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Beetles of the genus Antherophagus are phoretic organisms that inhabit the nests of Bombus species. They migrate and colonize new nests using the same bumblebees as carriers. Although Antherophagus beetles from temperate Europe and North America are known to use some plant species to move between bumblebees, it is unknown which plants are used as transfer stations by neotropical Antherophagus. Here, we report for the first time how phoretic Antherophagus beetles of an undescribed species use the inflorescences of Chuquiraga jussieui to transfer between individuals of Bombus funebris in the páramos of Central Ecuador. Our observations are the highest records (at 4200 m asl) of a phoretic interaction performed so far. [ABSTRACT FROM AUTHOR]

Both the identity and prevalence of parasitoid dipterans associated with bumble bees (Bombus spp.) in southern South America are little known. Between 2009 and 2017, a total of 2978 bumble bees were individually collected in 63 localities from 11 provinces of the country. After dissections, the presence of parasitoids was observed in the native bumble bees Bombus pauloensis, B. bellicosus, B. opifex, and B. brasiliensis, plus in the exotic invasive species B. terrestris. A combination of both morphological and molecular analysis based on the COI gene allowed the isolation of two species of Physocephala (Conopidae) and one of Helicobia (Sarcophagidae), expanding their host range and geographic distribution. The second instar larva of Helicobia aurescens is described. [ABSTRACT FROM AUTHOR]

Bumblebees have become model organisms for cognitive ecology and social learning. Quantifying the foraging behavior of free-flying bees, however, remains a methodological challenge. We describe and provide the code for a method of studying bee free flying foraging behavior using the open source neural-network based markerless tracking software DeepLabCut. From videos of bees foraging in an arena we trained a neural network to accurately track the position of each bee. We then used this approach to study foraging behavior and show that the ratio between flying time and flower visiting time decreases over repeated foraging bouts, indicating increasing efficiency of bee foraging behavior with experience. Visit durations, a laborious metric to measure by hand, were significantly shorter on flowers that had previously been visited. This experiment illustrates the usefulness of DeepLabCut for objective quantification of behavior, and in this case study shows that previous experience increases bee foraging efficiency. [ABSTRACT FROM AUTHOR]

Due to recent changes in regulation, acetamiprid has become the only neonicotinoid that can be applied without restrictions and in open field cultivations in the EU from 2021. We provide an overview of the current knowledge on the effects of this insecticide on bumblebees and assessed whether available empirical evidence supports the claim that acetamiprid poses negligible risk to these pollinators. We found that there is limited data on the lethal and sublethal effects of this pesticide on bumblebees. While risk assessment results suggest that field-realistic concentrations of acetamiprid have minor acute and chronic toxicity, detrimental sublethal effects, including reduced reproductive output, have been observed when bumblebees were exposed to high doses of this insecticide. We propose that further research on the topic is warranted as the more extensive application of acetamiprid may lead to such high concentrations in the field. [ABSTRACT FROM AUTHOR]

Nectar-related traits influence the number of bee visits to sunflowers, but the effects of floret size on the diversity and composition of bee communities are unknown. In 4 year × planting date combinations, bees were collected from sunflowers with small (< 7.5 mm), medium (7.5–9 mm), or large (> 9 mm) florets, and counts of foraging bees were used to clarify bee responses to plant traits. No effect of floret size on diversity of foraging bees was found, but associations of bee tongue length and floret size led to differences in the communities foraging on sunflowers with small, medium, or large florets. Though most wild bees preferred to forage on plants with more nectar and smaller florets (≈ easier access to nectar), Bombus spp. showed an opposite response to floret size, foraging preferentially on lines with large florets. Changes in Melissodes spp. foraging preference in the presence of Bombus spp. also suggest interactions between small- and large-bodied bees may be important. [ABSTRACT FROM AUTHOR]

Mating is an important process in bumblebees that could affect queen diapause survival and offspring reproduction. Both queens and males could influence mating failure. Here, we used the indigenous bumblebee Bombus lantschouensis to evaluate the mating interactions of males and gynes. The effects of kin recognition and males and gynes from multiple colonies on mating latency, mating duration, and the mating success rate were investigated. The results showed that gynes mated with related males had a longer mating latency than those mated with unrelated males (42.88 ± 3.8 min and 24.15 ± 2.5 min, respectively, P < 0.05) and that the mating success rate was significantly higher in unrelated groups than in related groups (49.29 ± 4.1% and 36.74 ± 2.6%, respectively, P < 0.05). However, no preference for related or unrelated males was observed in the mixed mating groups (mating success rate 30.63 ± 3.1% and 30.73 ± 2.4%, respectively, P > 0.05). Interestingly, the occurrence of males from multiple sources significantly increased the mating success rate (one colony 39.1 ± 4.2% to four colonies 60.05 ± 5.7%, P < 0.05). Nonetheless, an increase in the number of gyne sources had no effect on the mating success rate (one colony 39.50 ± 4.9% to four colonies 43.52 ± 5.7%, P > 0.05). Mating latency was significantly more influenced by males and gynes from multiple colonies than by kin relationship, male number, and gyne number (P < 0.05). In conclusion, there is no evidence that the bumblebee B. lantschouensis can recognize kin relationships before mating. The presence of males and gynes from multiple colonies can influence mating latency. Moreover, males from multiple colonies can significantly enhance mating success, which has implications for bumblebee ecological conservation and artificial mass rearing. [ABSTRACT FROM AUTHOR]

Bumble bees (Bombus spp.) have been commercially propagated for over three decades. As the environmental conditions experienced by commercial bumble bees differ greatly from those experienced by wild bumble bees, commercial rearing of bumble bees may cause phenotypic changes. Here, we compare the foraging behavior and size of worker bumble bees (Bombus impatiens) from commercial and wild colonies. For this experiment, we measured worker body size, recorded if the workers returned with pollen, and examined the contents of pollen loads via microscopy. We found that, while commercial and wild bumble bees foraged on similar communities of flowers, wild bumble bees returned to colonies with purer pollen baskets (higher proportion of the most common species) and were more likely to return to the colony with pollen than their commercial counterparts. Commercial bumble bees were also smaller than wild bees. Our work highlights differences between commercial and wild bumble bees, in addition to raising important unanswered questions about the mechanism and drivers of these differences. [ABSTRACT FROM AUTHOR]

Bumblebees are important pollinators for many wild plants and crops. To explore gene expression characteristics in depth, stable reference genes will be essential across different developmental stages. In this context, we evaluated the stability of eight common reference genes at ten developmental stages in the bumblebee Bombus terrestris (B. terrestris) with four algorithms and two rank approaches. The results showed that all the primers for the reference genes exhibited high specificity, linear correlation (R2-value 0.9917~0.9978) and a good PCR amplification efficiency (E-value 95.4~108.6%). The combined use of RPL13 and RP49 was suggested to be the most suitable reference genes. Our candidate reference genes will help to improve the precision of the detection of gene expression at different developmental stages of bumblebee species. [ABSTRACT FROM AUTHOR]

Bombus terrestris is a bumblebee with a wide geographic range, with subspecies showing a variety of local adaptations. Global export of commercially-reared B. terrestris started in the 1980s; the bees are a mixture of subspecies bred for ease of rearing, bivoltinism and large nests. This paper investigated whether the increase in bivoltinism in UK resident B. terrestris audax populations was related to introgression with imported foreign subspecies. Workers were collected from wild populations in London and Bristol, as well as two commercial suppliers. Fourteen microsatellite loci were used to study population structure, hybridisation and introgression. No introgression with commercial B. t. dalmatinus was detected in wild populations. Hence, the increase in winter activity appears unrelated to introgression. [ABSTRACT FROM AUTHOR]

Body temperature changes can modify an insect's ability to fight infections by altering its immune activity. This work evaluated the impact of mild cold and heat thermal stress on the expression of different immune and heat shock genes in the species Bombus terrestris. Additionally, a thermal treatment was repeated under starvation to analyze a possible compromise of immune gene expression in favor of a thermal stress response when energetic resources are limited. Results pointed to a role of Hsc70 and Aha1 genes in tolerance to moderately high temperatures. Expression of the immune genes was not negatively affected by the cold or the heat treatments, and the receptor gene BGRP1 was upregulated with cold, possibly indicating an increase in the cellular immune activity. Under starvation, the effect of the heat and the cold treatments caused a higher upregulation in all genes analyzed, suggesting a synergistic effect of starvation and thermal stress on the activation of heat shock and immune gene expression. [ABSTRACT FROM AUTHOR]

China has many habitats supporting a wide diversity of bumblebees, some species of which are limited in distribution to the Tibet Plateau. The high-altitude Tibet Plateau, which has low air density as well as extremely low temperatures, strains the energy requirements for flight in most insects. However, high-altitude bumblebees have adapted to the harsh conditions of this type of habitat. Bumblebees are a particular group of insect pollinators that exclusively utilize carbohydrates from flowers for energy to sustain flight. Here, gene expression was compared between low-altitude species and Bombus longipennis, and the genes upregulated in B. longipennis were involved in aerobic metabolism, such as the oxidative phosphorylation and citric acid cycle (TCA cycle) pathways. Furthermore, a conjoint analysis of the transcriptomes of six bumblebee species from the high-altitude Tibet Plateau and two bumblebee species from the low-altitude North China Plain showed that 19 genes were commonly upregulated in high-altitude species. Among these 19 commonly upregulated genes, Pfk1 was enriched in multiple glycometabolic pathways, which are the main energy pathways in bees; this upregulation enhanced the aerobic and anaerobic glycolysis processes to produce more ATP molecules to supply energy for high-altitude bumblebee flight under severe cold conditions. In addition, glycolysis was enhanced by two other genes, Rac1 and AAC2. Relative quantitative real-time PCR was used to verify that the three genes Pfk1, Rac1, and AAC2 were upregulated in the six main bumblebee species inhabiting the Tibet Plateau. [ABSTRACT FROM AUTHOR]

In agricultural landscapes, differences in floral resources provided by crops compared with adjacent habitats promote the spillover of pollinators seeking to fulfil their feeding needs. These foraging patterns play an important role in both crop production and wild plant fitness. However, in classical observational studies, pollinator spillover patterns may be confounded by differences in pollinator phenologies and population sizes. To avoid these confounding effects, we quantified the combined effect of relative floral availability and season on pollinator spillover between strawberry crops and adjacent pinewoods by using commercial bumblebee colonies. We used 60 colonies that were placed in 6 open polytunnel strawberry crops and in 8 pinewoods adjacent to crops in landscapes with either low or high berry (mostly strawberry) crop cover. We repeated the experiment in winter and in spring to account for differences in flower resource availability. While strawberries were in bloom during the entire study period, wild flowering plants were scarce and abundant in winter and in spring, respectively. Spillover in crops was quantified as the percentage of bumblebee individuals that carried pollen from non-berry flowers, while spillover in pinewoods was quantified as the percentage of individuals that carried pollen from berry flowers. Overall, 526 bumblebees were collected. We found them carrying the pollen of 15 plant taxa in winter and 39 in spring, in accordance with seasonal floral availability. In crop colonies, around 30% of bumblebees spilled over into non-berry habitats in winter and 78% in spring, regardless of crop cover in the surrounding landscape. However, in pinewood colonies, we found an interaction effect between season and crop cover: even though on average 34% of bumblebees spilled over into berry crops, in winter it was almost twice in landscapes with high crop cover. Spillover patterns mainly mirrored seasonal changes in floral availability between habitats. [ABSTRACT FROM AUTHOR]

Thermotolerance has often been linked to species distribution for a diverse range of organisms. In the context of climate change, assessing heat resistance ability is useful for understanding potential future range shifts and the physiological response of populations. As bumblebee (Bombus) populations have been declining for several decades with several documented range shifts, an assessment of the hyperthermic resistance of species is urgently needed. In this study, we measure in males the heat resistance of ten bumblebee species living in temperate regions (northwestern Europe) with a static temperature methodology to evaluate the time before heat stupor (THS) which corresponds to a chill coma. Our results on heat stress resistance show that not all species are affected in the same way to heat stress. The most widespread species, B. terrestris (median THS 395 min) and B. lucorum (median THS 257 min) are the least sensitive to hyperthermic stress. The resistance time of bumblebee males is up to 10 times longer than the THS for declining species such as B. jonellus (median THS 48 min) and B. magnus (median THS 58 min). We highlight the high interspecific variability of heat resistance in a morphologically homogeneous genus such as bumblebees. From a conservation point of view, our research highlights the urgency for assessing the heat resistance of different species since each one can display a species-specific thermal sensitivity that is likely linked to a risk of decline in the case of heat waves. [ABSTRACT FROM AUTHOR]

We studied phototaxis, the directional movement relative to light, in the bumble bee Bombus terrestris. We first developed and validated a MATLAB-based system enabling reliable high-resolution tracking of a bee and a measurement of her distance relative to a changing LED light source. Using this system, we found in all our experiments that workers show positive phototaxis. The strength of the phototactic response was influenced by body size but not age, and this effect was significant when the light source was weak. In a separate experiment, foragers showed stronger phototactic response compared with nurses only in one of two trials in which they were larger and tested with weak light intensity. The evidence that phototaxis is associated with size-based division of labor in the bumble bee and with age-related division of labor in the honey bee lends credence to response threshold models implicating the response to light in the organization of division of labor in cavity dwelling social insects. [ABSTRACT FROM AUTHOR]

This study examined shifts over a 35-year period in the phenology of the four most important bumblebee species (Bombus terrestris, B. lapidarius, B. pascuorum and B. hortorum) in Central Europe. The species showed similar temporal trends, significantly advancing components of their main flight period in association with rising temperatures such that, for example, mid-dates of the main flight period advanced by 10–23 days over the study period. Drivers of this change differed between the four species. Trends in, and drivers of, the timing of first queens, first workers and first males were less consistent. Aspects of the phenology of the least common species, B. hortorum, were up to a month earlier than the other species and climatic effects less clear cut. There were some suggestions of differences between species trends. These results stress the importance of considering changes and drivers of change for the Bombus family on a species-specific basis with the need to pay more attention to the life history traits of the study organisms. [ABSTRACT FROM AUTHOR]

Phoretic mites associated with bumblebees are considered commensals that represent little or no risk for their hosts. The aim of the present study was to assess the potential role of the phoretic mites Pneumolaelaps longanalis and Parasitellus fucorum, as carriers of parasites that are known to affect bees. Mites were extracted from bumblebees dating between 1945 and 1981 which belong to museum collections, and from a freshly collected queen. The DNA was extracted and amplified, and the final products were sequenced and analyzed. Parasite's DNA was found in all samples. Ascosphaera spp., Crithidia bombi, Lotmaria passim, and Nosema ceranae were present in both mite species. Moreover, DNA from Apis mellifera filamentous virus (AmFV), Apicystis bombi, Ascosphaera apis, Nosema apis, and Nosema bombi was found in P. longanalis. This study represents the oldest report of parasite's DNA in bumblebee phoretic mites, highlighting the relevance of museum samples for historical studies in parasitology. [ABSTRACT FROM AUTHOR]

Bumblebees are important pollinating insects, but many species have suffered declines over the last century. Long-tongued bumblebees have been identified as particularly at risk, partly due to their more selective diet. Attempts to study these species in captivity have been impeded by stress-induced behaviours which cause queens to kill or abandon their brood. Here, we attempt to further develop techniques, using queen pairing and Bombus terrestris cocoons, to successfully rear two common long-tongued bumblebee species (B. pascuorum and B. hortorum) in captivity. Approximately half of queens laid eggs and 29% produced workers. Although challenges remain, there is a great deal to be gained from optimising the captive rearing of these species. [ABSTRACT FROM AUTHOR]

In an enclosed glasshouse with sucrose provisioned artificial flowers, we observed nectar-foraging bumble bees and honey bees under several resource conditions to determine potential for displacement. Different responses were displayed for varying resource treatments. Overall, bumble bees did not show reduced foraging in the presence of honey bees. When resources were reduced, bumble bees did not change their foraging behavior, whereas honey bees responded by decreasing their visitation rate. When a food resource of higher quality was introduced, bumble bee foragers shifted their foraging effort to the high-quality resources, whereas honey bees continued to forage on the lower quality resources they had been foraging on. We discuss these results by considering how the individual strategy of bumble bees compared with the colony-based strategy of honey bees may explain observed differences and highlight the potential advantages of each strategy in the natural environment. [ABSTRACT FROM AUTHOR]

We compare four honeybee and one bumblebee species with similar behaviors and ecological requirements but large differences in body size. The bees show allometric brain-body size relationships and scaling exponents similar to those found in vertebrates. Compared with three Asian honeybee species, the European honeybee Apis mellifera feature larger brains than expected for their body mass. Overall, the brains show moderate regional variation across species with two pronounced differences: A. dorsata have an enlarged visual lamina, possibly an adaptation for crepuscular vision. Second, the mushroom bodies are larger and comprise more intrinsic neurons in bumblebees than in honeybees. While these findings might suggest more advanced sensory associations in bumblebees, it is currently not possible to test this notion in the absence of quantitative and comprehensive behavioral comparisons across bee species. [ABSTRACT FROM AUTHOR]

Understanding how different pesticides influence bee health is inhibited by a limited knowledge about the interactions between different compounds to which bees are simultaneously exposed. Although research has demonstrated synergistic effects of some sterol biosynthesis inhibiting (SBI) fungicides on the toxicity of certain insecticides to bees, a high degree of variability exists in the relatively few SBI fungicide-insecticide interactions tested. Furthermore, most research has been conducted on honey bees, Apis mellifera, limiting our understanding of pesticide synergisms in native wild bees. We tested the effects of the SBI fungicides difenoconazole, myclobutanil, and fenhexamid on acute contact toxicity of the insecticides thiamethoxam (neonicotinoid) and bifenthrin (pyrethroid) to the common eastern bumble bee, Bombus impatiens. Based on range-finding trials, we selected a single dosage of each pesticide, with insecticides approximating LD20 values and fungicides approximating their maximum sublethal levels. We found that the triazole SBI fungicide difenoconazole interacted synergistically with bifenthrin, with a maximum synergy ratio of 1.48, while the triazole myclobutanil interacted synergistically with both bifenthrin and thiamethoxam, with maximum synergy ratios of 11.0 and 2.38, respectively. However, the hydroxyanilide SBI fungicide fenhexamid did not exhibit a synergistic effect on either insecticide. Our results suggest that certain SBI fungicides, and potentially those from particular SBI classes, may be particularly harmful to bumble bee health when co-exposure to insecticides occurs, despite their low toxicity when experienced in isolation. [ABSTRACT FROM AUTHOR]

Bumblebees are economically important insects which perform essential pollination tasks in natural and managed ecosystems. Recent research studying Neotropical bumblebee species in Brazil showed a clear decrease in genetic diversity over time in Bombus pauloensis. A new temporal assessment of genetic diversity is needed to know whether this was a location-specific result, or a more general phenomenon. This knowledge is essential to be able to prioritize conservation and management needs. Here, the genetic variability of B. pauloensis populations in Argentina was investigated over time using museum collection specimens from 1933 to 2016, and compared with reanalyzed data from Brazilian populations. Furthermore, specific time series were made for two Argentinean locations, Candelaria and La Plata, and compared with the time series of Porto Alegre (Brazil). All collected specimens were genotyped with 16 microsatellite loci to estimate genetic diversity parameters. Our results showed no drop in either allelic richness or expected heterozygosity over all Argentinean populations. However, a clear drop in genetic diversity was observed in two out of three location-specific time series. This loss of diversity will have negative impacts on population survival, especially over longer periods of time. Furthermore, the use and release of mass-reared specimens of B. pauloensis, which may be inbred and specifically selected for certain commercial but non-adaptive traits, could further diminish the genetic pool. Thus, our result implies the urgent need for regional conservation policies of B. pauloensis in South Brazil and North Argentina. [ABSTRACT FROM AUTHOR]

Floral enhancement schemes in agroecosystems are a common method to supplement bee dietary requirements, yet there is little information about how species used in these schemes influence bee physiology and how their nutritional value compares to the floral resources provided by the crop species. Here, we examined the pollen nutritional quality (macronutrient concentrations and protein:lipid ratio) of pumpkin (Cucurbita pepo, Cucurbitaceae), two species commonly used in enhancement schemes, Helianthus annuus (Asteraceae) and Crotalaria juncea (Fabaceae), a multifloral diet and an artificial diet. We tested effects of these diets on physiological characteristics of Bombus impatiens, a generalist pollinator. Bees performed best on real pollen diets, with consumption of C. juncea and multifloral pollen having the most pronounced effects on bee physiology. Our results underscore the importance of considering nutritional quality when selecting plant species for these schemes. [ABSTRACT FROM AUTHOR]

Understanding animal movement is critical for conservation planning, habitat management, and ecological study. However, our understanding is often limited by methodological constraints. These limitations can be especially problematic in the study of ecologically and economically important pollinators like bumble bees, where several aspects of their biology limit the feasibility of landscape-scale studies. We review the methods available for the study of bumble bee movement ecology, discussing common limitations and tradeoffs among several frequent data sources. We provide recommendations on appropriate use for different life stages and castes, emphasizing where recent methodological advances can help reveal key components of understudied parts of the bumble bee life cycle such as queen movement and dispersal. We emphasize that there is no one correct method and encourage researchers planning studies to carefully consider the data requirements to best address questions of interest. [ABSTRACT FROM AUTHOR]

Agricultural intensification can impact the availability and quality of resources. We analyzed resource use by bumble bees (Bombus spp.), important pollinators of highbush blueberry (Vaccinium corymbosum), collected from conventional highbush blueberry farms, organic highbush blueberry farms, and nearby natural areas in the lower Fraser River valley of British Columbia, Canada. We identified corbicular pollen and measured bee fat content as an indicator of body condition. Bumble bees use non-crop resources, including pollen from plant species not found on farms. Bees from natural areas had higher pollen protein content in corbicular pollen and higher body fat content than those from conventional and organic farms. There was no difference between farm types, and we could not demonstrate a relationship between pollen protein and bee fat content. Our findings illustrate the importance of resource availability throughout agro-ecological landscapes, including not only farms but also off-farm areas. [ABSTRACT FROM AUTHOR]

Bombus bicoloratus is an important pollinator of wild flowers in the oriental region. We confirmed a total of 451 specimens of B. bicoloratus from China based on DNA sequences from mitochondrial cytochrome oxidase subunit I (COI) barcodes. Bombus bicoloratus is distributed mainly in tropical and subtropical areas of southern China. This species exhibits a striking intraspecific colour-pattern polymorphism both in females and males. The distribution frequency of the different colour patterns is heavily skewed, with 50.9% of the workers sharing the same colour pattern that predominates in most locations. Workers from the islands of Hainan and Taiwan possess a very distinct colour pattern, and its spatial distribution is correlated with the climate factor irradiance. Bombus bicoloratus has been recorded to collect nectar and pollen from 14 plant families, indicating that this species is polylectic. This study will be helpful for recognising bumblebee species with variable colour patterns, especially B. bicoloratus, in Asia. [ABSTRACT FROM AUTHOR]

The use of commercial bumblebees to aid crop pollination may result in overcrowding of agricultural landscapes by pollinators. Consequently, transmission of parasites between pollinators via shared flowers may be substantial. In SW Spain, we assessed the initial infection status of commercial Bombus terrestris colonies and then explored spatial and seasonal influences on changes in parasite prevalence across a landscape where bumblebee colonies are intensively used to pollinate berry crops. Colonies were placed inside strawberry greenhouse crops and in woodlands adjacent and distant to crops, in winter and in spring, as representative periods of high and low use of colonies, respectively. Worker bumblebees were collected from colonies upon arrival from a producer and 30 days after being placed in the field. The abdomen of each bumblebee was morphologically inspected for a range of internal parasites. Upon arrival, 71% of the colonies were infected by spores of Nosema. Three bumblebees from two colonies harboured Apicystis bombi spores at the end of their placement in woodlands adjacent to the crops. Nosema colony prevalence did not change significantly either among sites or between seasons. We found no evidence for the density of commercial B. terrestris impacting Nosema prevalence in those commercial colonies, but our results highlight the potential risk for parasites to be transmitted from commercial bumblebees to native pollinators. [ABSTRACT FROM AUTHOR]

The rate of living theory posits that higher metabolic rates negatively affect lifespan. This relationship would influence trade-offs among life history traits associated with energy production and allocation. These trade-offs may also apply within a species, resulting in differences among individuals in life history traits. In this study, we use the bumble bee Bombus impatiens to test for a relationship between metabolic rate and lifespan. We measured the resting metabolic rates of workers throughout their lives and noted their lifespans in the laboratory. Our results show that (1) resting metabolic rate inversely correlated with potential lifespan and (2) resting metabolic rate was not affected by age. These results suggest that within a species, individual differences in life-history trade-offs may exist as predicted by the rate of living theory. [ABSTRACT FROM AUTHOR]

The male cephalic labial gland secretions of bumblebees are known to be species-specific semiochemicals. These secretions that are involved in bumblebee pre-mating recognition provide efficient diagnostic characters for species delimitation. The subgenus Thoracobombus is the largest group of bumblebees and is found in the Palearctic, Nearctic, and Neotropical regions. Here, the cephalic labial gland secretion (CLGS) composition of six Mexican Thoracobombus bumblebee species are analyzed: Bombus diligens, B. medius, B. mexicanus, B. pensylvanicus, B. trinominatus, and B. weisi. Our results suggest the presence of two new potential species into the formerly recognized B. weisi as well as one new potential species in the taxon presently identified as B. pensylvanicus. Moreover, the male of B. pensylvanicus, known to congregate at nest sites awaiting the emergence of virgin queens, is characterized by low concentrations of the C16 component. This observation raises the possibility that courtship behavior as well as environmental constraints could affect the role of the male bumblebees' CLGS. [ABSTRACT FROM AUTHOR]

The precise quantification of microRNAs (miRNAs) expression level is a critical factor in mastering its functions. We evaluate the suitability of two common genes and ten miRNAs as normalizers for miRNA quantification in the head and ovary at different reproductive status of bumblebees, Bombus lantschouensis by using four different algorithms and one consensus rank approach. For the head and ovary combination, miR-275 was the best candidate. For different tissues, miR-275 was the most stable candidate in the head, while the candidate for the ovary was miR-277. To test the best candidate accuracy, miR-315 was demonstrated to be downregulated based on miR-275 normalization in ovipositor bumblebees. The miR-275 and miR-277 combination is identified to be the most reliable and suitable reference genes for the head and ovary of bumblebees. [ABSTRACT FROM AUTHOR]

Species taxonomy of bumblebees (Bombus Latreille, 1802) is well known to be problematic due to a potentially high intra-specific variability of morphological traits while different species can converge locally to the same color pattern (cryptic species). Assessing species delimitation remains challenging because it requires to arbitrarily select variable traits whose accuracy continues to be debated. Integrative taxonomic approach seems to be very useful for this group as different independent traits are assessed to propose a rational taxonomic hypothesis. Among operational criteria to assess specific status, the reproductive traits involved in the pre-mating recognition (i.e., the male cephalic labial gland secretions, CLGS) have been premium information. Since these secretions are supposed to be species-specific, these chemical traits can bring essential information where species delimitation is debated. Here, we describe and compare the CLGS of 161 male specimens of nine Alpinobombus taxa: alpinus, balteatus, helleri, hyperboreus, kirbiellus, natvigi, neoboreus, polaris, and pyrrhopygus. We aim also to test the congruence between this new information (reproductive traits) and published genetic dataset. Our results emphasized six distinct groups with diagnostic major compounds: (a) alpinus + helleri with hexadec-9-en-1-ol; (b) polaris + pyrrhopygus with two major compounds hexadec-9-en-1-ol and hexadec-9-enal; (c) balteatus with tetradecyl acetate; (d) kirbiellus with geranyl geranyl acetate; (e) hyperboreus + natvigi with octadec-11-en-1-ol; (f) neoboreus with octadec-9-en-1-ol. Based on this new information, we can confirm the species status of B. alpinus, B. balteatus, B. hyperboreus, B. kirbiellus, B. neoboreus, and B. polaris. We also confirm the synonymy of helleri (Alps) with alpinus (Sweden). However, the specific status of natvigi (Alaska) and pyrrhopygus (Sweden) is questionable and these taxa do not have specific CLGS composition. [ABSTRACT FROM AUTHOR]

Gynandromorphy, which is characterized by the coexistence of male and female tissues in a single individual, is known in insects. Gynandromorphs exhibit diverse levels of defects in sexual behavior. The distribution pattern of both sexes within the nervous systems could be responsible for these differences in behavioral traits; however, most studies have mainly focused on the unique external morphological traits of gynandromorphs, and little attention has been paid to the evaluation of nervous systems, at least in Hymenoptera. In this study, we evaluated a gynandromorphic individual of bumblebee (Bombus ignitus) with a bilaterally dimorphic head and thorax (left side, male; right side, female) and a uniformly masculine gaster. The gynandromorph exhibited abnormal sexual behavior; it normally approached and touched virgin queens but rarely made subsequent copulation attempt. Dissection of the gaster indicated that it possessed a set of male reproductive organs. We analyzed the encephalic and antennal expression patterns of the fruitless (fru) gene, which shows sex-specific alternative splicing conserved in various insect orders and has been thought to act as the master regulator of sexual behavior in male nervous systems. The gynandromorph showed left-side-biased expression of male-type fru transcripts. We discuss a possible mechanism for the observed unusual interruption of sexual behavior of the gynandromorph by reference to the fru expression pattern and our recent findings on the sexually dimorphic response to female-derived pheromones. [ABSTRACT FROM AUTHOR]

In order to protect biodiversity, conservation genetics are of great importance. Until now, a few population genetic studies of Neotropical bumblebees are available but studies of temporal stability in genetic diversity are lacking. Here, genetic variability of three South Brazilian species Bombus bellicosus, B. pauloensis, and B. morio was investigated over time. Hereto, museum collection specimens of 1946 until 2012, from eight locations in Rio Grande do Sul, were genotyped at 16 microsatellite loci. During an additional sampling in the foraging season of 2015, no bumblebees could be collected possibly due to the super El Niño of 2015-2016. Our results on the collection specimens demonstrated a significantly higher genetic diversity in B. morio than in B. pauloensis. Genetic variability in B. pauloensis gradually and significantly decreased over time from 1946 until 2012; while in B. morio, genetic variability remained stable until the last time period (2010-2012). For B. bellicosus, not enough data was available. Although the studied populations became more vulnerable over time, for the conservation of Neotropical bumblebees, still more information is needed and could include more frequent monitoring of bumblebees. Adding B. bellicosus to the Brazilian list of threatened species is suggested. [ABSTRACT FROM AUTHOR]

Previous reports note that males of the Japanese bumblebee Bombus ardens ardens perform nest surveillance to mate with new queens. Here, we report that males of this species also perform patrolling and scent-marking for mating. We observed that many B. ardens ardens males fly together from May to June in circular paths through a wooded area in Tokyo, Japan. The flight activity is bimodal with peaks in the morning and late afternoon. When tethered new queens were presented at a focal point, males approached, touched, or grabbed them but ignored them at a foraging site. Males performed scent-marking on tree leaves only in the early morning (05:30 to 07:30), and compounds from the labial gland of B. ardens ardens males were detected on a scent-marked leaf. Based on these findings and previous reports, we conclude that males of this species have at least two mating tactics or strategies: nest surveillance and patrolling. [ABSTRACT FROM AUTHOR]

Bee populations are decreasing worldwide. The underlying causes are likely determined by factors at different scales. We tested the relative importance of local resources and landscape connectivity on 64 bumblebee ( Bombus impatiens) colonies in experimentally isolated and connected habitat fragments. We used colony mass, no. of workers, and no. of gynes to estimate colony performance. Landscape connectivity did not significantly affect colony performance, but local floral resources had a significantly positive effect, especially in isolated fragments. These results suggest that bumblebee colonies encountered sufficient floral resources within the local 1.4 ha habitat fragments to support colony growth, making long-distance foraging trips to neighboring fragments unnecessary. From a conservation perspective, we suggest that efforts to improve colony performance should prioritize boosting local floral resources over manipulation of large-scale landscape features. [ABSTRACT FROM AUTHOR]

As elsewhere in the world, bumble bees play a vital role as pollinators in Uruguay, but knowledge on their health status is still limited. Between September 2012 and May 2013, 403 adult individuals of the two species of Bombus known for the country ( Bombus atratus, Bombus bellicosus) were collected in six localities. We found that 177 (119 B. atratus, 58 B. bellicosus) were harboring one or two types of pathogens, parasites, or parasitoids. Identification of these natural enemies carried out by morphological or molecular procedures revealed the presence of two species of Microsporidia [ Nosema ceranae (prevalence: 18.2 % in B. atratus; 44.9 % in B. bellicosus), Tubulinosema pampeana (prevalence: 13 % in B. atratus)], two species of Nematoda [ Sphaerularia bombi (prevalence: 40.4 % in B. atratus; 40 % in B. bellicosus) and an unidentified Mermithidae (prevalence: 0.8 % in B. bellicosus)], and one species of Diptera parasitoid (prevalence: 3.2 % in B. atratus; 4.2 % in B. bellicosus). Except N. ceranae, none of the other species have been previously reported in Uruguay. [ABSTRACT FROM AUTHOR]

The abundance and the diversity of bumblebees have been declining for the past decades. While some species remain abundant and widespread, others have experienced vast declines. We tested if diet breadth and exclusiveness of floral resource use affected abundance and land-use response of bumblebees and honeybees in heterogeneous agricultural landscapes. Based on an ecological niche modelling approach, we discovered that three of 13 species (12 Bombus spp. and A. mellifera) responded negatively to land use, while no species responded positively. Overall abundance as well as land-use response of different bee species was unrelated to resource use. The generalist forager B. lapidarius, the slightly more specialised forager B. terrestris/lucorum species complex and the specialist forager B. wurflenii declined most with land use. Moreover, we found that honeybees and two bumblebee species contained higher levels of nitrogen than other non-predatory Hymenoptera and performed almost perfect homeostasis despite variable nitrogen contents of floral resources. We conclude that at least common species of social bees have good nitrogen homeostasis capacity. Generally, our data do not support the notion that species with more specialised floral resource use are more likely to suffer from land use. [ABSTRACT FROM AUTHOR]

Bumblebees collect pollen from some plants by grasping flowers and vibrating their flight muscles-a behavior termed buzz pollination, or sonication. The extent to which bees can and do alter their sonication has been scarcely documented. We show that bumblebees are capable of changing their vibration frequency. In two field studies, we found that relative humidity, date, and bee size are associated with sonication frequency and/or duration. We found that the frequency and duration of sonications differed on different plants. In a greenhouse study, we found that individual bumblebees change their sonication frequency and duration when collecting pollen from flowers of three different Solanum plants. This suggests that bees may change their sonication behavior to optimize pollen release from different types of flowers. [ABSTRACT FROM AUTHOR]

In this study, we investigated if oral administration of lactic acid bacteria could increase the colony performance of reared bumblebees. We found that a continuous administration of Lactobacillus kunkeei LMG 18925 and Lactobacillus crispatus LMG 9479 could partly compensate the effects of low nutritional pollen, but a permanent colonization in the gut was not detected with Illumina MiSeq 16S rRNA sequencing. Contrary to expectations, a single administration of L. kunkeei LMG 18925 to a high nutritional pollen led to a lower total drone mass. A Bombus-specific strain, Bifidobacterium actinocoloniiforme R-53049, showed potential to colonize the gut permanently after three administrations. Our study represents a first screening for the potential use of probiotic strains in bumblebees. We conclude that both diet and host specificity of bacteria might have an effect on colony performance of indoor-reared bumblebees and play a role in the gut colonization success. [ABSTRACT FROM AUTHOR]

Access to abundant and diverse floral plant sources is essential for generalist bees as they obtain all energy and nutrients required from pollen and nectar. Despite their importance, we still know little about the precise nutritional requirements of most bee species. Here, we investigated differences in floral and amino acid profiles of pollen collected by five bumblebee species in southern Germany, which had access to the same spectrum of plant species and thus sources of nutrition. We found that different bumblebee species visited different floral spectra for pollen collection but nevertheless had highly similar pollen amino acid profiles. This finding suggests that common bumblebee species only slightly differ in their nutritional target for amino acids in pollen. In fact, floral and chemical composition of pollen loads appear to be largely determined by the plant community present at a site as bumblebees attempt to maximize site-specific nutrient collection efficiency. [ABSTRACT FROM AUTHOR]

In most bumblebee species, queens mate with only one male, but males can mate more than once. However, the effects of male remating on colony foundation success of queens remain poorly understood. To test for effects of male remating, we assigned Bombus terrestris queens randomly to one of two groups: virgin males or non-virgin males that have mated once before. When males were allowed to mate for a second time with virgin queens, 58.57 % successfully remated. There was no significant difference in queen hibernation survival between groups, but queens mated with non-virgin males were more successful in founding a colony, and produced more workers and males than queens mated with virgin males. The mean copulation duration for the second mating of males (48.02 ± 14.36 min) was substantially longer than for the first mating (32.44 ± 8.74 min). Results also showed that male weight influenced both male remating success and copulation duration. [ABSTRACT FROM AUTHOR]

The article presents the study that investigates the expansion range of sedentary bumble bees in New Zealand.

Here, we describe a new species of genus Bombus Latreille, 1802 from northeastern Brazil, Bombus ( Thoracobombus) applanatus Oliveira, Françoso & Arias, sp. nov. Molecular analysis was initially performed to confirm the new species placement within the genus Bombus. Afterward, we performed an integrative approach combining molecular data (DNA barcoding and two nuclear regions) and morphology to confirm its taxonomic status. The genetic and morphological data were very consistent and congruent supporting this group as a new species. B. ( Thoracobombus) applanatus Oliveira, Françoso & Arias, sp. nov. has the body totally covered by black pilosity and can be distinguished from closer and/or sympatric species by clypeus shape, which has a distinct flattened dorsal platform, by length of malar area and the length and shape of the hairs, shorter and aligned as if it was trimmed. In addition, brief taxonomic notes on Bombus ( Thoracobombus) brevivillus Franklin (1913) and Bombus ( Thoracobombus) morio Swederus (1787), the sympatric species, are provided. A key for identification of Brazilian Bombus species, including the new species, was elaborated. [ABSTRACT FROM AUTHOR]

Declines in honey bee health and increasing demand for pollination services highlight a need to optimize crop pollination by wild bees. Apple is an economically important crop in eastern North America, requires insect pollination, and is visited by a diverse bee fauna, but a direct assessment of wild bee pollination in apple orchards is lacking. We combined measurements of two facets of pollination service, per-visit efficiency (fruit and seed set) and relative abundance, to estimate orchard-level, pollinator importance of mining bees ( Andrena subgenus Melandrena), bumble bees ( Bombus), and honey bees ( Apis mellifera L.). Average pollinator importance provided a relative measure that allowed comparison of pollination service among the three focal bees across the study region. On average, a wild bee visit resulted in higher pollen transfer to stigmas, but had the same probability of setting fruit and seed as a honey bee visit. Regionally, pollinator importance of Melandrena and Bombus were 32 and 14 % that of honey bees, respectively. Because per-visit performances were similar, such disparities in importance were based largely on differences in relative abundance. Although the summed pollinator importance of Melandrena and Bombus was less than that of the honey bee, these, and other, wild pollinators have a role to play in filling future pollination gaps, and thus, warrant further study and conservation. [ABSTRACT FROM AUTHOR]

The supposition that aggression in orphaned workers is used in a battle over reproductive rights was evaluated for Bombus impatiens. Ovarian development was experimentally stimulated or inhibited in orphaned sisters. The manipulation translated into differences in egg laying. Two groups of pairs differed as to whether both or just one of the workers had developed ovaries. The prediction that workers with higher reproductive potential in the unmatched groups would show less aggression overall, compared to those in the matched groups, was not borne out. Nonetheless, butting frequency by the worker with developed ovaries was significantly reduced, as was oophagy, whereas the butting frequency by the worker with undeveloped ovaries was significantly increased. In contrast with Bombus terrestris, overt conflict does not end with one worker gaining a reproductive edge. The results challenge the premise that aggression is a means of preventing reproduction by kin: aggression may possibly serve to promote it. [ABSTRACT FROM AUTHOR]

Many species display local variations in pre-mating signals and in mating preferences. This may lead to discrimination against potential foreign mates that may ultimately lead to reproductive isolation. However, the extent to which population differentiation in mating cues affects the species recognition has received little empirical support. Here, we investigate the consequence of geographic differentiation in male reproductive traits on female preferences to these traits in Bombus terrestris. We characterise (1) the geographic differentiation in male cephalic labial gland secretions (CLGS), a key trait for mate attraction, and (2) the preference of virgin females to the CLGS of different subspecies. Our results show geographic CLGS differences parallel with divergences in female preferences for these secretions. This geographic CLGS differentiation in males, along with female preference for sympatric males, could lead to or reflect a pre-mating isolation among subspecies. [ABSTRACT FROM AUTHOR]

Bumblebee queens require a continuous supply of flowering food plants from early spring for the successful development of annual colonies. Early in spring, Corydalis cava provides essential nectar and pollen resources and a choice of flower colour. In this paper, we examine flower colour choice (purple or white) in C. cava and verify the hypothesis that bumblebee queens differ in their choice of flower colour. A total of 10,615 observations of flower visits were made in spring 2011 and spring 2014 near Poznań, western Poland. Our results suggest that Bombus lucorum/cryptarum used purple flowers less, while Bombus terrestris used purple flowers more and Bombus hortorum showed no preference. Therefore, the colour morphs of C. cava are probably co-evolutionary adaptations to the development of another part of the insect community which has different colour preferences. [ABSTRACT FROM AUTHOR]

Managed bees are used to transfer pollen from male to female flowers in kiwifruit, but the contribution of wild insects has been long overlooked. We approached such contribution with multiple criteria (pollinator abundance, foraging behavior, pollinating efficiency, and response to weather conditions) in the absence of imported colonies. An abundant and rich community of pollinators (57 % were non- Apis insects) visited kiwifruit flowers and assured a fruit set and size not different from those obtained by optimal hand pollination. Honeybees were more abundant and visited more flowers per time but bumblebees were more efficient on a per-visit basis. Other taxa are expected to contribute less because of their lower numbers (hoverflies, wild bees, butterflies, beetles) or their passive behavior (non-syrphid flies). Visitation patterns of pollinators were complementary. Our results highlight the important contribution of wild insects to the pollination of kiwifruit. [ABSTRACT FROM AUTHOR]

Immune responses of invertebrates imply more than developing a merely unspecific response to an infection. Great interest has been raised to unveil whether this investment into immunity also involves fitness costs associated to the individual or the group. Focusing on the immune responses of honeybees, we use the well-studied insect bumblebee for comparison. Bumblebees are capable of producing specific immune responses to infections whereas this has not been assessed for honeybees so far. We investigated whether a prior bacterial encounter provides protection against a later exposure to the same or a different bacterium in honeybees. Additionally, we studied whether the foraging activities of honeybees and bumblebees are affected upon immune stimulation by assessing the flight performance. Finally, the acceptance behavior of nestmates toward immune-challenged honeybees was determined. Results show that despite stimulating the immune system of honeybees, no protective effects to infections were found. Further, honeybees were not affected by an immune challenge in their flight performance whereas bumblebees showed significant flight impairment. Immune-challenged honeybees showed lower survival rates than naive individuals when introduced into a regular colony. Here, we reveal different immune response-cost scenarios in honeybees and bumblebees for the first time. [ABSTRACT FROM AUTHOR]

Bombus ( Megabombus) koreanus (Skorikov) is a long-tongued bumblebee that specialises in visiting deep flowers. To describe the distribution, colour-pattern variation and food plants of B. koreanus, we collected specimens and DNA cytochrome oxidase I (COI) barcodes were obtained. Bayesian phylogenetic analysis of barcodes for Megabombus species shows that B. koreanus is one of the more recently diverged species and the sister species to Bombus consobrinus. Our results show that specimens with previously unknown colour patterns also belong to B. koreanus. We describe nine different colour patterns for workers and three for queens, in which the hair of the thorax varies from black to orange-brown. However, there is a lack of covariation between COI and colour-pattern variation. B. koreanus has been recorded to visit 11 species of food plants showing that B. koreanus is polylectic. Our results demonstrate that COI barcoding is an effective method for studying closely related taxa and for recognising species with variable colour patterns. [ABSTRACT FROM AUTHOR]

Mites have been observed on the bumblebee's body and inside their nest for over 150 years, and parasitic relationships between them have occasionally been reported. One of the most interesting animal associations between mites and bees is phoresy. At present, no study has evaluated the distribution patterns of phoretic mites on bumblebees nor the factors that might be influencing such association. The main goal of this research was to determine whether an aggregation of external mites on bumblebees is influenced by (a) the phoretic mite load per bee, (b) the host species, (c) the caste of bumblebee, (d) the interaction between mite load and bee species, and (e) the presence of a suitable physical place for the mites to accommodate on the bee body. The following mite species were recorded on Bombus atratus and Bombus opifex: Kuzinia laevis, Kuzinia americana, Kuzinia affinis, Kuzinia sp., Pneumolaelaps longanalis, Pneumolaelaps longipilus, Scutacarus acarorum, and Tyrophagus putrescentiae. Our results indicate that Kuzinia mites have a strong preference for a particular region on the propodeum, which has shorter hairs than on most areas of the body. In addition, generalized linear model analysis demonstrated that mite aggregation was influenced by the caste and host species. [ABSTRACT FROM AUTHOR]