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Flowering plants attract pollinators via various stimuli such as odor, color, and shape. Factors determining the foraging behavior of pollinators remain a major theme in ecological and evolutionary research, although the floral traits and cognitive ability of pollinators have been investigated for centuries. Here we show that the autofluorescence emitted from pollen and anthers under UV irradiation may act as another attractant for flower-visiting insects. We have identified fluorescent compounds from pollen and anthers of five plant species as hydroxycinnamoyl derivatives. The fluorescent compounds are also shown to quench UV energy and exhibit antioxidant activity, indicating a function as protectants of pollen genes from UV-induced damage. A two-choice assay using honeybees in the field demonstrated that they perceived the blue fluorescence emitted from the fluorescent compounds and were attracted to it. This result suggested that the fluorescence from pollen and anthers serves as a visual cue to attract pollinators under sunlight. [ABSTRACT FROM AUTHOR]

The Afro-tropical scarab Oplostomus haroldi (Witte) is a pest of honeybees in East Africa with little information available on its chemical ecology. Recently, we identified a female-produced contact sex pheromone, ( Z)-9-pentacosene, from the cuticular lipids that attracted males. Here, we investigated the kairomonal basis of host location in O. haroldi. We used coupled gas chromatography/electroantennographic detection (GC/EAD) and GC/mass spectrometry to identify antennally-active compounds from volatiles collected from honeybee colonies. Antennae of both sexes of the beetle consistently detected seven components, which were identified as 3-hydroxy-2-butanone, 2,3-butanediol, butyl acetate, isopentyl acetate, butyl butyrate, hexyl acetate, and methyl benzoate. In olfactometer bioassays, both sexes responded to the full seven-component synthetic blend over solvent controls, but chose honeybee colony odors over the blend. These findings suggest that the seven compounds are components of a kairomone from honeybee colonies used by O. haroldi. [ABSTRACT FROM AUTHOR]

Honeybees ( Apis mellifera) use odors to identify and discriminate among flowers during foraging. This series of experiments examined the ability of bees to detect and discriminate among the floral odors of different varieties of two species of canola ( Brassica rapa and Brassica napus) and also among three varieties of snapdragons ( Antirhinnum majus). Individual worker honeybees were trained using a proboscis extension assay. The ability of bees to distinguish a floral odor from an air stimulus during training increased as the number of flowers used during training increased. Bees conditioned to the odor of one variety of flower were asked to discriminate it from the odors of other flowers in two different training assays. Bees were unable to discriminate among flowers at the level of variety in a randomized presentation of a reinforced floral odor and an unreinforced floral odor. In the second type of assay, bees were trained with one floral variety for 40 trials without reinforcement and then tested with the same variety or with other varieties and species. If a bee had been trained with a variety of canola, it was unable to differentiate the odor of one canola flower from the odor of other canola flowers, but it could differentiate canola from the odor of a snapdragon flower. Bees trained with the odor of snapdragon flowers readily differentiated the odor of one variety of a snapdragon from the odor of other varieties of snapdragons and also canola flowers. Our study suggests that both intensity and odor quality affect the ability of honeybees to differentiate among floral perfumes. [ABSTRACT FROM AUTHOR]

In honeybees, the cuticular hydrocarbon profiles are partly genetically based and differ between subfamilies, which suggests that they might be used by the workers as labels for subfamily recognition. This ability could potentially form the basis for nepotistic conflicts between subfamilies that would be detrimental to the inclusive fitness of the colony. Here we have compared the subfamily hydrocarbon profiles of 5-day-old workers maintained in isolation with those kept in their parental colony. We demonstrate that the cuticular hydrocarbon profiles tend to be less distant between most subfamilies within the hive compared with those held in isolation. The main consequence of this partial homogenization of the majority of subfamily signatures may result in a reduction of the number of recognizable subfamilies in the colony. Nevertheless, a few subfamilies retain very distinct cuticular hydrocarbon profiles. [ABSTRACT FROM AUTHOR]

Complex odor recognition in the honeybee was investigated using two behavioral assays: (1) the conditioning of the proboscis extension (CPE) with restrained individuals, and (2) the observation of foragers visiting an artificial feeder in a flight room. Nine compounds, previously identified as oilseed rape flower volatiles, were tested either individually or in mixtures. Different sets of experiments were done to determine: (1) the acquisition rate of the nine compounds in the CPE assay, and (2) the discrimination of the individual compounds after conditioning to a mixture, using the CPE assay and free-flying foragers. After conditioning to a complex mixture, honeybees established a hierarchy among the components, with some of them accounting for a major part of the behavioral activity of the mixture. Both behavioral assays led to the same classification of compounds, indicating good agreement between discriminating abilities of restrained individuals and of a population of foragers. The key compounds for recognition of these mixtures were those that were well learned when presented individually. However, the recognition of some compounds was affected by the other components of the mixture, with the activity of some compounds being either enhanced or reduced. [ABSTRACT FROM AUTHOR]

Volatiles from oilseed rape, Brassica napus, flowers were sampled by air entrainment and their relevance to the natural odor profile of the flowers was confirmed by conditioned proboscis extension (CPE) assays with honeybee, Apis mellifera L., foragers. Coupled gas chromatography (GC)-CPE analysis of the air entrainment samples was used to locate key compounds involved in the recognition of B. napus flowers, and the compounds were then identified using coupled gas chromatography-mass spectrometry and comparison with authentic samples. Six regions of the gas chromatograms elicited CPE responses from bees previously conditioned to the total extract, and from these areas 16 compounds were identified that elicited CPE activity from conditioned bees when tested with synthetic samples. Eight of the 16, α-pinene, phenylacetaldehyde, p-cymene, α-terpinene, linalool, 2-phenyl-ethanol, ( E, E)-α-farnesene, and 3-carene, gave the highest responses. When the bees were conditioned to the total extract of flower volatiles, a mixture of the eight components elicited responses from 83% of the individuals, suggesting that the eight-component mixture accounted for a major part of the CPE activity of the total extract. In addition, a mixture of the three most active compounds, phenylacetaldehyde, linalool, and ( E, E,)-α-farnesene, evoked responses from 85% of the bees after the latter had been conditioned to the eight-component mixture. Thus, these three compounds appear to play a key role in the recognition of the eight component mixture and, by inference, of oilseed rape flowers. [ABSTRACT FROM AUTHOR]

Queens and workers of five honeybee species ( Apis mellifera A. cerana A. dorsata A. floreaand A. andreniformis) were analyzed for their mandibular gland components. In A. melliferathe queen mandibular pheromone consists of 9-hydroxy- and 9-keto-2( E)-decenoic acids. (9-HDA and ODA), methyl p-hydroxybenzoate (HOB), and 4-hydroxy-3-methoxyphenyl-ethanol (HVA), and is responsible for retinue attraction, among other functions. In retinue bioassays with workers of A. cerana (whose queens lack HVA), ODA, 9-HDA, and HOB were sufficient to elicit maximal retinue behavior. This suggests that the known queen mandibular pheromone components detected in mandibular glands of A. cerana queens constitute the functional queen mandibular pheromone in this species. Both castes of A. mellifera produce 10- and 8-carbon acids that are functionalized at the last position in the chain, and these are the predominant compounds found in worker mandibular glands. Workers of the other species also had these compounds, along with 9-HDA and ODA that are normally not present in A. mellifera worker glands. Queens and workers of each species had a unique combination of mandibular compounds. The aromatic compounds were characteristic of queens from the cavity-nesting species A. mellifera (HOB and HVA) and A. cerana (HOB). These two species also had more pronounced differences in the mandibular blends of queens and workers than the open-nesting species A. dorsata A. floreaand A. andreniformis. Our results indicate that the more derived cavity-nesting species of Apis have evolved greater caste-specific differences between queens and workers and a higher number of queen pheromone components, compared to the open-nesting species. [ABSTRACT FROM AUTHOR]