Pollinators optimise their foraging behaviours in response to changes in floral rewards, which may consequently affect pollen transfer and plant reproductive success, especially in plants that require cross-pollination. In a red clover field grown for seed production, we conducted a three-year experiment to compare the foraging behaviours of naturally occurring bumble bee species and their pollination contributions. Specifically, we investigated how the visitation of a flower head by one bumble bee may affect the foraging behaviours of any second visiting bee. We also measured relative abundance, stigmatic pollen deposition, and plant traits including flowering intensity, corolla tube length, and seed set. We found that bees can identify previously visited flower heads: the second visiting bees increased their rejection probabilities with the flower exploitation rate of the first visiting bees. The second bees also had a higher foraging speed than the first visiting bees, either due to the depletion of floral rewards or the reduced pressure required to trip the florets. Among the five bumble bee species naturally occurring during the peak flowering, different bumble bees showed varied preferences for the co-flowering cultivars. At the flower head level, one visit from Bombus pascuorum and Bombus muscorum was sufficient for the seed set, similar to the seed set in the open pollination. However, Bombus hortorum that caused high stigmatic pollen deposition did not result in comparable high seed set.this might be related to a limited number of cross-pollen transferred, caused by the abundant floral resources during the peak flowering or an intrinsic characteristic of this bumble bee species.

Varroa destructor is the most significant pest of honey bees worldwide, and oxalic acid (OA) is widely used for its control. However, its effects on brood physiology remain unclear. We examined the impact of oxalic acid-glycerine (OA-G) strips and chalkbrood (Ascosphaera apis) infection on gene expression in Apis mellifera prepupae. Twelve colonies were assigned to control, OA-G, A. apis, and combined OA-G + A. apis groups. Gene expression of antimicrobial peptides (AmPs), vitellogenin (Vg), and Vg-like B was analyzed seven days post-treatment using RT-qPCR. OA-G treatment significantly upregulated defensin1 and hymenoptaecin in both healthy and infected brood, indicating strong immune activation. In contrast, abaecin was downregulated, while apidaecin increased only under infection. Vitellogenin was consistently suppressed across all treatments, whereas Vg-like B remained unchanged. These results demonstrate differential immune and nutritional trade-offs in brood following OA exposure and infection, underscoring the complex physiological consequences of varroosis management.

Pollen is a source of protein, lipids, vitamins and minerals for bees and other flower-visiting insects. The composition of macro- and micronutrients of pollen vary among different plant species. Honey bees are long-distance foragers, collecting nectar and pollen from plants within several kilometers of their hive. Availability of pollen within the foraging range of honey bees is highly dynamic, changing seasonally, and across different landscapes. In the present study, the aim was to investigate the composition of pollen collected by honey bees in rural-urban landscape mosaics typical of Northern Europe. Samples of corbiculate pollen were collected 3-9 times during the growing season by citizen scientist bee keepers from a total of 25 observation apiaries across Denmark in 2014-2015. Palynological analysis was conducted identifying 500 pollen grains per sample to pollen type (mostly plant genus). Pollen diversity denoted the number of different pollen types in a sample, while relative abundance was calculated as the proportional representation of a pollen type, if found in >1% of the sample. The quantity of pollen types across study years and sites was measured as the occurrence of each pollen type (number of samples with the pollen type present) and abundance (total number of pollen grains). Pollen diversity was highly variable, with effects of season, year, and area of green urban spaces. In terms of quantity, a few key pollen types occurred repeatedly and abundantly in the samples. Only 17 pollen types were present in >15 samples. These pollen types were consistent across study years and different landscapes. Pollen diversity may impact colony health, and hence foraging decisions by honey bees, especially in late summer. However, the bulk of the pollen collected by colonies came from a limited number of pollen sources, regardless of year and landscape context in the rural-urban landscape mosaics of Denmark.

Introducing beekeepers to a reduced use of varroa treatment is the purpose of our project "Better Beekeeping Practise". The policy of the EU is to reduce the use of pesticides dramatically in agriculture. Beekeeping does not hold a unique position; not to take part in these efforts. However; beekeepers are not well prepared for change. In order to engage beekeepers; we meet them in local organisations during winter; and in summer we visit school apiaries in order to introduce better practise. Many are still mainly applying the calendar in their varroa strategy. To actually follow the guidelines of any approved medicine; and examine the colony before applying treatment; is bewildering. Many ask; “why?” This stubbornness is a major hinderance to ever achieving the goals of sustainable beekeeping. Beekeepers who treat all colonies equally; regardless of varroa infestation levels; will never notice; those colonies that have lower increase in mite populations. Hence these beekeepers are unable to breed from these better bees. This is frustrating; since beekeepers keep experiencing episodes of high losses; due to misguided learnings; like "better be safe than sorry"; or "if a little helps a bit; then more helps a lot". Clearly, we need to reform teaching at the beginners’ level and take old practises out of the existing handbooks.

Here we cover a wide range of methods currently in use and recommended in modern queen rearing, selection and breeding. The recommendations are meant to equally serve as standards for both scientific and practical beekeeping purposes. The basic conditions and different management techniques for queen rearing are described, including recommendations for suitable technical equipment. As the success of breeding programmes strongly depends on the selective mating of queens, a subchapter is dedicated to the management and quality control of mating stations. Recommendations for the handling and quality control of queens complete the queen rearing section. The improvement of colony traits usually depends on a comparative testing of colonies. Standardized recommendations for the organization of performance tests and the measurement of the most common selection characters are presented. Statistical methods and data preconditions for the estimation of breeding values which integrate pedigree and performance data from as many colonies as possible are described as the most efficient selection method for large populations. Alternative breeding programmes for small populations or certain scientific questions are briefly mentioned, including also an overview of the young and fast developing field of molecular selection tools. Because the subject of queen rearing and selection is too large to be covered within this paper, plenty of references are given to facilitate comprehensive studies.

Pollen and nectar consumed by honey bees contain plant secondary metabolites (PSMs) with vital roles in plant-insect interactions. While PSMs can be toxic to bees, they can also be health-promoting, e.g. by improving pesticide and pathogen tolerances. As xenobiotics, PSMs undergo post-ingestion chemical modifications that can affect their bioactivity and transmission to the brood. Despite the importance of understanding honey bee PSM metabolism and distribution for elucidating bioactivity mechanisms, these aspects remain largely unexplored. In this study, we used HPLC-MS/MS to profile 47 pollen PSMs in honey bees and larvae. Both adult bees and larvae had distinct PSM profiles that differed from their diet. This is likely due to post-ingestion metabolism and compound-dependent variations in PSM transmission to the brood via nurse bee jelly. Phenolic acids and flavonoid aglycones were most abundant in bees and larvae, whereas alkaloids, cyanogenic glycosides and diterpenoids had the lowest abundance despite being consumed in higher concentrations. This study documents larval exposure to a variety of PSMs for the first time, with concentrations increasing from early to late larval instars. Our findings provide novel insights into the post-ingestion fate of PSMs in honey bees, providing a foundation for further exploration of biotransformation pathways and PSM effects on honey bee health.

Honey bee subspecies originate from specific geographical areas in Africa, Europe and the Middle East, and beekeepers interested in specific phenotypes have imported genetic material to regions outside of the bees' original range for use either in pure lines or controlled crosses. Moreover, imported drones are present in the environment and mate naturally with queens from the local subspecies. The resulting admixture complicates population genetics analyses, and population stratification can be a major problem for association studies. To better understand Western European honey bee populations, we produced a whole genome sequence and single nucleotide polymorphism (SNP) genotype data set from 870 haploid drones and demonstrate its utility for the identification of nine genetic backgrounds and various degrees of admixture in a subset of 629 samples. Five backgrounds identified correspond to subspecies, two to isolated populations on islands and two to managed populations. We also highlight several large haplotype blocks, some of which coincide with the position of centromeres. The largest is 3.6 Mb long and represents 21% of chromosome 11, with two major haplotypes corresponding to the two dominant genetic backgrounds identified. This large naturally phased data set is available as a single vcf file that can now serve as a reference for subsequent populations genomics studies in the honey bee, such as (i) selecting individuals of verified homogeneous genetic backgrounds as references, (ii) imputing genotypes from a lower-density data set generated by an SNP-chip or by low-pass sequencing, or (iii) selecting SNPs compatible with the requirements of genotyping chips.

On the geographical basis, sub-Saharan Africa is the origin of small hive beetles (SHBs), Aethina tumida Murray, 1867 (Family: Nitidulidae) (Neumann et al., 2016; Neumann & Elzen, 2004). SHBs have been able to invade new regions outside their native range and spread to America, Asia, Australia and Europe (Neumann et al., 2016). SHBs were reported in the United States in 1996 (Elzen et al., 1999; Hood, 2004; Hood & Miller, 2005), and other continents such as Australia in 2002 (Hood, 2004), Asia in 2010 (Lee et al., 2017), Europe in 2014 (Mutinelli et al., 2014), South America in 2017 (Al Toufailia et al., 2017), the islands of Philippines 2014 (Cervancia et al., 2016) and Mauritius in 2016 (Muli et al., 2018). They have succeeded to invade and establish in the USA and across the east coast of Australia (Hood, 2000; Neumann et al., 2016; Neumann & Elzen, 2004), however, the invasion does not always mean the establishment of SHBs in new country, as SHB detection has been reported from Egypt and Portugal without any strong evidence of establishment (Abou-Shaara et al., 2018; El-Niweiri et al., 2008; Hassan & Neumann, 2008; Mostafa & Williams, 2000; Murilhas, 2004). In 2014, SHBs were detected in Italy (Mutinelli, 2014; Mutinelli et al., 2014; Neumann et al., 2016; Palmeri et al., 2015) and the authorities have been active since detection trying to eradicate the SHBs and prevent their spread towards other EU countries.

BACKGROUND:Whole-genome sequencing has become routine for population genetic studies. Sequencing of individuals provides maximal data but is rather expensive and fewer samples can be studied. In contrast, sequencing a pool of samples (pool-seq) can provide sufficient data, while presenting less of an economic challenge. Few studies have compared the two approaches to infer population genetic structure and diversity in real datasets. Here, we apply individual sequencing (ind-seq) and pool-seq to the study of Western honey bees (Apis mellifera). METHODS:We collected honey bee workers that belonged to 14 populations, including 13 subspecies, totaling 1347 colonies, who were individually (139 individuals) and pool-sequenced (14 pools). We compared allele frequencies, genetic diversity estimates, and population structure as inferred by the two approaches. RESULTS:Pool-seq and ind-seq revealed near identical population structure and genetic diversities, albeit at different costs. While pool-seq provides genome-wide polymorphism data at considerably lower costs, ind-seq can provide additional information, including the identification of population substructures, hybridization, or individual outliers. CONCLUSIONS:If costs are not the limiting factor, we recommend using ind-seq, as population genetic structure can be inferred similarly well, with the advantage gained from individual genetic information. Not least, it also significantly reduces the effort required for the collection of numerous samples and their further processing in the laboratory.

In order to investigate the geographical distribution of morphological and mitochondrial variation of the Western honey bee in West and Central Africa, 175 colonies, sampled from 44 localities (or a subset therefrom), were subjected to geometric morphometric (GM), traditional morphometric (TM) and mitochondrial DNA analyses. The shape of the forewing differed significantly between the three ecological zones (rainforest, savanna and Sahel) and significantly correlated with latitude, longitude and altitude. A one-way ANOVA revealed a highly significant difference between the ecological zones in respect of the size of the forewing. Based on TM, no clear geographic clustering was observed, and the samples could not be unambiguously assigned to reference data of A. m. adansonii or A. m. jemenitica. However, a conspicuous geographic pattern was observed, with bees increasing in size northward in the west of the area, but southward in the east. Four mitochondrial haplotypes, previously reported from Africa, were found: A1 (n = 60), A4 (n = 58), A4 ' (n = 14) and A14 (n = 1). The overall haplotype diversity was low (h = 0.485 +/- S. E. 0.062) and small bees were found to bear the A1 haplotype while large bees had either A4 or A4 ' haplotype.

The losses of honey bee colonies and declines of other insect pollinators have been associated with negative effects of pesticides. Honey bees as well as other pollinators are nectar and pollen foragers and thus are exposed to an extensive range of phytochemicals. Understanding the synergistic, additive, and antagonistic effects of plant secondary metabolites and pesticides in honey bees may help to protect honey bee colonies against agrochemicals. In this study, we used untargeted metabolomics to investigate the impact of dietary phytochemical composition on the residual concentration of three pesticides: imidacloprid, tau-fluvalinate and tebuconazole in exposed honey bees. Honey bees were given different diets based on pollen or nectar from four plants: Reseda odorata, Borago officinalis, Phacelia tanacetifolia, and Trifolium repens for two days. Thereafter, they were orally exposed to 10 ng/bee imidacloprid or contact-exposed to 0.9 μg/bee tau-fluvalinate or 5 μg/bee tebuconazole. After 1 h of oral exposure or 24 h of contact exposure, the honey bees were anaesthetised with CO2, sacrificed by freezing, extracted with a validated QuEChERS method, and residual pesticide concentrations were determined by LC-QTRAP-MS/MS. The phytochemical composition in the given diets were profiled with an UHPLC-Q Exactive-MS/MS. The results revealed that the dietary phytochemical composition has a noteworthy influence on the concentration of residual pesticides in honey bees. The correlation coefficient analysis demonstrated that flavonoids have a reducing effect on the residual concentration of imidacloprid and tau-fluvalinate in honey bees. The results also highlighted that exposure to imidacloprid impaired the metabolism of sugars in honey bees. Exploiting flavonoid-rich plants may protect honey bees against pesticides and hold promise as forage plants in future beekeeping.

Honey bees are important pollinators and are subject to numerous stressors, such as changing floral resources, parasites, and agrochemical exposure. Pesticide exposure has been linked to the decline in the global honey bee population. We have limited knowledge of the metabolic pathways and synergistic effects of xenobiotics in bees. Quercetin is one of the most abundant phytochemicals in plants and is therefore abundant in the honey bee diet. Quercetin can upregulate the detoxification system in honey bees; however, it is still unknown to what extent quercetin ingestion can reduce the content of absorbed pesticides. In this study, we investigated the effect of dietary quercetin on the contents of three pesticides in honey bees: imidacloprid (insecticide), tebuconazole (fungicide), and tau-fluvalinate (insecticide and acaricide). Bees were divided into two main groups and fed either quercetin-sucrose paste or only sucrose for 72 h. Thereafter, they were orally exposed to ∼10 ng/bee imidacloprid or contact-exposed to ∼0.9 μg/bee tau-fluvalinate or ∼5.2 μg/bee tebuconazole. After 1 h of oral exposure or 24 h of contact exposure, the bees were anaesthetised with CO2, sacrificed by freezing, and extracted with a validated QuEChERS method. Subsequently, the concentrations of the three pesticides and quercetin in the bees were determined with a triple quadrupole tandem mass spectrometer coupled to an HPLC system. No significant effect on the concentration of tebuconazole or tau-fluvalinate was observed in bees fed quercetin. Intake of quercetin led to a reduction in the concentration of imidacloprid in honey bees. Quercetin-rich plants may be exploited in future beekeeping.