Samuel Boff

Organic farming has been shown to offer advantages over conventional farming in protecting insect biodiversity, but our overall understanding of its relationship with wild bee population parameters, especially cuticular lipids, remains limited. In the current study, we installed bee hotels at different farming sites in southern Germany and hypothesized that the local farming system (organic vs. conventional), the extent of organic farming, and the extent of forest (percentage of each component in the analyzed landscape) influence the abundance of nests and individuals of small‐bodied solitary bees of the genus Hylaeus . Moreover, at the species level, we investigated the influence of the same agricultural landscape elements and forest cover on the number of nests, bee abundance, sex ratio, and body size of H. communis , the most common Hylaeus species at our study sites. We further investigated how this landscape variables influence the composition of cuticular lipids in females and males of this species. Our results were more conclusive at the species level. We found that organic farming positively influenced the abundance of H. communis , whereas abundance decreased with increasing forest cover. In contrast, the sex ratio was higher at conventional farming sites and increased with forest cover. Although females were larger than males, no effect of landscape variables on body size was detected. The chemical composition of cuticular lipids of H. communis was significantly influenced by the farming system. These findings raise concerns about potential mechanisms through which farming practices may influence the reproduction of cavity‐nesting wild bees in agricultural environments. In conclusion, our findings show a positive effect of organic farming on the abundance of H. communis , while also highlighting potential effects of farming practices on physiological traits and population‐level parameters of this small wild bee species.

Orchid bee species are important pollinators in the Neotropics. While male orchid bees are known to have a close interaction with odor-rewarding flowers, orchid bee females are often pollen generalists. In the current study, we investigated differences in the pollen diet diversity of orchid bees in various vegetation types and across sites with varying levels of forest cover by means of an analysis of the frass pellets of the orchid bee, Euglossa cordata (Linnaeus, 1758), and multiple species based on a literature review. The pollen grains found in the inner part of brood cells were used to assess the plant composition making up the diet of E. cordata in various areas of the state of São Paulo in Brazil. We found that this plant composition differed among vegetation types, and that diet specialization was lower in forested areas. Forest cover appeared to be the factor mostly associated with pollen richness in nests of E. cordata. Number of brood cells per nest were also associated with forest cover. The model used to assess the effect of forest cover on plant richness as part of brood diet of E. cordata was tested with the inclusion of published data and a newly generated data for E. annectans. This new data set allowed to understand the influence of forest in the pollen diet of multiple species in a more extensive geographic scale. Forest cover appeared to be important for a diversified pollen diet in several orchid bee species. Implications for insect conservation: Since a diversified pollen diet offered to larva bees is associated with bee survival and health, our results indicate that orchid bees relying on areas with higher forest cover have a more resilient population. Such findings emphasize the importance of conservation of forests, especially in the Neotropical region where many pollinator species are adapted to continuous forest environments.

The antagonistic interaction between wasps and bees has long driven the attention of beekeepers and evolutionary entomologists. In the most classic reported interaction, Vespa velutina may invade the nest of honeybees and kill many of workers. Although this interaction has been registered to Asian honeybees, which was shown how to defend the nests, little or no attention has been given to similar interactions in the Neotropical region. Here, we report for the first time an antagonistic interaction between the wasp Polybia ignobilis and the stingless bees, Tetragonisca angustula. The wasp of this species was recorded killing and chewing guard bees near at the nest entrance of the stingless bee. Although our report is limited to answer evolutionary aspects of this interaction, it raises questions which may help to understand in the future the reasons this behavior evolved.

The aboveground oligolectic bee, Heriades truncorum, is a particularly good model for studying the impact of pesticides on sexual communication, since some aspects of its mating behavior have previously been described. We have tested (1) the interference of the pesticide flupyradifurone on male precopulatory behavior and male mating partner preferences, (2) the way that the pesticide interferes in male quality assessment by the female, and (3) the effects of the pesticide on the chemical compounds in the female cuticle. We exposed bees of both sexes to a sublethal concentration of flupyradifurone. Various behaviors were registered in a mating arena with two females (one unexposed and one exposed) and one male (either unexposed or exposed). Unexposed males were quicker to attempt to mate. Treatment also impacted precopulatory behavior and male quality assessment by females. Males approached unexposed females more quickly than insecticide‐exposed ones. Females exposed to insecticide produced lower amounts of some cuticular hydrocarbons (sex pheromone candidates) and appeared less choosy than unexposed females. Our findings suggest that insecticide exposure affects sexual communication, playing a role both in male preference and in male quality assessment by the female.

Hymenopteran females are mostly highly selective, choosing their mating partner according to male quality signals, and may also signal their fertility through chemical advertisement. Male insects, in turn, often display a complex set of courtship behaviors to allure females to mate. In this study we explored the mechanisms triggering courtship behaviors in the oligolectic bee Heriades truncorum. In this species, males perform wing fanning followed by a sideways rocking motion before copulation. We tested the role of chemical cues in partner recognition by exposing males to dead females washed from cuticular extracts (i.e., sex pheromones) that were posteriorly coated, or not, with an extract of unmated females. Additionally, we experimentally reduced male wing length to test whether wing fanning was responsible for triggering sideways rocking motions. We found males to interact more often with females coated by extracts from unmated females, and to display wing fanning in the presence of these pheromones. Male wing fanning was important to perform sideways rocking motions, which are an essential behavior for successful mating and possibly an element used by females to evaluate male quality. Our study shows that both chemical and mechanical signals from female and male bees, respectively, are important elements in the mating system of H. truncorum.

Bumble bees (Bombus terrestris) are important pollinators of wild and crop plants. Despite their importance in the process of fruit and seed production on crop sites, their activity may be impaired due to exposure to pesticides. This species has a yearly life cycle and colony success may rely on effective foraging of workers on ruderal plants late in summer when most crops are no longer flowering. In the current study, we investigated the effect of chronic exposure to Sulfoxaflor on aspects of the foraging behavior of bumble bees and whether Sulfoxaflor influences the body size of workers of B. terrestris in a crop landscape. We found that 2 weeks of continuous exposure to Sulfoxaflor influenced workers’ foraging dynamics and collection of resources. However, there was no evidence that the 5 ppb dose of the pesticide impacted the ability of bees to handle flowers with different traits. Workers from colonies exposed to Sulfoxaflor were smaller. The effect on worker size may be explained as a consequence of the reduced pollen income per unit of worker foraging. Thus, if the effects of Sulfoxaflor applied directly to crops had the same effect as that observed on commercial bumble bees after our chronic exposure, it might negatively impact colony success due to the impact on pollen collection and the reduction in the size of workers.

Recent reports on bee health suggest that sublethal doses of pesticides have negative effects on wild bee reproduction and ultimately on their population growth. Females of the solitary horned mason bee Osmia cornuta, evaluate thoracic vibrations and odours of males to assess male quality. When certain criteria are met, the female accepts the male and copulates. However, these signals were found to be modified by sublethal doses of pesticides in other hymenopterans. Here, we tested whether sublethal doses of a commonly used fungicide (Fenbuconazole) impact male quality signals and mating success in O. cornuta. Males exposed to fenbuconazole exhibited reduced thoracic vibrations and an altered cuticular hydrocarbon profile compared to the control bees. Moreover, males exposed to the fungicide were less successful in mating than control males. Synthesis and applications. Our results indicate that a low toxicity fungicide can negatively affect male reproductive success by altering behavioural and chemical cues. This could explain the decreasing pollinator populations in a pesticide‐polluted environment. This study highlights the need for a more comprehensive approach, including behaviour and chemical cues, when testing new pesticides and a more cautionary approach to the pesticides already used on crops.