health of the African savannah honey bee, Apis mellifera scutellata.

Propolis is a hive product composed of biologically active plant resins, and has been shown to enhance individual honey bee (Apis mellifera L.) health. Propolis has also been demonstrated to mitigate, in part, the negative effects caused by the ecto-parasitic mite Varroa destructor and its associated viruses on the health of managed European honey bee colonies. However, its effect on the health status of African honey bees remains largely unknown. Here, we found that the African savannah honey bees, A. m. scutellata in Kenya, deposited approximately two and half-fold more propolis in their colonies during periods of increased than reduced worker brood rearing. This finding suggested that A. m. scutellata may use high quantities of propolis prophylactically to protect their young brood; yet, we observed no significant correlation between the quantity of propolis and the amount of worker brood or mite-infestation level on adult workers. Furthermore, whereas propolis volatiles or propolis placed in direct contact with the mites had no effect on mite survival under laboratory conditions, the ethanolic extract of propolis significantly reduced mite survival when compared with untreated control. These results suggest the presence of mite deterrent compounds in the ethanolic extract of the African honey bee propolis.

Tracking individual honeybees among wildflower clusters with computer vision-facilitated pollinator monitoring.

Monitoring animals in their natural habitat is essential for advancement of animal behavioural studies, especially in pollination studies. Non-invasive techniques are preferred for these purposes as they reduce opportunities for research apparatus to interfere with behaviour. One potentially valuable approach is image-based tracking. However, the complexity of tracking unmarked wild animals using video is challenging in uncontrolled outdoor environments. Out-of-the-box algorithms currently present several problems in this context that can compromise accuracy, especially in cases of occlusion in a 3D environment. To address the issue, we present a novel hybrid detection and tracking algorithm to monitor unmarked insects outdoors. Our software can detect an insect, identify when a tracked insect becomes occluded from view and when it re-emerges, determine when an insect exits the camera field of view, and our software assembles a series of insect locations into a coherent trajectory. The insect detecting component of the software uses background subtraction and deep learning-based detection together to accurately and efficiently locate the insect among a cluster of wildflowers. We applied our method to track honeybees foraging outdoors using a new dataset that includes complex background detail, wind-blown foliage, and insects moving into and out of occlusion beneath leaves and among three-dimensional plant structures. We evaluated our software against human observations and previous techniques. It tracked honeybees at a rate of 86.6% on our dataset, 43% higher than the computationally more expensive, standalone deep learning model YOLOv2. We illustrate the value of our approach to quantify fine-scale foraging of honeybees. The ability to track unmarked insect pollinators in this way will help researchers better understand pollination ecology. The increased efficiency of our hybrid approach paves the way for the application of deep learning-based techniques to animal tracking in real-time using low-powered devices suitable for continuous monitoring.