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The neuropeptide Pigment-Dispersing Factor (PDF) plays a prominent role in the circadian clock of many insects including honey bees. In the honey bee brain, PDF is expressed in about 15 clock neurons per hemisphere that lie between the central brain and the optic lobes. As in other insects, the bee PDF neurons form wide arborizations in the brain; but certain differences are evident. For example, they arborize only sparsely in the accessory medulla (AME), which serves as important communication center of the circadian clock in cockroaches and flies. Furthermore, all bee PDF neurons cluster together, which makes it impossible to distinguish individual projections. Here, we investigated the developing bee PDF network and found that the first three PDF neurons arise in the 3rd larval instar and form a dense network of varicose fibers at the base of the developing medulla that strongly resembles the AME of hemimetabolous insects. In addition, they send faint fibers toward the lateral superior protocerebrum. In last larval instar, PDF cells with larger somata appear and send fibers toward the distal medulla and the medial protocerebrum. In the dorsal part of the medulla serpentine layer, a small PDF knot evolves from which PDF fibers extend ventrally. This knot disappears during metamorphosis and the varicose arborizations in the putative AME become fainter. Instead a new strongly stained PDF fiber hub appears in front of the lobula. Simultaneously, the number of PDF neurons increases and the PDF neuronal network in the brain gets continuously more complex. This article is protected by copyright. All rights reserved.

The benefits of honey bee dance communication for colony performance in different resource environments are still not well understood. Here, we test the hypothesis that directional dance communication enables honey bee colonies to maintain a diverse pollen diet, especially in landscapes with low resource diversity. To test this hypothesis, we placed 24 Apis mellifera L. colonies with either intact or experimentally disrupted dance communication in eight agricultural landscapes that differed in the diversity of flowering plants and in the dominance of mass-flowering crops. Pollen from incoming foragers was collected and identified via DNA metabarcoding. Disrupting dance communication affected the way the diversity of honey bee pollen diets was impacted by the dominance of mass-flowering crops in available flower resources (p = .04). With increasing dominance of mass-flowering crops in resource environments, foragers of colonies with intact communication foraged on an increasing proportion of available plant genera (p = .01). This was not the case for colonies with disrupted dance communication (p = .5). We conclude that the honey bee dance communication benefits pollen foraging on diverse plant resources and thereby contributes to high quality nutrition in environments with low-resource diversity.

Increasingly frequent warm periods during winter, which are associated with climate change, may cause mismatches between the colony phenology of the western honey bee, Apis mellifera L., and their floral resources. Warmer winter periods can also affect colony brood rearing activity and consequently the reproduction of the invasive brood parasite Varroa destructor Anderson and Trueman. Until now little is known about the effects of climate change on biotic interactions in such a multitrophic system comprising flowering plants, a pollinator, and its parasite. We performed a reciprocal translocation experiment with honey bee colonies to simulate climate change-induced phenology shifts. Honey bee brood phenology was highly sensitive to environmental conditions in late winter. Colonies in which phenology was experimentally delayed had smaller worker populations in early spring and reduced amounts of stored honey during the following months. During summer, the varroa load in colonies with non-shifted phenology was three times higher than in colonies with delayed phenology. High varroa loads during summer were negatively correlated with worker population growth. Despite a remarkable resilience of colony development to phenology shifts, our results show that mismatches between the phenology of honey bee colonies and flowering plants can affect the build-up of resource stores. Further, an advanced onset of brood rearing activity after hibernation can reinforce the negative impact of the brood parasite V. destructor. We conclude that trade-offs between synchronisation with earlier flower phenology and prolonged brood phases with build-up of varroa populations might constrain the honey bees' capability to adapt to climate warming.

International audience; AbstractIn the last few decades, different hyperthermia devices have been developed to kill Varroa destructor mites in the colony. Intriguingly, effects of hyperthermia on Varroa destructor and honeybee brood have hardly been investigated. We exposed honeybee brood to temperatures of 41°C to 45°C to investigate effects on Varroa destructor in the hive and on drone fertility of treated colonies. Drone fertility is an important issue in keeping healthy and viable honeybee populations. We show that temperatures of 42°C for 3 hours or higher kill all the Varroa destructor but, unfortunately, also part of the honeybee brood. Temperatures below 42°C are ineffective against adult Varroa destructor. A temperature of 41°C and 2 hours duration is highly effective against immature Varroa destructor and thus interrupts their reproduction without harming the viability or fertility of drones, while longer durations or higher temperatures kill the spermatozoa of the drones.

Chronobiological studies of individual activity rhythms in social insects can be constrained by the artificial isolation of individuals from their social context. We present a new experimental set-up that simultaneously measures the temperature rhythm in a queen-less but brood raising mini colony and the walking activity rhythms of singly kept honey bees that have indirect social contact with it. Our approach enables monitoring of individual bees in the social context of a mini colony under controlled laboratory conditions. In a pilot experiment, we show that social contact with the mini colony improves the survival of monitored young individuals and affects locomotor activity patterns of young and old bees. When exposed to conflicting Zeitgebers consisting of a light–dark (LD) cycle that is phase-delayed with respect to the mini colony rhythm, rhythms of young and old bees are socially synchronized with the mini colony rhythm, whereas isolated bees synchronize to the LD cycle. We conclude that the social environment is a stronger Zeitgeber than the LD cycle and that our new experimental set-up is well suited for studying the mechanisms of social entrainment in honey bees.

The demand for crop pollination is increasing and honey bees are frequently used, in particular as wild pollinators are in decline. Temporal and spatial variation of flower resources affects foraging decisions of wild and honey bees. To optimise crop pollination management a better understanding of potential competition for pollinators in mass- and minor-flowering crops is needed. We combined waggle dance decoding, pollen load analysis and field surveys to identify the habitat preferences and pollen use of honey bees in response to spatio-temporal changes in resource availability. Observation hives were placed on the edge of eleven fields of blooming strawberries (mean 2.24 ha) located in landscapes with different amounts of oilseed rape (OSR), semi-natural habitats (SNH) and apple trees in Germany. In addition, we surveyed honey bees and wild bees in strawberry fields. Honey bee dances more often indicated strawberry, OSR fields and SNH than expected given their landscape-wide areas. Honey bees collected on average 7.9 % strawberry, 49.0 % OSR, 30.2 % Pyrus type (e.g. apple) and 12.9 % other pollen types. The mean honey bee foraging distance was 740 m, and decreased with OSR availability. In the observation hives, dances for strawberry fields were not directly affected by OSR availability or SNH land cover. But large amounts of OSR reduced overall honey bee and bumble bee abundance in strawberry fields, while solitary bees were unaffected. Bumble bees were most abundant in strawberry fields (54.1%) and together with solitary bees (19.7%) they represented about 75.0% of the observed bees. Minor-flowering strawberry fields represent a preferred resource for honey bees, especially for small colonies as indicated by decoding of waggle dances. However, the availability of more attractive OSR and local strawberry flower cover moderates the abundance of social bees (honey bees and bumble bees) in strawberry fields while other wild bees were less affected. Hence, we conclude that wild bee conservation plays a major role for strawberry pollination. If pollination services by solitary bees are limited, small honey bee hives can be used scrupulously to supplement pollination services in strawberries.

In order to save resources, honey bee (Apis mellifera) colonies in the temperate zones stop brood rearing during winter. Brood rearing is resumed in late winter to build up a sufficient worker force that allows to exploit floral resources in upcoming spring. The timing of brood onset in hibernating colonies is crucial and a premature brood onset could lead to an early depletion of energy reservoirs. However, the mechanisms underlying the timing of brood onset and potential risks of mistiming in the course of ongoing climate change are not well understood. To assess the relative importance of ambient temperature and photoperiod as potential regulating factors for brood rearing activity in hibernating colonies, we overwintered 24 honey bee colonies within environmental chambers. The colonies were assigned to two different temperature treatments and three different photoperiod treatments to disentangle the individual and interacting effects of temperature and photoperiod. Tracking in-hive temperature as indicator for brood rearing activity revealed that increasing ambient temperature triggered brood onset. Under cold conditions, photoperiod alone did not affect brood onset, but the light regime altered the impact of higher ambient temperature on brood rearing activity. Further the number of brood rearing colonies increased with elapsed time which suggests the involvement of an internal clock. We conclude that timing of brood onset in late winter is mainly driven by temperature but modulated by photoperiod. Climate warming might change the interplay of these factors and result in mismatches of brood phenology and environmental conditions.

International audience; AbstractIn agricultural landscapes all over the world, honey bees are exposed to genetically modified (GM) pollen. Stacked Bt-maize varieties combine multiple Bt proteins against different insect taxa with herbicide resistance. To test for potential effects on non-target organisms, we conducted an in vitro larvae-rearing experiment where we fed increasing amounts of stacked Bt pollen to honey bee larvae. Bt pollen was equally well digested as two control maize varieties. No dose-dependent effects of Bt maize were detected in terms of survival and developmental delay. However, for prepupal weight we did find a dose-dependent response, suggesting a pleiotropic effect. Comparing this finding with the literature we conclude that the found effect is not likely to occur in a field situation. We could however show that dose-dependent effects are detectable. Our results underline the importance of testing dose-depending effects of GM plant material in an environmental risk assessment (ERA).

BackgroundArtificial rearing of honey bee larvae is an established method which enables to fully standardize the rearing environment and to manipulate the supplied diet to the brood. However, there are no studies which compare learning performance or neuroanatomic differences of artificially-reared (in-lab) bees in comparison with their in-hive reared counterparts.MethodsHere we tested how different quantities of food during larval development affect body size, brain morphology and learning ability of adult honey bees. We used in-lab rearing to be able to manipulate the total quantity of food consumed during larval development. After hatching, a subset of the bees was taken for which we made 3D reconstructions of the brains using confocal laser-scanning microscopy. Learning ability and memory formation of the remaining bees was tested in a differential olfactory conditioning experiment. Finally, we evaluated how bees reared with different quantities of artificial diet compared to in-hive reared bees.ResultsThorax and head size of in-lab reared honey bees, when fed the standard diet of 160 µl or less, were slightly smaller than hive bees. The brain structure analyses showed that artificially reared bees had smaller mushroom body (MB) lateral calyces than their in-hive counterparts, independently of the quantity of food they received. However, they showed the same total brain size and the same associative learning ability as in-hive reared bees. In terms of mid-term memory, but not early long-term memory, they performed even better than the in-hive control.DiscussionWe have demonstrated that bees that are reared artificially (according to the Aupinel protocol) and kept in lab-conditions perform the same or even better than their in-hive sisters in an olfactory conditioning experiment even though their lateral calyces were consistently smaller at emergence. The applied combination of experimental manipulation during the larval phase plus subsequent behavioral and neuro-anatomic analyses is a powerful tool for basic and applied honey bee research.

The increasing demand for insect pollinated crops and high recent losses of honey bee colonies raise concerns about food security. Systemic insecticides are recognized as one of the drivers of worldwide honey and wild bee declines. Particularly honey bees in agricultural environments are exposed to pesticides when they collect crop pollen and nectar. However, landscape scale studies which analyze pollen use and foraging distances of honey bees on mass-flowering crops like maize to evaluate potential exposure risks are currently lacking. In an experimental approach on a landscape scale we took advantage of intra-colonial dance communication to gather information about the location of utilized pollen resources. During maize flowering, four observation hives were placed in and rotated between 11 different landscapes which covered a gradient from low to high maize acreage. A higher frequency of dances for foraging locations on maize fields compared to other land use types shows that maize is an intensively used pollen resource for honey bee colonies. Mean foraging distances were significantly shorter for maize pollen than for other pollen origins. The percentage of maize pollen foragers did not increase with maize acreage in the landscape. The proportion of grassland area providing alternative pollen sources did not reduce the percentage of maize pollen foragers. Our findings allow estimating the distance-related exposure risk of honey bee colonies to pollen from surrounding maize fields treated with systemic insecticides. Similarly, the results can be used to estimate the exposure to transgenic maize pollen, which is relevant for honey production in European countries. Provision of alternative pollen resources within agri-environmental schemes could potentially reduce exposure risk to pesticide contaminated crop pollen.

International audience; Honey bee colonies are characterised by well-developed reproductive division of labour between the queen and workers. Here, we test whether this reproductive division of labour is evident in both the socially parasitic workers that invade a colony as well as in their offspring generation. We infected six Apis mellifera scutellata host colonies with pseudo-clonal socially parasitic Cape honeybee workers (Apis mellifera capensis). We show that the first generation of socially parasitic workers can monopolize reproduction within host colonies. Of the initially invading parasites, 94.4% became reproductive pseudoqueens with activated ovaries and produced queen-like pheromones. Their offspring, however, had much lower levels of ovary activation (3.1%), yet 89% showed fatty acid synthesis typical of the queen substance (9-oxo-2(E)-decenoic acid) biochemical pathway. However, in these second-generation workers, the last oxidation step from the precursor (9-hydroxy-2(E)-decenoic acid) to the queen substance was interrupted and appears to be required for reproductive dominance in honeybee workers. Our data show that despite the absence of genetic diversity, residual queen mandibular pheromone (QMP) variation is sufficient to establish reproductive dominance hierarchies among parasitic workers. Consequently, QMP produced by a group of workers can maintain reproductive division of labour in queenless honeybee colonies.

Summary 1. To sustain the vital ecosystem service of pollination, new methodical developments are needed for research on the underlying factors of globally observed bee losses. In particular, robust laboratory methods for assessing adverse effects on honey bee brood are required. In addition, from a statistical point of view, the shared origin of test individuals must be considered when analysing ecotoxicological data. 2. To improve honey bee in vitro rearing, we adopted a nongrafting method to collect honey bee larvae without direct manipulation. Linear mixed effects model to evaluate LD50 ,l arvae survival and prepupae weights integrated the colony background of larvae as a random factor into the statistical analyses. The novel rearing approach and appropriate statistical tools for data analyses are illustrated in an in vitro case study on acute oral dimethoate toxicity. 3. We recommend our honey bee larvae collection approach for in vitro larvae-rearing applications, because of (i) a mere 3% background mortality upon the prepupae stage, (ii) a high quantitative capacity and (iii) because of robustness of performance which are great benefits for standardization. 4. The analyses indicate clear adverse effects of dimethoate by a significant survival reduction and prepupae weight reduction. For second instars, the acute 48-h LD50 was 1AE67 lg dimethoate per larva. 5. We conclude that both our larvae collection method and the applied statistical approaches will help to improve the quality of environmental risk assessment studies on honey bees, to secure honey bee pollination and to sustain biodiversity.

SummaryComprehensive information on the spatial resource use of honey bees is rare, but highly relevant to assess the consequences of habitat loss and fragmentation, agricultural intensification or extensification on colony fitness, pesticide exposure risks and pollination functions.

Determining the extent and causes of barriers to gene flow is essential for understanding sympatric speciation, but the practical difficulties of quantifying reproductive isolation remain an obstacle to analysing this process. Social parasites are common in eusocial insects and tend to be close phylogenetic relatives of their hosts (= Emery’s rule). Sympatric speciation caused by reproductive isolation between host and parasite is a possible evolutionary pathway. Socially parasitic workers of the Cape honeybee, Apis mellifera capensis, produce female clonal offspring parthenogenetically and invade colonies of the neighbouring subspecies A. m. scutellata. In the host colony, socially parasitic workers can become pseudoqueens, an intermediate caste with queenlike pheromone secretion. Here, we show that over an area of approximately 275.000 km 2 , all parasitic workers bear the genetic signature of a clone founded by a single ancestral worker genotype. Any gene flow from the host to the parasite is impossible because honeybee workers cannot mate. Gene flow from the parasite to the host is possible, as parasitic larvae can develop into queens. However, we show that despite sympatric coexistence for more than a decade, gene flow between host and social parasite (Fst = 0.32) and hybridizations (0.71%) are rare, resulting in reproductive isolation. Our data suggest a new barrier to gene flow in sympatry, which is not based on assortative matings but on thelytoky and reproductive division of labour in eusocial insects, thereby suggesting a new potential pathway to Emery’s rule.

The relaxation and the thermal vibrations of the NaF(100) surface are investigated in the temperature range between 25 K and 230 K by means of low-energy electron diffraction (LEED) and a subsequent I(V) structure analysis based on the tensor LEED approach (TLEED). According to the experiments, the NaF(100) surface is not significantly relaxed and has the ideal truncated bulk structure. The thermal vibrational amplitudes of the ions in the topmost layer are significantly enhanced compared to the bulk by a factor of 1.35 ± 0.15 and are equal within the error-bars for Na + and F − ions. Moreover, the relaxation and the dynamics of the NaF(100) surface are investigated using periodic density functional theory (DFT) calculations using pseudopotentials. In agreement with the experimental findings, the calculated relaxation of the NaF(100) surface is weak with static shifts of the ions of 0.01 A to 0.02 A. In the topmost layer, the Na + ions are predicted to be slightly inward shifted, whereas the F − ions are outward shifted, in accordance to predictions of previous shell-model calculations. A Born Oppenheimer molecular dynamics (BO-MD) simulation of the dynamics at the NaF(100) surface leads to a smaller enhancement of thermal motions of the ions at the surface compared to the experiment.

Honey bees (Apis mellifera L.) show a large variation in foraging distances and use a broad range of plant species as pollen resources, even in regions with intensive agriculture. However, it is unknown how increasing areas of mass-flowering crops like oilseed rape (Brassica napus; OSR) or a decrease of seminatural habitats (SNH) change the temporal and spatial availability of pollen resources for honey bee colonies, and thus foraging distances and frequency in different habitat types. We studied pollen foraging of honey bee colonies in 16 agricultural landscapes with independent gradients of OSR and SNH area within 2 km and used waggle dances and digital geographic maps with major land cover types to reveal the distance and visited habitat type on a landscape level. Mean pollen foraging distance of 1347 decoded bee dances was 1015 m (± 26 m; SEM). In spring, increasing area of flowering OSR within 2 km reduced mean pollen foraging distances from 1324 m to only 435 m. In summer, increasing cover of SNH areas close to the colonies (within 200 m radius) reduced mean pollen foraging distances from 846 to 469 m. Frequency of pollen foragers per habitat type, measured as the number of dances per hour and hectare, was equally high for SNH, grassland, and OSR fields, but lower for other crops and forests. In landscapes with a small proportion of SNH a significantly higher density of pollen foragers on SNH was observed, indicating that pollen resources in such simple agricultural landscapes are more limited. Overall, we conclude that SNH and mass-flowering crops can reduce foraging distances of honey bee colonies at different scales and seasons with possible benefits for the performance of honey bee colonies. Further, mixed agricultural landscapes with a high proportion of SNH reduce foraging densities of honey bees in SNH and thus possible competition for pollen resources.

Social parasitism is widespread in the eusocial insects. Although social parasites often show a reduced worker caste, unmated workers can also parasitize colonies. Cape honeybee workers, Apis mellifera capensis, can establish themselves as social parasites in host colonies of other honeybee subspecies. However, it is unknown whether social parasitism by laying workers also occurs among Cape honeybee colonies. In order to address this question we genotyped worker offspring of six queenless A. m. capensis colonies and determined the maternity of the reproducing workers. We found that three non-nestmate workers dominated reproduction in a host colony and produced 62.5% of the progeny. Our results show that social parasitism by laying workers is a naturally occurring part of the biology of Cape honeybees. However, such social parasitism is not frequently found (6.41% of the total worker offspring) probably due to co-evolutionary processes among A. m. capensis resulting in an equilibrium between selection for reproductive dominance in workers, colony maintenance and queen adaptation.

Les ouvrieres de l'Abeille du Cap (Apis mellifera capensis) sont des parasites sociaux de l'abeille A. m. scutellata. Depuis 1990 elles provoquent des pertes elevees parmi les colonies de cette derniere dans le nord de l'Afrique du Sud. L'action des ouvrieres de l'Abeille du Cap sur les colonies sauvages d'A. m. scutellata n'a pas ete quantifiee jusqu'a present. On a recherche les symptomes de parasitisme dans 166 essaims d'A. m. scutellata provenant de 27 localites situees en zones d'apiculture ou dans des reserves naturelles (Tab. I, Fig. 1). Pour determiner avec precision le nombre de colonies infestees, on a caracterise a l'aide de six microsatellites d'ADN le genotype d'ouvrieres (N = 72) possedant des tergites noirs (symptome d'infestation) et jaunes prises dans des colonies (N = 8) potentiellement infestees (Tab. II). Le genotype des ouvrieres aux tergites noirs se rapportait dans 86 % des cas au genotype presume de la reine et en aucun cas on n'a pu etablir de concordance avec le genotype du clone d'ouvrieres parasites (Tab. II). Par consequent ces essaims n'etaient absolument pas infestes. Les essaims preleves dans les reserves naturelles, ou il n'y a pas d'apiculture, ne sont pas infestes et ne comportent que des ouvrieres aux tergites jaunes. Bien que la majorite des colonies avec tergites noirs soit infestee, la couleur des tergites ne doit neanmoins pas servir sur le terrain de critere fiable afin d'eviter des diagnostics faussement positifs. Il est recommande aux entreprises apicoles de verifier dans les essaims recemment recoltes la presence d'ouvrieres a tergites noirs et d'eliminer ces colonies. C'est la seule facon efficace de reduire le nombre de diagnostics faussement negatifs. La presence d'essaims infestes pose un probleme pour la pratique apicole, puisqu'un essaim infeste peut infester rapidement tout un rucher. La presence d'essaims infestes (12,6 %) indique que ceux-ci contribuent de facon importante au maintien du « syndrome de colonie deperissante ». Les populations protegees ne presentent aucune infestation, indiquant que les reserves naturelles sont d'importants refuges pour l'Abeille africaine A. m. scutellata.

The western honeybee, Apis mellifera, has been globally transported for honey production and pollination for hundreds of years and is often kept in large numbers in beekeeping operations. Concern has been expressed that it might act as an invasive species with large impact on biodiversity. However, although the honeybee has spread into the wild and has established feral populations in Australia and the Americas, the extent to which introduced honeybees alter biodiversity remains controversial. Here we focus on the best documented cases of A. mellifera invasions and discuss the effects on biodiversity under three different conditions: 1) regions where other subspecies of A. mellifera are endemic (Europe, Africa, and western Asia), 2) regions where A. mellifera is not endemic, but other species of Apis naturally occur (central and eastern Asia), 3) regions where Apis species are not endemic (America, Australia). Although some studies show an impact on native bee survival, fecundity, or population d...

The identification of pollen plays an important role in ecology, palaeo-climatology, honey quality control and other areas. Currently, expert knowledge and reference collections are essential to identify pollen origin through light microscopy. Pollen identification through molecular sequencing and DNA barcoding has been proposed as an alternative approach, but the assessment of mixed pollen samples originating from multiple plant species is still a tedious and error-prone task. Next-generation sequencing has been proposed to avoid this hindrance. In this study we assessed mixed pollen probes through next-generation sequencing of amplicons from the highly variable, species-specific internal transcribed spacer 2 region of nuclear ribosomal DNA. Further, we developed a bioinformatic workflow to analyse these high-throughput data with a newly created reference database. To evaluate the feasibility, we compared results from classical identification based on light microscopy from the same samples with our sequencing results. We assessed in total 16 mixed pollen samples, 14 originated from honeybee colonies and two from solitary bee nests. The sequencing technique resulted in higher taxon richness (deeper assignments and more identified taxa) compared to light microscopy. Abundance estimations from sequencing data were significantly correlated with counted abundances through light microscopy. Simulation analyses of taxon specificity and sensitivity indicate that 96% of taxa present in the database are correctly identifiable at the genus level and 70% at the species level. Next-generation sequencing thus presents a useful and efficient workflow to identify pollen at the genus and species level without requiring specialised palynological expert knowledge.

The environmental impacts of genetically modified crops is still a controversial issue in Europe. The overall risk assessment framework has recently been reinforced by the European Food Safety Authority(EFSA) and its implementation requires harmonized and efficient methodologies. The EU-funded research project AMIGA − Assessing and monitoring Impacts of Genetically modified plants on Agro-ecosystems − aims to address this issue, by providing a framework that establishes protection goals and baselines for European agro-ecosystems, improves knowledge on the potential long term environmental effects of genetically modified (GM) plants, tests the efficacy of the EFSA Guidance Document for the Environmental Risk Assessment, explores new strategies for post market monitoring, and provides a systematic analysis of economic aspects of Genetically Modified crops cultivation in the EU. Research focuses on ecological studies in different EU regions, the sustainability of GM crops is estimated by analysing the functional components of the agro-ecosystems and specific experimental protocols are being developed for this scope.

Honey bee pollination is a key ecosystem service to nature and agriculture. However, biosafety research on genetically modified crops rarely considers effects on nurse bees from intact colonies, even though they receive and primarily process the largest amount of pollen. The objective of this study was to analyze the response of nurse bees and their gut bacteria to pollen from Bt maize expressing three different insecticidal Cry proteins (Cry1A.105, Cry2Ab2, and Cry3Bb1). Naturally Cry proteins are produced by bacteria (Bacillus thuringiensis). Colonies of Apis mellifera carnica were kept during anthesis in flight cages on field plots with the Bt maize, two different conventionally bred maize varieties, and without cages, 1-km outside of the experimental maize field to allow ad libitum foraging to mixed pollen sources. During their 10-days life span, the consumption of Bt maize pollen had no effect on their survival rate, body weight and rates of pollen digestion compared to the conventional maize varieties. As indicated by ELISA-quantification of Cry1A.105 and Cry3Bb1, more than 98% of the recombinant proteins were degraded. Bacterial population sizes in the gut were not affected by the genetic modification. Bt-maize, conventional varieties and mixed pollen sources selected for significantly different bacterial communities which were, however, composed of the same dominant members, including Proteobacteria in the midgut and Lactobacillus sp. and Bifidobacterium sp. in the hindgut. Surprisingly, Cry proteins from natural sources, most likely B. thuringiensis, were detected in bees with no exposure to Bt maize. The natural occurrence of Cry proteins and the lack of detectable effects on nurse bees and their gut bacteria give no indication for harmful effects of this Bt maize on nurse honey bees.

International audience; The honey bee is a key non-target arthropod in environmental risk assessments of genetically modified crops. We analyzed for the first time combined effects of three Bt proteins conferring insect resistances, and a CP4-protein conferring an herbicide resistance as simultaneously expressed in one GM maize. Furthermore, the biosafety of Galanthus nivalis agglutinin (GNA lectin), a candidate protein for pest control was tested. Under worst-case exposure scenario, by using controlled in vitro larvae rearing, the combination of Bt proteins showed no adverse effects on bee larvae. In contrast, the GNA lectin was toxic at a 144 h LD50 of 16.3 μg/larva. The prepupal weight was found to differ between the larvae collection days and between the colonies used for the experiment, explaining up to five times more data variance than the protein treatments (N = 709 prepupae). In conclusion, neither single nor a mix of different Bt proteins were found harmful to honey bee larvae.

The recent invasion by self-replicating socially parasitic Cape honeybee workers, Apis mellifera capensis, of colonies of the neighbouring African subspecies Apis mellifera scutellata represents an opportunity to study evolution of intraspecific parasitism in real time. As honeybee workers compete pheromonally for reproductive dominance, and as A. m. capensis workers readily produce queen-like pheromones, we hypothesized that these semiochemicals promoted the evolution of intraspecific social parasitism. Remarkably, the offspring of a single worker became established as a parasite in A. m. scutellata's range. This could have resulted from extreme selection among different clonal parasitic worker lineages. Using pheromonal contest experiments, we show that the selected parasitic lineage dominates in the production of mandibular gland pheromones over all other competitors to which it is exposed. Our results suggest that mandibular gland pheromones played a key role in the evolution of intraspecific social parasitism in the honeybee and in the selection of a single genotype of parasitic workers.

The removal of small hive beetle (SHB) eggs and larvae was studied in seven Apis mellifera scutellata colonies. Because female beetles can protect their eggs by oviposition in small cracks we introduced unprotected eggs and protected eggs into these colonies. Whereas all unprotected eggs were removed within 24 hours, 66 ± 12% of the protected eggs remained, showing that SHB eggs are likely to hatch in infested colonies. However, all larvae introduced into the same seven colonies were rejected within 24 hours. Workers responded quickly to the presence of SHB offspring in the colonies because 72 ± 27% of the unprotected eggs and 49 ± 37% of the larvae were removed within the first hour after introduction. The removal of SHB eggs and larvae was not correlated with colony phenotypes (size, amount of open and sealed brood, pollen and honey stores). Our data show that African colonies remove both SHB unprotected eggs and larvae within short periods of time. Therefore, we conclude that this removal behavior plays an important role for the apparent resistance of African honeybees towards SHB infestations. Aethina tumida / Apis mellifera / honeybee / host-parasite relationship / small hive beetle

Experiment was focused on the conditioning of the Apis mellifera carnica colony to search for DNT and TNT scent in controlled environment. After preparation of the testing mesh tent and feeders, 10 training and testing trials were performed. Majority of the experiments was carried out in a period from April to July 2012. For the training and testing of bees, artificial targets were designed. Six observers counted bees crossing and/or lending on the six targets, from which three targets were with and three without scent (control). Crossing bees were counted in the area of 20 cm above the target. Landing bees need to touch or sit on any part of the target. In average, 29.22 bees were crossing above TNT and 28.69 bees above control targets. The average number of landing bees was 9.72 on TNT and 2.78 on controls. When the target scent was DNT, in average 61.19 bees were crossing targets, and 42.64 controls. Results were more distinct in landing on DNT, when in average 40.42 bees landed on target with scent in comparison to 2.91 bees on controls. The number of bees recognizing DNT was higher in comparison to TNT due to its more intense smell. These results indicate that bees from trained colony can clearly distinguish target with odor by lending on it.