Honey bee colonies are group-level adaptive units

It is not widely recognized that natural selection has produced adaptive units at the level of groups. Multilevel selection theory shows that groups can evolve a high level of functional organization when between-group selection predominates over within-group selection. Strong empirical evidence that natural selection has produced adaptive units at the group level comes from studies of social insects in which we find colonies in certain species functioning as highly integrated units. The functional organization of a social insect colony is best understood for honey bees. Recent experimental analyses of honey bee colonies have revealed striking group-level adaptations that improve the foraging efficiency of colonies, including special systems of communication and feedback control. These findings are reviewed with the aim of showing that evolution has produced adaptively organized entities at the group level.     

Honey bee foraging profitability and round dance correlates

Summary The purpose is to examine the relationships between several aspects of the honey bee's round dance and the caloric costs and gains and net gains per time experienced by bees while foraging between two artificial flowers. The distance between the two flowers and the concentration of nectar rewards were varied. Nine bees were tested, each over several days. Of the three dance variables examined, the number of reversals in the dance per minute (RATE) most often gave the highest and consistently signed correlation coefficients when paired with the mean caloric reward received per flower visit (CALGAIN), the net caloric gain per unit time (NET), and the mean caloric cost to fly to and visit a flower (CALCOST). In general, RATE is positively correlated with CALGAIN (range of positive coefficients, 0.12 to 0.50) and NET (range, 0.15 to 0.40) and negatively correlated with CALCOST (range, –0.01 to –0.28). Additionally, the probability of dancing after foraging is generally positively associated with CALGAIN and negatively associated with CALCOST. The results suggest that caloric gains and costs may be integrated by the bee and output as a measure of profitability in the form of the round dance. This information may be communicated to potential recruits, although this is not demonstrated.     

Honey bee (Apis mellifera) preference towards micronutrients and their impact on bee colonies

Honey bees are important pollinators and take micronutrients from different natural floral resources and turbid water to adequately meet their nutritional requirements. But the role of micronutrients for honey bee health is not well understood. Here, the present study was conducted to determine honey bees' micronutrients preference in summer and winter seasons. Also, the impact of micronutrients on foraging behaviour and brood increase was studied in different honey bee colonies. The results elucidated that honey bees exhibited a strong preference for a salt solution compared to deionized water during the summer and winter seasons. However, there was a notable switch in salt preference between seasons. Overall, honey bees showed significantly more foraging activity, more pollen collection, and increased brood area after sodium consumption compared to other minerals in the summer season. Further, pollen collection and brood area were significantly higher after the use of potassium in the winter season. Thus, the food preference of honey bees is strongly linked with the seasons and the availability of the floral resources. Our data suggested that honey bees may seek specific nutrients during variation of the seasonal conditions.     

Honey bee kin recognition: learning self and nestmate phenotypes

It is known that there is a genetic basis to the labelling of individuals for kin recognition in the honey bee, Apis mellifera. This study shows that individual workers reared in total isolation are able to discriminate between their full sisters and maternal half sisters. When individuals were reared with a half sister, recognition of their own patritype persisted, together with a comparable awareness of the patritype of their half sisters. Workers, when reared in mixed patritype groups of 10, showed no tendency to discriminate between full and half sisters, i.e. they appeared to learn both nestmate patritypes equally well. However, the labelling phenotypes of individuals reared together became more uniform, possibly through the transfer of substances during trophallaxis and mutual grooming. Workers exposed to 10 patritypes from their full sister patriline were more likely to accept an unfamiliar full sister than workers exposed to only five. Finally, workers reared in the hive appeared to retain an ability to discriminate their own patritype; i.e., even though the hive consisted of two worker patritypes, they discriminated between unfamiliar full and half sisters that had been reared under the same controlled conditions in an incubator.     

Honey bee and bumblebee trypanosomatids: specificity and potential for transmission

Abstract 1. Experimental studies of multihost parasite dynamics are scarce. Understanding the transmission dynamics of parasites in these systems is a key task in developing better models of parasite evolution and to make more accurate predictions of disease dynamics. 2. Bumblebee species (Bombus spp.) host the trypanosomatid parasite, Crithidia bombi. Its transmission in the field occurs through the shared use of flowers. Flowers are a perfect scenario for inter‐taxa transmission of diseases because they are used by a wide range of animals. 3. Honey bees host a poorly studied trypanosomatid, Crithidia mellificae. In this study, five questions have been experimentally addressed: (a) Can C. bombi infect honey bees? (b) Can C. mellificae infect bumblebees? (c) Can the honey bee act as a vector for C. bombi? (d) Are C. bombi cells present in honey‐bee faeces? (e) Does C. bombi have an effect on the mortality of honey bees after ingestion? 4. While both parasites were found to be specific to their hosts at the genus level, results suggest that honey bees may play a role in the epidemiology of C. bombi transmission.     

Honey bee pathology: current threats to honey bees and beekeeping

Managed honey bees are the most important commercial pollinators of those crops which depend on animal pollination for reproduction and which account for 35% of the global food production. Hence, they are vital for an economic, sustainable agriculture and for food security. In addition, honey bees also pollinate a variety of wild flowers and, therefore, contribute to the biodiversity of many ecosystems. Honey and other hive products are, at least economically and ecologically rather, by-products of beekeeping. Due to this outstanding role of honey bees, severe and inexplicable honey bee colony losses, which have been reported recently to be steadily increasing, have attracted much attention and stimulated many research activities. Although the phenomenon “decline of honey bees” is far from being finally solved, consensus exists that pests and pathogens are the single most important cause of otherwise inexplicable colony losses. This review will focus on selected bee pathogens and parasites which have been demonstrated to be involved in colony losses in different regions of the world and which, therefore, are considered current threats to honey bees and beekeeping.     

Honey bee dispersal of biocontrol agents: An evaluation of dispensing devices

Many reports have been published lately on the use of honey bees to disseminate biocontrol agents to flowers, using various kinds of inoculum dispensers. This technique is mainly used to deliver agents for controlling fire blight and gray mold. The present study evaluated the relative efficiency of a newly developed 'Triwaks' dispenser with three other dispenser types, 'Peng', 'Tub', and 'Harwood', with respect to effects of the dispensers on bee activity, and effectiveness for contaminating bees with high levels of inoculum for a long period of time after its application. We found differences in these parameters of performance between dispenser types, with the Triwaks dispenser having the overall best performance. This dispenser could prove to be an effective tool for biocontrol. The evaluation methods that we present could be used for evaluating other dispenser types.     

生物行为变化研究的新模式——工蜂

蜜蜂群体由1只蜂王、几百只雄蜂和数千只工蜂组成,工蜂数量巨大,除蜂王和雄蜂共同完成生殖任务,巢内外活动均由工蜂完成,其行为呈现多样性。工蜂发育经过卵、幼虫、蛹、成虫4个阶段,其活动范围由温度、湿度相对稳定的巢内环境发展到复杂的巢外自然环境。随发育阶段和生活环境的变化,工蜂的生理、行为等方面也发生相应变化,这种变化为综合研究生物行为的分子机理提供了可能。又因工蜂数量多、体积较大易于观察、标记、饲养管理简单,而且目前对其形态、发育、生理、分子生物学、神经、社会生态等各方面的研究比较充分,所以工蜂成为研究生物体行为变化、发育机理和个体与群体关系的理想模式生物。该文介绍工蜂活动由巢内发展到巢外时出现的一系列变化以及部分变化的机制,主要包括行为的变化、激素的分泌、代谢活动、飞行能力、神经系统等。     

Honey bee orientation behaviour and the influence of flower distribution on foraging movements

ABSTRACT.

• 1 Directional movement by foraging honey bees (Apis mellifera L.) was studied on several flower arrays. The most frequent move among equidistant flower stalks was straight ahead from stalk to stalk with frequencies decreasing for increasing turn angles. Turns to the left were about equal in frequency to turns to the right.
• 2 Bees maintained directionality when moving from flower stalks that had been rotated 90° counterclockwise while the bee was on the stalk (no difference between moves from rotated stalks and unrotated controls). Thus, directionality is maintained by the bee and is not an artefact of flower distribution.
• 3 Bees also maintained directionality when the entire array was rotated around the flower stalk the bee was on. Thus, bees use an external cue to orientate in a given direction rather than fixing on an inflorescence within the flower array.
• 4 Bees foraging on very different flower arrays differed in patterns of directionality and in distances flown between flower stalks. Therefore, even though bees maintain directionality using external cues, flower distribution can nevertheless influence flight patterns.

     

Honey bee dance communication: waggle run direction coded in antennal contacts?

The behaviour of 38 honeybee dance followers and the patterns of antennal contact between followers and dancer were monitored during ten waggle runs for a feeding site 1200 m from the hive. The analysis was restricted to waggle runs with a maximum of 5 followers, allowing the followers to choose between different positions around the dancer. At the beginning of the waggle run, followers are rather evenly spaced around the dancer. During the waggle run, the followers tend to accumulate at the rear end of the dancer. At the end of the waggle run, all followers are found in a ±60° arc behind the dancer. The body orientation angles of the followers depend on their position relative to the dancer. The follower bees have intense antennal contact with the dancer. At least one temporal parameter of the contact pattern may inform the followers about their position relative to the dancer, may guide the dance followers to the rear end of the dancer and may allow them to extract information about the location of the food source advertised by the dance. The role of antennal contact for dance communication appears to have been underestimated in previous studies. Accepted: 20 February 1999     

Honey bee colony collapse disorder is possibly caused by a dietary pyrethrum deficiency

Industrialized farming relies on bee keepers transporting hives to the vicinity of large areas of mono-crops for crop pollination. Hives are typically moved multiple times per growing season to satisfy the pollination need. A phenomenon wherein colonies of honey bees collapse in large numbers has been threatening crops in North America. Honey bees are hosts to at least two pathogenic mites; Varroa destructor and Acarapis woodi (a tracheal mite). Pyrethrums are a group of flowering plants which include Chrysanthemum coccineum, Chrysanthemum cinerariifolium, Chrysanthemum marschallii, and related species. These plants produce potent insecticides, also named pyrethrums, which are powerful mite toxins. We believe that a honey bee dietary deficiency of pyrethrums and other micro-nutrients from pyrethrum producing plants allows parasitic mites to either kill the honey bees directly or reduce honey bee resistance to other pathogens. Intermittent feeding of honey bees on pyrethrum producing plants might reverse or prevent colony collapse disorder.     

Honey bee handling behaviour on the papilionate flower of Robinia pseudoacacia L.

Papilionate flowers, such as those of Robinia pseudoacacia L., show tripping mechanisms that prevent pollen release: only those bees which apply the right force on petals induce pollen to be deposited on their bodies. Apis mellifera is considered a poor visitor of such flowers, since individuals are usually too weak to trip the mechanism. Despite this, the honey bee pays frequent visits to flowers of R. pseudoacacia and produces a much appreciated unifloral honey. We investigated how bees manipulate R. pseudoacacia flowers, whether they contact the plant’s reproductive core and if there is any appreciable difference related to the manipulation of individual flowers. Honey bees showed two strategies for resource collection, namely legitimate visits and robberies. Legitimate visits were more frequent and about 63 % entailed contact with the flower’s reproductive core. We distinguished two behaviours, one to achieve successful positioning on the flower and the other for nectar intake. These behaviours were clearly perceptible and described by different curves of time frequency distribution. From the beginning to the end of anthesis, flowers were classified into four types on the basis of their morphological and phenological traits. Positioning time differed significantly depending on the flower type, with less time needed for more ageing flowers. Time spent in nectar intake was instead highly variable and independent of flower ageing. Selecting the right flower type would appear to lead to obtaining the R. pseudoacacia reward, overcoming species-specific physical inability. Moreover, the role of honey bees as pollinators of R. pseudoacacia is considered. Finally, the relations between petal characteristics and strength needed to trip the mechanism in papilionate flowers is also discussed in the light of nectar foragers.     

Honey bee hygienic behaviour does not incur a cost via removal of healthy brood

In the honey bee, hygienic behaviour, the removal of dead or diseased brood from capped cells by workers, is a heritable trait that confers colony‐level resistance against brood diseases. This behaviour is quite rare. Only c. 10% of unselected colonies show high levels of hygiene. Previous studies suggested that hygiene might be rare because it also results in the removal of healthy brood, thereby imposing an ongoing cost even when brood diseases are absent. We tested this hypothesis by quantifying hygienic behaviour in 10 colonies using a standard technique, the freeze‐killed brood (FKB) bioassay. At the same time, we also quantified the removal of untreated brood. The study colonies showed a wide range in hygienic behaviour, removing 19.7–100% of the FKB. The removal of untreated brood ranged from 2% to 44.4%. However, there was no correlation between the two removal rates for any of the four age groups of untreated brood studied (eggs, young larvae, older larvae from uncapped cells and larvae/pupae from capped cells). These results do not support the cost‐to‐healthy‐brood hypothesis for the rarity of hygienic behaviour.     

Honey bee queen mandibular pheromone inhibits ovary development and fecundity in a fruit fly

A key feature of eusocial insects is their reproductive division of labour. The queen signals her fecundity to her potentially reproductive daughters via a pheromone, which renders them sterile. In contrast, solitary insects lack division in reproductive labour and there is no such social signalling or need for ovary‐regulating pheromones. Nonetheless, females from both non‐social and eusocial lineages are expected to regulate their ovaries to maximize inclusive lifetime reproductive success. It is not known, however, whether the underlying networks that regulate ovary activation are homologous between non‐social and eusocial taxa, especially when these taxa are phylogenetically distant. In this study, we provide evidence that solitary fruit flies may share a conserved ovary‐regulating pathway with a eusocial honey bee, Apis mellifera L. (Hymenoptera: Apidae). Specifically, we demonstrate that honey bee queen mandibular pheromone (QMP) inhibits fly ovaries in much the same way as it suppresses worker ovaries. Drosophila melanogaster Meigen (Diptera: Drosophilidae) exposed to sufficient doses of QMP showed a reduction in ovary size, produced fewer eggs, and generated fewer viable offspring, relative to unexposed controls. Drosophila melanogaster therefore responds to an interspecific social cue to which it would not normally be exposed. Although we cannot strictly rule out an incidental effect, this conspicuous response suggests that these two species may share an underlying mechanism for ovary regulation. Why a non‐social species of fly responds to a highly social bee's pheromone is not clear, but one possibility is that solitary and social insects share pathways associated with female reproduction, as predicted by the ‘groundplan’ hypothesis of social evolution.     

Honey bee waggle dance communication increases diversity of pollen diets in intensively managed agricultural landscapes

The benefits of honey bee dance communication for colony performance in different resource environments are still not well understood. Here, we test the hypothesis that directional dance communication enables honey bee colonies to maintain a diverse pollen diet, especially in landscapes with low resource diversity. To test this hypothesis, we placed 24 Apis mellifera L. colonies with either intact or experimentally disrupted dance communication in eight agricultural landscapes that differed in the diversity of flowering plants and in the dominance of mass‐flowering crops. Pollen from incoming foragers was collected and identified via DNA metabarcoding. Disrupting dance communication affected the way the diversity of honey bee pollen diets was impacted by the dominance of mass‐flowering crops in available flower resources (p = .04). With increasing dominance of mass‐flowering crops in resource environments, foragers of colonies with intact communication foraged on an increasing proportion of available plant genera (p = .01). This was not the case for colonies with disrupted dance communication (p = .5). We conclude that the honey bee dance communication benefits pollen foraging on diverse plant resources and thereby contributes to high quality nutrition in environments with low‐resource diversity.