Pollen Foragers Research Articles

Fuel provisioning for pollen collection by solitary bee, Andrena taraxaci orienticola

Female solitary bees collect pollen for their brood at the expense of using sugars in the nectar as fuel for flight. When flowers provide both pollen and nectar, solitary bees can refuel from the flowers to sustain pollen foraging. However, not all flowers provide both pollen and nectar. This study investigates how females of the solitary bee Andrena taraxaci orienticola secure fuel to sustain pollen foraging when flowers provide scarce nectar. By using DNA barcoding, we identified the Japanese dandelion Taraxacum platycarpum as their primary food source. This dandelion produces almost no nectar in the early morning when female bees collect almost no nectar but collect substantial amounts of pollen. We also found that these bees leave the nest with significantly more nectar at the first flight of the day than at later flights. When we restricted their fuel load by preventing nectar feeding, significantly more females failed to collect pollen on the first flight of the following day. These results suggest females hold back some part of the nectar collected at the end of a day’s foraging and use it the following morning as fuel to sustain pollen foraging from flowers providing little nectar.

Foraging task specialization in honey bees (Apis mellifera): the contribution of floral rewards on the learning performance of pollen and nectar foragers.

Social insects live in communities where cooperative actions heavily rely on the individual cognitive abilities of their members. In the honey bee (Apis mellifera), the specialization in nectar or pollen collection is associated with variations in gustatory sensitivity, affecting both associative and non-associative learning. Gustatory sensitivity fluctuates as a function of changes in motivation for the specific floral resource throughout the foraging cycle, yet differences in learning between nectar and pollen foragers at the onset of food collection remains unexplored. Here, we examined nectar and pollen foragers captured upon arrival at food sources. We subjected them to an olfactory PER conditioning using a 10% sucrose solution paired (S10%+P) or unpaired (S10%) with pollen as a co-reinforcement. For non-associative learning, we habituated foragers with S10%+P or S10%, followed by dishabituation tests with either a 50% sucrose solution paired (S50%+P) or unpaired (S50%) with pollen. Our results indicate that pollen foragers show lower performance than nectar foragers when conditioned with S10%. Interestingly, performance improves to levels similar to those of nectar foragers when pollen is included as a rewarding stimulus (S10%+P). In non-associative learning, pollen foragers tested with S10%+P displayed a lower degree of habituation than nectar foragers and a higher degree of dishabituation when pollen was used as the dishabituating stimulus (S10%+P). Altogether, our results support the idea that pollen and nectar honey bee foragers differ in their responsiveness to rewards, leading to inter-individual differences in learning that contribute to foraging specialization.

Influence of Pollen Trapping on Honey Production of Apis mellifera L. (Hymenoptera: Apidae) High Strength Colony under Mustard Flowering Season

Background: Bee colonies are fed with pollen supplemented diets to sustain them during unfavourable conditions. These pollen loads are collected from foraging bees using pollen traps mounted on colonies. However, intensive trapping may interfere with honey production. Therefore, a need was felt to regulate frequency of trapping to ensure sufficient honey storage in the colonies. Methods: In this field based study, performed under mustard flowering seasons of 2016-17 and 2017-18, traps were mounted on colonies with varying frequencies namely, daily, alternate day, third day, weekly and control under two different mustard flowering locations in Haryana. Honey area and proportion of incoming pollen foragers were recorded from tested colonies. Result: Daily trapping triggered 29% bees for pollen foraging that contributed to considerable reduction in the honey area (-103 cm2). In contrast, colonies with weekly trapping regimes exhibited large honey area (4054 cm2). Among the locations, large honey area was stored in the weekly trapping colonies at Kaul, Haryana than Hisar, Haryana.

First Report of Nesting Habits, Nest Architecture and Foraging Behaviour of the Stingless bee, Tetragonula (Tetragonula) ruficornis (Smith) (Hymenoptera: Apidae: Meliponini) from India

The present study aimed to understand nesting habits, nest architecture, and foraging behavior of the stingless bee, Tetragonula (Tetragonula) ruficornis Smith, a widespread species in the north Indian plains from Varanasi to Punjab. Among the 47 wild, unmanaged colonies studied, 27 were situated in the cavities of tree trunks and 20 in the cavities of building walls. The internal nest structure revealed that brood cells were arranged in clusters at the center of the cavity with encircling pollen and honey pots. Further, the natural nesting cavity’s total length, width, and height varied from 105 to 168 mm, 129 to 216 mm, and 283 to 472 mm, respectively. The foraging activity of outgoing and incoming foragers of T. ruficornis varied significantly during different hours of the day, across the seasons and prevailing weather conditions. Further, activity was limited to daytime from 08:00 to 18:00 h, with peak activity of outgoing and incoming forager bees between 10:00 and 12:00 h during all seasons. Irrespective of seasons, the foraging activity of outgoing, pollen, and nectar foragers was at its maximum at 12:00 h. However, foraging ceased during December and January due to low temperatures, while peak activity was observed during April. The foraging pattern showed a significant positive correlation with mean monthly maximum and minimum temperatures and a significant negative correlation with relative humidity. The current investigation delivers crucial information on nest architecture and foraging behavior, which could be exploited for designing bee hives and utilization in directed pollination services.

Modelling foraging strategies of honey bees as agents in a dynamic landscape representation

Introduction: Both intrinsic colony mechanisms and external environmental variables affect the honey bee colony development rates and response and a key aspect of this is the use of resources within the landscape by honey bees. Although several models have been developed to explore the foraging behaviour of bees, none fully considered the spatial and temporal dynamics of landscape resources and the role of the colony in the process. Methodology: Here, we introduce a new honey bee foraging model being developed as a part of the ApisRAM honey bee colony model. Based on agent-based modelling, we used a dynamic ALMaSS landscape model enhanced with floral resource modelling to assess the impacts of weather conditions and resource availability on the possible foraging behaviour of honey bees. Several possible mechanisms (defined, based on honey bee traits) for scouting and foraging were investigated, separately for nectar and pollen collection, including prioritising foraging polygons for nectar foraging according to their distance to the colony, the quality or the energetic efficiency and, for pollen foraging, according to their distance to the colony and pollen quantity. Results: If model foraging bees prioritised the polygons, based on their distance from the colony, the number of unsuccessful flights increased compared to other tested strategies and the total amount of sugar collected showed a high variability. Contrary to expectations, the energetic efficiency strategy did not provide the colony with the highest amount of sugar. Overall, the tested strategies provide different outcomes on the collection of resources, the number of performed flights and their success rate, evidencing that the model's outcome at the colony level arises from the individual types of behaviour. Conclusions and Relevance: Variability in the mass of collected nectar and pollen was found mostly when scout bees applied the distance strategy. This higher variability in sugar collection means that model bees were not able to find the most profitable foraging sites at the landscape level, but only at the local level. Other strategies showed less dependence on the surrounding landscape (i.e. quality or random), but it comes at a cost (i.e. lower production for both nectar and pollen collection). These outputs help us evaluate which strategies could be used for future model development and confirm the models' ability to create dynamic responses. These responses at the colony level were only possible thanks to the implementation of a dynamic landscape model and dynamic spatiotemporal resource model, as well as implementing a social communication mechanism for bees to share information about the resources. Plant nectar production and quality information is essential to predict honey bee foraging distribution. In future model development, the implementation of pollen quality should also be explored to evaluate if it influences the overall pollen collection.

Honey bee colonies change their foraging decisions after in-hive experiences with unsuitable pollen.

Pollen is the protein resource for Apis mellifera and its selection affects colony development and productivity. Honey bee foragers mainly lose their capacity to digest pollen, so we expect that those pollen constituents that can only be evaluated after ingestion will not influence their initial foraging preferences at food sources. We predicted that pollen composition may be evaluated in a delayed manner within the nest, for example, through the effects that the pollen causes on the colony according to its suitability after being used by in-hive bees. To address whether pollen foraging is mediated by in-hive experiences, we conducted dual-choice experiments to test the avoidance of pollen adulterated with amygdalin, a deterrent that causes post-ingestion malaise. In addition, we recorded pollen selection in colonies foraging in the field after being supplied or not with amygdalin-adulterated pollen from one of the dominant flowering plants (Diplotaxis tenuifolia). Dual-choice experiments revealed that foragers did not avoid adulterated pollens at the foraging site; however, they avoided pollen that had been offered adulterated within the nest on the previous days. In field experiments, pollen samples from colonies supplied with amygdalin-adulterated pollen were more diverse than controls, suggesting that pollen foraging was biased towards novel sources. Our findings support the hypothesis that pollen assessment relies on in-hive experiences mediated by pollen that causes post-ingestive malaise.

Supplementing honey bee (Hymenoptera: Apidae) colonies with pollen increases their pollinating activity on nectariferous crops with anthers isolated from stigmas.

The western honey bee (Apis mellifera L.) is the most globally used managed pollinator species, but it can have limited pollinating activity on nectariferous crops displaying anthers isolated from stigmas, i.e., when anthers are spatially or temporally separated from stigma within or between flowers. We supplemented honey bee colonies with pollen in the combs or in paste form laid on top of the hive frames to test if these treatments could reduce their pollen foraging and increase their pollinating activity in a monoecious and nectariferous cultivar of cantaloupe melon (Cucumis melo L.), in comparison with control colonies not supplemented. We recorded the pollen forager density per flower, the number of pollen grains deposited per stigma and their resulting fruit set, seed set and fruit mass, before and after the colony pollen supplementations. The number of pollen grains deposited by honey bees on stigmas increased gradually after pollen supplementation in the combs. But pollen foraging decreased only moderately, and no effect could be observed on any yield component except the seed set. On the other hand, there was no effect of the pollen paste laid on top of the frames either on stigmatic pollen loads, on colony pollen foraging or on any yield component. Supplementing honey bee colonies with pollen in the combs can therefore be an effective means for increasing their pollinating activity in nectariferous crops displaying anthers isolated from stigmas, e.g., Amaryllidaceae, Apiaceae, Cucurbitaceae, avocado, all hybrid seed productions. The context for the potential use of pollen substitutes is discussed.

Passively crowdsourcing images online for measuring broad-scale fly (Diptera) floral interactions and biodiversity

Flies (Diptera) represent one of the largest and most important groups of pollinators on the planet; however, little is known about the interactions between flies and flowers compared to well-known pollinators, such as bees. Understanding pollinator assemblages is key to conserving biodiversity and ecosystem services, but monitoring Diptera is time and cost intensive. Using photographs of blooming flowers taken by photographers worldwide and uploaded on internet repositories, we built a dataset of 1,275 images of fly-flower visitations and extracted fly and flower taxonomic information, flower characteristics (shape and color), and fly activity (pollen carrying and foraging). The resulting dataset shows taxonomic and other biases but can still provide an initial overview of factors that affect pollination by Diptera. We identified 22 families of flies, with blow flies (Family Calliphoridae) most represented (29%) and 63 families of flowers, with Asteraceae (42%) and Apiaceae (21%) as the most common. Using logistic regression, we found that the likelihood of flies carrying pollen was determined by the interaction between flower color and shape: pollen-carrying was more likely when elongate cluster flowers were green-yellow. Fly foraging on flowers was determined by flower color: flies were more likely to feed on green-yellow and white flowers. Overall, Syrphidae flies were less likely to forage for nectar than non-Syrphidae, but were more likely to carry pollen. While biases exist in crowdsourced data, we show that data from photographs collected through citizen science offers potentially valuable information for monitoring pollinator-flower interactions and augment our understanding of pollinator ecology in an era of global insect declines.

Honeybees’ foraging choices for nectar and pollen revealed by DNA metabarcoding

Honeybees are the most widespread managed pollinators of our food crops, and a crucial part of their well-being is a suitable diet. Yet, we do not know how they choose flowers to collect nectar or pollen from. Here we studied forty-three honeybee colonies in six apiaries over a summer, identifying the floral origins of honey and hive-stored pollen samples by DNA-metabarcoding. We recorded the available flowering plants and analyzed the specialized metabolites in honey. Overall, we find that honeybees use mostly the same plants for both nectar and pollen, yet per colony less than half of the plant genera are used for both nectar and pollen at a time. Across samples, on average fewer plant genera were used for pollen, but the composition was more variable among samples, suggesting higher selectivity for pollen sources. Of the available flowering plants, honeybees used only a fraction for either nectar or pollen foraging. The time of summer guided the plant choices the most, and the location impacted both the plants selected and the specialized metabolite composition in honey. Thus, honeybees are selective for both nectar and pollen, implicating a need of a wide variety of floral resources to choose an optimal diet from.

Stingless bee (Tetragonula carbonaria) foragers prioritise resin and reduce pollen foraging after hive splitting

Stingless bees are increasingly in demand as pollinators in agricultural crops within the tropics and subtropics. Hive splitting, where one strong managed hive is “split” into two independent daughter colonies, is commonly used to increase hive numbers. However, how splitting impacts foraging behaviour or the time taken for the colony to recover from splitting has not previously been studied. We assessed the impact of splitting on the foraging behaviour of Tetragonula carbonaria colonies. The number of returning forager trips and foraged proportions of pollen, nectar and resin was observed after splitting and compared with unsplit control hives over a 31-day period. We found the total amount of returning foragers in split hives reduced to less than a third of unsplit hives (unsplit median, 184–288; split median, 19–61) for 16 days, while returning nectar (unsplit median, 89–147; split median, 16–28) and pollen (unsplit median, 55–155; split median, 1–7) foragers reduced to less than a quarter of unsplit hives for 9 days following splitting. After 31 days, the number of total, nectar and pollen foraging trips had still not recovered to levels observed in unsplit hives. Resin foraging trips however were not significantly different to unsplit hives after only 10 days. The colony foraging allocation to resin (proportion) increased after splitting and was significantly higher in split hives until day 16 of the experiment (unsplit median, 0.03–0.05; split median, 0.10–0.16). Our results demonstrate that split colonies prioritise resin collection and foraging on floral resources is reduced. We recommend that hives should not be split within 31 days of being used for pollination, and resin sources should be conserved where possible and supplemented where necessary due the vital roles of the resource.

Changes in resource perception throughout the foraging visit contribute to task specialization in the honey bee Apis mellifera

Division of labor is central to the ecological success of social insects. Among foragers of the honey bee, specialization for collecting nectar or pollen correlates with their sensitivity to sucrose. So far, differences in gustatory perception have been mostly studied in bees returning to the hive, but not during foraging. Here, we showed that the phase of the foraging visit (i.e. beginning or end) interacts with foraging specialization (i.e. predisposition to collect pollen or nectar) to modulate sucrose and pollen sensitivity in foragers. In concordance with previous studies, pollen foragers presented higher sucrose responsiveness than nectar foragers at the end of the foraging visit. On the contrary, pollen foragers were less responsive than nectar foragers at the beginning of the visit. Consistently, free-flying foragers accepted less concentrated sucrose solution during pollen gathering than immediately after entering the hive. Pollen perception also changes throughout foraging, as pollen foragers captured at the beginning of the visit learned and retained memories better when they were conditioned with pollen + sucrose as reward than when we used sucrose alone. Altogether, our results support the idea that changes in foragers' perception throughout the foraging visit contributes to task specialization.

Foraging distances, habitat preferences and seasonal colony performance of honeybees in Central European forest landscapes

Abstract Unmanaged forest is considered as native habitat of the Western honeybee Apis mellifera and is assumed to provide important pollen and nectar sources. However, resource supply might be spatially and temporally restricted in managed forests and landscape‐scale studies in European forest regions are currently lacking. Capitalizing on a unique communication behaviour, the waggle dance, we investigated honeybee foraging in a deciduous forest region in southern Germany. We analysed 2022 waggle dances performed by bees of 12 colonies placed in the centre of landscapes with varying degree of forest cover (50%–99% at a 2‐km radius) from March to August 2019, thereby identifying foraging distances and habitat preferences over almost an entire foraging season. By connecting dance information with colony weight recordings, we assessed the role of landscape composition and the contribution of different habitat types to colony weight gain. Foraging distances generally increased with the amount of forest in the surrounding landscape pointing to inferior food resources in the forest. Yet, this effect strongly depended on the season and was more pronounced for pollen than for nectar foraging. Even though colonies in forest‐dominated landscapes had to fly further, colony weight was not significantly affected by forest cover. Compared to expectations based on the proportions of different habitats, colonies foraged more frequently in grassland and cropland than in deciduous and coniferous forests, with late summer being an especially difficult period for pollen foraging in forests. During a phase of colony weight gain in early summer, the use of forests for nectar/honeydew foraging was close to the expectation, highlighting forests as an important complementary source of carbohydrates during short periods of the year. Policy implication. The ecological and economic value of managed forest as habitat for honeybees could be significantly increased by the continuous provision of floral resources, especially for pollen foraging. Therefore, we recommend diversifying forest stands with insect‐pollinated trees, permitting secondary successions in forest gaps, and at larger scales, creating forest landscapes with high habitat diversity. This will not only help native, wild‐living honeybees and beekeepers' colonies residing in forest areas but will also foster social bees in general.

Proboscis Extension Response of Three Apis mellifera Subspecies toward Water and Sugars in Subtropical Ecosystem

The proboscis extension response (PER) assay revealed the responsiveness of three subspecies of the honeybee Apis mellifera [A. m. jemenitica (AMJ), A. m. carnica (AMC), and A. m. ligustica (AML)] to water and different concentrations (0.00001, 0.0001, 0.001, 0.01, 0.1, 0.5, 1.0, and 1.5 M) of three sugars (fructose, glucose, and sucrose) during the summer and fall seasons. The tested bee subspecies showed significantly different PERs to sugar types across the seasons. The water responsiveness of AMJ, a native bee subspecies, was significantly lower than that of AMC and AML, which showed an equally higher water response in both seasons. During the summer season, AMJ and AMC were equally responsive to each sugar type at all tested concentrations. AML was relatively less responsive to glucose at 0.001, 0.001, 0.01, 0.1, 0.5, and 1.0 M than to fructose and sucrose during the summer season. During the fall season, AMJ was equally responsive to glucose and sucrose at all tested concentrations but showed a significantly different response between fructose and sucrose at 0.001, 0.01, 0.1, 0.5, and 1.0 M concentrations. The PER of AMJ to fructose was lower than that of glucose and sucrose. AMC was equally responsive to all tested sugars at all concentrations, and AML showed a differential response between glucose and sucrose at different concentrations during the fall season. The inter-specific species comparisons revealed that all tested subspecies were equally responsive to fructose at all tested concentrations, and AMJ was more responsive to glucose and sucrose than AMC and AML during both seasons. AMC and AML showed no differences in PER to glucose and sucrose in either season. The AMJ, AMC, and AML nectar and pollen foragers showed no significant differences in PER to glucose and sucrose. The AMC nectar foragers were highly responsive to sucrose than pollen foragers at higher sucrose concentrations (0.1, 0.5, 1.0, and 1.5 M). The AML (nectar forager vs. pollen forgers) showed identical PER to sucrose and glucose but a higher response of nectar foragers to high glucose concentrations (0.5, 1.0, and 1.5 M) than pollen foragers. For water responsiveness, AMJ nectar and pollen foragers showed similar PER to water, whereas AMC and AML pollen foragers were significantly more responsive to water than nectar foragers.

Diversity, abundance and foraging behaviour of pollinators in early sown rapeseed-mustard genotypes

A study was carried out on the diversity, abundance and foraging behaviour of pollinators in early sown rapeseed-mustard genotypes through observing a total of 17 insect species visited flowers of early sown genotypes viz., 9 Hymenopterans, 3 Dipterans, 4 Lepidopterans, and 1 Coleopteran. The abundance (bees/m2/5 min) of A. florea was highest (8.5) followed by A. mellifera (3.9), A. dorsata (3.6) and A. cerana (3.1). The abundance of bee species was maximum (5.6 bees/m2/5 min) in genotypes TH 68 and SANGAM. A. cerana foraged a maximum number of flowers per minute (18.20) followed by A. dorsata (17.57), A. mellifera (17.32) and A. florea (6.45). The foraging rate (flowers/min) of all bee species was maximum (14.98 and 14.90) in genotypes TH 68 and SANGAM. Time spent per flower (sec) was maximum (5.3) by A. florea followed by A. dorsata (1.7), A. mellifera (1.6) and A. cerana indica (1.3). The maximum time spent per flower by all bee species (2.6) was in genotype PDZ 9. Nectar or pollen gatherers were maximum in A. dorsata (37.8% and 25.6%, respectively), while both nectar and pollen gatherers were maximum in A. cerana (45.3%). Nectar foraging, pollen foraging and both nectar and pollen foraging were maximum at peak flowering (36.0%), peak flowering (23.8%) and flowering cessation (42.9%), respectively. Out of the total foragers, top workers were maximum in A. dorsata (97.8%), while side workers were maximum in A. florea (41.0%).

Role of Entomophily and Artificial Pollination in Enhancing Quality and Yield of Seed Onion (Allium cepa L.) in Indian Himalayas

Abstract Onion (Allium cepa L.) is a highly cross pollinated crop that needs insect pollination (entomophily) for optimum seed set. In the present study, more than 120 insect species were noted to visit onion flowers, out of which fifty-nine species were collected through in-situ sampling technique and identified up to species level. The Indian bee (Apis cerana indica) was the most abundant insect pollinator visiting onion flowers in the study location. The pollination behaviour and foraging activity of A. c. indica were assessed, and the pollen foragers were observed to be swift flyers visiting a significantly higher number of flowers per minute during the peak flowering period and spending less time per flower (3 seconds) to collect nectar from deep seated nectaries of the flowers. The seed yield enhancement assessed through entomophily and artificial pollination methods showed that the open pollinated flowers recorded the highest yield statistically, followed by A. c. indica and A. mellifera pollinated flowers. However in artificial pollination treatments, sponge puff pollinated flowers recorded significantly high seed yield per hectare and percentage seed set per umbel, followed by camel brush, hand gloves (cloth) and hand gloves (rubber). In conclusion, all the cross pollination treatments were statistically significant on the closed pollination treatment concerning to the entire yield parameters calculated.

Dance-communicated distances support nectar foraging as a supply-driven system.

Much like human consumers, honeybees adjust their behaviours based on resources' supply and demand. For both, interactions occur in fluctuating conditions. Honeybees weigh the cost of flight against the benefit of nectar and pollen, which are nutritionally distinct resources that serve different purposes: bees collect nectar continuously to build large honey stores for overwintering, but they collect pollen intermittently to build modest stores for brood production periods. Therefore, nectar foraging can be considered a supply-driven process, whereas pollen foraging is demand-driven. Here we compared the foraging distances, communicated by waggle dances and serving as a proxy for cost, for nectar and pollen in three ecologically distinct landscapes in Virginia. We found that honeybees foraged for nectar at distances 14% further than for pollen across all three sites (n = 6224 dances, p < 0.001). Specific temporal dynamics reveal that monthly nectar foraging occurs at greater distances compared with pollen foraging 85% of the time. Our results strongly suggest that honeybee foraging cost dynamics are consistent with nectar supply-driven and pollen demand-driven processes.

Ambophily in Olea ferruginea: a transitional state in the pollination syndrome

A number of plants species believed to be wind pollinated (anemophilous) are actually pollinated both by wind as well as insects (ambophily) because all the traits of the two pollination modes have not evolved simultaneously. Comparatively few angiosperms exhibit ambophily and the significance of such a mechanism is not fully understood. During the present investigation, ambophily was studied in Olea ferruginea, over a period of three years. It is an andromonoecious and out-crossing tree species of the olive complex. The species is predominately pollinated by wind because it shows fruit set even when the insect pollinators were excluded. Moreover, a substantial amount of pollen was observed on the body parts of insect visitors and, comparatively, fruit set was enhanced in open-pollinated flowers receiving insect visitors. Floral structure of O. ferruginea displays floral traits favoring both wind and insect pollination. Furthermore, the flowers of this species were found to be visited by 20 insect species classified under three orders with Diptera and Hymenoptera being the leading pollen foragers. The results of linear regression of the hanging slide experiment showed that the dispersal of pollen grains decreased significantly with increasing distance from the canopy and the pollen density increased significantly with an increase in insect activity. The present work provides an insight to understand the ecological and evolutionary adaptations and consequences of spatio-temporal variation in plant – pollinator interactions. It is, therefore, useful for addressing both basic and applied questions in community structure and function including the evolution of floral traits, reproductive assurance, and the development of optimal conservation strategies.

Differences in olfactory sensitivity and odor detection correlate with foraging task specialization in honeybees Apis mellifera

Division of labor is central to the ecological success of social insects. Among honeybees foragers, specialization for collecting nectar or pollen correlates with their sensitivity to gustatory stimuli (e.g. sugars). We hypothesize that pollen and nectar foragers also differ in their sensitivity to odors, and therefore in their likelihood to show odor-mediated responses. To assess foragerś sensitivity to natural odors, we quantified the conditioning of the proboscis extension reflex (PER) to increasing concentrations (0.001; 0.01; 0.1; 1 M) of linalool or nonanal. Furthermore, we compared electroantennogram (EAG) recordings to correlate bees’ conditioned responses with the electrophysiological responses of their antennae. To further explore differences of the antennal response of foragers in relation to task-related odors, we registered EAG signals for two behaviorally ‘‘meaningful’’ odors that mediate pollen collection: fresh pollen odors and the brood pheromone (E)-β-ocimene. Pollen foragers performed better than nectar foragers in PER conditioning trials when linalool and nonanal were presented at low concentrations (0.001, 0.01 M). Consistently, their antennae showed stronger EAG signals (higher amplitudes) to these odors, suggesting that differences in sensitivity can be explained at the periphery of the olfactory system. Pollen and nectar foragers detect pollen odors differently, but not (E)-β-ocimene. Pollen volatiles evoked EAG signals with hyper and depolarization components. In pollen foragers, the contribution of the hyperpolarization component was higher than in nectar foragers. We discuss our findings in terms of adaptive advantages to learn subtle olfactory cues that influence the ability to better identify/discriminate food sources.

A fungal-based pesticide does not harm pollination service provided by the African stingless bee Meliponula ferruginea on cucumber (Cucumis sativus)

Stingless bees (Apidae: Meliponini) provide pollination services to crops and produce high–quality honey. The application of agrochemicals during the management of crop pests is an increasing threat to pollinators and the ecosystem services they provide. Biopesticides are considered as better alternatives; however, there is limited evidence of their impact on stingless bees. We evaluated the effect of the most widely used African fungal biopesticide (Metarhizium anisopliae ICIPE 69) on mortality, foraging behavior and pollination success of the African stingless bee Meliponula ferruginea under semi-field conditions. Colonies of M. ferruginea were introduced into four 24 m2 greenhouse compartments containing blooming cucumber (Cucumis sativus) plants. Cucumber plants were sprayed with a suspension of the biopesticide alongside a sterile 0.05% Triton–100–X (control). The experiment was repeated three times during different cucumber growing seasons. Biopesticide application did not significantly affect M. ferruginea mortality, flight activity, flower visitation, pollen foraging, C. sativus fruit set or C. sativus yield. Forager bees acquired a high number of conidia (7,600 ± 54 conidia /bee) immediately after biopesticide application; however, a significant decline was observed in the subsequent days. Conidial persistence and viability on plant surfaces declined significantly with days. There was no correlation between conidial acquisition and pollen load by forager bees (657 ± 29 pollen/bee). This study demonstrates that M. anisopliae ICIPE 69 did not negatively impact M. ferruginea mortality, pollination behaviour and success, and can therefore be safely used in stingless bee–dependent crop systems.

Colony-Level Viral Load Influences Collective Foraging in Honey Bees.

Nutrition is an important component of social insect colony health especially in the face of stressors such as parasitism and viral infections. Honey bees are known to preferentially select nectar and pollen based on macronutrient and phytochemical contents and in response to pathogen loads. However, given that honey bees live in colonies, collective foraging decisions may be impacted directly by forager infection status but also by colony health. This field experiment was conducted to determine if honey bee viral infections are correlated with pollen and nectar foraging and if these associations are impacted more by colony or forager infection. By comparing regressions with and without forager and colony variables and through structural equation models, we were able to determine the relative contributions of colony and forager virus loads on forager decisions. We found that foragers had higher numbers and levels of BQCV and CBPV but lower levels of DWV viruses than their respective colonies. Overall, individuals appeared to forage based a combination of their own and colony health but with greater weight given to colony metrics. Colony parasitism by Varroa mites, positively correlated with both forager and colony DWV-B levels, was negatively associated with nectar weight. Further, colony DWV-B levels were negatively associated with individually foraged pollen protein: lipid ratios but positively correlated with nectar weight and sugar content. This study shows that both colony and forager health can simultaneously mediate individual foraging decisions and that the importance of viral infections and parasite levels varies with foraging metrics. Overall, this work highlights the continued need to explore the interactions of disease, nutrition, and genetics in social interactions and structures.