Honey bees save energy in honey processing by dehydrating nectar before returning to the nest

Honey bees process nectar into honey by active evaporation on the tongue and passive evaporation involving nest ventilation and fanning behaviour, as well as enzymatic action. The elimination of excess water from nectar carries considerable energetic costs. The concentration of the nectar load is assumed to remain constant during transport. However, some of this water elimination may occur before foragers return to the nest and pass their nectar loads to receiver bees. In honey bees captured while foraging in Macadamia orchards, we show that the nectar in their crops has approximately twice the sugar concentration of the fresh nectar in fowers. This was true for four Macadamia cultivars, with up to 75% of the initial water content being removed. There is a further concentration increase in the crops of returning bees captured at the hive entrance. The only possible route of water elimination from the crop is via evaporation from the mouthparts. We calculate the savings in honey processing costs to be on average 35 times more than the reduction in fight costs due to reduced body mass. Pre-concentration of nectar in foraging honey bees may be widespread, and of crucial importance for honey storage.SAMAChttps://www.nature.com/srepZoology and Entomolog

Honeybees and nectar nicotine : deterrence and reduced survival versus potential health benefits

Secondary metabolites produced by plants for herbivore defence are often found in floral nectar, but their effect on the foraging behaviour and physiological performance of pollinators is largely unknown. Nicotine is highly toxic to most herbivores, and nicotine-based insecticides may contribute to current pollinator declines. We examined the effects of nectar nicotine on honeybee foraging choices and worker longevity. Free-flying honeybee (Apis mellifera scutellata) workers from six colonies were given a choice between multiple nicotine concentrations (0–1000 lM) in artificial nectar (0.15–0.63 M sucrose). The dose-dependent deterrent effect of nicotine was stronger in lower sugar concentrations, but even the highest nicotine concentrations did not completely repel honeybees, i.e. bees did not stop feeding on these diets. Nicotine in nectar acts as a partial repellent, which may keep pollinators moving between plants and enhance cross-pollination. In the second part of the study, newly emerged workers from 12 colonies were caged and fed one of four nicotine concentrations (0–300 lM) in 0.63 M sucrose for 21 days. Moderate (630 lM) nicotine concentrations had no significant detrimental effect, but high nicotine concentrations reduced the survival of caged workers and their nectar storage in the honey comb. In contrast, worker groups that survived poorly on sugar-only diets demonstrated increased survival on all nicotine diets. In the absence of alternative nectar sources, honeybees tolerate naturally occurring nectar nicotine concentrations; and low concentrations can even be beneficial to honeybees. However, high nicotine concentrations may have a detrimental effect on colony fitness.http://www.elsevier.com/ locate/ jinsphyshb2014ab201

A new design for honey bee hoarding cages for laboratory experiments

Honey bees are the subject of research around the world due to their great economic importance and current population declines (vanEngelsdorp and Meixner, 2010). Many studies cannot be conducted at the colony level. Controlled cage experiments provide insight into behavioural interactions (Elzen et al., 2001), diseases (Martín-Hernández et al., 2009), nutritional requirements (Altaye et al., 2010) and effects of insecticides and genetically engineered plants on these important pollinators (Malone et al., 1999; Medrzycki et al., 2003).A grant from BBSRC, Defra, NERC, the Scottish Government and the Wellcome Trust, under the Insect Pollinators Initiative (BBI000968/1)http://www.ibra.org.uk/am2014ab201

Reproductive traits and mandibular gland pheromone of anarchistic honey bee workers Apis mellifera occurring in China

International audienceAbstractIn honey bee colonies, workers, in particular of “anarchistic” lineages, can activate their ovaries and lay eggs, even in the presence of the queen. We identified three queenright colonies showing typical signs of worker reproduction. To characterize this new lineage, we extracted the mandibular gland and analyzed it using gas chromatography. The total amounts of the five main components of the mandibular gland, namely methyl p-hydroxyben-zoate (HOB), 9-oxo-2(E)-decenoic acid (9-ODA), (S)-9-hydroxy-(E)-2-decenoic acid (9-HDA), 10-HDA, and 10-hydroxyde-canoic acid (10-HDAA) were significantly higher in the mandibular gland profiles of workers with activated ovaries (AWs, 8.88 ± 1.71 μg) compared to workers with inactivated ovaries (IAWs, 4.00 ± 2.09 μg). Furthermore, the chemical profiles of IAWs were dominated by the “worker substances” 10-HDA (34.64 ± 8.19 %) and its precursor 10-HDAA (22.88 ± 4.95 %), while the chemical profiles in AWs were dominated by the precursor of the queen substance 9-HDA (40.04 ± 7.55 %). The ratios of two precursor substances 10-HDAA/9-HDA of IAWs were more worker like (>1.0) whereas AWs were more queen like (≤1.0). These results suggest that the mandibular pheromones of anarchistic workers resemble a more queen-like reproductive active profile and that these workers may represent a reversion to a more basal reproductive phenotype

Antibiotic treatment impairs protein digestion in the honeybee, Apis mellifera

Nutritional stress due to habitat transformation and loss is one of several factors contributing to current declines in global bee populations. Bees obtain protein from pollen, which in honeybees is consumed and digested by nurse bees. They then distribute the protein to the rest of the colony in the form of hypopharyngeal gland secretions. Little is known of how efficiently honeybees digest protein. Moreover, antibiotics are used by beekeepers as in-hive treatments for diseases and may interfere with microbial contributions to protein digestion. Caged, newly emerged workers of Apis mellifera scutellata were fed caseinate as protein source, to investigate the effects of protein intake and antibiotic treatment on digestive efficiency. These workers were fed protein:carbohydrate ratios of 1:120, 1:50 and 1:15 or pure sucrose for 9 days. Half the cages received dietary oxytetracycline at a concentration used by beekeepers. Antibiotic exposure did not affect survival or protein consumption. Protein digestive efficiency increased with increasing levels of protein in the diet, although a decrease would have contributed to maintaining nutrient balance. Importantly, we show that antibiotic exposure impaired protein digestive efficiency, especially on low-protein diets. This may be particularly important when colonies are restricted to a single protein deficient source of pollen.The University of Pretoria and by the National Research Foundation of South Africa.http://link.springer.com/journal/135922020-12-02hj2020BiochemistryGeneticsMicrobiology and Plant PathologyZoology and Entomolog

A novel vehicle-mounted sticky trap ; an effective sampling tool for savannah tsetse flies Glossina morsitans morsitans Westwood and Glossina morsitans centralis Machado

BACKGROUND: Black screen fly round (BFR) is a mobile sampling method for Glossina morsitans. This technique relies on the ability of operator(s) to capture flies landing on the screen with hand nets. In this study, we aimed to evaluate a vehicle-mounted sticky panel trap (VST) that is independent of the operator’s ability to capture flies against BFR, for effective and rapid sampling of G. m. morsitans Westwood and G. m. centralis Machado. We also determined the influence of the VST colour (all-blue, all-black or 1:1 blue-black), orientation and presence of odour attractants on tsetse catch. METHODOLOGY/PRINCIPAL FINDINGS: Using randomised block design experiments conducted in Zambia, we compared and modelled the number of tsetse flies caught in the treatment arms using negative binomial regression. There were no significant differences in the catch indices of the three colour designs and for in-line or transversely oriented panels for both subspecies (P > 0.05). When baited with butanone and 1-octen-3-ol, VST caught 1.38 (1.11–1.72; P < 0.01) times more G. m. centralis flies than the un-baited trap. Attractants did not significantly increase the VST catch index for G. m. morsitans (P > 0.05). Overall, the VST caught 2.42 (1.91–3.10; P < 0.001) and 2.60 (1.50–3.21; P < 0.001) times more G. m. centralis and G. m. morsitans respectively, than the BFR. The VST and BFR took 10 and 35 min respectively to cover a 1 km transect. CONCLUSIONS/SIGNIFICANCE: The VST is several times more effective for sampling G. m. morsitans and G. m. centralis than the BFR and we recommend its use as an alternative sampling tool.https://journals.plos.org/plosntdspm2022Zoology and Entomolog

Honeybees prefer warmer nectar and less viscous nectar, regardless of sugar concentration

The internal temperature of flowers may be higher than air temperature, and warmer nectar could offer energetic advantages for honeybee thermoregulation, as well as being easier to drink owing to its lower viscosity. We investigated the responses of Apis mellifera scutellata (10 colonies) to warmed 10% w/w sucrose solutions, maintained at 20–35°C, independent of low air temperatures, and to 20% w/w sucrose solutions with the viscosity increased by the addition of the inert polysaccharide Tylose (up to the equivalent of 34.5% sucrose). Honeybee crop loads increased with nectar temperature, as did the total consumption of sucrose solutions over 2 h by all bees visiting the feeders. In addition, the preference of marked honeybees shifted towards higher nectar temperatures with successive feeder visits. Crop loads were inversely proportional to the viscosity of the artificial nectar, as was the total consumption of sucrose solutions over 2 h. Marked honeybees avoided higher nectar viscosities with successive feeder visits. Bees thus showed strong preferences for both warmer and less viscous nectar, independent of changes in its sugar concentration. Bees may benefit from foraging on nectars that are warmer than air temperature for two reasons that are not mutually exclusive: reduced thermoregulatory costs and faster ingestion times due to the lower viscosity.University of Pretoria and the South African National Research Foundationhttp://rspb.royalsocietypublishing.org/hb2014ab201

The metabolic fate of nectar nicotine in worker honey bees

Honey bees (Apis mellifera) are generalist pollinators that forage for nectar and pollen of a very large variety of plant species, exposing them to a diverse range of secondary metabolites produced as chemical defences against herbivory. Honey bees can tolerate high levels of many of these toxic compounds, including the alkaloid nicotine, in their diet without incurring apparent fitness costs. Very little is known about the underlying detoxification processes mediating this tolerance. We examined the metabolic fate of nicotine in newly emerged worker bees using radiolabeled nicotine and LC-MS/MS analysis to determine the kinetic distribution profile of nicotine as well as the absence or presence and identity of any nicotine-derived metabolites. Nicotine metabolism was extensive; virtually no unmetabolised nicotine were recovered from the rectum. The major metabolite found was 4-hydroxy-4-(3-pyridyl) butanoic acid, the end product of 2'C-oxidation of nicotine. It is the first time that 4-hydroxy-4-(3-pyridyl) butanoic acid has been identified in an insect as a catabolite of nicotine. Lower levels of cotinine, cotinine N-oxide, 3'hydroxy-cotinine, nicotine N-oxide and norcotinine were also detected. Our results demonstrated that formation of 4-hydroxy-4-(3-pyridyl) butanoic acid is quantitatively the most significant pathway of nicotine metabolism in honey bees and that the rapid excretion of unmetabolised nicotine does not contribute significantly to nicotine tolerance in honey bees. In nicotine-tolerant insects that do not rely on the rapid excretion of nicotine like the Lepidoptera, it is possible that the 2'C-oxidation of nicotine is the conserved metabolic pathway instead of the generally assumed 5'C-oxidation pathway.The BBSRC, NERC, the Wellcome Trust, Defra, the Scottish Government under the Insect Pollinators Initiative (BB/I000968/1) as well as the National Research Foundation of South Africa and the University of Pretoria.http://www.elsevier.com/locate/jinsphys2018-04-30BiochemistryZoology and Entomolog

Economic and ecological implications of geographic bias in pollinator ecology in the light of pollinator declines

Understanding the causes and consequences of pollinator declines is a priority in ecological research. However, across much of the globe we have a poor understanding of pollinator assemblages, population trends and the ecological and economic importance of particular pollinators, due to a marked geographic bias in research eff ort. Here, we show that almost half the data cited in thirteen recent meta-analyses, which ask important and diverse questions in pollination ecology, were collected in just fi ve countries: Australia, Brazil, Germany, Spain and the USA. In contrast, the entire continent of Africa contributed only 4% of the data. We believe that the consequences of this geographic bias are severe. Foremost, pollinator assemblages (and possibly their sensitivity to ecological drivers) can greatly vary among these regions. In addition, many communities that rely on pollinators, bees in particular, for food security and wealth generation are in geographic regions where our understanding of pollination is poor. Collecting accurate information on pollinator populations in data defi cient areas will allow us to identify vulnerable populations and species and so better target conservation measures. Moreover, it will help us to determine if our current understanding of pollinator losses, based on data collected in a few locations and on the species that predominate in those regions, is representative of the wide diversity of ecosystems. We propose means of collecting such data given socioeconomic constraints.The BBSRC, NERC, the Wellcome Trust, Defra, and the Scottish Government under the Insect Pollinators Initiative (BB/I000968/1). National Research Foundation of South Africa and the University of Pretoria. LGC is funded by the EU FP7 projects.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-0706hb201

Digestibility and nutritional value of fresh and stored pollen for honey bees (Apis mellifera scutellata)

Pollen, the main protein source for honey bees, is mixed with regurgitated nectar or honey during collection and then stored as ‘bee bread’ before its consumption, mainly by young nurse workers. It has been suggested that storage of pollen improves its nutritional value and digestibility, but there is little evidence for such changes. We fed two fresh pollen types of different protein content (aloe and sunflower), and two stored pollen types (sunflower and a mixed pollen), to young caged worker bees. We measured daily consumption of pollen and sucrose solution, and survival after 14 days. At day 14 we recorded ovarian activation and extraction efficiency, by counting empty pollen grains in the rectal contents. Extraction efficiency is a measure of pollen digestibility. Contrary to our predictions, bees did not consume more fresh sunflower pollen than fresh aloe pollen to compensate for the lower protein content of sunflower pollen. In addition, they did not consume less sucrose solution when fed stored pollen diets that are already enriched in sugar. Consumption of stored sunflower pollen resulted in a low protein to carbohydrate (P:C) intake. Survival and ovarian activation were higher on diets giving higher P:C intakes. Extraction efficiency was high (up to 99%) for all pollen diets, and comparison of fresh and stored sunflower pollen showed that storage did not make it easier to digest. Changes to pollen during storage do not confer obvious benefits to honey bees.The National Research Foundation of South Africa.http://www.elsevier.com/locate/jinsphys2019-05-01hj2018Zoology and Entomolog