Pollen Collection Research Articles

Foraging patterns of bees on watermelon (<em>Citrullus lanatus</em> Thunb.) flowers in Panama

Watermelon is one of the most important fruit crops in the world, but their flowers require bees for pollination. In this study we determine bee species visiting watermelon flowers, their daily visits and the resource they forage during 84 observation days on crops in Los Santos, Panama. Native bees, especially stingless bees represented most of the visits, so they probably play a very important role on the pollination of the crops within the zone. The most frequent bee species visiting flowers were N. perilampoides (58.7%), A. mellifera (23%), and P. peckolti (4%). Most of the bees foraged nectar, with very similar numbers between staminate and pistillate flowers. Honeybees dedicated almost half of their visits (47.7%) for pollen collection, and made most of their daily visits between 7:00 and 8:00 hours, whereas stingless bees visits picked up between 8:00 and 9:00 hours. Nectar visits were shorter than pollen visits, and overall, honeybees made the shortest visits to watermelon flowers. We found significant differences in the daily foraging patterns between bee species foraging for resources during the 84 observation period (Friedman P<0.05). We also found bee characteristics (size, color and sociability) and hour of the day significantly influenced flower visits for resources (GLMM P<0.05). Our results can be useful for predicting behavior of some of the Central American bee species, and managing and protecting those species, and improving fruit production in local watermelon crops.

Individual bee foragers are less‐efficient transporters of pollen for plants from which they collect the most pollen in their scopae

Bees provision most of the pollen they remove from anthers to their larvae and transport only a small proportion to stigmas, which can negatively affect plant fitness. Though most bee species collect pollen from multiple plant species, we know little about how the efficiency of bees' pollen transport varies among host plant species, or how it relates to other aspects of generalist bee foraging behavior that benefit plant fitness, such as specialization on individual foraging bouts. We compared the pollen collected and transported by three bee species for 46 co-occurring plant species. Specifically, we compared the relative abundance of pollen taxa in individual bees' scopae, structures where bees store pollen to provision larvae, with the relative abundance of pollen taxa on the rest of bees' bodies, which is more likely to be transferred to stigmas. Bees carried five times more pollen grains in their scopae than elsewhere on their bodies. Within foraging bouts, bees were relatively specialized in their pollen collection, but transported proportionally less pollen for the host plants on which they specialized. Across foraging bouts, two bee species transported proportionally less pollen for some of their host plants than for others, though differences didn't consistently follow the same trend as at the foraging bout scale. Our results suggest that foraging bout specialization, which is known to reduce heterospecific pollen transfer, also results in less efficient pollen transport. Thus, bee foragers that visit predominantly one plant species may have contrasting effects on that plant's fitness. This article is protected by copyright. All rights reserved.

Pollenkitt is associated with the collectability of Malvoideae pollen for corbiculate bees

Pollen grains of Malvoideae (Malvaceae) which corbiculate bees cannot collect constitute a floral filter that excludes pollen-collecting bumble bees and honey bees from exploiting pollen resources. Although large, spiny pollen grains are in fact harder to compact for collection by corbiculate bees, pollen morphology (e.g., grain diameter, spine length) is not by itself a reliable indicator of pollen collectability. In this study, we discovered that two Malvoideae species, Anoda cristata and Malope trifida, possess large, spiny pollen grains that can be groomed and collected by corbiculate bees. To gain insight into the underlying cause of collectability of Malvoideae pollen, we tested pollen adhesion to bumble bee setae and found that significantly less of the collectable pollen grains of A. cristata and M. trifida adhere to bees’ setae compared to uncollectable pollen grains of Hibiscus trionum. As the primary mediator of pollen adhesion is pollenkitt, a viscous lipid-rich substance covering pollen of zoophilous plants, we examined the surface of uncollectable and collectable Malvoideae pollen using cryo-SEM. Fresh pollen grains were abundantly covered with pollenkitt that also coated the long spines and formed liquid bridges between the grains. Washing pollen with hexane removed all pollenkitt, whereas washing pollen with water only removed pollenkitt on the collectable pollen grains of M. trifida, but not the uncollectable pollen grains of Hibiscus syriacus. We hypothesise that pollenkitt composition differs between Malvoideae species with uncollectable and collectable pollen. Specific pollenkitt properties might elicit excessive viscidity which affects adhesion to insect visitors but prevents pollen collection by corbiculate bees.

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.

Artificial Pollination Technologies: A Review

Pollination is critical for the production of many crops, and both insect- and wind-based pollination systems are increasingly disrupted by bloom asynchrony, weather events, and high demand for available insect pollinators. Artificial pollination systems can provide a security of yield even in poor pollination scenarios, and have been attracting increasing attention over the past decade. Here, we review pollen collection and pollen application technologies that have been employed to date. Major categories of mechanical pollination technology include: hand-pollination, handheld and backpack devices, vehicle-mounted devices, unmanned aerial vehicles (UAVs), and robotic and autonomous pollinators. The majority of the artificial pollination systems above are used to supplement natural pollination, but for some crops, these systems were found to perform adequately by themselves, including kiwifruit, olive, date palm, walnut, tomato, and hybrid maize seed. These systems often treat pollen as a system input, creating a chicken-and-egg problem in which the system is not economical without pollen and the pollen is not economical to collect without wide uptake of the system. To combat this, there has been success in developing mechanical harvesters for some crop plants (particularly almond and maize), but future work is needed for artificial pollination to be a commercial reality for the increasing number of cropping systems that are experiencing pollination deficits.

Different effects of local and landscape context on pollen foraging decisions by two managed orchard pollinators, Osmia cornuta and Bombus terrestris

Populations of managed pollinators are often introduced in agricultural fields to increase pollination levels. Ideally, managed pollinators should show a strong affinity for the target crop, which depends on innate preferences, but also on the availability of alternative co-blooming flower resources. In this study we compared pollen collection in Osmia cornuta and Bombus terrestris populations introduced in orchards, and we analysed how it is affected by local and landscape floral context. Based on pollen preferences and foraging rates of the two species, we expected O. cornuta to collect more fruit tree pollen than B. terrestris and to be less influenced by landscape factors. We sampled 16 orchards of various fruit tree species (almonds, apricots, cherries, apples). In each orchard, we characterized local flower availability and landscape composition, and identified pollen samples from 20 to 30 individuals of each pollinator species. O. cornuta collected a greater proportion of fruit tree pollen than B. terrestris (92% vs 81%), irrespective of the availability of alternative flower resources at the local and landscape levels. The diversity of pollen collected by B. terrestris increased with the availability of alternative flower resources, both at the local and landscape levels, suggesting that some of the foraging by this species took place away from the target orchard. Our results demonstrate that wild flowers do not compete with fruit tree flowers for O. cornuta visitation. Therefore, the use of managed O. cornuta populations to supplement pollination services in orchards is compatible with the implementation of agri-environmental measures (flower strips, ecological focus areas) to promote wild pollinator communities.

Elevated temperature affects energy metabolism and behavior of bumblebees

Bumblebees (Bombus eximius) are one of the most prominent pollinators in the agricultural industry because of their adaptation to temperate climates and pollination behavior (buzz pollination). Several studies have explained the need to increase conservation efforts for bumblebees due to climate change, but studies on the impact of climate change on pollination behavior of bumblebees have been limited. The present study investigated the effect of elevated temperatures on the survival and physiology of bumblebees. The behavioral changes in flight ability and pollen collection were also determined. We found that elevated temperature affects the survival rate and appetite of bumblebees. Gene expression analysis suggested that the energy metabolic pathway tends to involve anaerobic respiration during heat stress. The energy produced is mainly used to maintain essential physiological functions, such as expression of heat shock proteins and conversion of peroxides to harmless molecules. Energy distributed to flight muscles is reduced during heat stress, resulting in lower wing beating frequency. In addition, the flight path of bumblebees is shortened during heat stress, thereby further contributing to reduced pollen collection. These results demonstrate that elevated temperatures cause detrimental effects to bumblebees and can also potentially reduce crop production.

Technology of storage of bee pollen and its effects on the development of honey bees

The article presents data on changes in the protein content of bee pollen due to different storage methods. In May, during the collection of bee pollen by bee colonies, in the conditions of the farm located in the Stryi district of the Lviv region, more than 30 types of flower pollen entered the nest. At the same time, for species identification, acetolysis of seven types of flower pollen was carried out, which differed in the maximum amount of arrival: apple (Malus), dandelion (Taráxacum), winter rape (Brassica napus), buckwheat (Fagopyrum esculentum), clover (Trifolium pratense), chestnut (Castánea) and raspberry (Rúbus idáeus). To study the nitrogen content according to the Kjeldahl method, all pollen was divided into three groups according to the storage method. Bee pollen of the first group was considered fresh. In it, the nitrogen content was determined immediately after determining the species. Calculations showed the maximum crude protein content in this group. Of all types of bee pollen that were determined to be fresh, the maximum amount of protein was found in bee pollen collected during the flowering of winter rape (Brassica napus) and apple (Malus). Its average content is 24.9 ± 2.09 and 23.4 ± 1.77 %, respectively. As a result of freezing at a temperature of 18 ºС and its storage for 8–12 months, the protein content practically did not change and decreased by only 0.3–0.9 %. A slight tendency to decrease the amount of nitrogen in bee honey was also found when stored in a dried state. Bee pollen, stored for 8–12 months under different conditions, was fed to newborn honey bees and kept in entomological boxes. It was found that bee pollen storage conditions affect honey bees' food consumption rate. The minor attractiveness of the feed was found in the dried bee pollen. The absence of a connection between the content of crude protein in feed and the rate of its consumption by bees was investigated.

Comparative analysis of 3 pollen sterilization methods for feeding bumble bees.

Pollen is an essential component of bee diets, and rearing bumble bees (Bombus spp.) for commercial use necessitates feeding pollen in mass quantities. This pollen is collected from honey bee (Apis mellifera L.) colonies because neither an artificial diet nor an economical, large-scale pollen collection process from flowers is available. The provenance of honey bee-collected pollen is often unknown, and in some cases has crossed international borders. Both deformed wing virus (DWV) and the fungal pathogen Ascosphaera apis (Claussen) Olive & Spiltoir (cause of chalkbrood disease); occur in honey bee-collected pollen, and infections have been observed in bumble bees. We used these pathogens as general surrogates for viruses and spore-forming fungal diseases to test the efficacy of 3 sterilization methods, and assessed whether treatment altered pollen quality for the bumble bee. Using honey bee-collected pollen spiked with known doses of DWV and A. apis, we compared gamma irradiation (GI), ozone fumigation (OZ), and ethylene oxide fumigation (EO) against an untreated positive control and a negative control. Following sterilization treatments, we tested A. apis spore viability, detected viral presence with PCR, and tested palatability to the bumble bee Bombus impatiens Cresson. We also measured bacterial growth from pollens treated with EO and GI. GI and EO outperformed OZ treatment in pathogen suppression. EO had the highest sterilizing properties under commercial conditions and retained palatability and supported bee development better than other treatments. These results suggest that EO sterilization reduces pathogen risks while retaining pollen quality as a food source for rearing bumble bees.

Pesticide Residues and Metabolites in Greek Honey and Pollen: Bees and Human Health Risk Assessment.

Bees encounter a plethora of environmental contaminants during nectar and pollen collection from plants. Consequently, after their entrance into the beehives, the transfer of numerous pollutants to apicultural products is inevitable. In this context, during the period of 2015-2020, 109 samples of honey, pollen, and beebread were sampled and analyzed for the determination of pesticides and their metabolites. More than 130 analytes were investigated in each sample by applying two validated multiresidue methods (HPLC-ESI-MS/MS and GC-MS/MS). Until the end of 2020, 40 determinations were reported in honey, resulting in a 26% positive to at least one active substance. The concentrations of pesticides ranged from 1.3 ng/g to 785 ng/g honey. For seven active substances in honey and pollen, maximum residue limits (MRLs) exceedances were observed. Coumaphos, imidacloprid, acetamiprid, amitraz metabolites (DMF and DMPF), and tau-fluvalinate were the predominant compounds detected in honey, while several pyrethroids such as λ-cyhalothrin, cypermethrin, and cyfluthrin were also found. Pollen and beebread, as expected, accumulated a higher number of active substances and metabolites (32 in total), exhibiting almost double the number of detections. Although the above findings verify the occurrence of numerous pesticide and metabolite residues in both honey and pollen, the human risk assessment in the majority of the cases does not raise any concerns, and the same applies to bee risk assessment.

Local and Landscape Factors Influence Plant-Pollinator Networks and Bee Foraging Behavior across an Urban Corridor

Given widespread concerns over human-mediated bee declines in abundance and species richness, conservation efforts are increasingly focused on maintaining natural habitats to support bee diversity in otherwise resource-poor environments. However, natural habitat patches can vary in composition, impacting landscape-level heterogeneity and affecting plant-pollinator interactions. Plant-pollinator networks, especially those based on pollen loads, can provide valuable insight into mutualistic relationships, such as revealing the degree of pollination specialization in a community; yet, local and landscape drivers of these network indices remain understudied within urbanizing landscapes. Beyond networks, analyzing pollen collection can reveal key information about species-level pollen preferences, providing plant restoration information for urban ecosystems. Through bee collection, vegetation surveys, and pollen load identification across ~350 km of urban habitat, we studied the impact of local and landscape-level management on plant-pollinator networks. We also quantified pollinator preferences for plants within urban grasslands. Bees exhibited higher foraging specialization with increasing habitat heterogeneity and visited fewer flowering species (decreased generality) with increasing semi-natural habitat cover. We also found strong pollinator species-specific flower foraging preferences, particularly for Asteraceae plants. We posit that maintaining native forbs and supporting landscape-level natural habitat cover and heterogeneity can provide pollinators with critical food resources across urbanizing ecosystems.

Studies on Pollen Morphology, Pollen Vitality and Preservation Methods of Gleditsia sinensis Lam. (Fabaceae)

Gleditsia sinensis Lam. (Fabaceae) is an endemic species in China, which has a wide range of ecological functions and high economic value. G. sinensis belongs to androdioecy, and the stamens of perfect flowers are aborted, meaning that a perfect flower is a functional female flower. Understanding the dynamic process of flowering and the characteristics of pollen morphology effectively determine the viability of pollen vitality, and the suitable conditions for short-term storage of pollen can provide theoretical basis and technical reference for hybrid breeding and germplasm conservation of G. sinensis. In this study, the male plants of G. sinensis in Guiyang area were used as research materials. The flowering dynamic process of male flowers was recorded through field observation. The morphology of pollen was observed and analyzed with a scanning electron microscope (SEM). The germination characteristics of pollen were studied with an in vitro germination method, and the pollen vitality was also determined using four staining methods. The effects of different storage temperatures and water contents on pollen germination rate were discussed. The results showed that the male flowers of G. sinensis had a short, single flowering period, lasting 2–3 days from the opening to the shedding. The dynamic opening process of a single flower was artificially divided into five stages. Pollen grains of G. sinensis are oblate spheroidal, tricolporate with equatorial elongated endoapertures and the sporoderm surface is reticulate. The MTT (Thiazolyl Blue Tetrazolium Bromide) staining method could accurately and quickly determine the pollen vitality of G. sinensis. The highest pollen germination rate was 65.89% ± 3.41%, and the length of the pollen tube was 3.96 mm after cultured in 15% sucrose + 100 mg/L boric acid + 20 mg/L calcium chloride for 24 h. It was necessary to collect the pollen at the big bud stage, which was conducive to improving the efficiency of pollen collection because the pollen had been mature with high pollen vitality at this stage. When it came to pollen preservation, the pollen germination rate was significantly affected by storage time, storage temperature and pollen water content. The pollen still had high vitality after being stored at −80 °C for 30 days when the moisture content of the pollen decreased to 9%, and the pollen germination rate only decreased by 28.84% compared with that before storage. In conclusion, this study has comprehensively and systematically studied the morphology, vitality determination and preservation methods of the pollen of G. sinensis, providing a theoretical basis for the cross regional breeding and the conservation and utilization of germplasm resources.

Luffa Cylindrica (L.) As Potential Foraging Source For Insect Pollinators During Post Monsoon Season – A Study In Gangetic Plain Of West Bengal

Pollination is an important ecosystem service and insects play the most vital role of its. Insect pollinators need good foraging resources all year long to survive, which are provided by both wild and cultivated plants. However, although being crucial for pollinator survival during scarcity, these wild plants receive little attention. Present study had been carried out in Gangetic plain of West Bengal to document the potentiality of the wild creeping plant, Luffa cylindrica L. as foraging resource for insect pollinators during the post monsoon season, when flowering in major trees is sparse. Active netting explore diversity of flower visitors, while palynological study confirms the pollen foraging activity of two reared honey bees, Apis mellifera L. and Apis cerana indica F. on the creeper. Insects belonged to orders viz. Hymenoptera, Diptera, Lepidoptera and Coleoptera were found to visit. Hymenopterans were the major insect visitors comprising 66.34% of total. Palynological study revealed that Apis mellifera and Apis cerana indica togetherly visit 17 and 16 plant species for pollen collection during the study months. In October, Luffa cylindrica contributed 10.53% and 11.27% of total pollen taxa foraged by Apis mellifera and Apis cerana indica respectively and grouped as important minor pollen for the honey bees. However, in the month of November it contributed 11.84% and 9.88% of total respectively. Being a creeper, however, these are not given much protection and are often weeded out, which can have a negative impact on native pollinator populations foraging on the crops.

Storage and In-vitro Germination of Some Olive Pollens

In this study, the effect of storage at different times and temperatures on in vitro olive pollen germination was investigated. Pollens of Gemlik and Domat cultivars and GE119 and GK138 genotypes were stored at +4 °C, -20 °C, and -80 °C for 7, 35, 200, and 365 days, respectively. In vitro germination status of pollen was determined by the petri agar method, by choosing the most suitable nutrient medium for each olive. The most suitable germination media for Gemlik, Domat, GE119, and GK138 pollens were 50 ml water + 15% sucrose + 0.7% agar + 75 ppm boric acid, 50 ml water + 15% sucrose + 0.7% agar, 50 ml water + 25% sucrose + 0.5% agar, 50 ml water respectively. The interaction effect between storage time, temperatures, and cultivar on pollen germination and diameter was determined. At the end of the storage period, the highest pollen germination and diameter were observed in the Gemlik cultivar. Additionally, -80 °C temperature for Gemlik and Domat cultivars and -20 °C temperature for GE119 and GK138 genotypes were suitable for 35 days of storage. All olive pollens in the current study had germination rates below 9% in the following storage periods. The results show that storing olive pollens at sub-zero temperatures will reduce the need for daily fresh pollen collection required for important scientific studies such as breeding and artificial pollination.

The diversity, evolution, and development of setal morphologies in bumble bees (Hymenoptera: Apidae: Bombus spp.).

Bumble bees are characterized by their thick setal pile that imparts aposematic color patterns often used for species-level identification. Like all bees, the single-celled setae of bumble bees are branched, an innovation thought important for pollen collection. To date no studies have quantified the types of setal morphologies and their distribution on these bees, information that can facilitate understanding of their adaptive ecological function. This study defines several major setal morphotypes in the common eastern bumble bee Bombus impatiens Cresson, revealing these setal types differ by location across the body. The positions of these types of setae are similar across individuals, castes, and sexes within species. We analyzed the distribution of the two most common setal types (plumose and spinulate) across the body dorsum of half of the described bumble bee species. This revealed consistently high density of plumose (long-branched) setae across bumble bees on the head and mesosoma, but considerable variation in the amount of metasomal plumosity. Variation on the metasoma shows strong phylogenetic signal at subgeneric and smaller group levels, making it a useful trait for species delimitation research, and plumosity has increased from early Bombus ancestors. The distribution of these setal types suggests these setae may serve several functions, including pollen-collecting and thermoregulatory roles, and probable mechanosensory functions. This study further examines how and when setae of the pile develop, evidence for mechanosensory function, and the timing of pigmentation as a foundation for future genetic and developmental research in these bees.

In-hive learning of specific mimic odours as a tool to enhance honey bee foraging and pollination activities in pear and apple crops

The areas devoted to agriculture that depend on pollinators have been sharply increased in the last decades with a concomitant growing global demand for pollination services. This forces to consider new strategies in pollinators’ management to improve their efficiency. To promote a precision pollination towards a specific crop, we developed two simple synthetic odorant mixtures that honey bees generalized with their respective natural floral scents of the crop. We chose two commercial crops for fruit production that often coexist in agricultural settings, the apple (Malus domesticus) and the pear trees (Pyrus communis). Feeding colonies with sucrose solution scented with the apple mimic (AM) or the pear mimic (PM) odour enabled the establishment of olfactory memories that can bias bees towards the flowers of these trees. Encompassing different experimental approaches, our results support the offering of scented food to improve foraging and pollination activities of honey bees. The circulation of AM-scented sucrose solution inside the hive promoted higher colony activity, probably associated with greater activity of nectar foragers. The offering of PM-scented sucrose solution did not increase colony activity but led to greater pollen collection, which is consistent with pear flowers offering mainly pollen as resources for the bees. Results obtained from apple and pear crops suggest that the offering of AM- and PM-scented sucrose solution increased fruit yields. This preliminary study highlights the role of in-hive olfactory learning to bias foraging preferences within pome fruit crops.

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%).

Bumble bees exploit known sources but return with partial pollen loads when foraging under low evening light

Diel activity of diurnal pollinating insects declines well before the end of day, but a few species, such as bumble bees, can continue foraging in the period before sunset, when light levels decrease. Foraging during this time could be costly for individuals, and key decisions regarding the daily cessation of foraging behaviour have to be made during this period of rapid abiotic change. However, little is known about the behaviour of diurnal bees under these light conditions. We conducted a field experiment in a mixed agricultural landscape to investigate pollen foraging in the hour before sunset in the buff-tailed bumble bee, Bombus terrestris , comparing it to an hour during the afternoon. We monitored activity at the colony entrance and collected pollen sacs from returning foragers. Overall, there were fewer exits and returns in the evening period than in the afternoon period. Evening foragers returned to the colony with partial pollen loads when compared to daytime foragers, and those returning in lower light levels had smaller loads. Additionally, we found that the same flower taxa were being exploited in the evenings as in the daytime. We found no effect of individual size on the likelihood of evening foraging or the size of pollen loads. Our results suggest that B. terrestris are facultative evening foragers that opportunistically exploit profitable flowers they have encountered during the day. Evening foragers decide to return to the colony with partial pollen loads in this period of the foraging day, which results in a largely reduced pollen influx to the colony at the end of the day. Our findings indicate that the gradual decline in light is likely to be an important factor guiding the decisions of bumble bees and other diurnal pollinators of whether to extend or end foraging, and when to return to the colony. • Bumble bees are facultative evening foragers. • Pollen foraging in the evening comes at an acquisition cost. • Light intensity is a key limiting factor for pollen collection. • Evening foragers have the same floral preferences as daytime foragers. • Individual size does not affect pollen foraging in the late evening.

Honeybee-inspired electrostatic microparticle manipulation system based on triboelectric nanogenerator

Electrostatic manipulation of particles or droplets has raised huge interests across many fields including biomedical analysis, microchemistry and microfabrication/patterning, because of its merits of simple configuration and easy operation. However, traditionally applied bulky high voltage sources for electrostatic manipulation not only have potential safety risk to the operator and the devices, but also limit the portability. Here, we proposed an electrostatic microparticle manipulation system (EMMS) based on a triboelectric nanogenerator (TENG). Inspired from the pollen collection principle of honeybees, the EMMS featured a simple pin-to-plate electrodes system, which was electrostatically powered by the high voltage of the TENG. Different manipulation modes, including contact manipulation and noncontact manipulation were systematically studied. With a sliding displacement of 5 cm, the TENG delivered an output voltage of ± 3.2 kV, which could manipulate dielectric microparticles with weights of 1.7 mg, 0.9 mg and 13.3 mg at contact manipulation mode, noncontact manipulation (vertical lift) and noncontact manipulation (parallel move) mode, respectively. Manipulation mechanisms for both dielectric and conductive microparticles under different configurations of the pin-to-plate electrodes system were investigated. Finally, potential applications including micropatterning, dust remove and drug release/microchemistry were demonstrated to show the great prospects of the proposed TENG-based EMMS.

Correlation of Pollen Concentration and Meteorological Factors with Medical Condition of Allergic Rhinitis in Shenyang Area.

Background The pathogenesis of allergic rhinitis (AR) was affected by meteorological and environmental factors. This study investigated the association between clinical symptoms of AR patients with pollen dispersal and meteorological conditions. Methods The clinical features of 10,838 AR patients who were treated in the Department of Otorhinolaryngology, The First Hospital of China Medical University, Shenyang, from March 2021 to October 2021 were retrospectively analyzed. We collected pollen by a pollen collector, read and counted it under a microscope, identified the species of the pollen particles, and recorded meteorological data (average daily temperature, maximum and minimum temperature, average daily wind, average daily precipitation, average daily humidity, average pressure, air quality index, PM2.5, PM10, SO2, NO2, CO, and O3), to analyze the correlation among meteorological conditions, pollen dispersal, and number of AR visits. Finally, pollen allergen-positive and symptoms were scored. Results Among the AR visits, patients >41 years old accounted for the highest proportion (64.15%). 43.67% of the patients were complicated with bronchial asthma, and the disease incidence peaked in September. During the period of the study, a total of 27,512 pollen grains were collected, and 17 species were identified. The pollens of Compositae and Moraceae were the main allergenic sources leading to the increase in AR visits from August to September. The peak of pollen dispersal was in spring, summer, and autumn. The total amount of pollen was not only related to the average daily minimum temperature, average daily precipitation, and average daily humidity but also had a significant correlation with air quality index and air pollutants (PM2.5 and PM10, SO2, NO2, and CO). In addition, there was a significant correlation between the number of daily pollen allergen-positive patients and the pollen concentration of Compositae and Moraceae as well as air pollution components. The clinical symptoms of pollen allergen-positive patients were mainly nasal congestion, red/itchy eyes, and epiphora. Conclusion The peak seasons of pollen dispersal in Shenyang were in spring, summer, and autumn, and the allergenic pollens were mainly Compositae and Moraceae. In addition, AR was substantially correlated with pollen concentration and meteorological factors. This study may help provide early warning information and prevention for AR patients.