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Cuckoo bumblebees (Bombus subgenus Psithyrus) are social parasites that have lost the ability to establish their own nests, and instead usurp the nest of a bumblebee host to reproduce. Accordingly, they are entirely dependent upon a host species to complete their life cycle, and are therefore vulnerable to co–extinction. Despite this, the current consensus is that there remains much we do not know about the fundamental ecology of many cuckoo bumblebee species, which is crucial for conservation.To investigate data gaps for cuckoo bumblebees, we conducted a systematic review to quantify the peer‐reviewed literature that has been produced, including which species have been most studied and which disciplines have been explored.Over half of all Psithyrus species were represented in fewer than 10 publications each, including 2 species listed as Critically Endangered by the IUCN.Research on cuckoo bumblebees is heavily weighted towards Europe and European species, while Asian species were under‐represented.Key research areas such as ecology and behaviour have received little attention for the majority of cuckoo bumblebees, which may hamper conservation effortsOur results quantitatively support observations made in other publications on the scarcity of data on cuckoo bumblebees, and highlight the need for further research on many species for whom fundamental knowledge is missing—particularly in light of the vulnerability of this subgenus to extinction. [ABSTRACT FROM AUTHOR]

Bees are essential pollinators of crops and wild plants and their ability to forage and pollinate are key aspects of their behaviour. Bee populations are under threat, with the use of insecticides a contributing factor. Most research has focused on neonicotinoid insecticides and bee mortality, and little is known about impacts on bee foraging and delivery of pollination services. However, other insecticide classes, such as organophosphates and pyrethroids, are increasingly used globally, but little is known about how these widely used substances may impact bees, particularly non‐honeybees.We exposed bumblebee Bombus terrestris colonies to field‐relevant doses of a pyrethroid (lambda‐cyhalothrin) and an organophosphate (dimethoate) and investigated sublethal effects on behaviour at the individual and colony level, in addition to pollination service delivery under semi‐field conditions.We show, for the first time, that exposure to these chemicals impacts the activity and pollen provisioning of bumblebee Bombus terrestris audax colonies, while no short‐term effects on flower handling behaviour or pollination service delivery were detected.We found that colonies exposed to dimethoate were less active, with 67% fewer bees leaving the colony to forage than control colonies, and of those that returned, 92% fewer returned pollen provisions to the nest. Colonies exposed to lambda‐cyhalothrin did not differ in activity; however, 62% fewer of these bees returned with pollen provisions.Policy implications. These findings give important insights into how exposure to different classes of insecticides could impact bumblebee activity and their provision of pollen required for colony development. With a focus on neonicotinoids in terms of policy changes regarding insecticides and bees, we show that other insecticide classes should also be re‐examined in relation to their potential risks for pollinators. We confirm the need to improve risk assessment of insecticides to assess sublethal effects, include non‐honeybee species in risk assessment processes and also consider key behaviours such as foraging and interactions with plants. [ABSTRACT FROM AUTHOR]

Grassland management under local-scale results-based agri-environmental payment schemes (RBAPSs) are designed to benefit some biodiversity groups like plants. However, it is unknown if RBAPSs affect plant-pollinator interaction networks, and whether local or landscape management is more influential. Most studies focus on traditional community structure measures like richness, neglecting the impacts management may have on network structure and stability, and thereby ecosystem function. Plant species that benefit from RBAPSs could also act as key forage plants for pollinators, but this has not been investigated. We sampled networks across 23 grasslands in the West of Ireland to investigate if grassland management at local (RBAPS) and/or landscape scale (proportion of semi-natural grassland) influence network size, connectance, nestedness, linkage density and specialization of networks. Species strength analysis was used to identify key plant species for bumblebees, solitary bees, hoverflies, and butterflies. Results indicate RBAPSs benefit network size and linkage density, where species-rich grasslands supported larger networks and higher linkage densities. Networks surrounded by higher proportions of semi-natural grassland also had larger network sizes and higher linkage densities. Nestedness was greater in landscapes with high proportions of improved grassland. Key plant species differed between pollinator groups. Our results highlight that managing grasslands to promote greater plant diversity through a local scale RBAPS positively influences the structure and stability of networks, with possible implications for pollination service delivery. However, networks are also influenced by landscape management suggesting that local-scale management by itself may not be sufficient to conserve networks. We conclude that measures aimed at pollinators should include grassland management at both spatial scales where possible and to promote the establishment of key plant species to help sustain a wider range of pollinator taxa. [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]

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]

Herbicides are the most widely used pesticides globally. Although used to control weeds, they may also pose a risk to bee health. A key knowledge gap is how bees could be exposed to herbicides in the environment, including whether they may forage on treated plants before they die. We used a choice test to determine if bumblebees would forage on plants treated with glyphosate at two time periods after treatment. We also determined whether glyphosate and its degradation product aminomethylphosphonic acid were present as residues in the pollen collected by the bees while foraging. Finally, we explored if floral resources (nectar and pollen) remained present in plants after herbicide treatment. In general bees indiscriminately foraged on both plants treated with glyphosate and controls, showing no avoidance of treated plants. Although the time spent on individual flowers was slightly lower on glyphosate treated plants, this did not affect the bees' choice overall. We found that floral resources remained present in plants for at least 5 days after lethal treatment with glyphosate and that glyphosate residues were present in pollen for at least 70 h posttreatment. Our results suggest that bees could be exposed to herbicide in the environment, both topically and orally, by foraging on plants in the period between herbicide treatment and death. Identifying this route of exposure is a first step in understanding the risks of herbicides to bees. The effects of herbicides on bees themselves are uncertain and warrant further investigation to allow full risk assessment of these compounds to pollinating insects. Environ Toxicol Chem 2022;41:2603–2612. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Bumblebees are a key pollinator group globally which have declined over time. However, while some species remain common others are rare and have declined at a sharper rate. The Great Yellow Bumblebee (Bombus distinguendus Morawitz) is classified as 'Endangered' on the Irish Red List, and 'Vulnerable' at European level. We aimed to investigate the ecology of B. distinguendus within the wider bumblebee community in its only remaining Irish population to inform conservation management. Eight true bumblebee species were recorded in total in four habitat types surveyed, with highest species richness in species-rich grassland and highest abundance in urban habitats. Highest numbers of B. distinguendus were found in two designated nature reserves. However, outside these reserves the species was only found in three of twelve sites surveyed in both species-rich and coastal grassland habitats. B. distinguendus is a late emerging species in this region with a foraging preference for Common Knapweed (Centaurea nigra). Availability of key forage species was lowest when numbers of B. distinguendus were highest, potentially limiting survival of this species. Some smaller suitable habitats in urban areas and roadside verges were not used by the species, which suggests potential issues with habitat connectivity, patch size and/or availability of nesting and hibernation sites. Implications for insect conservation: Based on our findings, we suggest that existing species-rich and coastal grassland sites should be conserved, and other areas restored, for B. distinguendus in Ireland. Conservation management should focus on delaying cutting grasslands until late September, winter grazing of stock and reducing pesticides and fertilisers with the aim of increasing forage availability in late season, and ensuring that suitable habitats are connected in the landscape to allow adequate habitat area as well as movement and dispersal of the species to new areas. [ABSTRACT FROM AUTHOR]

The ability to forage and return home is essential to the success of bees as both foragers and pollinators. Pesticide exposure may cause behavioural changes that interfere with these processes, with consequences for colony persistence and delivery of pollination services., We investigated the impact of chronic exposure (5-43 days) to field-realistic levels of a neonicotinoid insecticide (2·4 ppb thiamethoxam) on foraging ability, homing success and colony size using radio frequency identification ( RFID) technology in free-flying bumblebee colonies., Individual foragers from pesticide-exposed colonies carried out longer foraging bouts than untreated controls (68 vs. 55 min). Pesticide-exposed bees also brought back pollen less frequently than controls indicating reduced foraging performance., A higher proportion of bees from pesticide-exposed colonies returned when released 1 km from their nests; this is potentially related to increased orientation experience during longer foraging bouts. We measured no impact of pesticide exposure on homing ability for bees released from 2 km, or when data were analysed overall., Despite a trend for control colonies to produce more new workers earlier, we found no overall impacts of pesticide exposure on whole colony size., Synthesis and applications. This study shows that field-realistic neonicotinoid exposure can have impacts on both foraging ability and homing success of bumblebees, with implications for the success of bumblebee colonies in agricultural landscapes and their ability to deliver crucial pollination services. Pesticide risk assessments should include bee species other than honeybees and assess a range of behaviours to elucidate the impact of sublethal effects. This has relevance for reviews of neonicotinoid risk assessment and usage policy world-wide. [ABSTRACT FROM AUTHOR]

Insect pollinators are essential for both the production of a large proportion of world crops and the health of natural ecosystems. As important pollinators, bumblebees must learn to forage on flowers to feed both themselves and provision their colonies., Increased use of pesticides has caused concern over sublethal effects on bees, such as impacts on reproduction or learning ability. However, little is known about how sublethal exposure to field-realistic levels of pesticide might affect the ability of bees to visit and manipulate flowers., We observed the behaviour of individual bumblebees from colonies chronically exposed to a neonicotinoid pesticide (10 ppb thiamethoxam) or control solutions foraging for the first time on an array of morphologically complex wildflowers ( Lotus corniculatus and Trifolium repens) in an outdoor flight arena., We found that more bees released from pesticide-treated colonies became foragers, and that they visited more L. corniculatus flowers than controls. Interestingly, bees exposed to pesticide collected pollen more often than controls, but control bees learnt to handle flowers efficiently after fewer learning visits than bees exposed to pesticide. There were also different initial floral preferences of our treatment groups; control bees visited a higher proportion of T. repens flowers, and bees exposed to pesticide were more likely to choose L. corniculatus on their first visit., Our results suggest that the foraging behaviour of bumblebees on real flowers can be altered by sublethal exposure to field-realistic levels of pesticide. This has implications for the foraging success and persistence of bumblebee colonies, but perhaps more importantly for the interactions between wild plants and flower-visiting insects and ability of bees to deliver the crucial pollination services to plants necessary for ecosystem functioning. [ABSTRACT FROM AUTHOR]

Pollinators are beneficial for many wild and crop plants. As a mass-flowering crop, oilseed rape has received much focus in terms of its pollination requirements but despite a threefold increase in area of cultivation of this crop in Ireland over the past 5 years, little is known about its pollination here. We surveyed the flower visiting insects found in commercial winter oilseed rape fields and evaluated the importance of different pollinator groups, investigated the contribution of insect pollination to oilseed rape seed production, and estimated the economic value of insect pollination to the crop at a national level. Our data showed that winter oilseed rape is visited by a wide variety of insect species, including the honeybee, bumblebees, solitary bees, and hoverflies. The honeybee, Eristalis hoverflies and bumblebees (especially Bombus sensu stricto and B. lapidarius) were the best pollinators of winter oilseed rape based on the number of pollen grains they carry, visitation rates per flower and their relative abundance per field. Exclusion of pollinators resulted in a 27 % decrease in the number of seeds produced, and a 30 % decrease in seed weight per pod in winter crops, with comparable values from a spring oilseed rape field also. The economic value of insect pollination to winter oilseed rape was estimated as €2.6 million per annum, while the contribution to spring oilseed rape was €1.3 million, resulting in an overall value of €3.9 million per annum. We can suggest the appropriate conservation and management of both honeybees and wild pollinators in agricultural areas to ensure continued provision of pollination services to oilseed rape, as a decrease in insect numbers has the potential to negatively influence crop yields. [ABSTRACT FROM AUTHOR]

The Bombus sensu stricto species complex is a widespread group of cryptic bumblebee species which are important pollinators of many crops and wild plants. These cryptic species have, until now, largely been grouped together in ecological studies, and so little is known about their individual colony densities, foraging ranges or habitat requirements, which can be influenced by land use at a landscape scale. We used mass-flowering oilseed rape fields as locations to sample bees of this complex, as well as the second most common visitor to oilseed rape B. lapidarius, and molecular RFLP methods to distinguish between the cryptic species. We then used microsatellite genotyping to identify sisters and estimate colony densities, and related both proportions of cryptic species and their colony densities to the composition of the landscape surrounding the fields. We found B. lucorum was the most common member of the complex present in oilseed rape followed by B. terrestris. B. cryptarum was also present in all but one site, with higher proportions found in the east of the study area. High numbers of bumblebee colonies were estimated to be using oilseed rape fields as a forage resource, with B. terrestris colony numbers higher than previous estimates from non-mass-flowering fields. We also found that the cryptic species responded differently to surrounding landscape composition: both relative proportions of B. cryptarum in samples and colony densities of B. lucorum were negatively associated with the amount of arable land in the landscape, while proportions and colony densities of other species did not respond to landscape variables at the scale measured. This suggests that the cryptic species have different ecological requirements (which may be scale-dependent) and that oilseed rape can be an important forage resource for many colonies of bumblebees. Given this, we recommend sustainable management of this crop to benefit bumblebees. [ABSTRACT FROM AUTHOR]

Global declines in pollinating insects have been linked with agricultural intensification and land-use change. Increased production of novel crops for bioenergy is causing changes in agricultural practice, but the effects on different pollinating taxa have not yet been quantified. However, the major pollinating groups (social bees, solitary bees, hoverflies and butterflies) are likely to respond differently to changes in land use and shifts in crop cultivation patterns., We assessed the impacts of two bioenergy crops, oilseed rape Brassica napus L. and Miscanthus Miscanthus X giganteus on (i) the diversity and abundance of four taxonomic groups of pollinating insects, (ii) insect community composition, (iii) floral resources and (iv) nesting sites for bumblebees, by comparing bioenergy crops with conventional arable and grass crops in a large network of commercial fields., We found that although there were more bumblebees in oilseed rape fields, conventional crops and bioenergy crops did not differ greatly in species richness of most pollinator groups, although more floral resources were found in the bioenergy crops. However, solitary bees were more abundant and species rich in energy crops than conventional wheat, and more trap-nesting bees and wasps were found in Miscanthus than oilseed rape. In addition, novel assemblages of solitary bees were found in the bioenergy crops., All pollinator groups, and flowering plants, were more abundant in field margins than in the centre of crop fields. Although there were no differences among crop types, nest-searching bumblebees were confined to field margins. This highlights the importance of field margins as forage and nesting habitat for pollinators in farmland., Synthesis and applications. Differential responses to field-scale growth of bioenergy crops were displayed by the taxonomic groups studied, suggesting that effects on biodiversity cannot be generalized from studies based on a small suite of taxonomic groups and must include a range of taxa for overarching results. To optimize habitat for pollinators in agricultural areas, our data suggest that a diversity of crop types at small scales may have positive impacts and supports appropriate management and conservation of field margins and hedgerows during conversion to bioenergy production. [ABSTRACT FROM AUTHOR]

Exposure to agricultural pesticides is often cited as one of the primary drivers of pollinator decline. Most of the research has been focused on the impacts of insecticides but herbicides have been receiving more attention for their potential implications for bee health. However, little is known about how pollinators are being exposed to herbicides, whether it is through direct contact with herbicides during spraying, foraging on herbicide-treated plants or contact with herbicide residues within the wider environment. We examined the interactions between bumble bees (Bombus terrestris) and herbicide-treated plants, comparing behavior of bees when offered a choice between glyphosate-treated and untreated plants. We aimed to determine whether bees avoid herbicide-treated plants, thus reducing their potential exposure to herbicides. Individual foragers were released into an exclusion cage containing four Phacelia tanacetifolia plants: two sprayed with glyphosate and two untreated plants. We measured the frequency and duration of nectar feeding, pollen collecting and investigation (inspection but not foraging) of plants. We tested interactions between the bumble bees and plants which had been freshly sprayed (within 24 hours) and again once the glyphosate had begun to translocate within the plant – but before any significant physical effects began to appear (48 hours). Here, we present the preliminary results from this study. [ABSTRACT FROM AUTHOR]

Bumblebees are exposed to pesticides applied for crop protection while foraging on treated plants, with increasing evidence suggesting that this sublethal exposure has implications for pollinator declines. The challenges of navigating and learning to manipulate many different flowers underline the critical role learning plays for the foraging success and survival of bees. We assessed the impacts of both acute and chronic exposure to field-realistic levels of a widely applied neonicotinoid insecticide, thiamethoxam, on bumblebee odour learning and memory. Although bees exposed to acute doses showed conditioned responses less frequently than controls, we found no difference in the number of individuals able to learn at field-realistic exposure levels. However, following chronic pesticide exposure, bees exposed to field-realistic levels learnt more slowly and their short-term memory was significantly impaired following exposure to 2.4 ppb pesticide. These results indicate that field-realistic pesticide exposure can have appreciable impacts on learning and memory, with potential implications for essential individual behaviour and colony fitness. [ABSTRACT FROM AUTHOR]