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Bees are flexible and adaptive learners, capable of learning stimuli seen on arrival and at departure from flowers where they have fed. This gives bees the potential to learn all information associated with a feeding event, but it also presents the challenge of managing information that is irrelevant, inconsistent, or conflicting. Here, we examined how presenting bumblebees with conflicting visual information before and after feeding influenced their learning rate and what they learned. Bees were trained to feeder stations mounted in front of a computer monitor. Visual stimuli were displayed behind each feeder station on the monitor. Positively reinforced stimuli (CS +) marked feeders offering sucrose solution. Negatively reinforced stimuli (CS−) marked feeders offering quinine solution. While alighted at the feeder station the stimuli were likely not visible to the bee. The "constant stimulus" training group saw the same stimulus throughout. For the "switched stimulus" training group, the CS + changed to the CS− during feeding. Learning was slower in the "switched stimulus" training group compared to the constant stimulus" group, but the training groups did not differ in their learning performance or the extent to which they generalised their learning. The information conflict in the "switched stimulus" group did not interfere with what had been learned. Differences between the "switched" and "constant stimulus" groups were greater for bees trained on a horizontal CS + than a vertical CS + suggesting bees differ in their processing of vertically and horizontally oriented stimuli. We discuss how bumblebees might resolve this type of information conflict so effectively, drawing on the known neurobiology of their visual learning system. [ABSTRACT FROM AUTHOR]

In recent years, bumblebees have increasingly been used to study various aspects of bee biology, ecology and evolution. They are now broadly accepted as tractable model species, complementary to the domestic honey bees, for fundamental and applied apidology. Here, we provide a brief history of how bumblebee research developed since their domestication and commercialisation for crop pollination in the 1990s. Bumblebees are large social bees that can be kept and trained in the lab year-round. They are easy to manipulate and track individually in their small colonies. These practical advantages have offered new possibilities for experimental bee research, leading to major breakthroughs in different fields such as cognition, navigation, nutrition, host-parasite interactions, and insect declines. Many of these findings have later been confirmed in honey bees and other pollinators. We discuss some exciting directions for future apidology research based on bumblebees. [ABSTRACT FROM AUTHOR]

With the expansion of industrial activities, the escalation of pollution by trace metals poses an increasing threat to bees. While the effects of metals on adult bees have been extensively studied in ecotoxicological research, a critical gap persists concerning their impact on bee larvae. Here, we conducted the first study exposing bumble bee larvae to field-realistic concentrations of copper via an in vitro assay, over a span of 25 days. We monitored the duration of their developmental stages, including moments of defecation, pupation, and emergence, alongside their survival rates. Additionally, we recorded their area growth as well as their adult body mass post-emergence. Despite copper exposure exhibiting no discernible influence on the overall duration of development, survival, growth, or adult mass, a significant positive effect was observed on the pupation rate. This outcome is likely attributable to heightened copper-dependent metabolic activities and disturbances in the redox balance. Furthermore, our investigation underscored the pivotal role of initial body size in developmental success, with larger larvae showing elevated emergence and survival rates. Given the efficacy of this assay, we urge regulatory institutions responsible for approving pesticides and other xenobiotics for market use to embrace this experimental approach in future risk assessments. [ABSTRACT FROM AUTHOR]

Commercially reared bees provide economically important pollination services for a diversity of crops. Improving their health is important both to maximise their pollination services and to avoid possible pathogen spillover or spillback with wild pollinators. Diet quality may directly or indirectly affect diverse aspects of bumblebee health, including colony development, individual size and immune health, but the impact of this remains unclear. Here we investigate experimentally the effect of diet quality during bumblebee colony development using three diets: (1) a standard pollen diet used in commercial rearing of colonies for sale, (2) an enhanced diet comprised of a wildflower pollen mix that was expected to be nutritionally superior (including by having an elevated protein content) and (3) a diet of pollen substitute mixed with the standard diet that was expected to be nutritionally poorer. The effect of diet quality on colony health was quantified using colony-level measures (colony weight, size [number of live workers] and number of dead individuals), and individual-level measures (body size, fat body size [proportion of body weight], total haemocyte count and phenoloxidase immune enzyme activity). Diet quality significantly affected colony growth, with colonies fed the enhanced diet growing larger and producing more reproductives than those fed either a standard or poor diet. The enhanced diet also resulted in bees that were significantly larger and had better immune health. The results show that diet can have important effects on the health of commercially reared bumblebees and suggest that the enhancement of standard-rearing diets may improve colony health. [ABSTRACT FROM AUTHOR]

Simple Summary: This study examined how disturbances caused by humans affect the interactions between plants and pollinators in Terceira Island's native forests. Plant and pollinator native species dominate in preserved areas, while disturbed areas see a rise in introduced species of both study groups. Pollinator visits were mostly carried out by generalist species, especially hoverflies. In disturbed areas, non-native bees were key pollinators, while in undisturbed areas, native beetles played an important role. This research revealed that human disturbances alter species composition and the interactions between plants and pollinators. Native generalist species, of both plants and insects, appear to provide ecological opportunities that can facilitate the establishment of introduced species through their broad interaction networks. This study highlights how human activities change the natural biodiversity of island habitats. The native biodiversity of oceanic islands is threatened by human-driven disturbance and by the growing number of species introductions which often interfere with natural ecological processes. Here, we aim to evaluate the effect of anthropogenic disturbance on plant–pollinator interactions in the native forest communities of an oceanic island (Terceira, Azores, Portugal). We found that native species predominated in preserved sites compared to disturbed ones and that the extant plant–pollinator interactions were mostly dominated by generalist species. Dipterans, particularly hoverflies, emerged as the primary flower visitors, while introduced hymenopterans (Apis mellifera and Bombus terrestris) and native beetles were locally important, respectively, in disturbed and preserved sites. Human-driven disturbance seems to be responsible for the observed differences in flower abundance and species composition between sites and to drive changes in specific network metrics (namely nestedness, interaction strength asymmetry, and specialization), particularly in one of the study areas. Our findings also suggest that native generalist species provide ecological opportunities that can facilitate the establishment of introduced species through their broad interaction networks. [ABSTRACT FROM AUTHOR]

Summary Plants produce floral nectar as a reward for pollinators, which contains carbohydrates and amino acids (AAs). We designed experiments to test whether pollinators could exert selection pressure on the profiles of AAs in nectar. We used HPLC to measure the free AAs and sugars in the nectar of 102 UK plant species. Six distinct profiles of essential amino acids (EAAs) were defined using the relative proportions of AAs with a clustering algorithm; we then tested bumblebee (Bombus terrestris) preferences for the EAA profiles and proline using a two‐choice assay. We found a phylogenetic signal for the proportions of phenylalanine, methionine and proline as well as the total concentrations of essential and nonessential amino acids. However, there was no phylogenetic signal for EAA profile. Bumblebees did not exhibit a preference for any of the six EAA nectar profiles; however, four of the EAA profiles stimulated feeding. By contrast, bumblebees avoided proline in an inverse concentration‐dependent manner. Our data indicate that bees are likely to have mechanisms for the postingestive evaluation of free AAs in solution but are unlikely to taste EAAs at nectar‐relevant quantities. We predict that EAAs increase nectar value to bumblebees postingestively. [ABSTRACT FROM AUTHOR]

Mating success depends on many factors, but first of all, a male and a female need to meet at the same place and time. The circadian clock is an endogenous system regulating activity and sex-related behaviors in animals. We studied bumble bees (Bombus terrestris) in which the influence of circadian rhythms on sexual behavior has been little explored. We characterized circadian rhythms in adult emergence and locomotor activity under different illumination regimes for males and gynes (unmated queens). We developed a method to monitor adult emergence from the pupal cocoon and found no circadian rhythms in this behavior for either males or gynes. These results are not consistent with the hypothesis that the circadian clock regulates emergence from the pupa in this species. Consistent with this premise, we found that both gynes and males do not show circadian rhythms in locomotor activity during the first 3 days after pupal emergence, but shortly after developed robust circadian rhythms that are readily shifted by a phase delay in illumination regime. We conclude that the bumble bees do not need strong rhythms in adult emergence and during early adult life in their protected and regulated nest environment, but do need strong activity rhythms for timing flights and mating-related behaviors. Next, we tested the hypothesis that the locomotor activity of males and gynes have a similar phase, which may improve mating success. We found that both males and gynes have strong endogenous circadian rhythms that are entrained by the illumination regime, but males show rhythms at an earlier age, their rhythms are stronger, and their phase is slightly advanced relative to that of gynes. An earlier phase may be advantageous to males competing to mate a receptive gyne. Our results are consistent with the hypothesis that sex-related variations in circadian rhythms is shaped by sexual selection. [ABSTRACT FROM AUTHOR]

Bumblebees are crucial pollinators, providing essential ecosystem services and global food production. The success of pollination services relies on the interaction between sensory organs and the environment. The antenna functions as a versatile multi‐sensory organ, pivotal in mediating chemosensory/olfactory information, and governs adaptive responses to environmental changes. Despite an increasing number of RNA‐sequencing studies on insect antenna, comprehensive antennal transcriptome studies at the different life stages were not elucidated systematically. Here, we quantified the expression profile and dynamics of coding/microRNA genes of larval head and antennal tissues from early‐ and late‐stage pupa to the adult of Bombus terrestris as suitable model organism among pollinators. We further performed Pearson correlation analyses on the gene expression profiles of the antennal transcriptome from larval head tissue to adult stages, exploring both positive and negative expression trends. The positively correlated coding genes were primarily enriched in sensory perception of chemical stimuli, ion transport, transmembrane transport processes and olfactory receptor activity. Negatively correlated genes were mainly enriched in organic substance biosynthesis and regulatory mechanisms underlying larval body patterning and the formation of juvenile antennal structures. As post‐transcriptional regulators, miR‐1000‐5p, miR‐13b‐3p, miR‐263‐5p and miR‐252‐5p showed positive correlations, whereas miR‐315‐5p, miR‐92b‐3p, miR‐137‐3p, miR‐11‐3p and miR‐10‐3p exhibited negative correlations in antennal tissue. Notably, based on the inverse expression relationship, positively and negatively correlated microRNA (miRNA)–mRNA target pairs revealed that differentially expressed miRNAs predictively targeted genes involved in antennal development, shaping antennal structures and regulating antenna‐specific functions. Our data serve as a foundation for understanding stage‐specific antennal transcriptomes and large‐scale comparative analysis of transcriptomes in different insects. [ABSTRACT FROM AUTHOR]

The document explores the impact of environmental factors and management practices on bee health, focusing on the global crisis affecting honeybee, bumblebee, and solitary bee populations. Stressors such as pathogens, pests like Varroa destructor, pesticides, habitat loss, and climate change contribute to bee colony decline. Innovative control measures, including essential oils as alternatives to synthetic acaricides and advancements in diagnostic tools, are highlighted. Research also delves into the effects of urbanization, pesticide exposure, and agricultural intensification on bee health, emphasizing the need for interdisciplinary approaches to safeguard bee populations and ecosystem sustainability. [Extracted from the article]

In eusocial insects, the molecular basis of worker reproductivity, including how it changes with eusocial complexity, remains relatively poorly understood. To address this, we used mRNA-seq to isolate genes differentially expressed between ovary-active and ovary-inactive workers in the intermediately eusocial bumblebee Bombus terrestris. By comparisons with data from the advanced eusocial honeybee Apis mellifera , which shows reduced worker reproductivity, we characterized gene expression differences associated with change in worker reproductivity as a function of eusocial complexity. By comparisons with genes associated with queen-worker caste development in B. terrestris larvae, we tested the behavioral–morphological caste homology hypothesis, which proposes co-option of genes influencing reproductive division of labor in adults in morphological caste evolution. We conducted comparisons having isolated genes expressed in B. terrestris worker-laid eggs to remove the potential confound caused by gene expression in eggs. Gene expression differences between the B. terrestris worker phenotypes were mainly in fat body and ovary, not brain. Many genes (86%) more highly expressed in ovary of ovary-active workers were also expressed in worker-laid eggs, confirming egg-expressed genes were potentially confounding. Comparisons across B. terrestris and A. mellifera , and with B. terrestris larvae, returned significant percentage overlaps in differentially expressed genes and/or enriched Gene Ontology terms, suggesting conserved gene functions underpin worker reproductivity as it declines with increasing eusocial complexity and providing support for the behavioral–morphological caste homology hypothesis. Therefore, within bees, both a degree of conserved gene use and gene co-option appear to underlie the molecular basis of worker reproductivity and morphological caste evolution. [ABSTRACT FROM AUTHOR]

Bee populations are facing numerous stressors globally, including environmental pollution by trace metals and metalloids. Understanding whether bees can detect and avoid these pollutants in their food is pivotal, as avoidance abilities may mitigate their exposure to xenobiotics. While these pollutants are known to induce sublethal effects in bees, such as disrupting physiological mechanisms, their potential impacts on locomotive abilities, fat metabolism, and reproductive physiology remain poorly understood. In this study, utilising workers of the buff-tailed bumble bee and two prevalent trace metals, namely cadmium and copper, we aimed to address these knowledge gaps for field-realistic concentrations. Our findings reveal that workers did not reject field-realistic concentrations of cadmium and copper in sucrose solutions. Moreover, they did not reject lethal concentrations of cadmium, although they rejected lethal concentrations of copper. Additionally, we observed no significant effects of field-realistic concentrations of these metals on the walking and flying activities of workers, nor on their fat metabolism and reproductive physiology. Overall, our results suggest that bumble bees may not avoid cadmium and copper at environmental concentrations, but ingestion of these metals in natural settings may not adversely affect locomotive abilities, fat metabolism, or reproductive physiology. However, given the conservative nature of our study, we still recommend future research to employ higher concentrations over longer durations to mimic conditions in heavily polluted areas (i.e., mine surrounding). Furthermore, investigations should ascertain whether field-realistic concentrations of metals exert no impact on bee larvae. [ABSTRACT FROM AUTHOR]

Bumblebees play a significant role as pollinators for many wild plants and cultivated crops, owing to their elongated proboscis, resilience to diverse weather conditions, robustly furred bodies, and their unique capacity for buzz-pollination. To better understand the effect of greenhouse microclimates on bumblebee foraging behavior and working modes, a long-term record of foraging activity for each Bombus terrestris L. (Hymenoptera: Apidae) forager was monitored by the Radio-frequency identification system. The pattern of task performance, including constant housing, foraging, and day-off rotation, was examined under the microclimate. In addition, the correlation between foraging activity of bumblebees and temperature, relative humidity, illumination in the greenhouse, and pollen viability of tomato plants was further analyzed. Our findings revealed that B. terrestris can respond to microclimatic factors and plant resources while also exhibiting a suitable working pattern within the colony. Day-off rotation was observed as a strategy employed by foragers to prolong their survival time. This division of labor and task rotation may serve as strategies for the survival and development of the colony. Our research may contribute to fully understanding how microclimate and plants influence pollinator behavior within greenhouses, thereby optimizing the pollination management of bumblebees on greenhouse crops. [ABSTRACT FROM AUTHOR]

Recent studies have shown that old, traditionally managed semi‐natural grasslands (SNGs) harbour specific plant assemblages characterized by high species richness, diversity, evenness and a great abundance and diversity of floral resources. As nectar and pollen from many of these plants contain a multitude of favourable phytochemical compounds, we hypothesized that pollinator health and survival would improve in old, species‐rich hay SNGs compared to younger SNGs. We monitored experimental colonies of bumblebees placed in hay SNGs of different ages. The survival of bumblebees increased with grassland age, thus they lived longer and produced more workers in the old SNGs. The abundance of actinomorphic flowers (with radial symmetry) increased with the age of the SNGs and was positively correlated with the body size, body mass and lipid reserves of the bumblebees. The taxonomic composition of gut microbiota changed during the experiment, with a significant decrease of core taxa Bombiscardovia and Bifidobacterium in young SNGs, while the abundance of Bombilactobacillus increased in old SNGs. At the end of the experiment, the bumblebees of young SNGs hosted lower abundances of Gilliamella than those of old SNGs. In old SNGs, there was a positive relationship between floral richness and the abundance of six taxa, including the three core taxa Bombiscardovia, Bifidobacterium and Snodgrassella. Microbiota α‐diversity decreased and microbiota β‐diversity increased over time in young SNGs, while both remained stable in old SNGs. Both deterministic and stochastic processes acting simultaneously in bumblebee microbiomes within young SNGs seemed to explain these changes. Compared to old forests, very little attention has been paid to old, species‐rich grasslands. Considering their importance for pollinator health, as well as their high ecological and cultural values, it is crucial that the rare and endangered old, species‐rich hay SNGs are protected. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Pesticides and the lack of floral resources are key drivers of insect decline in agricultural areas. Both land‐use stressors can have a variety of synergistic and sublethal effects on pollinators, affecting their health and foraging behaviour. Pollinating insects include species with vastly different life histories, giving them potentially different vulnerability and resilience to stressors. However, most research has generally focused on bees. Here, we contrast synergistic effects of nutritional stress and pesticide use on social bumblebees and solitary hoverflies.We experimentally tested the effects of the neonicotinoid acetamiprid and low‐quality food on health traits of Bombus terrestris workers and Episyrphus balteatus adults (ovarian development, body size and colony development or survival). The foraging behaviour of treated pollinators was recorded in a semi‐field setup and, for B. terrestris, we measured the pollen amount on the body surface and the pollen deposited on stigmata after a single floral visit.Both stressors affected bumblebee health. Additionally, insecticide‐treated workers showed increased flower handling times and flight durations, while low‐quality food reduced the amount of pollen on the surface of bumblebees and the pollen deposited on stigmata. Syrphids were mostly affected by low‐quality food, which decreased their survival probability and changed their foraging behaviour. Furthermore, we found an interactive effect between the two stressors, reducing E. balteatus ovary development.Synthesis and applications. Insecticide and food stress affected fitness traits of both bumblebees and syrphid flies, possibly reducing pollinator populations under natural conditions. Especially for bumblebees, long‐term exposure led to a reduction in the provision of pollination services, both by changing their behaviour and reducing pollen transfer. We found differences between the two pollinator groups, showing that results gained from single groups like bees should not be extrapolated to all pollinators. Interactive effects indicate potential buffering effects of high‐quality food against other stressors and highlight the importance of considering synergies between multiple stressors in risk assessments. This further emphasizes the relevance of floral resources such as wild flower strips in agricultural areas to conserve pollinators and pollination services. [ABSTRACT FROM AUTHOR]

Wildlife faces an increasing threat from extreme climatic events, such as heatwaves, which can have a severe impact on various species, including crucial pollinators like bumblebees. Bumblebees are cold‐adapted and heterothermic, possessing the ability to regulate their internal temperature. The impact of heat stress seems species specific in bumblebees. While most species are impacted, some bumblebee species manage to survive, potentially by employing physiological mechanisms, including the modulation of their protein profile (e.g. Heat Shock Proteins). However, there is limited understanding of how their protein profiles are associated with heat exposure. In this study, we examined the global variation in the protein profile of males from two bumblebee species sampled in the wild: the heat‐tolerant Bombus terrestris and the heat‐sensitive Bombus magnus. After subjecting them to heat stupor at 40°C in controlled condition, it was observed that nearly all B. terrestris survived the stress, while over 50% of B. magnus individuals succumbed to the heat exposure. Through off‐gel bottom‐up proteomics and LC–MS/MS analysis of the hemolymph proteome, we identified 164 proteins in both species with a large part of differentially expressed proteins after heat exposure. Additionally, quantitative analysis of fat bodies revealed that the relative mass was stable in B. terrestris, while it was significantly lower in B. magnus exposed to heat stress. Our data suggest that compared with B. magnus, B. terrestris displays a higher adaptability of its hemolymph proteome in response to heat stress. This adaptability could be a key factor contributing to the high physiological resistance of B. terrestris and its ability to adapt to new, stressful environments expected due to climate change. Understanding these mechanisms of protein regulation in bumblebees could provide valuable insights into their resilience and vulnerability facing environmental stresses. [ABSTRACT FROM AUTHOR]

Epigenetic mechanisms, such as DNA methylation, are crucial factors in animal development. In some mammals, almost all DNA methylation is erased during embryo development and re‐established in a sex‐ and cell‐specific manner. This erasure and re‐establishment is thought to primarily be a vertebrate‐specific trait. Insects are particularly interesting in terms of development as many species often undergo remarkable morphological changes en route to maturity, that is, morphogenesis. However, little is known about the role of epigenetic mechanisms in this process across species. We have used whole‐genome bisulfite sequencing to track genome‐wide DNA methylation changes through the development of an economically and environmentally important pollinator species, the bumblebee Bombus terrestris (Hymenoptera:Apidae Linnaeus). We find overall levels of DNA methylation vary throughout development, and we find developmentally relevant differentially methylated genes throughout. Intriguingly, we have identified a depletion of DNA methylation in ovaries/eggs and an enrichment of highly methylated genes in sperm. We suggest this could represent a sex‐specific DNA methylation erasure event. To our knowledge, this is the first suggestion of possible developmental DNA methylation erasure in an insect species. This study lays the required groundwork for functional experimental work to determine if there is a causal nature to the DNA methylation differences identified. Additionally, the application of single‐cell methylation sequencing to this system will enable more accurate identification of if or when DNA methylation is erased during development. [ABSTRACT FROM AUTHOR]

Increasing evidence shows that wild bees, including bumble bees, are in decline due to a range of stressors, including pesticides. Our knowledge of pesticide impacts has consequently grown to enable the design of increasingly realistic risk assessment methods. However, one area where knowledge gaps may still hinder our ability to assess the full range of bee‐pesticide interactions is the field of exposure. Exposure has historically been linked to either direct contact with pesticides or the ingestion of contaminated pollen and nectar by bees. However, bumble bees, and other wild bees, may also be exposed to pesticides while using contaminated soil as an overwintering substrate. Yet knowledge of how soil‐mediated exposure affects bumble bee health is lacking. Here we take one of the first steps towards addressing this knowledge gap by designing a method for testing the effects of soil‐mediated pesticide exposure on bumble bee queen hibernation success. We measured hibernation survival, body weight change and abdominal fat content and found that none of these responses were affected by a field realistic soil exposure to the novel insecticide cyantraniliprole. Our study may help in developing a standardised method to test the effects of the soil‐mediated pesticide exposure route in bumble bee queens. [ABSTRACT FROM AUTHOR]

The Hunt bumble bee, Bombus huntii , is a widely distributed pollinator in western North America. The species produces large colony sizes in captive rearing conditions, experiences low parasite and pathogen loads, and has been demonstrated to be an effective pollinator of tomatoes grown in controlled environment agriculture systems. These desirable traits have galvanized producer efforts to develop commercial Bombus huntii colonies for growers to deliver pollination services to crops. To better understand Bombus huntii biology and support population genetic studies and breeding decisions, we sequenced and assembled the Bombus huntii genome from a single haploid male. High-fidelity sequencing of the entire genome using PacBio, along with HiC sequencing, led to a comprehensive contig assembly of high continuity. This assembly was further organized into a chromosomal arrangement, successfully identifying 18 chromosomes spread across the 317.4 Mb assembly with a BUSCO score indicating 97.6% completeness. Synteny analysis demonstrates shared chromosome number (n = 18) with Bombus terrestris , a species belonging to a different subgenus, matching the expectation that presence of 18 haploid chromosomes is an ancestral trait at least between the subgenera Pyrobombus and Bombus sensu stricto. In conclusion, the assembly outcome, alongside the minimal tissue sampled destructively, showcases efficient techniques for producing a comprehensive, highly contiguous genome. [ABSTRACT FROM AUTHOR]

Background: The evaluation of the impact of pesticides on non-target species, like bees, is a crucial factor in registration procedures. Therefore, standardized test procedures have been developed on OECD level assessing the effects of chemicals on honey bees or bumble bees. Unfortunately, these protocols cannot directly be adapted for testing products that contain microorganisms. Interest in the use of microorganisms has increased in recent years due to their specificity to target species while not harming non-target organisms. This study aimed to evaluate optimal conditions to assess the effects of microbial plant protection products on bee species according to currently available test protocols. Some of the most commonly used microorganisms for plant protection, Bacillus thuringiensis subspecies aizawai (B. t. a. ABTS 1857) and Beauveria bassiana (B. b. ATCC 74040) were tested on Apis mellifera, Bombus terrestris, and Osmia bicornis at different temperatures (18, 26, 33 °C) under laboratory conditions. Results: Exposure to the product containing B. t. a. ABTS 1857 resulted in higher mortality compared to B. b. ATCC 74040 in all tested bee species. A temperature-dependent effect towards higher mortality at higher temperatures of 26 °C or 33 °C was observed in O. bicornis exposed to both microorganisms. A. mellifera showed variable responses, but for B. terrestris there was mostly no effect of temperature when exposed to microorganisms in high concentrations. However, temperature affected longevity of bee species in the non-exposed control group. A. mellifera mortality increased with decreasing temperatures, while B. terrestris and O. bicornis mortality increased with increasing temperatures. A test duration of 15 or 20 days was found to be suitable for testing these microorganisms. Conclusion: In conclusion, 26 °C should be considered the worst-case scenario for testing B. bassiana on all tested bee species. For testing B. thuringiensis, a temperature of 33 °C is recommended for A. mellifera, whereas B. terrestris and O. bicornis should be tested at 26 °C. [ABSTRACT FROM AUTHOR]

Bumblebees (Bombus terrestris) have been shown to engage in string-pulling behavior to access rewards. The objective of this study was to elucidate whether bumblebees display means-end comprehension in a string-pulling task. We presented bumblebees with two options: one where a string was connected to an artificial flower containing a reward and the other presenting an interrupted string. Bumblebees displayed a consistent preference for pulling connected strings over interrupted ones after training with a stepwise pulling technique. When exposed to novel string colors, bees continued to exhibit a bias towards pulling the connected string. This suggests that bumblebees engage in featural generalization of the visual display of the string connected to the flower in this task. If the view of the string connected to the flower was restricted during the training phase, the proportion of bumblebees choosing the connected strings significantly decreased. Similarly, when the bumblebees were confronted with coiled connected strings during the testing phase, they failed to identify and reject the interrupted strings. This finding underscores the significance of visual consistency in enabling the bumblebees to perform the task successfully. Our results suggest that bumblebees’ ability to distinguish between continuous strings and interrupted strings relies on a combination of image matching and associative learning, rather than means-end understanding. These insights contribute to a deeper understanding of the cognitive processes employed by bumblebees when tackling complex spatial tasks. [ABSTRACT FROM AUTHOR]

Colorful flower patterns are key signals to attract pollinators. To produce such motifs, plants specify boundaries dividing petals into subdomains where cells develop distinctive pigmentations, shapes, and textures. While some transcription factors and biosynthetic pathways behind these characteristics are well studied, the upstream processes restricting their activities to specific petal regions remain enigmatic. Here, we unveil that the petal surface of Hibiscus trionum, an emerging model featuring a bullseye on its corolla, is prepatterned as the bullseye boundary position is specified long before it becomes visible. Using a computational model, we explore how pattern proportions are maintained while petals experience a 100-fold size increase. Exploiting transgenic lines and natural variants, we show that plants can regulate boundary position during the prepatterning phase or modulate growth on either side of this boundary later in development to vary bullseye proportions. Such modifications are functionally relevant, as buff-tailed bumblebees can reliably identify food sources based on bullseye size and prefer certain pattern proportions. [ABSTRACT FROM AUTHOR]

This document is a list of contributors and acknowledgements for a study on the generation and characterization of monoclonal antibodies for a specific protein. It also includes a conflict of interest statement and information about the availability of the data. The document does not provide a summary of the study's findings or any additional information about the topic Low. [Extracted from the article]

Simple Summary: To understand the processes behind the decline of pollinators, it is also essential to gain insight into their behaviour and identify the factors that drive it. This study focuses on the foraging behaviour of wild bumblebees in urban areas of Terceira, Azores, Portugal. We video-recorded buff-tailed bumblebees on flowering patches of Cretan bird's-foot trefoil, pink-headed knotweed, and red clover for five-minute intervals. We used computer vision-based deep learning models to detect bumblebees. Our results showed that flower cover was the only factor influencing the attractiveness of flower patches for flower-visiting bumblebees, while plant species had no effect. The time bumblebees spent on inflorescences was longer compared to their travelling time between inflorescences on the large-headed red clover than on the smaller-headed trefoil and knotweed. However, the overall time bumblebees spent on the inflorescences did not significantly differ among the plant species. Since our computer vision-based model achieved high accuracy in finding bumblebees on the target plant species, we confirmed that AI-based solutions can provide methods for studying pollinator behaviour and offer valuable insights to support conservation efforts. To understand the processes behind pollinator declines and for the conservation of pollination services, we need to understand fundamental drivers influencing pollinator behaviour. Here, we aimed to elucidate how wild bumblebees interact with three plant species and investigated their foraging behaviour with varying flower densities. We video-recorded Bombus terrestris in 60 × 60 cm quadrats of Lotus creticus, Persicaria capitata, and Trifolium pratense in urban areas of Terceira (Azores, Portugal). For the automated bumblebee detection and counting, we created deep learning-based computer vision models with custom datasets. We achieved high model accuracy of 0.88 for Lotus and Persicaria and 0.95 for Trifolium, indicating accurate bumblebee detection. In our study, flower cover was the only factor that influenced the attractiveness of flower patches, and plant species did not have an effect. We detected a significant positive effect of flower cover on the attractiveness of flower patches for flower-visiting bumblebees. The time spent per unit of inflorescence surface area was longer on the Trifolium than those on the Lotus and Persicaria. However, our result did not indicate significant differences in the time bumblebees spent on inflorescences among the three plant species. Here, we also justify computer vision-based analysis as a reliable tool for studying pollinator behavioural ecology. [ABSTRACT FROM AUTHOR]

Gut microbial communities confer protection against natural pathogens in important pollinators from the genera Bombus and Apis. In commercial species B. terrestris and B. impatiens, the microbiota increases their resistance to the common and virulent trypanosomatid parasite Crithidia bombi. However, the mechanisms by which gut microorganisms protect the host are still unknown. Here, we test two hypotheses: microbiota protect the host (1) through stimulation of its immune response or protection of the gut epithelium and (2) by competing for resources with the parasite inside the gut. To test them, we reduced the microbiota of workers and then rescued the microbial community by feeding them with microbiota supplements. We then exposed them to an infectious dose of C. bombi and characterised gene expression and gut microbiota composition. We examined the expression of three antimicrobial peptide genes and Mucin‐5AC, a gene with a putative role in gut epithelium protection, using qPCR. Although a protective effect against C. bombi was observed in bumblebees with supplemented microbiota, we did not observe an effect of the microbiota on gene expression that could explain alone the protective effect observed. On the other hand, we found an increased relative abundance of Lactobacillus bacteria within the gut of infected workers and a negative correlation of this genus with Gilliamella and Snodgrassella genera. Therefore, our results point to a displacement of bumblebee endosymbionts by C. bombi that might be caused by competition for space and nutrients between the parasite and the microbiota within the gut. [ABSTRACT FROM AUTHOR]

Resource competition between wild pollinators and managed honeybees (Apis mellifera) has the potential to detrimentally impact insect biodiversity as well as wild plant and crop pollination. As honeybees are central place foragers, their competitive impact on wild bees is expected to be structured by hive proximity, in conjunction with foraging decisions related to landscape‐level resource availability. Yet, how these factors structure dietary niche overlap between wild bees and managed honeybees remains unclear.We conducted a field experiment in seminatural grasslands, where honeybee foraging densities and niche overlap with buff‐tailed bumblebees (Bombus terrestris) were measured at four distances (<100, 500, 1000 and 2000 m) from experimentally placed apiaries, during and after the blooming period of mass‐flowering oilseed rape (Brassica napus). We measured honeybee foraging densities using standardized transect surveys, and quantified species diet composition and dietary niche overlap from pollen samples collected from both bee species.Honeybee foraging densities were highest near apiaries and declined sharply beyond 500 m from the apiaries. However, niche overlap was unrelated to hive proximity but positively related to the availability of oilseed rape. Furthermore, there were significant inter‐ and intraspecific differences in pollen diet composition and breadth throughout the season.Synthesis and applications: Niche overlap between honeybees and bumblebees in agricultural environments was due to resource sharing of mass‐flowering oilseed rape. When both honeybees and bumblebees predominantly forage on wild plants, they maintain distinct pollen diets, suggesting there is a low risk of resource competition between these generalist taxa. Conservation actions that promote floral resource availability and diversity in agricultural landscapes are crucial to maintain niche differentiation between managed honeybees and wild bees. [ABSTRACT FROM AUTHOR]

• The field cultivation of oil tree peony experienced a "medium" pollination deficit. • Excluding pollinator pollination reduced the yield of oil tree peony by 44.24%, and oil tree peony showed a high dependence on bumblebee pollination. • Supplemental bumblebee pollination increased the seed yield of oil tree peony by 82.87% and the oil yield by 10.21%, which reduced the degree of pollination defects to a lower level. • Pollination by bumblebees ensures the stability of yield and quality of oil tree peony over time. Oil tree peony is a unique woody oil crop found exclusively in China. Its seed oil is a highly nutritious edible vegetable oil. However, its seed production varies greatly and is often low. Oil tree peony is a plant that relies on insects for pollination, but inadequate pollination is a common occurrence. In this study, we focused on the Paeonia ostii 'Fengdan' species and conducted a five-year study (from 2017 to 2022) in Luoyang, China. Our objective was to assess the extent of pollination deficiency and dependence, as well as quantify the contribution of supplemented bumblebees (Bombus terrestris) to the yield of oil tree peony. We also examined the effect of supplemented bumblebees on the temporal variation in yield through various pollinator survey designs, including supplemented bumblebees (BP), open pollination (OP), pollinator exclusion (EP), self-pollination treatments (SP), and artificial cross-pollination (CP). The results revealed a medium pollination deficit (D = 0.50) at the study sites for three consecutive years from 2020 to 2022, indicating limited pollination for oil tree peony under natural conditions. Importantly, BP significantly compensated for this deficiency (D = 0.22). Over the course of five years, BP increased the yield of oil tree peony by 82.87% on average compared to EP. Furthermore, the yield variation coefficient of EP (CVt=0.20) increased by 100% compared to BP (CVt=0.10). And we also observed significant variability in other yield parameters. Additionally, oil tree peony production was reduced by 44.24% in the absence of flower visitors, and the dependence on BP reached a "high" level. The fatty acid content in the seed oil did not show significant differences across treatments, indicating its stability. Overall, our pollination practices demonstrate that supplementing bee pollination can provide sufficient and stable pollination services, resulting in a higher and more stable yield of oil tree peony seeds. [ABSTRACT FROM AUTHOR]

[Aim] Selecting appropriate internal reference genes is crucial for the analysis of gene expression in insects. Using real-time PCR, this study assessed the expression stability of five candidate reference genes across four tissue types in bumble bees, aiming to identify the most suitable reference gene for quantitative gene expression analysis. [Methods] Specific primers were designed for the five candidate internal reference genes of Bombus terrestris, including Actin5C, PLA2 (phospholipase A2), S18(ribosomal protein S18), S28(ribosomal protein S28), and EF-1 (elongation factor 1 alpha). Newly emerged workers, queens, and drones were labeled and reared in their original colonies. Total RNA was extracted from samples of the head, ovary, ventral nerve cord, and seminal vesicle taken at 1, 3, 5, 7, and 10 days of age. The fragments of candidate reference genes were cloned into a pMD19-T vector before being verified via sequencing. The amplification processes were then optimized and the standard curves established. The levels of candidate internal reference genes in queen, worker, and drone tissue samples were quantified using real-time PCR. The expression stability of the internal candidate internal reference genes was analyzed using NormFinder, BestKeeper, GeNorm, CT, and RefFinder. [Results] The expression stability of the candidate reference genes depended on the method of analysis used. However, results from a comprehensive analysis using RefFinder showed that PLA2 had the most stable expression level in the head of queens and drones, ventral nerve cord of workers and drones, and ovaries of workers. Actin5C was most stably expressed in the ovaries of queens and workers, whereas EF-1 had the most stable expression level in the ventral nerve cord of queens. Finally, S18 was the stably expressed gene in the seminal vesicle of drones. [Conclusion] These findings indicate that the quantitative stability of internal reference genes varies among castes and tissues of bumble bees. Therefore, it is crucial to select the most stable internal reference genes based on the sample tissue type to ensure the reliability of the results. [ABSTRACT FROM AUTHOR]

Food security is threatened by climate change and associated abiotic stresses that affect the flowering stage and the biochemistry of flowers and fruits. In tomato, managed insect pollination and grafting elite tomato varieties onto robust rootstocks are widely practiced commercially to enhance tomato crop profitability, particularly under suboptimal conditions. However, little is known about rootstock–pollinator interactions and their impact on the chemical composition of fruit. In this study, a commercial tomato F1 hybrid (Solanum lycopersicum L.) was self-grafted and grafted onto a set of experimental rootstocks and cultivated under optimal and saline (75 mM NaCl) conditions in the presence of managed bumblebee pollinators (Bombus terrestris). The number of visits (VN) and total visiting time (TVT) by pollinators to different grafted plants were monitored through an RFID (radio-frequency identification) tracking system, while targeted metabolites (hormones, sugars, and organic and amino acids) and mineral composition were analyzed in the fruit juice by UHPLC-MS and ICP-OES, respectively. Pollinator foraging decisions were influenced by the rootstocks genotype and salinity treatment. Experimental rootstocks predominantly increased pollinator attraction compared to the self-grafted variety. Interestingly, the pollinator parameters were positively associated with the concentration of abscisic acid, salicylic acid, malate and fumarate, and tyrosine in salinized fruits. Moreover, a high accumulation of sodium was detected in the fruits of the plants most visited by pollinators, while rootstock genotype-specific responses were found for nitrogen and potassium concentrations. In addition to the known effect on yield, these findings underscore the synergic interactions between rootstocks, pollinators, and environmental stressors on tomato fruit composition. [ABSTRACT FROM AUTHOR]

Global climate change disrupts key ecological processes and biotic interactions. The recent increase in heatwave frequency and severity prompts the evaluation of physiological processes that ensure the maintenance of vital ecosystem services such as pollination. We used experimental heatwaves to determine how high temperatures affect the bumblebees' ability to detect floral scents. Heatwaves induced strong reductions in antennal responses to floral scents in both tested bumblebee species (Bombus terrestris and Bombus pascuorum). These reductions were generally stronger in workers than in males. Bumblebees showed no consistent pattern of recovery 24 h after heat events. Our results suggest that the projected increased frequency and severity of heatwaves may jeopardize bumblebee-mediated pollination services by disrupting the chemical communication between plants and pollinators. The reduced chemosensitivity can decrease the bumblebees' abilities to locate food sources and lead to declines in colonies and populations. [ABSTRACT FROM AUTHOR]

Summary: Increased temperature can induce plastic changes in many plant traits. However, little is known about how these changes affect plant interactions with insect pollinators and herbivores, and what the consequences for plant fitness and selection are.We grew fast‐cycling Brassica rapa plants at two temperatures (ambient and increased temperature) and phenotyped them (floral traits, scent, colour and glucosinolates). We then exposed plants to both pollinators (Bombus terrestris) and pollinating herbivores (Pieris rapae). We measured flower visitation, oviposition of P. rapae, herbivore development and seed output.Plants in the hot environment produced more but smaller flowers, with lower UV reflectance and emitted a different volatile blend with overall lower volatile emission. Moreover, these plants received fewer first‐choice visits by bumblebees and butterflies, and fewer flower visits by butterflies. Seed production was lower in hot environment plants, both because of a reduction in flower fertility due to temperature and because of the reduced visitation of pollinators. The selection on plant traits changed in strength and direction between temperatures.Our study highlights an important mechanism by which global warming can change plant–pollinator interactions and negatively impact plant fitness, as well as potentially alter plant evolution through changes in phenotypic selection. [ABSTRACT FROM AUTHOR]

Nectar composition is an important driver of insect attractiveness. Although bumblebees prefer sucrose-rich nectar, they were found to be the main pollinators of Gentiana lutea, whose nectar is low on sucrose. Therefore, we tested the hypothesis that bumblebees are attracted to the amino acids proline and β-alanine, which are both naturally occurring at high concentrations in the nectar of G. lutea. We analysed the solution consumption and survival of Bombus terrestris L. (Hymenoptera: Apidae) workers fed with artificial nectars enriched with proline, β-alanine or both, at natural and twice the natural concentrations. We found that consumption of nectar enriched with proline at twice the natural concentration was strongly positively correlated with bumblebee weight. However, when adjusting for individual weight, we found that this solution was the least consumed, suggesting the presence of a regulatory mechanism of proline intake to reduce negative effects on survival. We did not find any direct effect of β-alanine on consumption, although our findings suggest a potential interplay between proline and β-alanine in the regulation of proline intake. Bumblebee survival was not affected by any nectar composition. These results suggest that the high visitation rate to flowers of G. lutea by bumblebees observed in natural populations can be partially related to its nectar amino acidic composition, and that protein and non-protein amino acids can affect pollinator preference and foraging behaviour. [ABSTRACT FROM AUTHOR]

Heteranthery, the presence of different types of anthers on the same flower, is a floral adaptation that aims to balance the need for pollinators to collect pollen as a food resource while ensuring sufficient pollen for pollination. We investigate the role of heteranthery in the pollination of Senna arnottiana flowers and how it is affected by the behaviour of visiting bee species, with a particular focus on the impact of the invasive bumblebee Bombus terrestris.In three populations of S. arnottiana we measured the size of three sets of anthers and style, stigma–anther separation, pollen quantity and fruit set, and contrasted it with the body size, behaviour, and pollination effectiveness of all floral visitors.Different bee species visited S. arnottiana flowers, and their foraging behaviour varied. Large‐bodied native bees, including Centris cineraria, Caupolicana sp. and Cadeguala occidentalis, preferentially visited short anthers, whereas B. terrestris, an exotic bumblebee, foraged from both short and long anthers without distinction. In addition, B. terrestris contacted the stigma at a lower rate than large‐bodied native bees.Instead of concentrating its pollen‐gathering efforts on the feeding anthers, as predicted by the "division of labor" hypothesis, B. terrestris indiscriminately visited both types of anthers similarly. This behaviour of B. terrestris may disrupt the adaptive significance of heteranthery by mixing the roles of pollination and feeding anthers of S. arnottiana. Therefore, our results highlight the potential disruption of this relationship by exotic pollinators and the need to consider it in conservation efforts. [ABSTRACT FROM AUTHOR]

Development and maintenance of neural architecture supporting learning and memory, as well as active storage of learnt information, are predicted to carry significant energetic costs. Here we explored whether the demands of learning about fitness-relevant stimuli come at a cost to the reproductive success of an insect model. Bumble bee (Bombus spp.) queens found nests alone, and early in the colony cycle must invest simultaneously in learning about rewarding floral resources and colony founding. We exposed queens of Bombus terrestris audax emerging from diapause to a 6-day reversal learning task and compared colony founding success of these individuals to two control groups that did not learn but received equal food. Additionally, we limited carbohydrate intake in half of queens across all treatments. Nutritionally stressed queens had a lower probability of egg laying, delayed nest initiation and lower offspring production compared with nutritionally unrestricted queens, suggesting resource availability at this life cycle stage is crucial to founding successful colonies and population growth. Nevertheless, potential energetic demands of learning did not reduce colony founding success in a laboratory set-up, even in nutritionally stressed groups. Our findings provide a rare real-world test of the costs associated with learning and suggest they do not affect reproductive potential in bumble bee queens. • Development and use of neural architecture carries potential energetic costs. • We test whether such costs compromise reproductive success in bumble bee queens. • The demands of learning did not affect colony founding success, even under stress. • Nutritional stress negatively affected egg laying and offspring production. • Resource-poor environments may affect bumble bee population dynamics. [ABSTRACT FROM AUTHOR]

Wild bees are crucial pollinators of flowering plants and concerns are rising about their decline associated with pesticide use. Interspecific variation in wild bee response to pesticide exposure is expected to be related to variation in their morphology, physiology, and ecology, though there are still important knowledge gaps in its understanding. Pesticide risk assessments have largely focussed on the Western honey bee sensitivity considering it protective enough for wild bees. Recently, guidelines for Bombus terrestris and Osmia bicornis testing have been developed but are not yet implemented at a global scale in pesticide risk assessments. Here, we developed and tested a new simplified method of pesticide exposure on wild bee species collected from the field in Belgium. Enough specimens of nine species survived in a laboratory setting and were exposed to oral and topical acute doses of a sulfoximine insecticide. Our results confirm significant variability among wild bee species. We show that Osmia cornuta is more sensitive to sulfoxaflor than B. terrestris, whereas Bombus hypnorum is less sensitive. We propose hypotheses on the mechanisms explaining interspecific variations in sensitivity to pesticides. Future pesticide risk assessments of wild bees will require further refinement of protocols for their controlled housing and exposure. [ABSTRACT FROM AUTHOR]

Flight plays a crucial role in the fitness of insect pollinators, such as bumblebees. Despite their relatively large body size compared with their wings, bumblebees can fly under difficult ambient conditions, such as cooler temperatures. While their body size is often positively linked to their foraging range and flight ability, the influence of age remains less explored. Here, we studied the flight performance (distance, duration and speed) of ageing bumblebee workers using tethered flight mills. Additionally, we measured their intertegular distance and dry mass as proxies for their body size. We found that the flight distance and duration were predominantly influenced by age, challenging assumptions that age does not play a key role in foraging and task allocation. From the age of 7 to 14 days, flight distance and duration increased sixfold and fivefold, respectively. Conversely, the body size primarily impacted the maximum and average flight speed of workers. Our findings indicate that age substantially influences the flight distance and duration in bumblebee workers, affecting foraging performance and potentially altering task allocation strategies. This underscores the importance of considering individual age and physiological changes alongside body size/mass in experiments involving bumblebee workers. [ABSTRACT FROM AUTHOR]

A common management intervention to support declining wild pollinators is 'pollinator planting'. However, despite years of inclusion in conservation initiatives, global pollinator declines continue.Using the agent‐based model BEE‐STEWARD with two example species, Bombus terrestris (L. 1758) and B. pascuorum (Scopoli, 1763) (Hymenoptera: Apidae), we explore when during the year bumblebee resource demand is the highest and how that relates to seasonal changes in colony composition (numbers of eggs, larvae, pupae and adults). We then examine the impact of two‐week periods of resource scarcity across the year. Finally, we explore how enhancement with early spring‐blooming herbaceous species or trees changes colony survival and queen production.In the United Kingdom, there is a previously under‐appreciated 'hungry gap' for bumblebees in March–April, before the peak flight period, driven by the demands of larvae for protein and thermoregulation in the colony, rather than the number of adult bees.A 2‐week gap in forage availability during this period drives a 50%–87% drop in the production of daughter queens. Adding early‐blooming species in the model had significant, positive, long‐term effects on colony survival probability and daughter queen production.Pollinator‐planting initiatives in both national and international conservation schemes need to include plants that flower up to 1 month before the adults of target social pollinator species are apparent in the field, during the period that larvae dominate the colony. This approach is likely to increase colony survival and queen production, contributing towards halting and reversing global pollinator decline. [ABSTRACT FROM AUTHOR]

This study is among the first monographs on Algerian apoid fauna. Conducted from March 2022 to June 2022, it involves inventorying wild bees across three stations in the Tlemcen Mountains along an altitude gradient. An exhaustive list of 70 species was compiled, with the Apidae family containing 9 species. Apis mellifera was the most prevalent, comprising 33.43% of the population, followed by Bombus terrestris (20%), Xylocopa pubescens (17.14%), Xylocopa violacea (15.71%), Anthophora vestita (7.14%), Eucera notata and Eucera colaris (2.86%), and Eucera punctatissima and Eucera nigrilabris (1.43%). New apoid fauna species discovered in the Tlemcen Mountains include members of the Andrenidae family (Andrena flavipes, Andrena nigroanea), the Megachilidae family (Hoplitlis sp.), and other Vespoidea species such as Vespula vulgaris and Dasyscolia ciliata. Studies on the diversity and structure of bee populations indicated significant diversity, illustrated by the Shannon-Weaver diversity index, with the highest value of 2.65 recorded in Beni Snous. Additionally, it was observed that most species were well represented in May and June, with a notable shortage in March and April due to drought and a delayed spring. The relationships between plants and bees were examined by studying the plants visited during the flowering season. The chi-square test revealed a significant and medium correlation between bees and regions, and a significant and very strong correlation between plants and bees. The results underscore the richness of Apoids in the area and highlight the necessity of their protection, given their critical role in pollination and maintaining biodiversity in natural ecosystems and agrocenoses. [ABSTRACT FROM AUTHOR]

Worldwide declines in critical hymenopteran pollinators, such as bumble bees and honey bees, in recent decades have sparked a surge in research aimed at identifying the factors behind these declines. Among the suspected contributors, infectious diseases have garnered significant attention. In this context, we conduct a comprehensive review of the potential impact of naturalized Palearctic exotic bumble bee species, specifically Bombus terrestris and Bombus ruderatus, on the occurrence of Apicystis bombi in southern South America. Apicystis bombi is a unique apicomplexan protist that belongs to the neogregarines, which as a group exhibit relatively high virulence towards a range of insects. Our review encompasses the available information on its morphology, molecular characteristics, pathology, host range, and geographic distribution. Additionally, we explore three plausible hypotheses, each not necessarily exclusive of the others, in an effort to shed light on the occurrence of A. bombi in South America. These hypotheses include the two classically accepted, but less supported in view of current data (entry via B. terrestris, entry via B. ruderatus), and one postulated for the first time here with arguably better support (pre-existing presence before the introduction of B. terrestris and B. ruderatus, plus the possibility of multiple Apicystis species coexisting). We aim for this review to stimulate interest in this relatively obscure parasitic microbe that affects crucial insect pollinators. [ABSTRACT FROM AUTHOR]

Pollination of entomophilous crops by the bumblebee Bombus terrestris in greenhouses and open fields depends on the state of the colony and the impact of unfavorable environmental factors. The most important indicators of the colony state are the number of workers and the condition of the queen. The foraging activity of bumblebees in greenhouses and the longevity of their colonies are negatively affected by the use of high-pressure sodium lamps with spectra unsuitable for bumblebees' orienting in flight, as well as by air temperatures above 29°C and a lack of pollen. Predators, parasites, and nest destroyers pose a particular danger to bumblebees in open fields. [ABSTRACT FROM AUTHOR]

Simple Summary: Many plants depend on pollination by bees, whereas bees depend on flowers as food sources. Bees use a variety of floral cues such as the color, scent, or shape of the flower to find host plants. The preferred cues of honeybees and bumblebees are well studied, but the preferences of other bee species are almost unknown. Thus, we have performed behavioral experiments with artificial flowers to test whether three common bee species of the genera Lasioglossum, Bombus, and Osmia are attracted by the same or different floral cues. Our experiments showed consistent behaviors across species in experiments testing flower sizes and scent mixtures that differed in compound richness and identities. The color hue experiments, however, revealed different preferences that were probably influenced by previous foraging experience. Within colors, bee species preferred mostly intense colors that formed a high contrast to background colors. A high attractiveness of floral cues enables bees to effectively find foraging plants. With this study, we learned more about flower choice in bee species that are not used as model organisms but are important for pollination. The interaction between bees and flowering plants is mediated by floral cues that enable bees to find foraging plants. We tested floral cue preferences among three common wild bee species: Lasioglossum villosulum, Osmia bicornis, and Bombus terrestris. Preferences are well studied in eusocial bees but almost unknown in solitary or non-eusocial generalist bee species. Using standardized artificial flowers altered in single cues, we tested preferences for color hue, achromatic contrast, scent complexity, corolla size, and flower depth. We found common attractive cues among all tested bees. Intensively colored flowers and large floral displays were highly attractive. No preferences were observed in scent complexity experiments, and the number of volatiles did not influence the behavior of bees. Differing preferences were found for color hue. The specific behaviors were probably influenced by foraging experience and depended on the flower choice preferences of the tested bee species. In experiments testing different flower depths of reward presentation, the bees chose flat flowers that afforded low energy costs. The results reveal that generalist wild bee species other than well-studied honeybees and bumblebees show strong preferences for distinct floral cues to find potential host plants. The diverse preferences of wild bees ensure the pollination of various flowering plants. [ABSTRACT FROM AUTHOR]

Bumblebees are important pollinators in agricultural ecosystems, but their abundance is declining globally. There is an urgent need to protect bumblebee health and their pollination services. Bumblebees possess specialized gut microbiota with potential to be used as probiotics to help defend at‐risk bumblebee populations. However, evidence for probiotic benefits on bumblebees is lacking. Here, we evaluated how supplementation with Lactobacillus melliventris isolated from bumblebee gut affected the colony development of Bombus terrestris. This native strain colonized robustly and persisted long‐term in bumblebees, leading to a significantly higher quality of offspring. Subsequently, the tyrosine pathway was upregulated in the brain and fat body, while the Wnt and mTOR pathways of the gut were downregulated. Notably, the field experiment in the greenhouse revealed the supplementation of L. melliventris led to a 2.5‐fold increase in the bumblebee survival rate and a more than 10% increase in the number of flowers visited, indicating a better health condition and pollination ability in field conditions. Our study represents a first screening for the potential use of the native gut member, L. melliventris, as probiotic strains in hive supplement for bumblebee breeding, which may be a practical approach to improve immunity and hive health. [ABSTRACT FROM AUTHOR]

Background: The gut microbiota and their hosts profoundly affect each other's physiology and evolution. Identifying host-selected traits is crucial to understanding the processes that govern the evolving interactions between animals and symbiotic microbes. Current experimental approaches mainly focus on the model bacteria, like hypermutating Escherichia coli or the evolutionary changes of wild stains by host transmissions. A method called atmospheric and room temperature plasma (ARTP) may overcome the bottleneck of low spontaneous mutation rates while maintaining mild conditions for the gut bacteria. Results: We established an experimental symbiotic system with gnotobiotic bee models to unravel the molecular mechanisms promoting host colonization. By in vivo serial passage, we tracked the genetic changes of ARTP-treated Snodgrassella strains from Bombus terrestris in the non-native honeybee host. We observed that passaged isolates showing genetic changes in the mutual gliding locus have a competitive advantage in the non-native host. Specifically, alleles in the orphan mglB, the GTPase activating protein, promoted colonization potentially by altering the type IV pili-dependent motility of the cells. Finally, competition assays confirmed that the mutations out-competed the ancestral strain in the non-native honeybee gut but not in the native host. Conclusions: Using the ARTP mutagenesis to generate a mutation library of gut symbionts, we explored the potential genetic mechanisms for improved gut colonization in non-native hosts. Our findings demonstrate the implication of the cell mutual-gliding motility in host association and provide an experimental system for future study on host-microbe interactions. ArN8Xjm3N6Dubzus4DCSQm Video Abstract [ABSTRACT FROM AUTHOR]

InsectSound1000 is a dataset comprising more than 169000 labelled sound samples of 12 insects. The insect sound level spans from very loud (Bombus terrestris) to inaudible to human ears (Aphidoletes aphidimyza). The samples were extracted from more than 1000 h of recordings made in an anechoic box with a four-channel low-noise measurement microphone array. Each sample is a four-channel wave-file of 2500 kHz length, at 16 kHz sample rate and 32 bit resolution. Acoustic insect recognition holds great potential to form the basis of a digital insect sensor. Such sensors are desperately needed to automate pest monitoring and ecological monitoring. With its significant size and high-quality recordings, InsectSound1000 can be used to train data-hungry deep learning models. Used to pretrain models, it can also be leveraged to enable the development of acoustic insect recognition systems on different hardware or for different insects. Further, the methodology employed to create the dataset is presented in detail to allow for the extension of the published dataset. [ABSTRACT FROM AUTHOR]