Evidence for competition between honeybees and bumblebees; effects on bumblebee worker size

Numerous studies suggest that honeybees may compete with native pollinators where introduced as non-native insects. Here we examine evidence for competition between honeybees and four bumblebee species in Scotland, a region that may be within the natural range of honeybees, but where domestication greatly increases the honeybee population. We examined mean thorax widths (a reliable measure of body size) of workers of Bombus pascuorum, B. lucorum, B. lapidarius and B. terrestris at sites with and without honeybees. Workers of all four species were significantly smaller in areas with honeybees. We suggest that reduced worker size is likely to have implications for bumblebee colony success. These results imply that, for conservation purposes, some restrictions should be considered with regard to placing honeybee hives in or near areas where populations of rare bumblebee species persist.     

Biotope Associations and the Decline of Bumblebees (Bombus spp.)

Much of the ecology of rare bumblebee species remains poorly understood and in need of further study. It has recently been suggested that differences in the range and rate of decline among bumblebee species may relate to differences in their degree of habitat specialization. We examine biotope use by 17 bumblebee species in the Hebrides, southern UK and South Island, New Zealand. We identify a cluster of widespread and abundant species that occur in almost all biotopes and exploit man-made environments such as gardens and arable margins, this group corresponding to the “mainland ubiquitous” species of previous studies. A second grouping of species includes those associated to varying degrees with heathland. It is notable that some species occupy markedly different biotopes in different parts of their range; for example B. soroeensis is found largely on upland heaths in the Hebrides, but on calcareous grassland in the south. Some species, such as B. subterraneus and B. distinguendus, now survive only in specific rare biotopes and could be mistaken for habitat specialists, but it is clear from their historic distributions that they formerly occupied a broader range of biotopes. Surviving populations of several of the species that have declined most (B. distinguendus, B. sylvarum, B. muscorum sladeni, B. humilis) exhibit a markedly coastal distribution, when once they were widespread inland. We suggest that this is probably simply because some coastal biotopes are less amenable to agricultural improvement, and so more have escaped the detrimental effects of intensive farming. Our results concur with previous suggestions that bumblebees are generally not habitat specialists, so that the conservation of most bumblebee species could be achieved by restoration of flower-rich unimproved meadows.     

Bumblebees experience landscapes at different spatial scales: possible implications for coexistence

Coexistence in bumblebee communities has largely been investigated at local spatial scales. However, local resource partitioning does not fully explain the species diversity of bumblebee communities. Theoretical studies provide new evidence that partitioning of space can promote species coexistence, when species interact with their environment at different spatial scales. If bumblebee species possess specific foraging ranges, different spatial resource utilisation patterns might operate as an additional mechanism of coexistence in bumblebee communities. We investigated the effects of the landscape-wide availability of different resources (mass flowering crops and semi-natural habitats) on the local densities of four bumblebee species at 12 spatial scales (landscape sectors with 250–3,000 m radius) to indirectly identify the spatial scales at which the bumblebees perceive their environment. The densities of all bumblebee species were enhanced in landscapes with high proportions of mass flowering crops (mainly oilseed rape). We found the strongest effects for Bombus terrestris agg. and Bombus lapidarius at large spatial scales, implying foraging distances of 3,000 and 2,750 m, respectively. The densities of Bombus pascuorum were most strongly influenced at a medium spatial scale (1,000 m), and of Bombus pratorum (with marginal significance) at a small spatial scale (250 m). The estimated foraging ranges tended to be related to body and colony sizes, indicating that larger species travel over larger distances than smaller species, presumably enabling them to build up larger colonies through a better exploitation of food resources. We conclude that coexistence in bumblebee communities could potentially be mediated by species-specific differences in the spatial resource utilisation patterns, which should be considered in conservation schemes.     

The fine structure of the tarsal glands of the honeybee Apis mellifera L. (Hymenoptera)

Summary Tarsal glands are located in the 6th tarsomere of adult honeybee queens, workers and drones. Their structural features are not cast or sex specific. The glandular epithelium is lined by a thin endocuticular layer. A cuticular pocket is formed from a postimaginal delamination of the cuticle secreted by the glandular epithelium. The apical plasma membrane of the glandular cells shows numerous cristae and microvilli lining large crypts that communicate with the subcuticular space. Pinocytotic vesicles, multivesicular bodies and residual dense bodies are present in the apical part of the glandular cells. The RER is well developed in perinuclear and basal parts of the glandular cells, but the Golgi apparatus is a discrete organelle without secretory granules. No exocytotic secretory structures were observed. To reach the glandular pocket, the non-proteinaceous secretory product must pass across the subcuticular space, the cuticular intima, the space between the intima and the cuticular wall, and the cuticular wall of the glandular pocket.     

农田边界生物多样性与边界属性相互关系研究

农田边界 (田埂ｆｉｅｌｄｂｏｕｎｄａｒｙ)可定义为农田(作物田块 )间过渡带 (ｅｃｏｔｏｎｅ) [4 ] 。不同类型农田边界所包含的景观要素不同。农田边界包括的景观要素有树篱、防护林、草带、墙、篱笆、沟渠、道路、作物边界带等。半自然生境的农田边界是重要的动植物栖息地和扩散廊道[6] ,而农田边界的生物多样性和物种的扩散 ,又受边界结构属性、农作系统及农作措施和区域景观结构及动态的影响[1,7] 。随着人口的增加和农业集约化的发展 ,农业景观中非生产性(半自然生境 )用地面积逐渐减少 ,在一定程度上引起生物多样性下降及影响农田…     

Foraging behaviour of honey bees (Apis mellifera L.) on transgenic oilseed rape (Brassica napus L.var. oleifera)

The impact of genetically modified oilseed rape (Brassica napus L.) on the foraging behaviour of honey bees (Apis mellifera L.) was evaluated on two different lines transformed to express constitutively heterologous chitinase in somatic tissue for enhanced disease resistance. Experiments were conducted in confinement in an indoor flight room with controlled conditions and in an outdoor flight cage with conditions more representative of the open environment. Foraging behaviour was analysed by observations of general bee behaviour (total number of visits) and of individual bee behaviour (using a video camera coupled with a special software program to process the data). The plants were analysed in terms of nectar quantity and quality (nectar volume and sugar content). The results showed no effects on bee foraging behaviour due to the modification of the genome of these plants by the introduction of a chitinase gene even though some differences between lines were found in the nectar. The methods applied in this original approach for the evaluation of the impact of genetically modified oilseed rape were shown to be sufficiently sensitive to detect changes in bee behaviour resulting from differences between plants.     

Discrimination of nestmate workers and drones in honeybees

Summary Discrimination of nestmates from non-nestmates has mainly been investigated in female social insects. Little is known about discrimination of males. Here we show that under natural conditions at the nest entrance, honeybee workers can discriminate nestmate drones from non-nestmate drones as effectively as they can discriminate nestmate workers from non-nestmate workers.     

The effects of season,pretraining, and scent on the efficiency of traps for capturing recruited honey bees (Hymenoptera: Apidae)

A portable trap was designed to capture honey bees recruited to the field by dancers. An infrared phototransistor placed in the entrance tunnel of the trap sensed an incoming bee and turned on a talking clock, which in turn activated a voice-actuated audio tape recorder that recorded the time. We tested the effectiveness of traps for capturing bees recruited by four dancer bees (1) during two seasons when local flower densities differed, (2) with or without a group of bees pretrained to enter traps for food, and (3) when the scent used in traps and at the dancers' feeding station was changed just prior to recruitment trials or was not changed. One trap was put out at each of four distances (50, 100, 150, and 200 m) from the hive, while dancers fed on concentrated sucrose at the feeding station located at 150 m in the same direction. Recruited bees that approached the traps but did not enter were counted by observers. More bees were recruited and captured in traps when the local flora was sparse (fall) than when flowers were abundant (summer), when bees were pretrained versus not pretrained, and when the scent was not changed just prior to recruitment trials versus changed. The distributions of number of bees counted at the four distances at scented recruit stations and trapped were similar only when bees were pretrained and the scent was not changed during recruitment trials. However, the highest proportion of bees trapped in a trial at 150 m (distance to dancers' feeding station) was when bees were pretrained and the scent was changed.     

The role of trophallaxis in the distribution of Perizin in a honeybee colony with regard to the control of the Varroa mite

It is claimed that Perizin, a pesticide to control the mite Varroa jacobsoni, acts systemically and is distributed by trophallaxis of the bees. We studied the role of trophallactic interactions in the distribution of coumaphos, the active ingredient, among the colony members and whether coumaphos can reach all mites by systemic activity. Colonies were divided into three compartments by a screen, one receiving a Perizin treatment by sprinkling, the others receiving no Perizin. In this way it was possible to trace the amount of coumaphos transferred between bees through the screen from the treated part to the untreated one by trophallaxis. After different periods of time the number of fallen mites was counted and the amount of coumaphos in bees was determined for all hive compartments. We found that trophallactic interactions are of minor importance in the distribution of Perizin between the two compartments. The recommended method of sprinkling Perizin over the bees was shown to be very inefficient; only 24% of the applied amount reaches the alimentary canal of the bees; the rest must therefore remain at other places: on the outside of the bees, in the combs and on the hive-parts.     

Queen attendance behavior of worker honey bees (Apis mellifera L.) that are high and low responding to queen mandibular pheromone

Summary Queen attendance behavior of workers from selected honey bee colonies with high and low worker retinue response to synthetic queen mandibular gland pheromone (QMP) was investigated. Antennating, licking, grooming, and feeding of the queen by workers from high and low responding colonies were examined. High and low QMP responding workers did not attend the queen differently. However, workers originating from different colonies antennated and licked the queen more frequently than others, suggesting there may be a genetic basis for queen attendance behavior not necessarily associated with response to QMP. The median age of queen attendance was independent of strain.     

Effect of host brood type on the number of offspring laid by the honeybee parasite Varroa jacobsoni

The number of offspring laid by individual mites, varies depending on the type (drone or worker) of honeybee brood cell invaded. The number of offspring laid by individual mites increases when artificially transferred from worker to drone brood and vice versa when moved in the opposite direction.     

The perception of small objects by the drone honeybee

Drones (Apis mellifera ) were attracted to a lure scented with queen pheromone suspended at a height of 11–18m. An unscented test object, usually a black sphere, was lowered on a vertical string at a horizontal distance of 50 cm or 103 cm from the scented lure. Drones often made a rapid, direct, displacement from the scented lure to the test object. Drones responded to objects that subtended an angle as small as 0.41° which is less than the acceptance angle of a single ommatidium. We calculate that a drone can respond to a stimulus corresponding to a reduction in the light incident on one ommatidium at a time of 8%; the brevity of the stimulus on each ommatidium would seem to be a factor in the design of the eye.     

Clique formation of super-sister honeybee workers (<Emphasis Type="Italic">Apis mellifera</Emphasis>) in experimental groups

Summary One day old honeybee workers (Apis mellifera) were observed in small experimental groups (10 workers per group). These groups were either composed of offspring workers of singly inseminated queens (super-sister groups) or multiply inseminated queens (mixed groups). The groups thus consisted of either super-sisters or a mix of super- and halfsisters. The positions of the individually labelled workers were observed with infrared sensitive video equipment over a 24 h period and analysed with digital image analysis. The spatial distribution of workers in super-sister and mixed groups differed significantly. The distance between super-sister workers was significantly less than in mixed groups (n = 339; p < 0.01). Also the distance of the workers from the group centre was significantly less in super-sister groups as compared to mixed groups (n = 3440, p<0.05). The super-sisters thus formed tighter groups than the groups including half-sisters. A genotypic analysis of the mixed groups with microsatellite DNA markers revealed that workers were significantly more frequently observed next to a super-sister rather than a half-sister (p < 0.001). Irrespective whether this results from kin recognition or not, we expect clique formation to be an important factor for the development of task specialisation among worker bees.Received 26 August 2002; revised 22 April 2003; accepted 25 July 2003.     

The Significance of Odor Cues and Dance Language Information for the Food Search Behavior of Honeybees (Hymenoptera: Apidae)

Although several independent lines of evidence show that bees can make use of information provided by their dance language, there is an ongoing controversy about the significance of the dance information versus odor cues in the search behavior of recruited bees. A series of experiments was performed to assess the relative significance of dance information and odors for the site-specific search of recruit bees. In these experiments recruit bees were trapped automatically at arrays of artificial flowers at various distances from the hive. The distribution of directions in which the recruits searched for food was compared between recruitment by dancers performing well-oriented dances on the vertical side of the comb and dancers performing disoriented dances on a horizontal comb. The results show quantitatively that bees use both odor cues and the dance information. The greater the distance to the feeding site, the greater is the relative significance of the dance information.     

Number of reproductive cycles of Varroa jacobsoni in honey-bee (Apis mellifera) colonies

Very little data exists concerning the number of reproductive cycles performed by individual Varroa mites. To understand the population dynamics of the Varroa mite it is necessary to know the number of fertile female offspring each Varroa female produces during her lifetime. The lifetime reproduction capacity of the mite consists of the mean number of fertile female offspring produced during each reproductive cycle multiplied by the mean number of cell passages. This paper describes an experimental design to estimate the number of reproductive cycles where mites are transferred to new mite-free colonies for reproduction in sealed brood cells. The data presented suggests that the mean number of reproductive cycles performed by the individual female mite is larger than previously accepted. Under optimal conditions, the mean number of reproductive cycles by Varroa females is probably greater than 1.5 but less than 2. Furthermore, the results show that the reproductive success of Varroa females going into cells to reproduce is not influenced by previous brood cycles.     

Hearing in honeybees: the mechanical response of the bee's antenna to near field sound

In the dance language, honeybees use airborne near field sound signals to inform their nestmates of the location of food sources. In behavioral experiments it has recently been shown that Johnston's organ, a chordotonal organ located in the pedicel of the antenna, is used to perceive these sound signals. In the present study the mechanical response of the antennal flagellum to stimulation with near field sound signals was investigated using laser vibrometry. The absolute amplitudes of antennal deflection with acoustical stimulation, the response to sounds of different displacement and velocity amplitudes, the shape of movement of the flagellum, the mechanical frequency response and the mechanical directional sensitivity of the auditory sense organ of the honeybee are described. Using pulsed stimuli simulating the dance sounds it is shown that the temporal pattern of the dance sound is resolved on the level of antennal vibrations.     

The avoidance of diploid drones in closed population honeybee breeding

Honeybee breeding systems dependent on identification of the sex-determining alleles need to minimize the number of those alleles. A 4-allele system is proposed.