Apidologie最新文献

In the darkness of their nests, most social insect species communicate relying on chemical, tactile, electrical and mechanical signals. In honeybees, vibrational signals play a role not only in worker communication but also in communication among virgin queens in the process of swarming. Whereas the sensitivity to vibrations has been well studied in worker bees, vibrational sensitivity of queens and drones has never been investigated. We therefore studied the sensitivity to vibrations comparatively in workers, virgin and laying queens and in drones, focusing on the frequency range mainly used by virgin queens (350–500 Hz). Bees were tested behaviorally for responses to pulses of substrate borne vibrations in arenas placed on vibrational exciters. Vibrational amplitudes were measured using (LDV-calibrated) accelerometers. Real stimuli and sham stimuli were presented in a pseudorandom order. The threshold was defined as the lowest tested amplitude at which significantly more behavioral reactions were shown to real stimuli than to sham stimuli. Workers and virgin queens respond to amplitudes down to 0.25 m/s². The thresholds of laying queens are substantially higher and they respond to minimum amplitudes of 0.55 m/s². Drones show responses to amplitudes down to 0.6 m/s². We conclude that sex and caste have effects on vibrational sensitivity in honeybees: virgin queens are significantly more sensitive than laying queens, indicating that a high sensitivity is crucial for survival during the process of swarming; workers are likewise highly sensitive to execute efficient everyday work; drones are significantly the least sensitive.

Our insights into the responses of immature stages of vernal solitary bees to the thermal challenges of spring weather mostly come from studies of cavity-nesting megachilid bees in constant temperature incubators. Most of these studies reported either the average timing of adult emergence or the general pace of immature development. In this study, we tracked the longevity and developmental fates of eggs laid by nearly 200 female Osmia lignaria (Hymenoptera: Megachilidae) occupying observation nests set outdoors in a nature preserve. In the spring of 2022, the nesting population was challenged by a prolonged period of unseasonably chilly wet weather. As a consequence, fewer nest cells were provisioned, and hatching among the 2416 eggs was delayed for as much as a month. Surprisingly, these delays incurred no ill-effects on either egg survival or subsequent larval development, both of which were comparable to the much warmer spring of 2021 (3630 eggs). The population’s 33% reproductive shortfall in 2022 was instead attributable to limited hours warm enough for flight and foraging, in part evidenced by the paucity of multi-cell days. Eggs and larvae of this bee, and probably other vernal solitary bees, readily tolerate prolonged episodes of cold springtime weather.

Bees are often exposed to pesticide residues during their foraging trips in agricultural landscapes. The analysis of in-hive stored pollen reflects the spectrum of visited plants and can be almost used to link the exposure to pesticides.In the current study, bee bread samples were collected in May and July from 17 sites located in southern Slovakia. Samples were analysed using a multi-residue pesticide analysis method for a broad spectrum of active substances and microscopic for pollen identification.Our results revealed a bee bread contamination with 19 different active substances, with fungicides being predominant. Sixteen of them are authorized in the EU, but chlorpyrifos, chlorpyrifos-methyl, and chloridazon are not. The highest concentrations for pendimethalin (1400 µg/kg), fluazifop-butyl (640 µg/kg), fenpropidin (520 µg/kg), fluopyram (130 µg/kg), and difenoconazole (95 µg/kg) were detected. The total residue load in bee bread sampled in the early season (May) was significantly higher than in the late season (July). The mean residue load of insecticides analysed in July comprised 46% of May’s load, which is alarming due to the importance of bee bread in the diet for winter-rearing bees. Moreover, results from both sampling periods showed that fungicides were positively associated with plant families Apiaceae and Papaveraceae and herbicides with Aceraceae, Salicaceae, and Brassica-type/Brassicaceae.Hence, bee bread can be considered a suitable matrix and a good bio-indicator reflecting honey bee exposure to pesticides over the season.

Bees are crucial pollinators in terrestrial ecosystems, responsible for 80% of insect-driven pollination and playing a vital role in the pollination of 75% of crops. The honey bee, Apis mellifera, is not only used in honey production but also serves as a pollinator in agriculture. However, A. mellifera faces various challenges, including exposure to pathogens such as the Microsporidia Nosema ceranae, which has been linked to decreased crop yields and colony losses. Nosema ceranae spores infect adult honey bees by penetrating the midgut lumen and invading the cytoplasm of epithelial cells, completing their life cycle. However, the midgut possesses a protective mechanical barrier called the peritrophic matrix, composed of chitin and proteins, which prevents epithelial infection. Nevertheless, N. ceranae overcomes this primary defense mechanism, though the specific mechanisms it employs to cross the peritrophic matrix and reach the midgut epithelium are not yet well understood. This study aimed to investigate the potential role of the predicted endochitinase from N. ceranae to infect bees. We tested the hypothesis that inhibiting the expression of N. ceranae endochitinase through RNA interference would impact the pathogen infection of A. mellifera. Bees treated with dsRNA targeting endochitinase, administered 12 and 24 h after spore inoculation, exhibited suppressed endochitinase gene expression and a decrease in the number of total and viable N. ceranae spores in the midgut. These results indicate that inhibiting the expression of the target gene through RNA interference affects Microsporidia infection, underscoring the importance of this enzyme in the infection process.

How beekeepers can propagate the Varroa-resistant traits they have in their colonies depends on how varroa resistance, i.e. the key hygienic behavioural traits, is passed onto the next generation. This study investigates if the key hygienic traits are passed between workers via learning as is known to happen in bumble bees, or are the resistant traits encoded into the queens and thus her offspring. To test this, we re-queened known mite-resistant colonies with mite-naïve (susceptible) queens in both Hawaii and the UK. We also placed resistant queens in susceptible colonies in the UK. After 5 months in Hawaii and 12 months in the UK, mite levels in adults and brood were measured. In Hawaii, mite removal and cell recapping levels were also assessed. In both locations, the mite levels in colonies headed by suspectable (mite-naïve) queens or their daughters significantly exceeded that found in colonies headed by resistant queens or their daughters. The initial presence of resistant or suspectable workers did not affect the result. Therefore, to propagate mite-resistant traits, beekeepers only need to re-queen a colony with a locally mated queen from an established resistant population, as some UK and Hawaiian beekeepers are already doing.

Nectar, an important reward in plant-pollinator interactions, mainly provides sugars, but also other nutrients. Nectar sugar content is known to affect pollinator preferences, while the effect of other nectar nutrients on flower visitor choices is less well understood. To explore whether nectar nutrients affect the foraging preferences of the stingless bee Trigona fulviventris, we conducted feeding choice experiments with sucrose solution enriched with either an amino acid mixture (in high and low concentrations), sodium chloride (table salt), a fatty acid mixture, or quinine (a bitter tasting substance used as negative control) against pure sucrose solution in a lowland rainforest in Costa Rica. Bees were first trained to feeders presenting either a yellow (only sucrose solution) or a blue (sucrose solution plus tested substance) visual cue that the bees could use to associate with the solution content. They were subsequently offered a choice between the blue and yellow feeders in an unrewarded test. The bees preferred pure sucrose solutions over sucrose solutions with quinine, amino acids, or fatty acids, but not over solutions with salt. Our findings indicate that T. fulviventris is able to differentiate various nutrients in nectar and prefers pure sucrose solution or sucrose solutions with salt. Sugar and salt may therefore represent important nutrients in nectar and are likely key cues to assess nectar quality in tropical stingless bees. In contrast, other nutrients appear to compromise the bees’ taste for nectar and are likely obtained from other sources.

Honey bee (Apis mellifera) breeding has intensified as populations experience increasing stress and pollination demand increases. Breeding programmes risk genetic diversity losses as mating is focused on a small group of individuals. Loss of diversity at the complementary sex determiner (csd) locus results in decreased viability and reduced honey production. Bees that are homozygous at csd become inviable males rather than workers. We examined csd diversity in four Australian breeding populations: a queen bee breeder from New South Wales, another from Queensland, a Western Australian breeding programme involving 11 bee breeders, and a research population at the NSW Department of Primary Industries. We found 82 unique csd alleles across the four populations, 16 of which have not been previously reported. This study provides a snapshot of csd diversity in Australia which will be useful for the national honey bee genetic improvement programme (Plan Bee).

Climate change and/or land use change were repeatedly reported as important for both range expansion of alien bee species and range shrinking for native bee species. However, environmental changes may also positively affect native species that may expand across contiguous areas to their native ones. Here, we focused on Halictus scabiosae (Rossi, 1790) (Hymenoptera: Halictidae), a ground-nesting, primitively eusocial wild bee that has its primary distribution in Western-Southern Europe but that was recently recorded in Eastern-Central Europe. In particular, we studied the range expansion patterns of H. scabiosae, and we hypothesized that previously unsuitable areas may be currently colonized because of environmental changes. In the last 5 years, H. scabiosae moved its densest record areas to North-Eastern Europe, but its ecological niche remained almost unchanged from 1970 to date, suggesting that this bee species is following its preferred conditions (high temperature, high temperature seasonality, and low precipitation seasonality). Potential distribution models revealed high suitability in still unoccupied North-Eastern areas, with urbanization increasingly important as potential stepping stones towards the expansion. The relevant role of urbanization is confirmed by the increase in the number of urban records through time and by the fact that cities with greater population density and greater fragmentation are more likely associated with this species’ occurrence. Halictus scabiosae is thus expanding its range because climate change is producing—and urban environment is offering—suitable conditions in areas previously inadequate for its establishment.