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Nectar-foraging bees change their use of floral resources as plant species appear in the environment and disappear over their lifetimes. The new flowers used may involve different cues and different nectar extraction tactics. Although bumble bees can adapt to changes in floral cues and required tactics, little is known about whether bees prioritize switching tactics or floral cues when deciding which plant species to switch to. In a laboratory assay, we forced common eastern bumble bee, Bombus impatiens , workers either to switch the handling tactic they were using or to continue using the tactic but to switch the colour of artificial flowers foraged on. We examined whether bees' tendency to change their tactics was influenced by how similar in colour novel flowers were to familiar ones. We conducted a 2 × 2 factorial experiment using artificial flowers, manipulating the handling tactic that bees were initially trained to use (legitimate visit or nectar robbing) and the similarity between novel and trained colours (similar or distinct). We found that under most conditions bees preferred to switch flower colours and retain handling tactics. However, when given experience with legitimate visits and when novel flowers were markedly different in colour from those they had experienced previously, bees tended to switch tactics while continuing to forage on flowers of the same colour. These findings suggest that the similarity in colour of a new floral resource to the currently exploited resource and the flower-handling tactic used by bees both play an important role in decision making by foraging bumble bees. • We examined bumble bees' switching decisions to novel types of flowers. • Bees were trained to legitimately visit or rob blue flowers to obtain reward. • Novel (dark blue or yellow) flower rewards required the trained tactic. • Bees switched to dark blue flowers using the trained tactic. • Bees switched to robbing blue flowers when the novel flower was yellow. [ABSTRACT FROM AUTHOR]

Simple Summary: Working in lowbush blueberry fields, we studied how to provide a holistic measure of pesticide exposure to bees. Several different taxa of bees can be involved in blueberry pollination, including honey bees, bumble bees (which are native), and other native bees, such as mason, mining, and leafcutter bees. Using chemical analysis, we compared and contrasted samples from different sources to (1) measure pesticide exposure and (2) predict exposure risk in light of established levels of concern established by the U.S. Environmental Protection Agency. We trapped honey bee pollen as foragers entered the hive and, within the three years of the study, found considerable similarity of these samples to treated flowers; the measures were the number and concentration of pesticide residues, as well as the predicted level of risk. We found differences among two or three of these measures when comparing trapped honey bee pollen and trapped mason bee pollen, as well as between trapped honey bee pollen and whole bodies of captured honey bees. In these comparisons, the number of residues detected in honey bee pollen was typically greater, as was the estimated risk. The residues found when comparing whole body analysis of honey bee workers, bumble bee queens, and other native bees showed similarity in total residue concentrations and risk, but there was a higher number of different residues detected on honey bees. This research complements another study (Part I) focused on honey bee pollen trapping in lowbush blueberry and cranberry. Both studies provide a toxicological baseline for pesticide residue exposure to pollinators in the lowbush blueberry agroecosystem. In lowbush blueberry fields, we conducted residue analysis comparing flowers, trapped pollen (honey bee and Osmia spp.), and collected bees (honey bee workers, bumble bee queens, and non-Bombus spp. wild native bees). The study was conducted from 2012 to 2014. The number of pesticide residues, total concentrations, and risk to honey bees (Risk Quotient) on flowers were not significantly different from those determined for trapped honey bee pollen (except in one study year when residues detected in flower samples were significantly lower than residue numbers detected in trapped pollen). The compositions of residues were similar on flowers and trapped pollen. The number of residues detected in honey bee pollen was significantly greater than the number detected in Osmia spp. pollen, while the total concentration of residue was not different between the two types of pollen. The risk to honey bees was higher in trapped honey bee pollen than in trapped Osmia spp. pollen. The analysis of honey bee workers, native bumble bee queens, and native solitary bees showed that although more pesticide residues were detected on honey bee workers, there were no differences among the bee taxa in total residue concentrations or risk (as estimated in terms of risk to honey bees). [ABSTRACT FROM AUTHOR]

Insect pollination is an important process in the natural ecosystem and plays a vital role in crop reproduction. The bumblebee, Bombus terrestris (L.), is a widely used pollinator for crops, especially tomato. The efficiency of bee pollination is related to many factors, including biotic factors such as bee species, nutrition plants, and herbivores. Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is one of the most common and serious pests of tomato plants. However, whether B. tabaci affects the pollination behaviour of B. terrestris on tomato, and how plant–herbivore–pollinator interactions are unclear. In this study, we found that B. terrestris preferred B. tabaci-damaged plants. Furthermore, plant volatiles of tomato plants damaged by B. tabaci were detected and analysed. Electroantennogram (EAG) and the Y-tube bioassay were used for olfactory responses of B. terrestris to plant volatiles. Interestingly, methyl hexanoate and eugenol induced by B. tabaci in tomato plants were found to significantly attract B. terrestris. Therefore, Bemisia tabaci influenced B. terrestris preference through volatiles. The plant volatile-mediated interaction between B. tabaci and B. terrestris could enrich our understanding of the interaction between herbivores and pollinators. In addition, methyl hexanoate and eugenol could be applied for synergist of pollination. [ABSTRACT FROM AUTHOR]

As a consequence of ongoing climate change, heatwaves are predicted to increase in frequency, intensity, and duration in many regions. Such extreme events can shift organisms from thermal optima for physiology and behaviour, with the thermal stress hypothesis predicting reduced performance at temperatures where the maintenance of biological functions is energetically costly. Performance includes the ability to resist biotic stressors, including infectious diseases, with increased exposure to extreme temperatures having the potential to synergise with parasite infection.Climate change is a proposed threat to native bee pollinators, directly and through indirect effects on floral resources, but the thermal stress hypothesis, particularly pertaining to infectious disease resistance, has received limited attention. We exposed adult Bombus impatiens bumblebee workers to simulated, ecologically relevant heatwave or control thermal regimes and assessed longevity, immunity, and resistance to concurrent or future parasite infections.We demonstrate that survival and induced antibacterial immunity are reduced following heatwaves. Supporting that heatwave exposure compromised immunity, the cost of immune activation was thermal regime dependent, with survival costs in control but not heatwave exposed bees. However, in the face of real infections, an inability to mount an optimal immune response will be detrimental, which was reflected by increased trypanosomatid parasite infections following heatwave exposure.These results demonstrate interactions between heatwave exposure and bumblebee performance, including immune and infection outcomes. Thus, the health of bumblebee pollinator populations may be affected through altered interactions with parasites and pathogens, in addition to other effects of extreme manifestations of climate change. [ABSTRACT FROM AUTHOR]

Flowering phenology of alpine plant communities and seasonal dynamics of flower visitors have been scarcely studied in the tropical/subtropical alpine regions. We report flowering phenology, flower production, and flower‐visiting insects in an alpine site of central Taiwan. Throughout the research period (2017–2018), we recorded flowering phenology of 130 plant species, flower production of 81 species, and 15,127 insects visiting alpine flowers. Most of the alpine plants were visited by dipteran insects and/or hymenopteran insects. The seasonal patterns of flowering were more apparent in bee‐visited plants compared to fly‐visited plants in which the flowering of bee‐visited plants clearly increased as the season progressed. About 63% of flower visitors were dipteran insects (syrphid and non‐syrphid flies), and 30% were hymenopteran insects (mostly bumble‐bee workers). Although the seasonal trend in fly abundance was less clear between years, bumble‐bee abundance consistently increased in the middle to late seasons, reflecting colony development. There was a positive correlation between bee abundance and the number of flowering species of bee‐visited plants, but there was no correlation between fly abundance and the number of flowering species of fly‐visited plants throughout the season. These results suggest that the flowering phenology of subtropical alpine communities is influenced by the seasonal availability of pollinators. Bumble bees, syrphid flies, and non‐syrphid flies had wide ranges of foraging flowers, but their niche overlap was relatively small. Because cold‐adapted bumble bees are threatened by climate change in Taiwan, plant–pollinator interactions may be disturbed by global warming. [ABSTRACT FROM AUTHOR]

Many pollinators, such as bees, hummingbirds and bats, use multi-destination routes (traplines) to exploit familiar plant resources. However, it is not clear to what extent the mechanisms underpinning trapline development and optimisation are comparable across species. Here we compared route formation, repeatability and efficiency by foragers of two social bee species, the solo foraging bumblebee Bombus terrestris and the mass foraging honey bee Apis mellifera, in the same laboratory conditions. In a simple routing task (with four artificial flowers), all bumblebees and honey bees developed a route, although honey bees were slower to do so. In a more complex routing task (with six flowers), however, only bumblebees developed a route between the 6 flowers. Honey bees took a longer time to discover all flowers and developed routes between fewer flowers. Comparing bumblebees and honey bees using the same experimental paradigm thus revealed key behavioural differences likely resulting from their contrasting collective foraging strategies. Significance statement: Pollinators face some of the most complex foraging challenge among animals: collecting small amounts of nectar from large numbers of flowers in a minimum of time. Previous studies report bees, birds and bats rely on spatial memory to develop routes optimising foraging efficiency. Here we compared this routing behaviour in two major pollinators, the buff-tailed bumblebee and the Western honey bee, in the same experimental conditions. We found that bumblebees were much faster and more efficient at visiting flowers following repeatable sequences than honey bees. This behavioural difference suggests bee cognition is shaped by their social ecology and illuminates about the known complementarity of different bee species for pollination. [ABSTRACT FROM AUTHOR]

Green roofs offer an integrated response to sustaining ecosystem services in urban settings. Surprisingly, however, few studies have compared arthropod richness and abundance at urban ground level and green roofs to other habitats. The main objective of this study was to compare the composition and pollen collecting habits of bee communities visiting green roof, urban, and coastal barren habitats in the Halifax Region of Nova Scotia. We found that relative to ground level habitats, green roof wild bee communities were less abundant and species rich, but shared species with all habitat types. Pollen collection of bumble bees on green roofs was similar to that observed in urban and barren habitats. These results suggest that green roofs may offer harmonized solutions to multiple urban problems. Our study also yielded new provincial record, Hylaeus affinis Smith (Hymenoptera: Colletidae), for Nova Scotia. [ABSTRACT FROM AUTHOR]

The spatial distribution of flowers has important impacts on pollinator movement and foraging decisions. For example, it is well established that bumble bees typically visit larger plants at a higher rate per plant, but the visit rate per flower typically declines as the number of flowers increases. However, much less is known about how honey bee foraging patterns are influenced by plant size and flower number, despite honey bees' importance as agricultural pollinators and their strong competitive impact on other bees. Using a combination of field observations and manipulative experiments with two different wild plant species, we confirmed that honey bees visit larger plants at a higher rate, not only per plant but also per inflorescence. This foraging pattern seems surprising, because it means that there is greater forager density and thus competition for resources on larger plants. We examine three hypotheses to explain why honey bees might nevertheless preferentially visit floral resources on larger plants: (1) larger plants are more salient, making them easier to find and advertise; (2) larger plants offer greater nectar rewards, making visits to them more worthwhile; (3) larger plants have more densely packed flowers, so they are less costly to navigate. We found that honey bee visit rates were indeed influenced by the costs and rewards of their local foraging experience, but the total number of flowers on the plant still positively affected visit rate even when controlling for those local factors. We suggest several ways that the collective foraging strategy of honey bees could lead to an aggregation of foragers on plants with more flowers and discuss the potential implications for agricultural pollination and wild bee conservation as well as foraging theory. • Honey bee visits/inflorescence were higher for large plants than for small plants. • Honey bees' focus on larger plants may stem from their collective foraging strategy. • Prior work has shown that bumble bee visits/flower typically decrease with plant size. • Variation in plant size may reduce competition between honey bees and native bees. [ABSTRACT FROM AUTHOR]

Bees are the most important pollinators and, like many other insects, are facing a global decline that threatens crop pollination services. Both honey bees and some wild bee species are used commercially for pollination, including pollination in blueberry and cherry orchards. In our study, we assessed bee visits to experimental blueberry and cherry orchards immersed in an urban landscape to understand how air-temperature affects the potential contribution of honey bees and wild bees to pollination services. The potential contribution to pollination services was estimated using the Pollination Importance Value index, where the pollen collected by the floral visitor is a determining variable. In our study, bumble bees and honey bees were the most important floral visitors in the orchards, followed by the wild bee Anthophora plumipes. We found that honey bees were affected by changes in air-temperature and their decrease in the potential contribution to pollination services was offset by the niche complementarity provided by bumble bees. Implications for insect conservation Even small changes in air-temperature can alter bee communities by affecting bee species susceptible to low temperatures. Our work is a first assessment of how climate change may affect the complementarity of pollinator communities in orchards. We suggest that strategies to mitigate local air-temperature changes in urban areas, focusing primarily on these species, could potentially have cascading effects that would support the overall pollination services provided by bee communities. [ABSTRACT FROM AUTHOR]

This study explored the flower visiting behaviors and pollination abilities of mason bees (Osmia excavata Alfken (Hymenoptera: Megachilidae)), bumble bees (Bombus terrestris (Linnaeus, 1758) (Hymenoptera: Apidae)), and Italian honey bees (Apis mellifera ligustica Spinola (Hymenoptera: Apidae)) in apple orchards in early spring in Jinan (located in the central region of Shandong) and Yantai (located in the Peninsula of Shandong). We compared the pollen collection patterns, flower visiting behavior, flying speed, and effects on apple pollination of the 3 types of bees. The frequencies of flower visits were significantly higher for mason bees (12.89/min in Jinan and 10.63/min in Yantai) than bumble bees and Italian honey bees in the 2 regions. The single flower residence times were significantly higher for Italian honey bees (8.22 s in Jinan and 9.43 s in Yantai), but Italian honey bees were most affected by the climate. The 3 bees differed significantly in terms of the amount of apple pollen collected and their effects on the fruit setting rate in apples (mason bees > bumble bees > Italian honey bees). The results showed that the mason bee was the most suitable pollinating species for spring apple orchards; Bumble bees were more suitable as alternative pollinators during cloudy and low temperatures; Italian honey bees were able to take advantage of their large number of worker bees in sunny and warm weather. Compared to individual bee species, a combination of 2 or 3 species of bees might be more advantageous in dealing with complex and variable weather conditions. [ABSTRACT FROM AUTHOR]

Agricultural practices and intensification during the past two centuries have dramatically altered the abundance and temporal continuity of floral resources that support pollinating insects such as bumble bees. Long‐term trends among bumble bees within agricultural regions suggest that intensive agricultural conditions have created inhospitable conditions for some species, while other species have maintained their relative abundances despite landscape‐level changes in flower availability. Bumble bee responses to spatiotemporal resource heterogeneity have been explored at the colony and behavioral level, but we have yet to understand whether these conditions drive community structure and ultimately explain the diverging patterns in long‐term species trends. To explore the relationship between landscape‐level floral resource continuity and the likelihood of bumble bee occurrence, we mapped the relative spatial and temporal availability of floral resources within an intensive agricultural region in the US Upper Midwest and related this resource availability with bumble bee species relative abundance. Across the bee community, we found that relative bumble bee occurrence increases in landscapes containing more abundant and more temporally continuous floral resources. Declining species, such as Bombus terricola, exhibited the strongest, positive responses to resource abundance and continuity whereas common, stable species, such as Bombus impatiens, showed no statistical relationship to either. Together with existing experimental evidence, this work suggests that efforts to increase spatiotemporal flower availability, along with overall flower abundance at landscape scales may have positive effects on bumble bee communities in the US Upper Midwest. [ABSTRACT FROM AUTHOR]

Burmannia shows a set of floral traits that suggest elaborate mechanisms of animal mediated pollen transfer. These include flower coloration, septal nectaries and a long and narrow floral chamber. The stamens are synorganized with the common style restricting the entrance to the floral chamber, sometimes forming a gynostegium. Contrary to this apparent zoophilous floral syndrome, several species of Burmannia were reported to perform self-pollination via cleistogamy. Understanding of reproductive systems in Burmannia is complicated by scarcity of available results of direct observations on pollination process. Here we present data on pollination biology of B. disticha obtained during field investigations in Vietnam followed by laboratory analyses of ecologically important floral traits and the captured flower visitors. We found that the anthetic perianth is open, i.e. the flower is chasmogamous. The flowers are visited by various Diptera, Hymenoptera, Lepidoptera and Orthoptera. Of them, the bumblebees (Bombus burmensis), a bee (Coelioxys sp.) and some lepidopterans were revealed to carry pollen of B. disticha. Based on the amount of carried pollen, insect behavior during the visits and general knowledge on biology of these insect taxa, we concluded that the bumblebees act as the principal pollinators of B. disticha, whereas the lepidopterans are considered as its possible pollinators. We compared the lengths of proboscises of the captured insects to the depth of the floral chamber, and found that only the bumblebees and lepidopterans should be able to reach the nectar. Finally, we estimated the pollen-ovule ratio of B. disticha as 6.84, which is comparable to the ratio known in autogamous angiosperms. Based on its flower organization and pollination mechanism, we consider B. disticha an entomophilous and predominantly xenogamous species. Its gynostegium is likely an adaptation for pollen transfer by insects with long proboscises. At the same time, earlier investigations together with pollen-ovule ratio indicate that B. disticha possesses a labile pollination strategy, and autogamy sometimes occurs. Since Burmannia is one of the few angiosperm genera that comprise both mycoheterotrophic (achlorophyllous) and autotrophic (green) species, our study provides important evidence for reconstructions of ecological and morphological evolutionary pathways in relation to the mode of organic nutrition. [ABSTRACT FROM AUTHOR]

Vairimorpha (=Nosema) ceranae is a widespread pollinator parasite that commonly infects honeybees and wild pollinators, including bumblebees. Honeybees are highly competent V. ceranae hosts and previous work in experimental flight cages suggests V. ceranae can be transmitted during visitation to shared flowers. However, the relationship between floral visitation in the natural environment and the prevalence of V. ceranae among multiple bee species has not been explored. Here, we analyzed the number and duration of pollinator visits to particular components of squash flowers—including the petals, stamen, and nectary—at six farms in southeastern Michigan, USA. We also determined the prevalence of V. ceranae in honeybees and bumblebees at each site. Our results showed that more honeybee flower contacts and longer duration of contacts with pollen and nectar were linked with greater V. ceranae prevalence in bumblebees. Honeybee visitation patterns appear to have a disproportionately large impact on V. ceranae prevalence in bumblebees even though honeybees are not the most frequent flower visitors. Floral visitation by squash bees or other pollinators was not linked with V. ceranae prevalence in bumblebees. Further, V. ceranae prevalence in honeybees was unaffected by floral visitation behaviors by any pollinator species. These results suggest that honeybee visitation behaviors on shared floral resources may be an important contributor to increased V. ceranae spillover to bumblebees in the field. Understanding how V. ceranae prevalence is influenced by pollinator behavior in the shared floral landscape is critical for reducing parasite spillover into declining wild bee populations. [ABSTRACT FROM AUTHOR]

Body size is a trait that can affect plant–pollinator interaction efficiency and plant reproductive success. We explored the impact of intraspecific size shifts on the interactions between pollinators and flowering plants under controlled conditions. We considered two development conditions leading to the production of large and small individual flowers of Borago officinalis and Echium plantagineum. We also used the natural variability of worker size within bumblebee colonies to isolate small and large workers. We performed a fully crossed experiment with the two flower sizes of each plant species and the two sizes of bumblebee workers. Our results show that the size of both partners did not affect bee foraging behavior in most of the evaluated parameters and both bee sizes were equally efficient in depositing pollen. Significant differences were found only in pollen deposition across the life of a flower in small flowers of B. officinalis, with the greatest quantity of pollen deposited by small bees. We did not find a relationship between pollinator size and plant fitness. Our results suggest that generalist plant–pollinator interactions may be resilient to future potential mismatches in the size of the partners but remain to be tested if they are still resilient under the new environmental conditions resulting from global changes. [ABSTRACT FROM AUTHOR]

A key question in pollination biology is that of how pollinators identify and choose foraging patches. Several approaches have been employed for this, including field studies and large greenhouse flight chambers. Most methods used to date are limited, though, by reliance on a combination of artificial flowers, large spatial scales, or lack of spatially distinct floral patches. To address this issue, we designed and tested a y-maze flight arena and tested it using the bumblebee Bombus impatiens and canola plants. Our results indicate that the system is not biased by environmental conditions, or by an innate "handedness" of Bombus impatiens. We found that bees made all the expected patch choices when presented with soil, plants without flowers, or plants with flowers. This new method is important and useful as it allows researchers to ask questions of both plant health and insect behavior and the chamber system is modular allowing for simple changes to the setup to focus on different questions. Highlights: • Y-maze flight arena was designed to evaluate foraging behavior on intact plants. • No evidence of side preference in individual bees. • Behaviors observed in the y-maze appear to correspond to behaviors observed in other settings. [ABSTRACT FROM AUTHOR]

Telesonix jamesii, a rare and imperiled species of perennial saxifrage, is restricted to rocky habitats at high elevations across 21 isolated, known populations in the southern Rocky Mountains of Colorado and New Mexico. Despite its imperiled conservation status, very little is known about the natural history of T. jamesii. We studied pollination of this species during the summers of 2019-2021 at multiple locations on Pikes Peak, Colorado. We conducted a total of 899 min of pollinator surveys, identifying all floral visitors during this time period. We then examined floral visitors for the presence of T. jamesii pollen to determine which species might be effective pollinators. We found that flowers of T. jamesii are visited by a diverse assemblage of insects and one species of hummingbird. Bumble bees (Bombus) were the most commonly observed species visiting flowers, as well as the only group found carrying T. jamesii pollen on their bodies. Our findings suggest that T. jamesii is infrequently pollinated, and we speculate that gene flow for this species may be low. This work constitutes the first investigation into the field pollination ecology of T. jamesii. Our study warrants future investigation into the population genetics of this species as well as surveys of historical occurrences and high-suitability habitat for populations. [ABSTRACT FROM AUTHOR]

Bumblebees are splendid pollinators of various crop plants; they are known to improve fruit productivity by enhancing its biophysical and biochemical properties. In the present investigation, the impact of bumblebee (Bombus haemorrhoidalis Smith) pollination was recorded in comparison to honey bee pollination, open pollination and control (crop devoid of pollinators) in strawberry grown under caged conditions in Nauni, Himachal Pradesh. Bumblebee pollination resulted in higher fruit set (87.16%), longer fruits (39.88 mm/fruits), higher fruit breadth (30.94 mm/fruit), heavier berries (14.26 g/ fruit) and higher fruit yield per plant (402.26 g/ plant) in strawberry cv. Sweet Charlie which accounted for an increase of 10.38 and 7.87, 25.64 and 17.74, 16.22 and 13.41, 35.29 and 31.18 and 33.11 and 20.74%, respectively over control and open pollination. Bumblebee pollination was observed superior to control, open/ natural pollination and was equally good (at par) to honey bee pollination, in terms of all production parameters. These results signified the role of bumblebee pollination in enhancement of the quality and quantity of strawberries grown under caged conditions. [ABSTRACT FROM AUTHOR]

We studied α‐ and β‐diversity of pollinators, flowering plants and plant–pollinator interactions along the altitudinal gradient of Mt. Olympus, a legendary mountain and biodiversity hotspot in Central Greece.We explored 10 study sites located on the north‐eastern slope of the mountain, from 327 to 2596 m a.s.l. Insect surveys were conducted once a month using hand netting (years 2013, 2014 and 2016), and they were combined with recordings of flowering plant diversity (species richness and flower cover). We then calculated α‐ and β‐diversity of pollinators, plants in flower and plant–pollinator interactions, and explored their demographic response along the altitudinal gradient.Alpha diversity of pollinators, plants and plant–pollinator interactions were altitude dependent; α‐diversity of all pollinators, bees, non‐bumblebee bees, bee flies and butterflies showed linear declines with altitude, whereas those of hoverflies and bumblebees showed unimodal patterns. Beta diversity and its turnover component of all pollinators, hoverflies, bees, bumblebees, non‐bumblebee bees, butterflies and plants showed linear increases, whereas those of bee flies and of plant–pollinator interactions varied independently from the pairwise altitudinal difference.The high dissimilarity and uniqueness of pollination networks, which is probably a result of the high biodiversity and endemism of Mt. Olympus, is driven by species turnover and the formation of new interactions between new species. Contrasting to the monotonic decline of the remaining groups, the unimodal patterns of hoverfly and bumblebee α‐diversity are probably the effect of a higher tolerance of these groups to high‐altitude environmental conditions. Our findings highlight that the high turnover of species and of pollination interactions along the altitudinal gradient are the mainstay of hyperdiverse mountains, a fact that conveys important historical, ecological and conservational implications. [ABSTRACT FROM AUTHOR]

Quantifying the contributions of insect pollinators to crops provides insight into how pollination services should be managed and protected into the future.Faba bean, Vicia faba var minor (Linneaus), is a widely grown crop globally that can benefit from pollinator visitation, but only from species that are morphologically compatible with the plant's long‐corollae flowers. Here, we rank insect pollinators in terms of their potential importance to faba bean pollination and quantify the economic value of pollination for Irish faba beans.Our findings demonstrate that bee pollination contributes significantly to the pod set of faba beans, and, consequently, the crop's production value. We find that pollination services account for almost half of Ireland's total faba bean market value, with the pollinator contribution estimated at almost €4,000,000 per year.We estimate that, relative to other pollinators, wild bumblebees contribute to approximately 70% of the economic value of pollination services in faba bean fields, driven mainly by the contributions of a long‐tongued bumblebee species, Bombus hortorum (Linneaus; Hymenoptera: Apidae).Based on these results, we suggest that B. hortorum populations be encouraged on farmland through appropriate management to ensure the continued delivery of pollination services to Irish faba beans. [ABSTRACT FROM AUTHOR]

In response to anthropogenic environmental change, the cues that animals use throughout their lifecycle to optimize fitness may become unreliable, resulting in an ecological trap.Here we investigated whether commercial bumble bee Bombus impatiens colonies managed for early spring crop pollination act as ecological traps for wild nest‐searching Bombus queens by subverting their natural nest usurpation behaviour.An average of 10 dead wild queens were recovered from each standard colony during the 2‐week period of the experiment, but colonies with queen excluders were successful in preventing wild queen deaths. The use of queen excluders did not impact colony performance in terms of resident queen survival, colony reproduction, colony weight gain or worker body size.Sites where wild nest‐searching queens were small had higher rates of failed usurpation, suggesting smaller‐sized queens are disproportionately at risk from failed usurpation. Furthermore, sites where commercial colonies without queen excluders were introduced for spring crop pollination had fewer bumble bee visits to a later‐blooming crop compared to sites without commercial colonies.Synthesis and applications. Our findings reveal a novel mechanism by which commercial colonies can negatively impact wild bumble bee populations and their pollination services. At the same time, we demonstrate a simple and inexpensive risk mitigation tool—a queen excluder—was 100% effective at eliminating this risk without compromising colony performance. Commercial colonies used outdoors during the bumble bee nest‐searching period should be fit with queen excluders to prevent negative impacts on wild pollinator communities and their services. [ABSTRACT FROM AUTHOR]

Insect pollination, and in particular pollination by bees, is a highly valued ecosystem service that ensures plant reproduction and the production of high-quality crops. Bee activity is known to be influenced by the weather, and as the global climate continues to change, the flying frequency and foraging behaviour of bees may also change. To maximise the benefits of pollination in a changing world, we must first understand how current weather conditions influence the activity of different bee species. This is of particular interest in a country such as Ireland where inclement weather conditions are nominally sub-optimal for foraging. We observed honeybee (Apis mellifera) and buff-tailed bumblebee (Bombus terrestris) activity across a variety of weather conditions at seven apple orchards to determine how four weather variables (temperature, relative humidity, solar radiation, wind) influenced the flight activity of each species. Each orchard contained three honeybee and three bumblebee colonies, and so we were able to observe a colony of each species concurrently in the same weather conditions. Overall, honeybees were more sensitive to changes in weather than bumblebees and could be more predisposed to future changes in within-day weather conditions. Our results indicate bumblebees could compensate for low honeybee activity in inclement conditions, which supports the theory that pollinator diversity provides resilience. This may be particularly important in management of pollinators in crops that flower in the spring when weather is more variable, and to allow varied responses to global climate change. [ABSTRACT FROM AUTHOR]

Bees provide pollination services in both agricultural and natural ecosystems. However, invasive ants that exploit floral nectar in these landscapes can compete with bees for resources, with implications for pollinator resource acquisition, plant fitness, and, ultimately, ecosystem function. While interference competition has been described between bees and nectivorous, non-pollinator antagonists, the behaviors and sensory mechanisms involved remain largely unresolved. Here, we studied the mechanisms by which invasive Argentine ants influence bee nectar foraging behavior. In a series of laboratory assays, we assessed the foraging behavior of bumble bees (Bombus impatiens) in response to live Argentine ants (Linepithema humile) or to a subset of ant chemical cues. Bees were clearly deterred by live ants at a nectar source: they consumed less, fed less frequently, and fed for a shorter duration when live ants were present. Bees were also deterred by a combination of olfactory and gustatory ant chemical cues, consistent with both innate and learned avoidance behavior. Naïve and ant-experienced bees were deterred through chemosensation of ants, feeding less from nectar infused with ant chemicals as compared to nectar lacking ants or their associated cues. Some ant-experienced bees showed a unique behavior, displaying aggression toward ants as well as in response to ant chemicals. The marked effects of this invasive ant on bee foraging behavior—through physical interaction and chemical cues—highlights Argentine ants as a serious pest whose control should be considered when developing pollinator conservation and management strategies. [ABSTRACT FROM AUTHOR]

Keywords: agonistic behaviors; dominance hierarchy; ethological observations; flower visitor insects; flowers; Paris; urban parks EN agonistic behaviors dominance hierarchy ethological observations flower visitor insects flowers Paris urban parks 1 5 5 03/06/23 20230301 NES 230301 A few minutes of observation of flowers are sufficient to notice that some flower-visiting insects threaten, harass, or attack individuals from other species. We observed that large hoverflies and gray bees tended to attack most of the other individuals, whereas honeybees and yellow-striped bumblebees were much calmer and more peaceful. Thus, large hoverflies, gray bees, "other wild bees" and the "Other" categories are more aggressive than honeybees, yellow-striped bumblebees, and "other bumblebees" (Appendix S1: Figure S3). Honeybees, yellow-striped bumblebees, and the "other bumblebees" and "other wild bees" categories mainly attacked within their own morphospecies. [Extracted from the article]

Colourful patterns on flowers are thought to benefit both pollinators and the plants they visit, by increasing the plants' pollination success via an increased foraging efficiency of the pollinators. This increased efficiency is assumed to result from a guidance effect of the flower patterns, correspondingly termed 'nectar guides', which indicate the position of the nectary to visiting pollinators, thus reducing their flower handling time.Although it is well established that flower patterns play an important role in flower choice, the mechanisms by which they improve the foraging efficiency of flower‐visiting insects remain poorly understood.In this study, we quantified the contributions of patterns to all phases of flower interaction in the buff‐tailed bumblebee Bombus terrestris. We analysed the bees' flight paths, as well as landing positions and walking tracks on artificial flowers with different pattern types.We reveal that flower patterns reduced the overall flower handling time of the bees by up to 30%, by guiding their approach flight, landing positions and departure decisions. Surprisingly, we observed no improvement in nectary discovery time after the bees landed on the flower.Since we tested experienced foragers, which represent the majority of insect pollinators active in nature, the newly described nectary‐independent guidance effects of flower patterns are of high ecological relevance. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Simple Summary: Why do plants have showy flowers? Clearly, many plant species must attract pollinators and have floral adaptations for this. However, some flowers attract insects without showy petals. This suggests that a key function of showy visual signals is to attract naïve, first-time pollinator visitors. This is similar to how a restaurant with a large sign and showy visual signals may be especially important in gaining first-time visits when competing with other establishments or plants. Customers or pollinators will know if the first visit is rewarding and use this to decide whether to revisit. First, they must visit. Most flowers and restaurants would benefit from more visitors. Restaurants usually have empty tables, and many flowers are pollen limited in their reproduction. Here, we manipulated the ray petals of inflorescences of two garden flowers to test the hypothesis that the role of showy visual signals is to attract naïve visitors. On their first inflorescence visit to both species, naïve honey bees and bumble bees were more likely to visit intact inflorescences, than those with ray petals removed. However, by the tenth consecutive inflorescence, bees showed no preference. A positive correlation was observed between the visitation of inflorescences with no petals and the inflorescence number on both study plants, for both bees. These results strongly suggest that a key function of showy petals is to attract naïve, first-time visitors. Flower evolution includes a range of questions concerning the function of showy morphological features such as petals. Despite extensive research on the role of petals in attracting pollinators, there has been little experimental testing of their importance in attracting naïve versus experienced flower-visitors. In an exploratory field study, we manipulated the ray petals of inflorescences of two garden flowers, Rudbeckia hirta and Helenium autumnale, to test the hypothesis that these showy structures primarily function to attract first-time, naïve, visitors. On their first inflorescence visit to both species, naïve honey bees and bumble bees were more likely to visit intact inflorescences, than those with ray petals removed. However, by the tenth consecutive inflorescence on the same visit to the flower patch, test insects showed no preference. A positive correlation was observed between the visitation of inflorescences with zero petals and inflorescence number on both study plants, for both bees. These results suggest that a key function of showy petals is to attract naïve, first-time visitors. Similar to how a restaurant attracts diners with a large sign, showy signals may be vital to enticing first-time visitors when competing with other establishments or plants for customers or pollinators. We hope the findings of this exploratory study will stimulate further work in this area. [ABSTRACT FROM AUTHOR]

Understanding interactions between insects and the flora of the Black Belt Prairie is imperative to the conservation of this waning ecosystem. Spiranthes magnicamporum (Great Plains Lady's Tresses) is an imperiled orchid found in the prairies of Mississippi. In the fall of 2020, we examined several clusters of S. magnicamporum at a remnant prairie in Osborn, MS. Over a period of 3 weeks, we observed each cluster for 30 minutes, both during the day and at night, and collected any insects interacting with S. magnicamporum. We found possible evidence of Bombus fraternus (Southern Plains Bumble Bee) pollination and recorded floral visitation by other insects. This information can help land management professionals better understand how to promote healthy populations of S. magnicamporum. [ABSTRACT FROM AUTHOR]

Globally, honey bees are the most utilized animal pollinator in agriculture. However, fluctuations in honey bee colony availability have led to a demand for diversification among crop pollinators. Managed bumble bees are commercially available and highly efficient at pollinating many crops, including cranberries, yet utilization of these managed bees has remained relatively low in North America, with the cranberry industry remaining heavily reliant on honey bees. Here, we surveyed growers from Wisconsin (WI) and Quebec (QC), two of the world's largest cranberry producers, to assess their current crop pollination practices and attitudes regarding managed bumble bees as crop pollinators. To this end, we inquired about their farm demographics, usage of pollination practices, factors influencing those pollination practices, sources of information on crop pollination, and perceptions of managed bumble bees. QC respondents placed a greater importance on their relationships with beekeepers than WI respondents, while WI respondents were more concerned about fruit quality than QC respondents. QC respondents also stocked bumble bees and planted pollinator gardens at a higher percentage than WI respondents, believed that honey bees are more efficient pollinators of cranberry than bumble bees, and a greater proportion of QC respondents reported feeling well informed about bumble bees compared to WI respondents. Importantly, respondents in both regions rank bumble bees' ability to pollinate in inclement weather as their greatest benefit, and the costs of bumble bees as the greatest barrier to their use. We propose that trusted sources of pollination information in both regions, including university specialists, crop consultants, and beekeepers, are well suited to clarify misconceptions regarding bumble bee pollination. [ABSTRACT FROM AUTHOR]

Historic pollination networks are important to understand interactions between different plant and pollinator species, as well as to differentiate between causes and consequences of present insect population decline. Natural history collections in museums store biological proxy data, which is used to reconstruct historic pollination networks of bumble bees. Four bumble bee species (Bombus terrestris, B. ruderatus, B. hortorum and B. subterraneus) were introduced to Aotearoa New Zealand in 1885 specifically for pollination purposes. Pollen samples were collected from museum specimens of three of the four NZ species of bumble bee (excluding B. subterraneus) collected between 1954 and 1972 from 56 locations across the South Island, New Zealand. The most common plants identified on all three bumble bee species were Calluna vulgaris (heather), Ulex (gorse), Cytisus (broom), and Trifolium repens (white clover). However, all three bumble bee species also carried pollen from several native plants (e.g. Arthropodium, Weinmannia, Plagianthus, Quintinia, Veronica, Melicytus) and potentially had been involved in the pollination of these species. This study adds new plant species known to be foraged upon by bumble bees in Aotearoa New Zealand. Further studies on pollination networks in New Zealand will help us understand any changes in host plant preferences over time and after the time period covered by this study. [ABSTRACT FROM AUTHOR]

Agri-environmental schemes (AES) are used to enhance pollinator diversity on agricultural farms within the UK. Though the impacts of these schemes on archetypal pollinator species such as the bumblebee (Bombus) and honeybee (Apis) are well-studied, the effects on non-target bee species like solitary bees, in the same environment, are generally lacking. One goal of AES is to alter floral provision and taxonomic composition of plant communities to provide better forage for pollinators, however, this may potentially impact other ecological communities such as fungal diversity associated with plant-bee communities. Fungi are integral in these bee communities as they can impact bee species both beneficially and detrimentally. We test the hypothesis that alteration of the environment through provision of novel plant communities has non-target effects on the fungi associated with solitary bee communities. We analyse fungal diversity and ecological networks formed between fungi and solitary bees present on 15 agricultural farms in the UK using samples from brood cells. The farms were allocated to two categories, low and high management, which differ in the number of agri-environmental measures implemented. Using internal transcribed spacer metabarcoding, we identified 456 fungal taxa that interact with solitary bees. Of these, 202 (approximately 44%) could be assigned to functional groups, the majority being pathotrophic and saprotrophic species. A large proportion was Ascosphaeraceae, a family of bee-specialist fungi. We considered the connectance, nestedness, modularity, nestedness overlap and decreasing fill, linkage density and fungal generality of the farms' bee–fungi ecological networks. We found no difference in the structure of bee–fungi ecological networks between low and high management farms, suggesting floral provision by AES has no significant impact on interactions between these two taxonomic groups. However, bee emergence was lower on the low management farms compared to high management, suggesting some limited non-target effects of AES. This study characterizes the fungal community associated with solitary bees and provides evidence that floral provision through AES does not impact fungal interactions. [ABSTRACT FROM AUTHOR]

Understanding how niche‐based and neutral processes contribute to the spatial variation in plant–pollinator interactions is central to designing effective pollination conservation schemes. Such schemes are needed to reverse declines of wild bees and other pollinating insects, and to promote pollination services to wild and cultivated plants. We used data on wild bee interactions with plants belonging to the four tribes Loteae, Trifolieae, Anthemideae and either spring‐ or summer‐flowering Cichorieae, sampled systematically along a 682 km latitudinal gradient to build models that allowed us to 1) predict occurrences of pairwise bee–flower interactions across 115 sampling locations, and 2) estimate the contribution of variables hypothesized to be related to niche‐based assembly structuring processes (viz. annual mean temperature, landscape diversity, bee sociality, bee phenology and flower preferences of bees) and neutral processes (viz. regional commonness and dispersal distance to conspecifics). While neutral processes were important predictors of plant–pollinator distributions, niche‐based processes were reflected in the contrasting distributions of solitary bee and bumble bees along the temperature gradient, and in the influence of bee flower preferences on the distribution of bee species across plant types. In particular, bee flower preferences separated bees into three main groups, albeit with some overlap: visitors to spring‐flowering Cichorieae; visitors to Anthemideae and summer‐flowering Cichorieae; and visitors to Trifolieae and Loteae. Our findings suggest that both neutral and niche‐based processes are significant contributors to the spatial distribution of plant–pollinator interactions so that conservation actions in our region should be directed towards areas: near high concentrations of known occurrences of regionally rare bees; in mild climatic conditions; and that are surrounded by heterogenous landscapes. Given the observed niche‐based differences, the proportion of functionally distinct plants in flower‐mixes could be chosen to target bee species, or guilds, of conservation concern. [ABSTRACT FROM AUTHOR]

Evidence documenting the decline of insect populations is accumulating. Efforts have increased to mitigate pollinator losses by establishing gardens to support pollinator diversity. However, knowledge of the specific garden characteristics, landscape features, and environmental factors that affect pollinator diversity and abundance is limited, particularly in biodiverse regions in North America. In order to better understand how garden characteristics affect pollinator attraction, we compared pollinator composition across 16 pollinator gardens in the Appalachian ecoregion in North America. We evaluated the effects of garden characteristics (e.g., plant richness, flower abundance, garden size, and proportion of native species), landscape features (land‐use type and distance to forest), and environmental factors (sunlight exposure) on pollinator richness, overall visitation rate, and visitation rate by defined pollinator groups (i.e., solitary native bees, bumblebees, honeybees, lepidopterans, and other insects). Solitary bees (i.e., native bees besides Bombus) were the most frequent visitors (61%). We found differences in pollinator species composition between urban and rural gardens. Moreover, plant richness had a positive effect on pollinator richness and an increase in flower abundance increased the pollinator visitation rate. Flower abundance, plant richness, and high sunlight exposure increased visitation rate of solitary bees. Visitation rate of solitary bees however decreased with increasing proportion of native plants. Overall, our results indicate that garden characteristics, landscape features, and environmental factors all are important mediators of pollinator diversity and abundance. Solitary bees were most affected by garden (i.e., plant richness, number of flowers, and proportion of native plants) and environmental factors (i.e., sunlight exposure). However, we also identified differential effects of garden and environmental factors across pollinator groups. We suggest that an integrated management approach that considers multiple garden and environmental characteristics could help improve the effectiveness of pollinator garden as a conservation tool and help preserve this key ecosystem service. [ABSTRACT FROM AUTHOR]

Bumblebee activity interaction with solar irradiation, solar irradiation and HPS lighting irradiation, the HPS effect of photoperiod, day temperature and hive density were assessed with tomato fruit weights in a commercial tomato glass greenhouse in 2020-2021. Pollination activity was measured by observing ten randomly chosen cv. ‘Beorange’ tomato plants and by counting bumblebee bruised tomato flowers. MANOVA was conducted between factors and bee activity, followed by Pearson’s correlation. A Mann-Whitney U test was calculated to determine the significance between tomato flower bruising levels and fruit weights, followed by Cliff’s delta (d). Pollination activity decreased mainly in December and January when solar irradiation decreased to below 110 J cm-2 day-1. Bumblebee activity was significantly affected by solar irradiation with HPS lighting (p<0.001; p<0.01). There was a significant correlation between bumblebee activity and solar irradiation (r= 0.75; p<0.05), and solar irradiation with HPS lighting (r= 0.70; p<0.05). There was no correlation between bumblebee activity and fruit weights (r= -0.20; p<0.05). Bruised flowers had significantly greater fruit weight increases (165.7 g) compared to unbruised flowers (123.4 g) (d= 0.12; p<0.05). Bee activity rates between 60% to 80% can be concluded as an effective rate for tomato growers. Bumblebees need at least 110-154 J cm-2 day-1 of solar irradiation to achieve a high pollination activity rate in temperate climate zones during the winter season. [ABSTRACT FROM AUTHOR]

Bees are important pollinators in wild and agricultural ecosystems, and understanding the factors driving their global declines is key to maintaining these pollination services. Learning, which has been a focus of previous ecotoxicological studies in bees, may play a key role in driving colony fitness. Here we move beyond the standard single-stressor approach to ask how multiple stressors, an agrochemical (sulfoxaflor, a relatively new insecticide) and a parasite (Crithidia bombi, a prevalent gut parasite of bumblebees), impact learning in the bumblebee Bombus terrestris. We developed a modified version of the classic proboscis extension reflex assay to assess the combined effects of acute oral sulfoxaflor exposure and infection by C. bombi on olfactory learning of bumblebee workers. We found no evidence that either sulfoxaflor, C. bombi, or their combination had any significant effect on bumblebee olfactory learning, despite their known negative impacts on other aspects of bumblebee health. This suggests that losses in cognitive ability, as measured here, are unlikely to explain the impacts of sulfoxaflor and its interactions with other stressors on bumblebees. Our novel methodology provides a model system within which to test interactive effects of other key stressors on bee health. [ABSTRACT FROM AUTHOR]

• Honey bees increased yield for five commonly planted blueberry varieties • Blueberry yields still show a pollen deficit • Honey bees can be effective pollinators of blueberries in areas which lack bumble bees • Benefit of bees and pollination deficit differs between varieties Agricultural crops are often dependent on insect pollination for commercially viable yields. Blueberries are an example of such a crop and owing to their proposed health benefits they are grown around the world, including locations where their native bumble bee pollinators do not occur. In the absence of bumble bees, blueberry pollination in South Africa and many other parts of the non-native, commercial range is performed primarily by honey bees. Despite this, the effectiveness of honey bee pollination on blueberries remains understudied. This study determined the effect of honey bee pollination on components of fruit yield (fruit set and mass) of five blueberry varieties that are extensively planted in South Africa. For each variety, two metrics were calculated: 1) the benefit of bees — a comparison of fruit yields after exposure to honey bees and fruit yields after honey bee exclusion, 2) the pollination deficit — the difference in yield between hand pollination (maximum yield potential) and yields after exposure to honey bee pollinators. Honey bee pollination consistently resulted in improved yields, although the magnitude of this improvement (i.e., the benefit of bees) was dependent on the variety considered. Similarly, the pollination deficit also varied considerably across varieties and while some varieties appeared to perform close to maximum potential (small pollination deficit), others yielded well below their maximum potential under honey bee pollination. This study demonstrates that honey bees are functional pollinators of blueberries in areas where native blueberry pollinators are absent. However, in such areas, it is important that special focus is given to selecting blueberry varieties that perform well with honey bees as their primary pollinator. Further research is necessary to determine how the pollination deficit of blueberry varieties can be decreased as well as how to increase the effectiveness of honey bee pollination. [ABSTRACT FROM AUTHOR]

The findings of this study revealed that honey bees and bumble bees had different EAG responses to tomato flower volatiles, and the two bee species showed different behavioral choices to the same compound. It has been widely known that bumble bees are effective bee pollinators of tomato as they are capable of buzz pollination to vibrate tomato anthers in order to release pollen grains, and only one visit is sufficient for full tomato pollination [[43]]. Keywords: Apis mellifera; Bombus terrestris; EAG; behavior; tomato flower volatiles EN Apis mellifera Bombus terrestris EAG behavior tomato flower volatiles 987 12 11/17/22 20221101 NES 221101 1. Bees play an important role in the pollination of tomatoes, yet the relationship between foraging choices and olfactory cues is unclear because of the difference in foraging behavior between honey bees and bumble bees on tomato flowers. [Extracted from the article]

Commercialized bumble bees (Bombus) are primary pollinators of several crops within open field and greenhouse settings. However, the common eastern bumble bee (Bombus impatiens Cresson, 1863) is the only species widely available for purchase in North America. As an eastern species, concerns have been expressed over their transportation outside of their native range. Therefore, there is a need to identify regionally appropriate candidates for commercial crop pollination services, especially in the western U.S.A. In this study, we evaluated the commercialization potential of brown-belted bumble bees (Bombus griseocollis De Geer, 1773), a broadly distributed species throughout the U.S.A. by assessing nest initiation and establishment rates of colonies produced from wild-caught gynes, creating a timeline of colony development, and identifying lab-reared workers' critical thermal maxima (CTMax) and lethal temperature (ecological death). From 2019 to 2021, 70.6% of the wild-caught B. griseocollis gynes produced brood in a laboratory setting. Of these successfully initiated nests, 74.8% successfully established a nest (produced a worker), providing guidance for future rearing efforts. Additionally, lab-reared workers produced from wild-caught B. griseocollis gynes had an average CTMax of 43.5°C and an average lethal temperature of 46.4°C, suggesting B. griseocollis can withstand temperatures well above those commonly found in open field and greenhouse settings. Overall, B. griseocollis should continue to be evaluated for commercial purposes throughout the U.S.A. [ABSTRACT FROM AUTHOR]

Bee memory has been well characterized in laboratory experiments, but its relevance for foraging in an ecological context is less well studied. A new study shows that short-term memory in bumble bees correlates with springtime foraging efficiency, when floral resources are abundant, but not with summer foraging efficiency, when resources are scarce. [ABSTRACT FROM AUTHOR]

Bumble bees are important pollinators for many temperate crops. Because of the growing demand for food from entomophilous crops, bumble bee colonies are commercially reared and placed in fields or greenhouses to guarantee sufficient pollination services. Besides, commercial colonies are increasingly used in laboratories for various bioassays under controlled conditions. For both usages, bumble bee colonies are commonly provided with sugar solution and honey bee-collected pollen pellets. However, the latter display several disadvantages since they may contain pollutants, pathogens, or toxic phytochemicals. Consequently, companies have developed pollen-free artificial diets to sustain colonies. Such diets are designed to boost worker health in the field, in complement of floral pollen collected by workers outside the colonies, but their suitability in 'closed' systems without access to floral pollen, such as in laboratory bioassays, is arguable. Here, we used microcolonies of the commercially important bumble bee Bombus terrestris L. (Hymenoptera: Apidae) to assess the suitability of five artificial pollen substitutes and three mixed diets. We also assessed the evaporation rate of the different diets as it could impact their suitability. At the end of the bioassays, microcolonies fed the artificial diets showed a reduced offspring development when compared to microcolonies fed natural pollen, which was partly offset by mixing these diets with natural pollen. By contrast, the artificial diets did not have deleterious effects on worker's health. We discuss the potential nutritional and physical causes of artificial diets unsuitability for offspring development and encourage further research to accordingly establish appropriate pollen-free diets for bumble bee breeding. [ABSTRACT FROM AUTHOR]

• Diversity and spatial arrangement of cultivars can influence pollination and yields. • Pollinator behavior interacts with spatial arrangement to affect pollination. • Blueberry yields were highest when cultivars were mixed within rows. • Yields were lowest in single-cultivar plots. • Bumble bees and honey bees switched between cultivars more when mixed within rows. Bees can facilitate cross-pollination in crops by moving pollen between distinct crop genotypes or cultivars, with pollination success dependent on both bee behavior and planting arrangement. Previous research suggests that bees forage primarily along crop rows, and deposit pollen relatively close to its source, which suggests that cross-pollination would be enhanced by mixing cultivars within crop rows at relatively fine spatial scales. However, minimal research has explored how bee-mediated cross-pollination is influenced by cultivar diversity and planting arrangement. In this study, we examined the effects of cultivar diversity and planting arrangement on bee-mediated cross-pollination in southern highbush blueberry. We used potted plants to create three arrangements including 1) single cultivar, 2) mixed cultivars across rows, and 3) mixed cultivars within rows, and observed bee visitation rates and behaviors across arrangements, and measured the number of fruit and fruit mass per flower across selected branches as indicators of pollination success and yield over two years. While the number of fruit was not affected by planting arrangement, fruit mass was highest in the mixed-within rows arrangement, 39 % higher than in the single cultivar arrangement. Mixing cultivars across rows resulted in intermediate fruit mass, which was 21 % higher than in the single cultivar arrangement. Additionally, we found that both bumble bees and honey bees were twice as likely to move between cultivars when cultivars were mixed within rows as compared to across rows. These results were further supported by a greenhouse experiment showing fruit mass per flower was higher with cross as compared to self-pollination by 20–38 % depending on pollen donor. Combined, data show that blueberries benefit from cross-pollination and mixed cultivar plantings and suggest that yields are optimized when cultivars are mixed within rows due to greater cross-cultivar movement by bees. [Display omitted] [ABSTRACT FROM AUTHOR]

Assuming that some wild bee populations are resource limited [[56]], the possible competition with early arriving bumble bees (as well as honey bees) may imply that some native bees need to work harder and invest more time and energy in order to collect the proteins (i.e., pollen) needed for provisioning their offspring. Bumble bees visited both pollen- and nectar-rewarding flowers earlier than the wild bees, and the pollen-rewarding flowers earlier than the carpenter bees, but with no significant difference compared to the honey bee for both type of flowers (Table 4). Bumble bees (and to lesser extent honey bees) arrive to pollen-rewarding flowers earlier in the morning and have the opportunity to deplete pollen rewards before the later arrival of the local wild bees ( I Xylocopa i and other wild bee taxa). [Extracted from the article]

Bumblebees are one among the anthophilous form and play a significant role in the pollination of major agricultural crops like medicinal, aromatic, ornamental and various other horticultural plants. They are abundant and mostly confined to flowers present in the temperate, alpine and arctic climates of the northern continents. The bumblebees are considered as most important pollinators and are mainly responsible for the conservation of high altitude vegetation germplasm where other insect pollinators are very much limited. They are more successful pollinators and can visit large number of flowers per minute than other bees and are perfect for picking up and transferring appreciable amount of compatible pollen to flowers and thus perform buzz pollination. It is quite evident that the population of bumblebee is gradually declining throughout the globe for the last 7 decades due to agricultural intensification, habitat loss, deforestation, overgrazing, pesticide poisoning and climate change. The present paper addresses this issue on the basis of literature survey. [ABSTRACT FROM AUTHOR]

As urban areas continue to expand globally, animal biodiversity is likely to experience altered habitat conditions, resource levels, and pathogen dynamics, with critical implications for insect pollinators. Specifically, local and regional land management may impact pollinator infectious disease prevalence, and this may be particularly relevant in urban garden systems where local food production depends on crop pollination. Further, because multi-host parasites can be spread across insect pollinator communities with varying impacts on host species, changes in pollinator community composition can lead to 'amplification' or 'dilution' effects, whereby increases in pollinator diversity could lead to higher or lower rates of parasitism, respectively. In this study, we investigate how urban garden management and regional landscape composition structure disease dynamics for a critical native pollinator, the bumble bee Bombus vosnesenskii. Parasite prevalence in our gardens was low in Nosema ceranae (1.06%) and Nosema bombi (1.06%), and Crithidia expoekii (0.5%), while we observed higher prevalence of Crithidia bombi (18%) and Apicystis bombi (6.4%). We found that gardens with higher pollinator taxonomic richness had significantly lower prevalence of Apicystis bombi in B. vosnesenskii hosts, providing evidence for the dilution effect. We also found that the prevalence of the parasite Crithidia bombi was significantly higher in gardens with higher mulch use and in gardens surrounded by greater proportions of impervious urban cover. Overall, we document a wide range of stressors facing urban bees, and show that parasitism is mediated by local ground management, regional land use, and pollinator community composition. [ABSTRACT FROM AUTHOR]

Bumble bees (Bombus; Hymenoptera) are crucial pollinators for many agricultural crops, but their numbers have declined - with climate change as a possible driver. Different aspects of local weather conditions can have substantial effects on bumble bees' ability to forage. Here we made 501 observations of bumblebee workers on bramble flowers (Rubus fruticosus) to explore how the characteristic sizes of foragers active and their individual rate of movement between flowers were correlated with aspects of weather. Firstly, we found that increased ambient temperature is correlated to reduced activity in larger workers. Moreover, while higher humidity was linked to an increase in smaller workers, an increase in cloud cover led their numbers to decrease. Visitation rate and temperature showed a significant negative relationship whereas no other weather aspect affected visitation rate significantly. Our results suggest that predicted rises in ambient temperatures will adversely affect bumble bee foraging, and particularly so for larger-bodied workers. We anticipate that this study can be used as a foundation for longer-term and more detailed studies on bumble bee foraging and colony performance. Such work is vital to identify management measures to mitigate pollinator declines and preserve food security. [ABSTRACT FROM AUTHOR]

Urbanization is associated with increases in impervious land cover, which alters the distribution of resources available to wildlife and concentrates activity in unbuilt spaces such as parks and gardens. How resource shifts alter the dynamics of parasite and pathogen transmission has not been addressed for many important species in urban systems. We focus on urban gardens, resource‐rich "islands" within the urban matrix, to examine how the availability of floral resources at local and landscape scales influences the prevalence of six RNA viruses and three parasites in honey bees and bumble bees. Because parasites and pathogens are transmitted at flowers between visitors, we expected that floral abundance would concentrate bees within gardens, amplifying infection rates in pollinators, unless increases in floral resources would enhance bee diversity enough to dilute transmission. We found that garden size and flowering perennial plant abundance had a positive, direct effect on parasite and pathogen richness in bumble bees, suggesting that resource provisioning amplifies transmission. We also found that parasitism rates in honey bees were positively associated with parasites and pathogens in bumble bees, suggesting spillover between species. Encouragingly, we found evidence that management may mitigate parasitism through indirect effects: garden size had a positive impact on bee diversity, which in turn was negatively associated with parasite and pathogen richness in bumble bees. Unexpectedly, we observed that that parasite and pathogen richness in honey bees had no significant predictors, highlighting the complexity of comparing transmission dynamics between species. Although floral resources provide bees with food, we suggest more research on the tradeoffs between resource provisioning and disease transmission to implement conservation plantings in changing landscapes. [ABSTRACT FROM AUTHOR]

Bumble bees belong to the genus Bombus, order Hymenoptera and family Bombidae, which includes approximately 250 species all over the world, out of which 48 species are found in India. Bumble bees are effective pollinators with high pollination efficiency and increasing demand of pollination services has highlighted the concept of commercialization of these pollinators. They generally have an annual life cycle with three castes viz., queen, workers and drones; only the queen undergoes diapause during winters. The oviposition rate and colony initiation percentage of the bumble bees are affected by different factors viz., foundation queen, feed, hygienic conditions, nesting material and environmental conditions. Amongst these, nesting material as well as feeding methods are the most important factors that affect the success rate and queen acceptance. Hence, it is very important to know which nesting material and feed is highly accepted by queens for colony initiation and development. The present review summarizes the literature about different domiciles and feed used for invitro rearing of bumble bees and their effect on colony development. [ABSTRACT FROM AUTHOR]

Insect pollinators provide important crop pollination services but are declining in response to lack of diverse flower resources and exposure to pesticides. Despite increasing evidence that the benefits of insect pollination for crop production depend on other ecosystem services and crop management practices, investigations have mostly been limited to how pollination benefits are affected by insect pest control and soil fertility levels. Here we used a factorial cage experiment in the field to test how pollination by bumble bees, manual weed removal and fungicide application interactively shape faba bean (Vicia faba) yield components, and how weed removal and fungicide application affect bumble bee foraging behaviour. We found that insect pollination and weed removal increased faba bean yield components mostly additively, with insect pollination being the most important factor to maximise yield. The fungicide treatment did not affect crop yield, probably due to the low fungal pathogen incidence in the experiment, but instead affected bumble bee visitation behaviour. Bumble bees visited flowers of fungicide-sprayed plants more often than fungicide-free plants. This has potential consequences on bee health that should be further assessed. Guidelines on pesticide use should be improved by weighing benefits to agricultural productivity against risks for pollinators according to integrated pest and pollinator management principles. Our results emphasise that insect pollination can be an important factor for crop yield. The additive benefits of insect pollination and weed removal to crop yield indicates that they are crop production factors which can be managed for independently. • Insect pollination and weed removal increased faba bean yield additively. • Insect pollination enhanced yield more than weed removal. • Fungicide use did not affect yield components. • Bumble bees visited fungicide-sprayed plants more often than fungicide-free plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pesticides contribute to decline of wild bees. • Pesticide mixtures can result in unpredictable interaction effects. • Development of new method for testing pesticide mixtures on bumblebees. • No effect of pesticide mixture on learning ability and flight activity of bumblebees. • Effects on solitary wild bees cannot be excluded. Bumblebees are among the most important wild bees for pollination of crops and securing wildflower diversity. However, their abundance and diversity have been on a steady decrease in the last decades. One of the most important factors leading to their decline is the frequent use of plant protection products (PPPs) in agriculture, which spread into forests and natural reserves. Mixtures of different PPPs pose a particular threat because of possible synergistic effects. While there is a comparatively large body of studies on the effects of PPPs on honeybees, we still lack data on wild bees. We here investigated the influence of the frequent fungicide Cantus® Gold (boscalid/dimoxystrobin), the neonicotinoid insecticide Mospilan® (acetamiprid) and their combination on bumblebees. Cognitive performance and foraging flights of bumblebees were studied. They are essential for the provisioning and survival of the colony. We introduce a novel method for testing four treatments simultaneously on the same colony, minimizing inter-colony differences. For this, we successfully quartered the colony and moved the queen daily between compartments. Bumblebees appeared astonishingly resilient to the PPPs tested or they have developed mechanisms for detoxification. Neither learning capacity nor flight activity were inhibited by treatment with the single PPPs or their combination. [ABSTRACT FROM AUTHOR]

Patterns of resource use by animals can clarify how ecological communities have assembled in the past, how they currently function and how they are likely to respond to future perturbations. Bumble bees (Hymentoptera: Bombus spp.) and their floral hosts provide a diverse yet tractable system in which to explore resource selection in the context of plant–pollinator networks. Under conditions of resource limitation, the ability of bumble bees species to coexist should depend on dietary niche overlap. In this study, we report patterns and dynamics of floral morphotype preferences in a mountain bumble bee community based on ~13 000 observations of bumble bee floral visits recorded along a 1400 m elevation gradient. We found that bumble bees are highly selective generalists, rarely visiting floral morphotypes at the rates predicted by their relative abundances. Preferences also differed markedly across bumble bee species, and these differences were well‐explained by variation in bumble bee tongue length, generating patterns of preference similarity that should be expected to predict competition under conditions of resource limitation. Within species, though, morphotype preferences varied by elevation and season, possibly representing adaptive flexibility in response to the high elevational and seasonal turnover of mountain floral communities. Patterns of resource partitioning among bumble bee communities may determine which species can coexist under the altered distributions of bumble bees and their floral hosts caused by climate and land use change. [ABSTRACT FROM AUTHOR]