Terrestris Colonies Research Articles

Chemotyping of terrestrial Nostoc-like isolates from alkali grassland areas by non-targeted peptide analysis

The Nostoc genus is a well-known heterocytous, filamentous cyanobacterium which can be found all over the world. The size of terrestrial and/or freshwater colonies can be microscopic and macroscopic as well. In addition, Nostoc species are one of the most common photosynthetic cyanobacterial partners in symbiotic interactions. Terrestrial cyanobacterial colonies were collected and isolated in this study from various alkali grassland habitats (Great Hungarian Plain). Altogether 133 colonies were isolated from the 65 collected samples. The peptide patterns of the Nostoc-like strains were examined using HPLC-ESI-MS/MS and 41 peptides were identified from 45 isolated Nostoc-like strains; these compounds belonged to 4 different peptide classes. Twelve nostoginin/microginin, 16 anabaenopeptin, 12 banyaside/suomilide variants were identified. 37% of our isolated Nostoc-like strains produced some of the peptide metabolites we tested. These strains showed distinct chemotypes according to their peptide patterns, and can be divided into 4 groups based on their metabolisms. Strains either contained: (1) nostoginins/microginins, (2) anabaenopeptins, (3) anabaenopeptins and banyasides or (4) banyasides as major compounds. Banyasides were present in many of our strains and showed very high intensity in some cases. A number of previously unknown banyaside variants have been identified.

Testing the efficacy of a thermal camera as a search tool for locating wild bumble bee nests

Research into how bumble bee colonies respond to the stressors affecting their populations are currently studied in the laboratory using commercially reared Bombus terrestris colonies. Understanding how these stressors affect wild bumble bee colonies in the field would be a crucial step forward for the conservation of bumble bee species. Currently, visual cues are used to locate bumble bee nests, using human searchers looking for the worker nest traffic, but the limitations of this method mean that low numbers of nests are found and so a new method that looks to tackle these limitations is needed. Thermal cameras have been considered as a potential nest searching tool because they reduce the visual complexity of the environment by displaying a homogenized thermal landscape to the searcher. In this study, we compare the use of a thermal camera to human searches using two trials: (i) using inexperienced volunteers to search along the transect for a known bumble bee nest and (ii) using an experienced individual to search across a number of novel locations. We found thermal cameras are not a better nest detection technique than human searches, having low success rates across both trials. We discuss the limitations of thermal cameras as a technique and propose how the technology could be improved for future studies.

Prevalence of Nosema microsporidians in commercial bumblebees (Bombus terrestris) is not related to the intensity of their use at the landscape scale

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

A spatial network analysis of resource partitioning between bumblebees foraging on artificial flowers in a flight cage

BackgroundIndividual bees exhibit complex movement patterns to efficiently exploit small areas within larger plant populations. How such individual spatial behaviours scale up to the collective level, when several foragers visit a common area, has remained challenging to investigate, both because of the low resolution of field movement data and the limited power of the statistical descriptors to analyse them. To tackle these issues we video recorded all flower visits (N = 6205), and every interaction on flowers (N = 628), involving foragers from a bumblebee (Bombus terrestris) colony in a large outdoor flight cage (880 m2), containing ten artificial flowers, collected on five consecutive days, and analysed bee movements using networks statistics.ResultsBee-flower visitation networks were significantly more modular than expected by chance, indicating that foragers minimized overlaps in their patterns of flower visits. Resource partitioning emerged from differences in foraging experience among bees, and from outcomes of their interactions on flowers. Less experienced foragers showed lower activity and were more faithful to some flowers, whereas more experienced foragers explored the flower array more extensively. Furthermore, bees avoided returning to flowers from which they had recently been displaced by a nestmate, suggesting that bees integrate memories of past interactions into their foraging decisions.ConclusionOur observations, under high levels of competition in a flight cage, suggest that the continuous turnover of foragers observed in colonies can led to efficient resource partitioning among bees in natural conditions.

Bombus terrestris in a mass-flowering pollinator-dependent crop: A mutualistic relationship?

Bumblebees (Bombus spp.) rely on an abundant and diverse selection of floral resources to meet their nutritional requirements. In farmed landscapes, mass‐flowering crops can provide an important forage resource for bumblebees, with increased visitation from bumblebees into mass‐flowering crops having an additional benefit to growers who require pollination services. This study explores the mutualistic relationship between Bombus terrestris L. (buff‐tailed bumblebee), a common species in European farmland, and the mass‐flowering crop courgette (Cucurbita pepo L.) to see how effective B. terrestris is at pollinating courgette and in return how courgette may affect B. terrestris colony dynamics. By combining empirical data on nectar and pollen availability with model simulations using the novel bumblebee model Bumble‐BEEHAVE, we were able to quantify and simulate for the first time, the importance of courgette as a mass‐flowering forage resource for bumblebees. Courgette provides vast quantities of nectar to ensure a high visitation rate, which combined with abundant pollen grains, enables B. terrestris to have a high pollination potential. While B. terrestris showed a strong fidelity to courgette flowers for nectar, courgette pollen was not found in any pollen loads from returning foragers. Nonetheless, model simulations showed that early season courgette (nectar) increased the number of hibernating queens, colonies, and adult workers in the modeled landscapes. Synthesis and applications. Courgette has the potential to improve bumblebee population dynamics; however, the lack of evidence of the bees collecting courgette pollen in this study suggests that bees can only benefit from this transient nectar source if alternative floral resources, particularly pollen, are also available to fulfill bees’ nutritional requirements in space and time. Therefore, providing additional forage resources could simultaneously improve pollination services and bumblebee populations.

Behavioral flexibility promotes collective consistency in a social insect

Deciphering the mechanisms that integrate individuals and their behavior into a functional unit is crucial for our understanding of collective behaviors. We here present empirical evidence for the impressive strength of social processes in this integration. We investigated collective temperature homeostasis in bumblebee (Bombus terrestris) colonies and found that bees are less likely to engage in thermoregulatory fanning and do so with less time investment when confronted with heat stress in a group setting than when facing the same challenge alone and that this down-regulation of individual stimulus-response behavior resulted in a consistent proportion of workers in a group engaged in the task of fanning. Furthermore, the bees that comprised the subset of fanning individuals changed from trial to trial and participation in the task was predominately unpredictable based on previous response behavior. Our results challenge basic assumptions in the most commonly used class of models for task allocation and contrast numerous collective behavior studies that emphasize the importance of fixed inter-individual variation for the functioning of animal groups. We demonstrate that bumblebee colonies maintain within-group behavioral heterogeneity and a consistent collective response pattern based on social responsiveness and behavioral flexibility at the individual level.

Sulfoxaflor exposure reduces bumblebee reproductive success.

Intensive agriculture currently relies on pesticides to maximize crop yield1,2. Neonicotinoids are the most widely used insecticides globally3, but increasing evidence of negative impacts on important pollinators4-9 and other non-target organisms10 has led to legislative reassessment and created demand for the development of alternative products. Sulfoximine-based insecticides are the most likely successor11, and are either licensed for use or under consideration for licensing in several worldwide markets3, including within the European Union12, where certain neonicotinoids (imidacloprid, clothianidin and thiamethoxam) are now banned from agricultural use outside of permanent greenhouse structures. There is an urgent need to pre-emptively evaluate the potential sub-lethal effects of sulfoximine-based pesticides on pollinators11, because such effects are rarely detected by standard ecotoxicological assessments, but can have major impacts at larger ecological scales13-15. Here we show that chronic exposure to the sulfoximine-based insecticide sulfoxaflor, at dosages consistent with potential post-spray field exposure, has severe sub-lethal effects on bumblebee (Bombus terrestris) colonies. Field-based colonies that were exposed to sulfoxaflor during the early growth phase produced significantly fewer workers than unexposed controls, and ultimately produced fewer reproductive offspring. Differences between the life-history trajectories of treated and control colonies first became apparent when individuals exposed as larvae began to emerge, suggesting that direct or indirect effects on a small cohort may have cumulative long-term consequences for colony fitness. Our results caution against the use of sulfoximines as a direct replacement for neonicotinoids. To avoid continuing cycles of novel pesticide release and removal, with concomitant impacts on the environment, a broad evidence base needs to be assessed prior to the development of policy and regulation.

Busier bees: increasing nest traffic in commercial bumblebee colonies

Commercially-reared bumblebee colonies contribute to the pollination of crops globally. If the efficiency of commercial colonies at providing pollination services could be increased, it would have implications for agricultural outputs. Commercial colonies are sold with an internal nectar reservoir on which bees can forage from within the nest. Nectar stores in naturally-produced nectar pots of colonies can affect forager recruitment and activity outside the nest. Thus, it is possible that artificial nectar reservoirs could impact the foraging activity of colonies. To investigate this, commercial Bombus terrestris audax colonies were placed in a university parkland campus. Colonies were split into three treatment groups: those with (1) access to an unaltered nectar reservoir; (2) access to a diluted reservoir; and (3) no reservoir access. Foraging observations were made for all colonies over a 19-day period. The mass of each colony was measured and demographic data were collected. Colonies with diluted reservoirs had 131% and 39% more bees entering and leaving than colonies with no reservoir access and unaltered reservoirs respectively. Both treatments with access to a nectar reservoir gained more mass, had a higher proportion of pollen foraging bees, and had more workers, males, larvae and pupae, than colonies with no access to a reservoir. These results demonstrate that manipulating the availability and concentration of internal nectar reservoirs of commercial B. terrestris colonies significantly affects the number of bees entering and leaving the colony. Dilution of the nectar reservoir could be a strategy for increasing the pollination services commercial colonies provide to crops. Further research in commercial crops is required before such a strategy could be implemented on farms.

Landscape Scale Study of the Net Effect of Proximity to a Neonicotinoid-Treated Crop on Bee Colony Health.

Since 2013, the European Commission has restricted the use of three neonicotinoid insecticides as seed dressings on bee-attractive crops. Such crops represent an important source of forage for bees, which is often scarce in agro-ecosystems. However, this benefit has often been overlooked in the design of previous field studies, leaving the net impact of neonicotinoid treated crops on bees relatively unknown. Here, we determine the combined benefit (forage) and cost (insecticide) of oilseed rape grown from thiamethoxam-treated seeds on Bombus terrestris and Apis mellifera colonies. In April 2014, 36 colonies per species were located adjacent to three large oilseed rape fields (12 colonies per field). Another 36 were in three nearby locations in the same agro-ecosystem, but several kilometers distant from any oilseed rape fields. We found that Bombus colony growth and reproduction were unaffected by location (distant versus adjacent) following the two month flowering period. Apis colony and queen survival were unaffected. However, there was a small, but significant, negative relationship between honey and pollen neonicotinoid contamination and Apis colony weight gain. We hypothesize that any sublethal effects of neonicotinoid seed dressings on Bombus colonies are potentially offset by the additional foraging resources provided. A better understanding of the ecological and agronomic factors underlying neonicotinoid residues is needed to inform evidence-based policy.

Bumblebee colony development following chronic exposure to field-realistic levels of the neonicotinoid pesticide thiamethoxam under laboratory conditions

Neonicotinoid pesticides are used in agriculture to reduce damage from crop pests. However, beneficial insects such as bees can come into contact with these pesticides when foraging in treated areas, with potential consequences for bee declines and pollination service delivery. Honeybees are typically used as a model organism to investigate insecticide impacts on bees, but relatively little is known about impacts on other taxa such as bumblebees. In this experiment, we chronically exposed whole mature bumblebee (Bombus terrestris) colonies to field-realistic levels of the neonicotinoid thiamethoxam (2.4ppb & 10ppb) over four weeks, and compared colony growth under laboratory conditions. We found no impact of insecticide exposure on colony weight gain, or the number or mass of sexuals produced, although colonies exposed to 2.4ppb produced larger males. As previous studies have reported pesticide effects on bumblebee colony growth, this may suggest that impacts on bumblebee colonies are more pronounced for colonies at an earlier stage in the reproductive cycle. Alternatively, it may also indicate that thiamethoxam differs in toxicity compared to previously tested neonicotinoids in terms of reproductive effects. In either case, assessing bumblebee colony development under field conditions is likely more informative for real world scenarios than tests conducted in laboratory conditions.

Quantifying the food requirements and effects of food stress on bumble bee colony development

Agricultural intensification has led to a reduction in semi-natural areas and in the abundance of wild flowering plants, reducing the availability of floral resources upon which pollinating insects depend. This is widely accepted as one of the major drivers of pollinator declines, but few studies have directly addressed the effects of dietary restrictions on pollinator fitness. Here, we investigated the effects of restricting pollen and nectar supply on bumble bee (Bombus terrestris) colony growth, adult size and number. Colonies required up to 6 g pollen/1 g protein and 50 g sugar to establish a colony of 5 workers, and consumed in excess of 176 g pollen/31 g protein and 1,186 g sugar in their lifetime. Regardless of restrictions on pollen or nectar availability, colonies consumed a ratio of 1 g protein to ~43 g sugar, though free-flying colonies require proportionally more sugar to fuel foraging. Food-limited colonies from an early stage grew little with anything less than ad-lib nectar, while more-established colonies increased in weight even with low levels of nectar suggesting a shortage of resources in early spring may be most damaging to bumble bee colonies. Dietary restriction reduced the number of reproductives produced, but had variable effects on the size of workers and males. Nosema ceranae infection was included as a covariate in analyses and had a significant negative effect on colony growth. This study provides a base line for the developmental requirements of bumble bee colonies, and indicates the effects a resource deficit may have on their development and reproduction.

A new aspect of grassland vegetation dynamics: cyanobacterium colonies affect establishment success of plants

AbstractAimsCyanobacteria may have considerable effects on community functioning, mostly because they produce various metabolites that adversely affect other organisms. Here we synthesized existing knowledge about the effects of toxic cyanobacteria on the germination and growth of terrestrial plants. We also aimed to test the chemical effects of a Nostoc (Cyanobacteria) extract on the germination and growth of species of alkali habitats to investigate whether cyanobacteria can alter community structure and diversity via affecting the establishment success of plants.LocationCyanobacterium colonies from the Hortobágy National Park, east Hungary; indoor experiments at the University of Debrecen, Hungary.MethodsTo review the effects of toxic cyanobacteria on terrestrial plants, we conducted a literature search. To test these effects on native plants, field‐collected Nostoc colonies were used to prepare a cell‐free water extract, and treatments (watering with Nostoc extract and watering with tap water) were tested on 3 × 100 seeds of nine alkali grassland species. After 5 wk, seedling number, seedling length and fresh and dry weights were measured.ResultsWe collected data on the effects of cyanobacteria on 27 species, but they were mostly focused on crops irrigated with cyanobacteria‐containing water, not on floras native to natural ecosystems. In the germination experiment species identity and treatment had a significant effect on almost all variables, but their interaction only affected germination rate and fresh weight. Fresh weight decreased significantly only in the invasive Hordeum jubatum, but germination rate decreased significantly in five species.ConclusionsBased on our findings, terrestrial cyanobacterium colonies can affect the establishment success of grassland plants, through which they may be important in determining which species can be incorporated into the community. Thus, cyanobacteria might play an important role in shaping diversity, species composition and the structure of natural plant communities.

Review of field and monitoring studies investigating the role of nitro-substituted neonicotinoid insecticides in the reported losses of honey bee colonies (Apis mellifera).

The nitro-substituted neonicotinoid insecticides, which include imidacloprid, thiamethoxam and clothianidin, are widely used to control a range of important agricultural pests both by foliar applications and also as seed dressings and by soil application. Since they exhibit systemic properties, exposure of bees may occur as a result of residues present in the nectar and/or pollen of seed- or soil-treated crop plants and so they have been the subject of much debate about whether they cause adverse effects in pollinating insects under field conditions. Due to these perceived concerns, the use of the three neonicotinoids imidacloprid, clothianidin and thiamethoxam has been temporarily suspended in the European Union for seed treatment, soil application and foliar treatment in crops attractive to bees. Monitoring data from a number of countries are available to assess the presence of neonicotinoid residues in honey bee samples and possible impacts at the colony level and these are reviewed here together with a number of field studies which have looked at the impact of clothiandin on honey bees in relation to specific crop use and in particular with oilseed rape. Currently there is considerable uncertainty with regards to the regulatory testing requirements for field studies. Accordingly, a testing protocol was developed to address any acute and chronic risks from oilseed rape seeds containing a coating with 10 g clothianidin and 2 g beta-cyfluthrin per kg seeds (Elado®) for managed honey bee (Apis mellifera) colonies, commercially bred bumble bee (Bombus terrestris) colonies and red mason bees (Osmia bicornis) as a representative solitary bee species. This is described here together with a summary of the results obtained as an introduction to the study details given in the following papers in this issue.

Impacts of commercialization on the developmental characteristics of native Bombus terrestris (L.) colonies

Bombus terrestris (L.) is naturally distributed mainly in Europe, and since 1988, it has been used commercially as a valuable pollinator of greenhouse crops in many countries, far beyond its natural range. Although the possible ecological impacts of this invasive species have been intensely discussed with respect to hybridization, we know little about the consequences of this nearly 30-year period of commercialization. We examined and compared the developmental characteristics of native and commercial colonies and their first-generation hybrids under the same laboratory conditions. Young queens and males produced in both native and commercial colonies were mated to generate four genotype groups: Native × Native (N♀ × N♂), Native × Commercial (N♀ × C♂), Commercial × Commercial (C♀ × C♂), and Commercial × Native (C♀ × N♂). The commercial genotype produced significantly more gynes and workers than did the native genotype. However, average gyne number of N♀ × N♂ was not significantly different from the pooled N♀ × C♂ and C♀ × N♂. The commercial genotype constructed more egg cells in the first brood and commenced egg laying earlier. Hybridization between commercial and native genotypes generally resulted in intermediate expression of the colony traits. Our data suggest that the maternal genotype primarily determines these colony traits. Our results imply that hybridization with the commercial genotype affected some colony traits of native B. terrestris colonies.

How landscape, pollen intake and pollen quality affect colony growth in Bombus terrestris

Abundance and diversity of bumblebees have been declining over the past decades. To successfully conserve bumblebee populations, we need to understand how landscape characteristics affect the quantity and quality of floral resources collected by colonies and subsequently colony performance. We therefore investigated how amount and composition of pollen collected by buff-tailed bumblebee Bombus terrestris colonies was affected by the surrounding landscape (i.e. the proportion of forest, urban, semi-natural habitats) and how they were related to colony growth. Thirty B. terrestris colonies were placed at grassland sites differing in surrounding landscape. Colonies were established in spring when availability of flowering plants was highest, and their weight gain was monitored for 1 month. We additionally recorded the quantity and compared plant taxonomic composition and nutritional quality (i.e. amino acid composition) of pollen stored. Bumblebee colonies varied little in the pollen spectra collected despite differences in surrounding landscape composition. They collected on average 80 % of pollen from woody plants, with 34 % belonging to the genus Acer. Early colony growth positively correlated with total amount of woody pollen and protein collected and decreased with increasing proportions of semi-natural habitats and total amino acid concentrations. Our results suggest that woody plant species represent highly important pollen sources for the generalist forager B. terrestris early in the season. We further show that colony growth of B. terrestris is predominantly affected by the quantity, not quality, of forage, indicating that several abundant plant species flowering throughout the bumblebees’ foraging season may cover the colonies’ nutritional needs.

Monitoring the effects of thiamethoxam applied as a seed treatment to winter oilseed rape on the development of bumblebee (Bombus terrestris) colonies.

The development of bumblebee (Bombus terrestris audax) colonies that had foraged for 5 weeks on flowering winter oilseed rape grown from seed treated with thiamethoxam (as Cruiser OSR) was assessed (two control, one treated field). Colony development was evaluated by monitoring the colony mass, forager activity was assessed, both at the hive and within the crop, and the contribution of oilseed rape to the pollen stored within the colony was analysed. Pollen collected from the treated crop contained residues of 1.0 µg thiamethoxam kg(-1) and 3.0 µg CGA322704 (metabolite likely equivalent to clothiandin) kg(-1) , and nectar contained residues of 1.8 µg thiamethoxam kg(-1) and no metabolite. No residues of thiamethoxam or CGA322704 were detected in samples from the control fields. Up to 93% of bumblebee collected pollen sampled from within the colonies originated from oilseed rape, and B. terrestris were observed actively foraging on all the fields. Colonies on all three fields showed similar rates of mass gain during the exposure phase and comparable production of gynes and drones. B. terrestris colonies placed adjacent to a field of flowering oilseed rape grown from thiamethoxam-treated seed developed at a comparable rate with colonies placed adjacent to oilseed rape grown from untreated seed. © 2015 Society of Chemical Industry.

Insect pollination reduces yield loss following heat stress in faba bean (Vicia faba L.)

Global food security, particularly crop fertilization and yield production, is threatened by heat waves that are projected to increase in frequency and magnitude with climate change. Effects of heat stress on the fertilization of insect-pollinated plants are not well understood, but experiments conducted primarily in self-pollinated crops, such as wheat, show that transfer of fertile pollen may recover yield following stress. We hypothesized that in the partially pollinator-dependent crop, faba bean (Vicia faba L.), insect pollination would elicit similar yield recovery following heat stress. We exposed potted faba bean plants to heat stress for 5 days during floral development and anthesis. Temperature treatments were representative of heat waves projected in the UK for the period 2021–2050 and onwards. Following temperature treatments, plants were distributed in flight cages and either pollinated by domesticated Bombus terrestris colonies or received no insect pollination. Yield loss due to heat stress at 30°C was greater in plants excluded from pollinators (15%) compared to those with bumblebee pollination (2.5%). Thus, the pollinator dependency of faba bean yield was 16% at control temperatures (18–26°C) and extreme stress (34°C), but was 53% following intermediate heat stress at 30°C. These findings provide the first evidence that the pollinator dependency of crops can be modified by heat stress, and suggest that insect pollination may become more important in crop production as the probability of heat waves increases.

Body reserves influence allocation to immune responses in capital breeding female northern elephant seals

Summary Mounting an immune response requires substantial energy. Ecological immunology theory predicts allocation trade‐offs between reproductive effort and immune responses under conditions of energy limitation. Little is known about the impact of capital breeding strategies on energy allocation to immune function in mammals. Northern elephant seals (NES) forage in the marine environment, breed in dense terrestrial colonies and exhibit high rates of energy expenditure for lactation while fasting. Body reserves strongly influence reproductive effort and lactation requires elevation of plasma cortisol for energy mobilization. We characterized immune response by measuring a suite of immune markers including cytokines, an acute phase protein, and immunoglobulins early and late in breeding and moult haul‐outs in 197 samples from 129 female NES. We explored potential impacts of breeding, body condition and plasma cortisol on immune function. Immune responses were greater and more varied during breeding. Adiposity had positive associations with innate immune responses across all life‐history stages. Body mass had positive associations with both adaptive and innate immune responses early in fasts. Females with lower fat reserves showed reduced innate immune responses at the end of lactation. Immunoglobulin E, a marker of immune response to parasitic infection, exhibited a significant negative association with cortisol across all life‐history stages. These data suggest that breeding carries an immune cost and provide evidence for allocation trade‐offs between immune function and breeding effort. These trade‐offs may reflect a compromise between immune costs inherent in colonial breeding and energetic limitations that arise in use of capital breeding strategies. Variation in evidence for immunosuppressive effects of cortisol suggests that decoupling of these effects may be limited to specific aspects of the immune response during terrestrial fasting. Immune responses that are required for survival may be modulated relative to the energetic demands required for successful reproduction.

Colony and individual life‐history responses to temperature in a social insect pollinator

Summary Pollinating insects are of major ecological and commercial importance, yet they may be facing ecological disruption from a changing climate. Despite this threat, few studies have investigated the life‐history responses of pollinators to experimentally controlled changes in temperature, which should be especially informative for species with complex life histories such as eusocial insects. This study uses the key pollinator Bombus terrestris, a eusocial bumblebee with an annual colony cycle, to determine how temperature affects life‐history traits at both individual and colony levels. In two laboratory experiments, we reared B. terrestris colonies at either 20 or 25 °C, and measured differences in a set of life‐history traits including colony longevity, queen longevity, worker longevity, production of workers, production of sexuals (queen and male production) and growth schedule, as well as effects on thermoregulatory behaviours. Higher rearing temperature had a significant positive effect on colony longevity in one of the two experiments but no significant effects on queen or worker longevity. Higher rearing temperature significantly increased colony size but did not affect the timing of peak colony size. It was also associated with significantly higher queen production but had no effect on the production of workers or males or the timing of male production. Higher temperature colonies exhibited significantly more wing fanning by workers and significantly less wax canopy construction. Hence, an increase in rearing temperature of a few degrees increased colony longevity, colony size and queen production. However, individual longevity was not affected and so may have been buffered by changes in costly thermoregulatory behaviours. We conclude that eusocial insects may show complex phenotypic responses to projected temperature increases under climate change, including effects on productivity and reproduction at the colony level. Such effects should be considered when predicting the impact of climate change on the provision of essential pollination services.

Effects of dietary lambda-cyhalothrin exposure on bumblebee survival, reproduction, and foraging behavior in laboratory and greenhouse

Bumblebees of Bombus terrestris are indispensible pollinators for ecosystems and for various agricultural crops. Unfortunately, bumblebees are challenged by various stress factors including insecticide applications. Today sublethal effects of various insecticides need to be thoroughly investigated to allow their combined use with pollinators and other beneficial organisms. In this study, we used lambda-cyhalothrin as a model pyrethroid insecticide and investigated lethal and sublethal effects by different dilutions, ranging from 1/10 to 1/100 of its maximum field recommended dosage (MFRC, 37.5 ppm), with the use of a chronic toxicity tests in the laboratory and in flight cages in the greenhouse. In the laboratory, small microcolonies with five bumblebee workers with one being pseudo-queen were used, while in the greenhouse we used queen-right mini-hives where the bumblebees need to fly for pyrethroid-contaminated food. We observed strong sublethal effects in the laboratory with treatments of 1/10 and 1/20 of the MFRC: the nest reproduction was reduced by 49 and 32 %, respectively, and the sugar water consumption by 36 %. With free-flying bumblebees, the toxic effects at 1/10 of the MFRC were more pronounced. A mortality of 88 ± 8 % was observed after only 2 weeks, being twice the mortality in the laboratory microcolonies test (43 ± 11 %). Besides, it should be mentioned that in the greenhouse experiment all queens were dead and most of the workers showed signs of incoordination and convulsion and gradually became apathetic. In conclusion, our results demonstrated the pyrethroid lambda-cyhalothrin with a range of lethal and sublethal effects, both crucial for the development and survival of the B. terrestris colonies. Moreover, this study supports the demand to test insecticide compounds on their safety, especially when the bees have to perform complex tasks such as foraging for their food.