Worker Honeybees Research Articles

Sublethal fluvalinate negatively affect the development and flight capacity of honeybee (Apis mellifera L.) workers

Fluvalinate has been heavily used to control the pest Varroa destructor and residues in honeybee colony causing long-term exposure threat for bees. But, little is known about the lifetime trips and homing ability of worker bees under fluvalinate stresses during the development period. In this study, honeybees from 2-day-old larvae to 7-day-old adults were continuously fed with different concentrations of fluvalinate (0, 0.5, 5 and 50 mg/kg) and the effects of fluvalinate on the development of larvae were examined. And then, all the treated bees were reintroduced into the original source colony and were monitored, and the homing ability of 20 days old bees at 1000 and 2000 m away from the beehive were tested using the radio frequency identification (RFID). We found that fluvalinate significantly activates the superoxide dismutase (SOD) activities of larvae and 5 mg/kg fluvalinate reduced the homing rate of workers at 2000 m away from colony. 50 mg/kg fluvalinate reduced proportion of capped worker cells, activated Cytochrome P450 (CYP450) activity of larvae, affected the foraging times, influenced the homing rate and homing time of one trip at 2000 m away from colony. Our results showed that the larvae can activate the activities of SOD and detoxification enzymes in detoxification of fluvalinate and reduce the influence on honeybees. But, when the concentration is higher than 5 mg/kg fluvalinate, it is difficult for bees to detoxify fluvalinate completely, which affect the homing rate. The results reflect the potential risk for honeybees in the development stage continuously exposed to fluvalinate.

Cannabis Extract Has a Positive-Immunostimulating Effect through Proteolytic System and Metabolic Compounds of Honey Bee (Apis mellifera) Workers.

Simple SummaryThe aim of our study was to test the immunostimulating effect of a diet with hemp extract on the resistance of the honey bee (Apis mellifera). The experiment compared the effect of supplementation between the bees receiving the extract in the form of a mixture with sugar syrup and on the strip with the extract, compared to the bees that had no contact with substance. In order to determine this effect, the biochemical indicators were analyzed: the proteolytic system (proteases, protease inhibitors, total protein concentration) responsible for the fight against pathogens/parasites, biomarkers (ALT, AST, ALP), and the basic components of metabolism (glucose and urea concentrations). Parameters were determined in the hemolymph of 2- and 7-day-old workers. Hemp extracts caused an increase in the protein concentrations. Regardless of the method of administration, proteases decreased. Protease inhibitors increased, except supplementation on strips where the activity decreased. The biomarker activities increased in the control group and workers feeding extract in syrup and decreased in workers supplemented with the extract on strips. The results of the metabolic component were as follows: glucose and urea concentrations indicate that the extract will not adversely affect metabolic changes in the insect’s organism. Hemp extract improves the natural immunity of bees.In the study, we assessed the effect of hemp extract on activities of resistance parameters and the metabolic compound concentration in adult workers’ hemolymph. Bees were divided into the following groups: (1) control group fed with mixture of sugar and water-glycerine solution, (2) experimental group with pure sugar syrup and inside with cotton strips soaked with hemp extract, (3) experimental group with a mixture of sugar syrup with hemp extract. Hemp extracts caused an increase in the protein concentrations and reduced the protease activities regardless of the administration method. The protease inhibitor activities were decreased only in the group that received hemp extract on the strips. The biomarker activities (ALP, ALT, AST) increased from the control group and workers feeding extract in syrup and decreased in workers supplemented with the extract on strips. In young, 2-day-old workers, the glucose concentration was higher in the groups feeding with the extract than in the control. Hemp extract influenced an increase in urea concentrations in workers’ hemolymph in comparison with the control. The hemp supplementation positively influences the immune system of workers, and the appropriate method of administration may be adapted to the health problems of bees.

Seasonal variations of colony activities linked to morphometric and glands characterizations of hybrid Carniolan honey bee (Apis mellifera carnica Pollmann) workers

ObjectivesThe activity and productivity of the honey bee colony depend upon many factors operating simultaneously and reacts to some environmental conditions. We aimed to study the morphometric characteristics and glands development of nurse and forager of hybrid Carniolan honey bee (Apis mellifera carnica Pollmann) workers in relation to activities of the colony during the different seasons. MethodsThe study was conducted during spring, summer, fall, then winter in 2020/2021. Ten colonies of hybrid Carniolan honey bees, every colony with about 14,000 bees, were utilizedz. The seasonal variations of foraging activity, hoarded pollen area, and sealed brood area were determined. Also, the body weight, some morphometric characteristics, and development of glands of nurses and foragers bees were measured. Results and conclusionsThe highest numbers of foragers and pollen foragers/colony/min., stored pollen area, and worker sealed brood area were recorded in May. Measurements of nurses reared during spring were larger than nurses and foragers of other seasons for body weight, mandibular and hypopharyngeal glands (HPGs), length and width of the 2nd wax mirror. The highest proboscis and corbicula lengths were found in foragers reared during spring, without significant differences between worker castes. It can be concluded that the performance of the colony, morphometric characteristics, and development of glands were dependent on the time of the year. Beekeepers in Kafrelsheikh province and similar environmental condition areas should provide the colonies with pollen substitutes or supplements during April, June, and October to February to maintain the strength of the colonies.

Effect of Honey and Syrup Diets Enriched with 1,3-1,6 β-Glucans on Honeybee Survival Rate and Phenoloxidase Activity (Apis mellifera L. 1758).

β-glucans can activate the animal innate immune system by acting as immune-modulators and inducing various stimulatory effects. The aim of this study was to investigate the effect of 1,3-1,6 β-glucans administered orally for 96 h on Apis mellifera workers (newly emerged and nurse bees). β-glucans were included in honey and syrup. Survival rate and phenoloxidase activity were measured. In both newly emerged and nurse bees, β-glucans supplementation did not affect survival rate (p > 0.05). Conversely, phenoloxidase activity was higher in both newly emerged bees (p = 0.048) and nurse bees (p = 0.014) fed with a honey diet enriched with β-glucans compared to those fed with only honey. In both the newly emerged and nurse bees, no statistical differences in phenoloxidase activity were recorded between the group fed with a syrup-based diet enriched with β-glucans and the control group (p > 0.05). The absence of significant variation in survival suggests that the potential negative effect of β-glucans in healthy bees could be mitigated by their metabolism. Conversely, the inclusion of β-glucans in a honey-based diet determined an increase of phenoloxidase activity, suggesting that the effect of β-glucan inclusion in the diet of healthy bees on phenoloxidase activity could be linked to the type of base-diet. Further investigations on β-glucans metabolism in bees, on molecular mechanism of phenoloxidase activation by 1,3-1,6 β-glucans, and relative thresholds are desirable. Moreover, investigation on the combined action of honey and β-glucans on phenoloxidase activity are needed.

The Pathogens Spillover and Incidence Correlation in Bumblebees and Honeybees in Slovenia.

Slovenia has a long tradition of beekeeping and a high density of honeybee colonies, but less is known about bumblebees and their pathogens. Therefore, a study was conducted to define the incidence and prevalence of pathogens in bumblebees and to determine whether there are links between infections in bumblebees and honeybees. In 2017 and 2018, clinically healthy workers of bumblebees (Bombus spp.) and honeybees (Apis mellifera) were collected on flowers at four different locations in Slovenia. In addition, bumblebee queens were also collected in 2018. Several pathogens were detected in the bumblebee workers using PCR and RT-PCR methods: 8.8% on acute bee paralysis virus (ABPV), 58.5% on black queen cell virus (BQCV), 6.8% on deformed wing virus (DWV), 24.5% on sacbrood bee virus (SBV), 15.6% on Lake Sinai virus (LSV), 16.3% on Nosema bombi, 8.2% on Nosema ceranae, 15.0% on Apicystis bombi and 17.0% on Crithidia bombi. In bumblebee queens, only the presence of BQCV, A. bombi and C. bombi was detected with 73.3, 26.3 and 33.3% positive samples, respectively. This study confirmed that several pathogens are regularly detected in both bumblebees and honeybees. Further studies on the pathogen transmission routes are required.

Effects of Plant Protection Products on Biochemical Markers in Honey Bees

Plant protection products (PPPs) are pesticides that protect crops and ornamental plants. PPPs include primarily insecticides, herbicides, and fungicides. Bees’ contact with PPPs can cause immediate death or, in sublethal dose, may affect their physiology and/or behavior. Understanding the effect of PPPs’ sublethal doses is especially important. Contact with a sublethal dose of PPPs generally allows the bee to return to the hive, which may expose the whole colony to the harmful substance. Biochemical changes may affect colony condition, health, and performance. Most of the research on the biochemical effects of PPP in honey bees focuses on insecticides and among them neonicotinoids (especially imidacloprid). The vast majority of research is carried out on Apis mellifera workers. A small part of the research has been conducted on drones and queens. Pesticides, including fungicides and herbicides, may alter antioxidant defense, detoxification, gene expression, and immune response of the bee. They affect the drones’ semen quality and metabolic rate of the queen. In this review, the biochemical effect of PPP products in the honey bee was examined, with a focus on the effect on cytochrome P450 monooxygenases, glutathione transferases, and carboxylesterases, which take part in toxin metabolism or the detoxification process. PPPs effects on the activity of glutathione peroxidase (GPX), catalase (CAT), superoxide dismutase (SOD), proteases, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and phenoloxidase (PO) are also presented.

Tropilaelaps mercedesae parasitism changes behavior and gene expression in honey bee workers.

Tropilaelaps mercedesae is one of the most problematic honey bee parasites and has become more threatening to the beekeeping industry. Tropilaelaps can easily parasitize immature honey bees (larvae and pupae) and have both lethal and sublethal effects on the individual worker bees. Our study for the first time experimentally assessed the effects of T. mercedesae on olfactory learning, flight ability, homing ability as well as transcriptional changes in parasitized adult honey bees. T. mercedesae infestation had negative impacts on olfactory associated function, flight ability, and homing rate. The volume of the mushroom body significantly increased in infested honey bees, which may be correlated to the lower sucrose responsiveness as well as lower learning ability in the infested bees. The gene expression involved in immune systems and carbohydrate transport and metabolism were significantly different between infested bees and non-infested bees. Moreover, genes function in cell adhesion play an essential role in olfactory sensory in honey bees. Our findings provide a comprehensive understanding of European honey bees in response to T. mercedesae infestation, and could be used to further investigate the complex molecular mechanisms in honey bees under parasitic stress.

Ratios rather than concentrations of nutritionally important elements may shape honey bee preferences for ‘dirty water’

1. Honey bees require minerals for a complete diet. However, minerals from flowers can be inadequate in concentration and composition. Therefore, honey bees may drink ‘dirty water’ from natural sources such as puddles. Some research has attempted to simulate this through honey bee bioassays, but to date, these have tested minerals individually, not as mixtures as would occur in nature. Here, for the first time, we use honey bees in bioassays in which a range of mineral mixtures are presented together in choice experiments.2. Six minerals (NaCl, KCl, CaCl2, MgCl2, NH4Cl, and KH2PO4) were used in mixtures to simulate different mineral stoichiometries, which may occur in ‘dirty water’, such as puddles, from which honey bees often drink. Based on the honey bee mineral tolerance ranges from the literature, these mixtures were offered in aqueous solutions at low, medium, high, and mixed molar concentrations. Deionised water and sucrose were neutral and positive controls, respectively. Petri dishes were set up in containers in a laboratory. Twenty worker honey bees (Apis mellifera L.) were placed into each container and observed for drinking behaviour for 1 h.3. Honey bees preferred the mixed molar treatment comprising a high Na:K ratio, a medium molarity of NaCl and a low molarity of the other minerals. This novel finding suggests that mixed mineral ‘dirty water’ should be investigated on a larger scale with multiple hives in the field and highlights the importance of stoichiometrically balanced honey bee diets.

NUTRITIONAL EFFECTS OF SOME POLLEN TYPES ON HYPOPHARYNGEAL AND ACID GLANDS IN HONEYBEE WORKERS (APIS MELLIFERA L.)

Pollen had a wide range of effects on honey bee. Caged honey bee workers were used to determine the nutritional effects of four main types of pollen collected by honey bee colonies from the study area on the food consumption rates, bees age, the development of the hypopharyngeal (HPG) acini and acid gland (AG) sacs in honey bee workers. Additionally, chemical analysis of the selected pollen types was performed. Pollen diets were as follows: broad bean pollen, date palm pollen, clover pollen, maize pollen and mixture of the for mentioned typrs beside the control pollen diet. The highest mean consumption was observed between 4th and 6th of day aged bees in all diets (23.05 mg./bee/3days). The highest quantity of food consumption was recorded in the 18th day when the workers were fed on date palm pollen (75.42 mg), while the lowest recorded 59.17 mg from maize pollen treatment. The highest mean acinal surface area of HPG was 0.0451mm2, which measured at 9 days-old of bees in all diets. While the workers fed on mixture pollen diet had the highest significant mean recorded the acinal surface area of HPG 0.0450mm2 comparing of 0.0223mm2 in control. The considering increment in average volume of acid gland sac with had been obtained at 18 days-old (0.7276mm3) that resembles the highest significant degree, the greatest mean volume of AG sacs was observed when bees were fed on broad bean pollen (0.6419mm3), while the lowest mean was 0.3643mm3 in control.

Acute toxicity of Siltac EC to the honey bee (Apis mellifera)

<b>Different types of pesticides are commonly used in modern agriculture. Honey bees (Apis mellifera) are sensitive indicators of environmental contamination with these substances. Exposure of honey bees to pesticides can lead to changes in their behaviour and increase mortality, so it is important to develop formulations that provide alternatives to common (‘chemical’) pesticides. The preparation Siltac EC, that has recently been developed (patent no. WO 2016/061259), shows promise as an effective substitute. This preparation is based on a physical interaction with the pest. It does not contain chemicals classified as pesticides. The aim of the current study was to evaluate the toxicity of Siltac EC to adult honeybee workers. The experiments showed that both contact and oral acute toxicity were very low and the preparation can be initially considered safe for honey bees.

Effect of the electric field at 50 Hz and variable intensities on biochemical markers in the honey bee's hemolymph.

The amount of artificial electromagnetic fields of various parameters in the honey bee’s environment increases globally. So far, it had been proven that exposure to an E-field at 50 Hz can cause changes in bee’s behavior, alter the activity of proteases, and enzymatic antioxidants. Due to the potentially harmful effect of this factor on honey bees, we decided to investigate the activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP), and the concentration of albumin and creatinine in bee’s hemolymph after exposure to 50 Hz E-field. Honey bee workers were placed in wooden cages (200 × 150 × 70 mm) and exposed to the 50 Hz E-field with the intensity of <1, 5.0, 11.5, 23.0, or 34.5 kV/m for 1, 3, 6, or 12h. A homogeneous 50 Hz E-field was generated in the form of a plate capacitor. Hemolymph samples for analysis were taken immediately after the end of exposure to the E-field from 100 bees from each group. According to our study, the activity of AST, ALT, and ALP in honey bees’ hemolymph decreased after exposure to 50 Hz E-field with various intensities. The decrease in AST, ALT, and ALP activity intensified with prolonged exposure time. 50 Hz E-field may cause the impairment of crucial metabolic cycles in the honey bees’ organism (such as the citric acid cycle, ATP synthesis, oxidative phosphorylation, β-oxidation). Moreover, exposure to E-Field altered the concentration of creatinine and albumin, which are important non-enzymatic antioxidants. Such changes may indicate a disturbance in protein metabolism and increased muscle activity.

Fermented pollen substitute diet affects the lifespan of honey bee workers under the effect of food consumption rate and vitellogenin expression

Fermented pollen substitute diet affects the lifespan of honey bee workers under the effect of food consumption rate and vitellogenin expression

Fatty acids and elemental composition changes in honey bee workers (Apis mellifera) irradiated with gamma radiation

The effect of gamma radiation on the whole body contents of fatty acids and elemental composition were investigated for honey bee workers Apis mellifera. The data indicated that the quantities of fatty acids and elemental composition within the whole body of the workers of A. mellifera were affected significantly especially at the dose of 20 rad. Data obtained indicated that the palmitic (C16:0), oleic (C18:1) and linolic (C18:2) acids increased when workers irradiated with 20 rad. Analysis of the 7 elements; Mg, P, K, Ca, Fe, Cu and Zn were detected by energy dispersive X- ray analyzer by using (EDX). The most dominant elements in control workers were K followed by P; the Fe occupied the last order. In irradiated adult workers with 20 rad, K recorded a higher percentage than its control. In the same dose (20 rad), the total heavy metals Copper + Zink (Cu + Zn) decreased from 19.81% to 14.8%.

Vitellogenin in the honey bee midgut

The alimentary canal carries out many functions critical to insect physiology, including digesting and absorbing nutrients and water, housing beneficial gut bacteria, and eliciting immunological responses. The midgut, in particular, is a compartment for digestion and absorption and serves as a first point of contact between ingested pathogens and the insect immune system. Recently, we found the protein vitellogenin (Vg) localized in midgut cells of some honey bee workers. Vg is an important egg-yolk precursor protein in nearly all oviparous animals, but it also has immunological functions shared across many taxa. Additional and unexpected Vg functions have been characterized in honey bees, but none of these functions involve the midgut directly. Therefore, we sought to map out how Vg is localized and expressed in this organ across the two most common worker bee behavioral groups, namely nurses and foragers. We used immunohistochemistry and quantitative reverse transcription PCR to show Vg has different localization patterns in nurses and foragers and limited gene expression. Our study provides a platform for building a more detailed understanding of the possible roles of Vg in insect midgut cells, and it adds to the current knowledge of this fascinating, multi-functional protein.

Sublethal effects of Isoclast™ Active (50% sulfoxaflor water dispersible granules) on larval and adult worker honey bees (Apis mellifera L.)

Sulfoxaflor is a novel sulfoximine insecticide which is widely used to control crop pests. Risk assessments have reported its high toxicity to pollinators. However, sulfoxaflor is not persistent in the environment and few studies have addressed its negative effects on larval and newly emerged honeybees at environmentally relevant concentrations. In the present study, the sublethal effects of a sulfoxaflor commercial product, Isoclast™ Active, were evaluated in the laboratory using larvae and newly emerged worker honeybees. The results of 96-h acute toxicity showed that Isoclast is moderately toxic to adult bees, and it could induce significant death and growth failure of larvae after continuous dietary intake. In addition, Isoclast induced significant changes in antioxidative (SOD, CAT), lipid peroxidation (POD, LPO, MDA), detoxification (GST, GR, GSH) and signal transduction-related (AChE, ACh) enzymes or products both in larvae and adult honey bees under residue levels. Here we firstly reported the lethal and sublethal effects of commercial sulfoxaflor to honeybees’ larvae and young workers. All these findings revealed the potential risks of sulfoxaflor residue in environment to honey bees, and may also to other pollinators. This is a laboratory mimic studies, and further studies are still needed to investigate the risks and in-depth mechanisms of sulfoxaflor to bees in field.

Potential risks from the accumulation of heavy metals in canola plants.

Concentrations of heavy metals in agricultural land near highways are a major concern for humans. This study was conducted to investigate the contamination level of heavy metals in soil, canola crop, and the potential health risk for honeybee and human. The average concentrations (mg/kg) of Co (15.94), Cr (169.66), Ni (55.39), Mn (765.34) Hg (2.99), and Cu (51.31) were elevated beyond their background reference values in world soil average, while Pb (9.45) was below to their respective background levels. This was confirmed by contamination factor (CF) and ecological risk factors (Er). Heavy metal concentrations in different parts of canola decreased in the following order: Fe> Mn > Cr > Pb > Co > Cu > Ni > Hg. Honey transfer factor (TFH) of heavy metals was less than unity except Ni and Hg. Human health (non-carcinogenic) risk assessment of heavy metals in the soil through potential exposure pathway (ingestion) recorded a dramatically increased risk for children (hazard index, HI=2.44). Hazard quotient via honey (HQH) consumption value of heavy metals were within the safe limits (HQ< 1). Probably, honeybees have a strong ability to transfer Co, Pb, Hg, and Mn (HQ> 1) from the canola to their hives during collecting pollen and nectar. HQ in honeybee workers from the consumption of honey can be used to derive HQ in humans using the hazard factor (HF). HF is 1481.482 (Pb), 2356.902 (Ni), and 3888.889 (Cr), respectively, for adult human (70kg) and 317.460 (Pb), 504.377(Ni), and 832.22 (Cr) for children (15kg).

Effects of larval exposure to the fungicide pyraclostrobin on the post-embryonic development of Africanized Apis mellifera workers

Among the more than twenty thousand bee species currently described, Apis mellifera stands out for its high economic relevance due to crop pollination. In recent decades, many studies have registered a decline in bee populations associating multiple factors, including pesticides. These molecules can arrive through residues present in the nectar and pollen, which can be ingested by the larvae. However, studies that contemplate the effects of fungicides on larvae and adults are rare. Thus, the objective of the study was to evaluate the effects of the exposure to pyraclostrobin in the larval phase and verify the late effects in newly emerged bees. The larvae were subjected to repeated exposure (third to the sixth day of the bioassay). The concentrations of pyraclostrobin consumption were 127.58 ng/larva (PT1), 13.16 ng/larva (PT2), and 4.24 ng/larva (PT3), both based on residues found in the field like as pollen and bee bread. The effects on larval mortality, pupation, emergence and survival rates, and median lethal time of newly emerged worker bees were evaluated. We also evaluated cell death and chitin marking of the peritrophic matrix in the intestine of larvae and newly emerged bees. No adverse effects were observed on the post-embryonic development of the larvae and survival time of the newly emerged workers, showing tolerance to the fungicide. However, the intestine epithelium of larvae (PT1 and PT2) and adults (PT1) showed immunostaining for cell death and increased intensity of chitin marking in the peritrophic matrix, indicating a late effect of the pyraclostrobin fungicide. Thus, the ingestion of the fungicide in the larval stage can impair the bee development and the health and performance of the colony. In this perspective, studies that consider the effects of fungicides in the different stages of bee development are crucial for a better interpretation of the risks of exposure.

Antioxidation Defenses of Apis mellifera Queens and Workers Respond to Imidacloprid in Different Age-Dependent Ways: Old Queens Are Resistant, Foragers Are Not.

Simple SummaryHoney bees are unique for studies on aging because queens live 40-fold longer than workers. An efficient antioxidant defense (ADS) is thought to be pivotal for longevity, but not always. How were different ADSs shaped by evolution in young and old queens and workers? Honey bees, the essential pollinators, are facing depopulation due, at least in part, to pesticides, such as imidacloprid, an oxidative stressor. Is an evolutionarily shaped ADS still useful for contemporary young and old queens/workers? Answering these questions is important for emerging oxidative-stress ecology and protecting contemporary honey bees. The ADS activity was determined in 1-day-old, 20-day-old, and 2-year-old queens and in 1-day-old and 20-day-old workers (foragers) fed without (control) or with low or high imidacloprid (in bee food). ADS was upregulated in workers with age but downregulated in queens. However, imidacloprid oxidative stress suppressed the active ADS in workers, particularly 20-day-old foragers, but not in 1-day-old queens. Unexpectedly, poor ADS activity in 2-year-old queens was highly upregulated by imidacloprid. Thus, queen and worker ADSs respond to imidacloprid in opposite ways, and old queens were still resistant, but foragers were not. This may be unfavorable for foragers dwelling in ecosystems that expose them to pesticides.We investigated how different antioxidant defenses (ADSs) were shaped by evolution in young/old Apis mellifera workers and queens to broaden the limited knowledge on whether ADSs are effective in contemporary pesticide environments and to complete bee oxidative-aging theory. We acquired 1-day-old, 20-day-old, and 2-year-old queens and 1-day-old and 20-day-old workers (foragers) fed 0, 5, or 200 ppb imidacloprid, a pesticide oxidative stressor. The activities of catalase, glutathione peroxidase, glutathione S-transferase, and superoxide dismutase and the level of total antioxidant potential were determined in hemolymph. The ADS was upregulated in workers with age but downregulated in queens. Imidacloprid suppressed the ADS in all workers, particularly in foragers with an upregulated ADS, but it did not affect the ADS in 1-day-old queens. In contrast to foragers, the downregulated ADS of 2-year-old queens was unexpectedly highly upregulated by imidacloprid, which has not been previously shown in such old queens. The principal component analysis confirmed that queen and worker ADSs responded to imidacloprid in opposite ways, and ADS of 2-year-queens was markedly different from those of others. Thus, evolutionary shaped ADSs of older queens and workers may be of the limited use for foragers dwelling in pesticide ecosystems, but not for old queens.

Pupal cannibalism by worker honey bees contributes to the spread of deformed wing virus

Transmission routes impact pathogen virulence and genetics, therefore comprehensive knowledge of these routes and their contribution to pathogen circulation is essential for understanding host–pathogen interactions and designing control strategies. Deformed wing virus (DWV), a principal viral pathogen of honey bees associated with increased honey bee mortality and colony losses, became highly virulent with the spread of its vector, the ectoparasitic mite Varroa destructor. Reproduction of Varroa mites occurs in capped brood cells and mite-infested pupae from these cells usually have high levels of DWV. The removal of mite-infested pupae by worker bees, Varroa Sensitive Hygiene (VSH), leads to cannibalization of pupae with high DWV loads, thereby offering an alternative route for virus transmission. We used genetically tagged DWV to investigate virus transmission to and between worker bees following pupal cannibalisation under experimental conditions. We demonstrated that cannibalization of DWV-infected pupae resulted in high levels of this virus in worker bees and that the acquired virus was then transmitted between bees via trophallaxis, allowing circulation of Varroa-vectored DWV variants without the mites. Despite the known benefits of hygienic behaviour, it is possible that higher levels of VSH activity may result in increased transmission of DWV via cannibalism and trophallaxis.

A fermented Pollen Substitute Diet Affects Wax Construction by Honey Bee Workers, (Apies mellifera L.)

Pollen substitute diets have become increasingly important for maintaining strong and healthy honey bee colonies. Palatability and nutritional value are key attributes of a good diet. Since beebread, which is pollen fermented by the bees, is the main food of the worker-nurse bees that feed and care for the bee larvae, pollen substitutes should have similar attributes. In an attempt to simulate this natural food source, an inoculum prepared from beebread was used to ferment a pollen substitute diet. In this study, it was determined the differences in the wax building by caged workers fed with different diets (sucrose syrup only, bee bread, unfermented pollen substitute diet and fermented pollen substitute diet). Comb building in honeybees was analyzed with respect to the type of food. The effects on wax combs building were assessed of the presence of beeswax foundation, and of feeding honey bees in cages. Workers fed on unfermented diets produced significantly less wax than did those fed on the fermented diets; although variation in wax production among the treatments was not significant. We conclude that fermentation by beebread-derived microorganisms could improve the palatability, consumption and nutritional value of the dies and the behavioral activities such as wax building by honey bee workers.