Showing papers on "Varroa sensitive hygiene published in 2016"

Ecology of Varroa destructor, the Major Ectoparasite of the Western Honey Bee, Apis mellifera

Abstract: Varroa destructor is the most important ectoparasite of Apis mellifera. This review addresses the interactions between the varroa mite, its environment, and the honey bee host, mediated by an impressive number of cues and signals, including semiochemicals regulating crucial steps of the mite's life cycle. Although mechanical stimuli, temperature, and humidity play an important role, chemical communication is the most important channel. Kairomones are used at all stages of the mite's life cycle, and the exploitation of bees' brood pheromones is particularly significant given these compounds function as primer and releaser signals that regulate the social organization of the honey bee colony. V. destructor is a major problem for apiculture, and the search for novel control methods is an essential task for researchers. A detailed study of the ecological interactions of V. destructor is a prerequisite for creating strategies to sustainably manage the parasite.

Non-cultivated plants present a season-long route of pesticide exposure for honey bees

Abstract: Recent efforts to evaluate the contribution of neonicotinoid insecticides to worldwide pollinator declines have focused on honey bees and the chronic levels of exposure experienced when foraging on crops grown from neonicotinoid-treated seeds. However, few studies address non-crop plants as a potential route of pollinator exposure to neonicotinoid and other insecticides. Here we show that pollen collected by honey bee foragers in maize- and soybean-dominated landscapes is contaminated throughout the growing season with multiple agricultural pesticides, including the neonicotinoids used as seed treatments. Notably, however, the highest levels of contamination in pollen are pyrethroid insecticides targeting mosquitoes and other nuisance pests. Furthermore, pollen from crop plants represents only a tiny fraction of the total diversity of pollen resources used by honey bees in these landscapes, with the principle sources of pollen originating from non-cultivated plants. These findings provide fundamental information about the foraging habits of honey bees in these landscapes.

Natural Varroa mite-surviving Apis mellifera honeybee populations

Abstract: The Varroa destructor mite is the largest threat to apiculture worldwide and has been responsible for devastating losses of wild honeybee populations in Europe and North America. However, Varroa mite-resistant populations of A. mellifera honeybees have been reported and documented around the world with a variety of explanations for their long-term survival with uncontrolled mite infestation. This review synthesizes the work on naturally occurring survival to Varroa mites and discusses what these honeybee populations can signify for apiculture.

Specific Cues Associated With Honey Bee Social Defence against Varroa destructor Infested Brood

Abstract: Social immunity forms an essential part of the defence repertoire of social insects. In response to infestation by the parasitic mite Varroa destructor and its associated viruses, honey bees (Apis mellifera L.) have developed a specific behaviour (varroa-sensitive hygiene, or VSH) that helps protect the colony from this parasite. Brood cells heavily infested with mites are uncapped, the brood killed, and the cell contents removed. For this extreme sacrifice to be beneficial to the colony, the targeting of parasitized brood for removal must be accurate and selective. Here we show that varroa-infested brood produce uniquely identifiable cues that could be used by VSH-performing bees to identify with high specificity which brood cells to sacrifice. This selective elimination of mite-infested brood is a disease resistance strategy analogous to programmed cell death, where young bees likely to be highly dysfunctional as adults are sacrificed for the greater good of the colony.

Social apoptosis in honey bee superorganisms.

Abstract: Eusocial insect colonies form superorganisms, in which nestmates cooperate and use social immunity to combat parasites. However, social immunity may fail in case of emerging diseases. This is the case for the ectoparasitic mite Varroa destructor, which switched hosts from the Eastern honeybee, Apis cerana, to the Western honey bee, Apis mellifera, and currently is the greatest threat to A. mellifera apiculture globally. Here, we show that immature workers of the mite's original host, A. cerana, are more susceptible to V. destructor infestations than those of its new host, thereby enabling more efficient social immunity and contributing to colony survival. This counterintuitive result shows that susceptible individuals can foster superorganism survival, offering empirical support to theoretical arguments about the adaptive value of worker suicide in social insects. Altruistic suicide of immature bees constitutes a social analogue of apoptosis, as it prevents the spread of infections by sacrificing parts of the whole organism, and unveils a novel form of transgenerational social immunity in honey bees. Taking into account the key role of susceptible immature bees in social immunity will improve breeding efforts to mitigate the unsustainably high colony losses of Western honey bees due to V. destructor infestations worldwide.

How Honey Bee Colonies Survive in the Wild: Testing the Importance of Small Nests and Frequent Swarming.

Abstract: The ectoparasitic mite, Varroa destructor, and the viruses that it transmits, kill the colonies of European honey bees (Apis mellifera) kept by beekeepers unless the bees are treated with miticides. Nevertheless, there exist populations of wild colonies of European honey bees that are persisting without being treated with miticides. We hypothesized that the persistence of these wild colonies is due in part to their habits of nesting in small cavities and swarming frequently. We tested this hypothesis by establishing two groups of colonies living either in small hives (42 L) without swarm-control treatments or in large hives (up to 168 L) with swarm-control treatments. We followed the colonies for two years and compared the two groups with respect to swarming frequency, Varroa infesttion rate, disease incidence, and colony survival. Colonies in small hives swarmed more often, had lower Varroa infestation rates, had less disease, and had higher survival compared to colonies in large hives. These results indicate that the smaller nest cavities and more frequent swarming of wild colonies contribute to their persistence without mite treatments.

Grooming by honey bees as a component of varroa resistant behavior

Abstract: Grooming behavior of honey bees can be considered in two major categories: autogrooming or self-grooming and inter-bee grooming, called allogrooming. Allogrooming can be one-on-one, or social, involving several nestmates acting collaboratively. In addition, some house bees become allogrooming specialists, and for them grooming their nestmates can be a full-time occupation for most of their lives. Early observations on the Eastern honey bee, Apis cerana, recorded autogrooming, one-on-one, and social allogrooming, all of which result in dead, visibly mutilated varroa mites falling to the hive floor. Similar behavior has been sought in the Western honey bee. Apis mellifera, with variant observations for the different subspecies. Most descriptions relate to A. m. carnica, some to A. m. ligustica, but with one notable exception, almost none to A. m. mellifera. The most impressive findings are from “Africanized” bees, which provide some of the best cases of natural, long-lasting tolerance to varroa mites in A. ...

Intensively Cultivated Landscape and Varroa Mite Infestation Are Associated with Reduced Honey Bee Nutritional State.

Abstract: As key pollinators, honey bees are crucial to many natural and agricultural ecosystems. An important factor in the health of honey bees is the availability of diverse floral resources. However, in many parts of the world, high-intensity agriculture could result in a reduction in honey bee forage. Previous studies have investigated how the landscape surrounding honey bee hives affects some aspects of honey bee health, but to our knowledge there have been no investigations of the effects of intensively cultivated landscapes on indicators of individual bee health such as nutritional physiology and pathogen loads. Furthermore, agricultural landscapes in different regions vary greatly in forage and land management, indicating a need for additional information on the relationship between honey bee health and landscape cultivation. Here, we add to this growing body of information by investigating differences in nutritional physiology between honey bees kept in areas of comparatively low and high cultivation in an area generally high agricultural intensity in the Midwestern United States. We focused on bees collected directly before winter, because overwintering stress poses one of the most serious problems for honey bees in temperate climates. We found that honey bees kept in areas of lower cultivation exhibited higher lipid levels than those kept in areas of high cultivation, but this effect was observed only in colonies that were free of Varroa mites. Furthermore, we found that the presence of mites was associated with lower lipid levels and higher titers of deformed wing virus (DWV), as well as a non-significant trend towards higher overwinter losses. Overall, these results show that mite infestation interacts with landscape, obscuring the effects of landscape alone and suggesting that the benefits of improved foraging landscape could be lost without adequate control of mite infestations.

Proteome Analysis of the Hemolymph, Mushroom Body, and Antenna Provides Novel Insight into Honeybee Resistance against Varroa Infestation

Abstract: Varroa destructor has been identified as a major culprit responsible for the losses of millions of honeybee colonies. Varroa sensitive hygiene (VSH) is a suite of behaviors from adult bees to suppress mite reproduction by uncapping and/or removing mite infested pupae from a sealed brood. Despite the efforts to elucidate the molecular underpinnings of VSH, they remain largely unknown. We investigated the proteome of mushroom bodies (MBs) and antennae of adult bees with and without VSH from a stock selected for VSH based on their response to artificially Varroa-infected brood cells by near-infrared camera observation. The pupal hemolymph proteome was also compared between the VSH-line and the line that was not selected for VSH. The identified 8609 proteins in the hemolymph, MBs, and antennae represent the most depth coverage of the honeybee proteome (>55%) to date. In the hemolymph, the VSH-line adapts a unique strategy to boost the social immunity and drive pupal organogenesis by enhancing energy metabolis...

Review of field and monitoring studies investigating the role of nitro-substituted neonicotinoid insecticides in the reported losses of honey bee colonies (Apis mellifera)

Abstract: The nitro-substituted neonicotinoid insecticides, which include imidacloprid, thiamethoxam and clothianidin, are widely used to control a range of important agricultural pests both by foliar applications and also as seed dressings and by soil application. Since they exhibit systemic properties, exposure of bees may occur as a result of residues present in the nectar and/or pollen of seed- or soil-treated crop plants and so they have been the subject of much debate about whether they cause adverse effects in pollinating insects under field conditions. Due to these perceived concerns, the use of the three neonicotinoids imidacloprid, clothianidin and thiamethoxam has been temporarily suspended in the European Union for seed treatment, soil application and foliar treatment in crops attractive to bees. Monitoring data from a number of countries are available to assess the presence of neonicotinoid residues in honey bee samples and possible impacts at the colony level and these are reviewed here together with a number of field studies which have looked at the impact of clothiandin on honey bees in relation to specific crop use and in particular with oilseed rape. Currently there is considerable uncertainty with regards to the regulatory testing requirements for field studies. Accordingly, a testing protocol was developed to address any acute and chronic risks from oilseed rape seeds containing a coating with 10 g clothianidin and 2 g beta-cyfluthrin per kg seeds (Elado®) for managed honey bee (Apis mellifera) colonies, commercially bred bumble bee (Bombus terrestris) colonies and red mason bees (Osmia bicornis) as a representative solitary bee species. This is described here together with a summary of the results obtained as an introduction to the study details given in the following papers in this issue.

Genome-Wide Association Study of a Varroa -Specific Defense Behavior in Honeybees ( Apis mellifera )

Abstract: Honey bees are exposed to many damaging pathogens and parasites. The most devastating is Varroa destructor, which mainly affects the brood. A promising approach for preventing its spread is to breed Varroa-resistant honey bees. One trait that has been shown to provide significant resistance against the Varroa mite is hygienic behavior, which is a behavioral response of honeybee workers to brood diseases in general. Here, we report the use of an Affymetrix 44K SNP array to analyze SNPs associated with detection and uncapping of Varroa-parasitized brood by individual worker bees (Apis mellifera). For this study, 22 000 individually labeled bees were video-monitored and a sample of 122 cases and 122 controls was collected and analyzed to determine the dependence/independence of SNP genotypes from hygienic and nonhygienic behavior on a genome-wide scale. After false-discovery rate correction of the P values, 6 SNP markers had highly significant associations with the trait investigated (α < 0.01). Inspection of the genomic regions around these SNPs led to the discovery of putative candidate genes.

Selection of VSH-derived “Pol-line” honey bees and evaluation of their Varroa -resistance characteristics

Abstract: Honey bees with Varroa sensitive hygiene (VSH) have good resistance to Varroa destructor. We bred “Pol-line” bees by outcrossing VSH queens to US commercial stocks from 2008 to 2014 and then selecting colonies with low mite infestations. Beginning in 2011, field performance of colonies with outcrossed Pol-line queens was compared to colonies with outcrossed VSH queens. Mite infestations after one season were comparable in colonies of the two bee types. Queens from the most functional colonies of both bee types were added to the Pol-line breeding population each year. Mite resistance was investigated further by exposing mite-infested brood to colonies for 1 week in lab tests. The two bee types did not differ in the percentage of infested brood they removed or in the percentage of non-reproduction among remaining mites. Introgressing the VSH trait into commercial honey bee stock shows promise in creating bees that have useful mite resistance and desirable beekeeping characteristics.

Varroa destructor mites can nimbly climb from flowers onto foraging honey bees

Abstract: Varroa destructor, the introduced parasite of European honey bees associated with massive colony deaths, spreads readily through populations of honey bee colonies, both managed colonies living crowded together in apiaries and wild colonies living widely dispersed in natural settings. Mites are hypothesized to spread between most managed colonies via phoretically riding forager bees when they engage in robbing colonies or they drift between hives. However, widely spaced wild colonies show Varroa infestation despite limited opportunities for robbing and little or no drifting of bees between colonies. Both wild and managed colonies may also exchange mites via another mechanism that has received remarkably little attention or study: floral transmission. The present study tested the ability of mites to infest foragers at feeders or flowers. We show that Varroa destructor mites are highly capable of phoretically infesting foraging honey bees, detail the mechanisms and maneuvers by which they do so, and describe mite behaviors post-infestation.

Combination of thymol treatment (Apiguard®) and caging the queen technique to fight Varroa destructor

Abstract: Guaranteeing high acaricide efficacy to control Varroa destructor is fundamental for colony survival. In this study, we verified the efficacy and impact of a commercial thymol-based veterinary product (Apiguard®) on colony honey bee populations when used alone or combined with the biotechnical method of caging honey bee queens to create an artificial brood interruption period in the colony. Apiguard® killed 76.1% of the mites while queen caging killed 40.6% of the mites. The combination of Apiguard® administration with queen caging killed 96.8% of the mites. Comparing bee numbers before and after treatment, Apiguard® treated colonies with caged queens had 48.7% fewer bees compared to before treatment, while Apiguard® alone reduced the number of adult bees by 13.6%. None of the treatments in the different groups resulted in elevated queen mortality.

Why do Varroa mites prefer nurse bees

Abstract: The Varroa mite, Varroa destructor, is an acarine ecto-parasite on Apis mellifera. It is the worst pest of Apis mellifera, yet its reproductive biology on the host is not well understood. In particular, the significance of the phoretic stage, when mites feed on adult bees for a few days, is not clear. In addition, it is not clear whether the preference of mites for nurses observed in the laboratory also happens inside real colonies. We show that Varroa mites prefer nurses over both newly emerged bees and forgers in a colony setting. We then determined the mechanism behind this preference. We show that this preference maximizes Varroa fitness, although due to the fact that each mite must find a second host (a pupa) to reproduce, the fitness benefit to the mites is not immediate but delayed. Our results suggest that the Varroa mite is a highly adapted parasite for honey bees.

Population growth of Varroa destructor (Acari: Varroidae) in honey bee colonies is affected by the number of foragers with mites.

Abstract: Varroa mites are a serious pest of honey bees and the leading cause of colony losses. Varroa have relatively low reproductive rates, so populations should not increase rapidly, but often they do. Other factors might contribute to the growth of varroa populations including mite migration into colonies on foragers from other hives. We measured the proportion of foragers carrying mites on their bodies while entering and leaving hives, and determined its relationship to the growth of varroa populations in those hives at two apiary sites. We also compared the estimates of mite population growth with predictions from a varroa population dynamics model that generates estimates of mite population growth based on mite reproduction. Samples of capped brood and adult bees indicated that the proportion of brood cells infested with mites and adult bees with phoretic mites was low through the summer but increased sharply in the fall especially at site 1. The frequency of capturing foragers with mites on their bodies while entering or leaving hives also increased in the fall. The growth of varroa populations at both sites was not significantly related to our colony estimates of successful mite reproduction, but instead to the total number of foragers with mites (entering and leaving the colony). There were more foragers with mites at site 1 than site 2, and mite populations at site 1 were larger especially in the fall. The model accurately estimated phoretic mite populations and infested brood cells until November when predictions were much lower than those measured in colonies. The rapid growth of mite populations particularly in the fall being a product of mite migration rather than mite reproduction only is discussed.

Current Pesticide Risk Assessment Protocols Do Not Adequately Address Differences between Honey Bees (Apis mellifera) and Bumble Bees (Bombus spp.)

Abstract: Recent research has demonstrated colony-level sublethal effects of imidacloprid on bumble bees, affecting foraging and food consumption, and thus colony growth and reproduction, at lower pesticide concentrations than for honey bee colonies. However, these studies may not reflect the full effects of neonicotinoids on bumble bees because bumble bee life cycles are different from those of honey bees. Unlike honey bees, bumble bees live in colonies for only a few months each year. Assessing the sublethal effects of systemic insecticides only on the colony level is appropriate for honey bees, but for bumble bees, this approach addresses just part of their annual life cycle. Queens are solitary from the time they leave their home colonies in fall until they produce their first workers the following year. Queens forage for pollen and nectar, and are thus exposed to more risk of direct pesticide exposure than honey bee queens. Almost no research has been done on pesticide exposure to and effects on bumble bee queens. Additional research should focus on critical periods in a bumble bee queen’s life which have the greatest nutritional demands, foraging requirements, and potential for exposure to pesticides, particularly the period during and after nest establishment in the spring when the queen must forage for the nutritional needs of her brood and for her own needs while she maintains an elevated body temperature in order to incubate the brood.

Varroa destructor (Mesostigmata: Varroidae) Parasitism and Climate Differentially Influence the Prevalence, Levels, and Overt Infections of Deformed Wing Virus in Honey Bees (Hymenoptera: Apidae)

Abstract: The prevalence and loads of deformed wing virus (DWV) between honey bee (Apis mellifera L.) colonies from a tropical and a temperate environment were compared. The interaction between these environments and the mite Varroa destructor in relation to DWV prevalence, levels, and overt infections, was also analyzed. V. destructor rates were determined, and samples of mites, adult bees, brood parasitized with varroa mites and brood not infested by mites were analyzed. DWV was detected in 100% of the mites and its prevalence and loads in honey bees were significantly higher in colonies from the temperate climate than in colonies from the tropical climate. Significant interactions were found between climate and type of sample, with the highest levels of DWV found in varroa-parasitized brood from temperate climate colonies. Additionally, overt infections were observed only in the temperate climate. Varroa parasitism and DWV loads in bees from colonies with overt infections were significantly higher than in bees from colonies with covert infections. These results suggest that interactions between climate, V. destructor, and possibly other factors, may play a significant role in the prevalence and levels of DWV in honey bee colonies, as well as in the development of overt infections. Several hypotheses are discussed to explain these results.

Comparison of Varroa destructor and Worker Honeybee Microbiota Within Hives Indicates Shared Bacteria

Abstract: The ectoparasitic mite Varroa destructor is a major pest of the honeybee Apis mellifera. In a previous study, bacteria were found in the guts of mites collected from winter beehive debris and were identified using Sanger sequencing of their 16S rRNA genes. In this study, community comparison and diversity analyses were performed to examine the microbiota of honeybees and mites at the population level. The microbiota of the mites and honeybees in 26 colonies in seven apiaries in Czechia was studied. Between 10 and 50 Varroa females were collected from the bottom board, and 10 worker bees were removed from the peripheral comb of the same beehive. Both bees and mites were surface sterilized. Analysis of the 16S rRNA gene libraries revealed significant differences in the Varroa and honeybee microbiota. The Varroa microbiota was less diverse than was the honeybee microbiota, and the relative abundances of bacterial taxa in the mite and bee microbiota differed. The Varroa mites, but not the honeybees, were found to be inhabited by Diplorickettsia. The relative abundance of Arsenophonus, Morganella, Spiroplasma, Enterococcus, and Pseudomonas was higher in Varroa than in honeybees, and the Diplorickettsia symbiont detected in this study is specific to Varroa mites. The results demonstrated that there are shared bacteria between Varroa and honeybee populations but that these bacteria occur in different relative proportions in the honeybee and mite bacteriomes. These results support the suggestion of bacterial transfer via mites, although only some of the transferred bacteria may be harmful.

Inheritance of reduced Varroa mite reproductive success in reciprocal crosses of mite-resistant and mite-susceptible honey bees (Apis mellifera)

Abstract: A well-documented population of honey bees on Gotland, Sweden is resistant to Varroa destructor mites and is able in some way to reduce the mite’s reproductive success. The aim of this study was to determine the genetic and maternal contribution to the inheritance of the reduced mite reproductive success trait in this population. Four genotypic groups of colonies were established by crossing the mite-resistant population of Gotland with a mite-susceptible population in Uppsala, Sweden, through artificial insemination of reared queens with drone semen. All the colonies in groups with a genetic origin from the resistant population expressed reduced mite reproductive success regardless if the genetic origin was maternal, paternal or both, and no statistical differences were observed between the reciprocal crosses. These results strongly imply a dominant genetic component to the trait’s inheritance, as opposed to maternal effects or epigenetic mechanisms, and that the trait can be easily produced through selective breeding using the mite-resistant Gotland bee stock.

The Honey Bee Pathosphere of Mongolia: European Viruses in Central Asia.

Abstract: Parasites and pathogens are apparent key factors for the detrimental health of managed European honey bee subspecies, Apis mellifera. Apicultural trade is arguably the main factor for the almost global distribution of most honey bee diseases, thereby increasing chances for multiple infestations/infections of regions, apiaries, colonies and even individual bees. This imposes difficulties to evaluate the effects of pathogens in isolation, thereby creating demand to survey remote areas. Here, we conducted the first comprehensive survey for 14 honey bee pathogens in Mongolia (N = 3 regions, N = 9 locations, N = 151 colonies), where honey bee colonies depend on humans to overwinter. In Mongolia, honey bees, Apis spp., are not native and colonies of European A. mellifera subspecies have been introduced ~60 years ago. Despite the high detection power and large sample size across Mongolian regions with beekeeping, the mite Acarapis woodi, the bacteria Melissococcus plutonius and Paenibacillus larvae, the microsporidian Nosema apis, Acute bee paralysis virus, Kashmir bee virus, Israeli acute paralysis virus and Lake Sinai virus strain 2 were not detected, suggesting that they are either very rare or absent. The mite Varroa destructor, Nosema ceranae and four viruses (Sacbrood virus, Black queen cell virus, Deformed wing virus (DWV) and Chronic bee paralysis virus) were found with different prevalence. Despite the positive correlation between the prevalence of V. destructor mites and DWV, some areas had only mites, but not DWV, which is most likely due to the exceptional isolation of apiaries (up to 600 km). Phylogenetic analyses of the detected viruses reveal their clustering and European origin, thereby supporting the role of trade for pathogen spread and the isolation of Mongolia from South-Asian countries. In conclusion, this survey reveals the distinctive honey bee pathosphere of Mongolia, which offers opportunities for exciting future research.

Impact of the Phoretic Phase on Reproduction and Damage Caused by Varroa destructor (Anderson and Trueman) to Its Host, the European Honey Bee (Apis mellifera L.).

Abstract: Varroa destructor is a parasitic mite of the honeybee that causes thousands of colony losses worldwide. The parasite cycle is composed of a phoretic and a reproductive phase. During the former, mites stay on adult bees, mostly on nurses, to feed on hemolymph. During the latter, the parasites enter brood cells and reproduce. We investigated if the type of bees on which Varroa stays during the phoretic phase and if the duration of this stay influenced the reproductive success of the parasite and the damage caused to bees. For that purpose, we used an in vitro rearing method developed in our laboratory to assess egg laying rate and the presence and number of fully molted daughters. The expression level of two Varroa vitellogenin genes (VdVg1 and VdVg2), known to vary throughout reproduction, was also quantified. Results showed that the status of the bees or time spent during the phoretic phase impacts neither reproduction parameters nor the Varroa vitellogenin genes levels of expression. However, we correlated these parameters to the gene expression and demonstrated that daughters expressed the vitellogenin genes at lower levels than their mother. Regarding the damage to bees, the data indicated that a longer stay on adult bees during the phoretic phase resulted in more frequent physical deformity in newborn bees. We showed that those mites carry more viral loads of the Deformed Wing Virus and hence trigger more frequently overt infections. This study provides new perspectives towards a better understanding of the Varroa-honeybee interactions.

Varroa destructor and viruses association in honey bee colonies under different climatic conditions

Abstract: Summary Honey bee colonies are threatened by multiple factors including complex interactions between environmental and diseases such as parasitic mites and viruses. We compared the presence of honeybee-pathogenic viruses and Varroa infestation rate in four apiaries: commercial colonies that received treatment against Varroa and non-treated colonies that did not received any treatment for the last 4 years located in temperate and subtropical climate. In addition, we evaluated the effect of climate and Varroa treatment on deformed wing virus (DWV) amounts. In both climates, DWV was the most prevalent virus, being the only present virus in subtropical colonies. Moreover, colonies from subtropical climate also showed reduced DWV amounts and lower Varroa infestation rates than colonies from temperate climate. Nevertheless, non-treated colonies in both climate conditions are able to survive several years. Environment appears as a key factor interacting with local bee populations and influencing colony survival beyond Varroa and virus presence.

Prolonged effects of in-hive monoterpenoids on the honey bee Apis mellifera.

Abstract: Honey bees are exposed in their environment to contaminants but also to biological stressors such as Varroa destructor that can weaken the colony. Preparations containing monoterpenoids that are essential oil components, can be introduced into hives to control Varroa. The long-term sublethal effects of monoterpenoids used as miticides have been poorly investigated. Analysis of behavior of free-moving bees in the laboratory is useful to evaluate the impact of chemical stressors on their cognitive functions such as vision function. Here, the walking behavior was quantified under a 200-lux light intensity. Weeks and months after introduction of the miticide (74 % thymol) into the hives, decreases of phototaxis was observed with both summer and winter bees. Curiously, in spring, bees collected in treated hives were less attracted by light in the morning than control bees. The survival of bees collected in spring was increased by treatment. After a 1-year period of observation, the colony losses were identical in treated and non-treated groups. Colony loss started earlier in the non-treated group. In public opinion, natural substances as essential oils are safer and more environmentally friendly. We demonstrated that a monoterpenoid-based treatment affects bee responses to light. The latter results have notable implications regarding the evaluation of miticides in beekeeping.

Bee guards detect foreign foragers with cuticular chemical profiles altered by phoretic varroa mites

Abstract: Detection of diseased individuals in a social group is a critical step of social immunity, to prevent the spread of parasites or pathogens. Parasite-induced alterations of the host phenotype might be used by healthy conspecific to identify an individual bearing a threat to the social group, and to prevent it from entering the colony. The ecto-parasitic varroa mite (Varroa destructor) is a crucial driver for the extensive worldwide honey bee losses, and the parasite is currently considered one of the major threats for apiculture. Here, we first investigated the alterations induced by phoretic varroa mites on the cuticular hydrocarbons profile of adult honey bees. Our gas chromatography–mass spectrometry analyses showed an increase in cuticular methyl-branched compounds of parasitized bees. Then, we used lure presentation experiments to evaluate the response of guard honey bees at the hive entrance towards foreign foragers with a parasite-altered cuticular profile. We found an increase in the aggressive res...

Drone and Worker Brood Microclimates Are Regulated Differentially in Honey Bees, Apis mellifera

Abstract: Background Honey bee (Apis mellifera) drones and workers show differences in morphology, physiology, and behavior. Because the functions of drones are more related to colony reproduction, and those of workers relate to both survival and reproduction, we hypothesize that the microclimate for worker brood is more precisely regulated than that of drone brood. Methodology/Principal Findings We assessed temperature and relative humidity (RH) inside honey bee colonies for both drone and worker brood throughout the three-stage development period, using digital HOBO® Data Loggers. The major findings of this study are that 1) both drone and worker castes show the highest temperature for eggs, followed by larvae and then pupae; 2) temperature in drones are maintained at higher precision (smaller variance) in drone eggs and larvae, but at a lower precision in pupae than the corresponding stages of workers; 3) RH regulation showed higher variance in drone than workers across all brood stages; and 4) RH regulation seems largely due to regulation by workers, as the contribution from empty honey combs are much smaller compared to that from adult workers. Conclusions/Significance We conclude that honey bee colonies maintain both temperature and humidity actively; that the microclimate for sealed drone brood is less precisely regulated than worker brood; and that combs with honey contribute very little to the increase of RH in honey bee colonies. These findings increase our understanding of microclimate regulation in honey bees and may have implications for beekeeping practices.