Effective monitoring is necessary to provide robust detection of bee declines. In the United States and worldwide, bowl traps have been increasingly used to monitor native bees and purportedly detect declines. However, bowl traps have a suite of flaws that make them poorly equipped to monitor bees. We outline the drawbacks of bowl traps, as well as other passive sampling methods. We emphasize that current methods do not monitor changes in bee abundance. We then propose future approaches to improve bee monitoring efforts, which include improving our understanding of the efficacy and drawbacks of current methods, novel molecular methods, nest censusing, mark-recapture, sampling of focal plant taxa, and detection of range contractions. Overall, we hope to highlight deficiencies of the current state of bee monitoring, with an aim to stimulate research into the efficacy of existing methods and promote novel methods that provide meaningful data that can detect declines without squandering limited resources.

Body size is an integral functional trait that underlies pollination‐related ecological processes, yet it is often impractical to measure directly. Allometric scaling laws have been used to overcome this problem. However, most existing models rely upon small sample sizes, geographically restricted sampling and have limited applicability for non‐bee taxa. Allometric models that consider biogeography, phylogenetic relatedness, and intraspecific variation are urgently required to ensure greater accuracy. We measured body size as dry weight and intertegular distance (ITD) of 391 bee species (4,035 specimens) and 103 hoverfly species (399 specimens) across four biogeographic regions: Australia, Europe, North America, and South America. We updated existing models within a Bayesian mixed‐model framework to test the power of ITD to predict interspecific variation in pollinator dry weight in interaction with different co‐variates: phylogeny or taxonomy, sexual dimorphism, and biogeographic region. In addition, we used ordinary least squares regression to assess intraspecific dry weight ~ ITD relationships for ten bees and five hoverfly species. Including co‐variates led to more robust interspecific body size predictions for both bees and hoverflies relative to models with the ITD alone. In contrast, at the intraspecific level, our results demonstrate that the ITD is an inconsistent predictor of body size for bees and hoverflies. The use of allometric scaling laws to estimate body size is more suitable for interspecific comparative analyses than assessing intraspecific variation. Collectively, these models form the basis of the dynamic R package, “ pollimetry, ” which provides a comprehensive resource for allometric pollination research worldwide.

Reversing biodiversity declines requires a better understanding of organismal mobility, as movement processes dictate the scale at which species interact with the environment. Previous studies have demonstrated that species foraging ranges, and therefore, habitat use increases with body size. Yet, foraging ranges are also affected by other life-history traits, such as sociality, which influence the need of and ability to detect resources. We evaluated the effect of body size and sociality on potential and realized foraging ranges using a compiled dataset of 383 measurements for 81 bee species. Potential ranges were larger than realized ranges and increased more steeply with body size. Highly eusocial species had larger realized foraging ranges than primitively eusocial or solitary taxa. We contend that potential ranges describe species movement capabilities, whereas realized ranges depict how foraging movements result from interactions between species traits and environmental conditions. Furthermore, the complex communication strategies and large colony sizes in highly eusocial species may facilitate foraging over wider areas in response to resource depletion. Our findings should contribute to a greater understanding of landscape ecology and conservation, as traits that influence movement mediate species vulnerability to habitat loss and fragmentation.

Continued reports of bee declines have prompted repeated calls for a national monitoring programme in the United States. Here, we argue that such a large‐scale surveillance monitoring programme would consume inordinate resources without providing the sought‐after data in a meaningful time period. Surveillance monitoring cannot provide reliable and timely measures of absolute or relative population size, species richness or diversity, host plant and nest site preferences or typical foraging ranges. In addition, the multitude of specimens captured by the passive traps commonly used to surveil overwhelm our identification capacity and, in some cases, may even accelerate species decline. Conversely, surveillance monitoring should be pursued when data can be collected non‐lethally for readily identifiable species or species groups (e.g., bumble bees) or when widely distributed sentinel plants can be observed (e.g., sunflowers). Lethal collections should continue at appropriate temporal intervals but only at a limited number of representative areas with accurate historic records. We advocate that emphasis be placed on a targeted, natural‐history approach aimed at addressing specific hypotheses and exploring solutions to conservation management problems. We already know enough about the drivers of bee decline to formulate and test potential solutions. While additional information is of value in understanding bee diversity, distributions and evolution, we do not need it to begin to take action; we should be focusing on the best ways to help bee species endure rather than attempting to accumulate even more evidence that they are in trouble.

1. Grassland ecosystems are imperiled by agricultural activity worldwide. Restoring grassland habitat is important to conserving grassland fauna and preserving ecosystem services, but more knowledge is needed on the impact that local and landscape factors have on patterns of diversity. We focused on whether prairie grassland restorations along a gradient of increasing agricultural cover in the surrounding landscape would be inhabited by less diverse and/or more homogenous native bee communities. Native bees are a specific target for many grassland restoration efforts, and supporting their local and β-diversity in reconstructed habitats is of mounting interest. We also investigated if higher floral resource richness within restorations could help ameliorate negative effects of agricultural landscapes. 2. We sampled 16 prairie restorations in Minnesota (USA) that varied along a gradient of increasing agricultural land cover around the site. We characterized floral resource richness at all sites beginning in mid-May and ending in mid-September. We used GLMMs and multivariate analyses to disentangle how floral resource richness and percentage of surrounding land cover in agricultural production are associated with the local and β-diversity of bee communities. 3. Local bee diversity increased with increasing local floral resource richness, independent of the surrounding landscape. Bee β-diversity was not impacted by local floral resource richness or percentage of agricultural cover in the surrounding landscape, indicating local and landscape factors are not substantially impacting the homogeneity of bee communities across restorations. 4. Synthesis and applications. We found that, regardless of agricultural cover in the surrounding landscape, more florally rich plantings attract more diverse bee communities. We recommend that habitat plantings prioritize local scale diversity, and that potential sites where the landscape is dominated by agricultural production should not be overlooked for restoration.

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Purposeful transport of pollen represents a key innovation in the evolution of bees from predatory wasps. Most bees transport pollen on specialized hairs on the hind legs or ventral metasoma in one of three ways: moist, dry, or Bglazed,^which combines dry and moist transport. The evolutionary pathway among these three transport modes is unclear, though dry transport has been hypothesized to be ancestral. We address this hypothesis using museum specimens and published records of the bee genera Perdita (Andrenidae) and Hesperapis (Melittidae), two distantly related groups whose pollen transport modes appear to have converged. Most species in both genera transport moistened pollen; glazed and dry transport are limited to derived clades of specialists on floral hosts in Asteraceae and Onagraceae, with specialization on Asteraceae associated with more elaborate scopal hairs. The associations between transport mode, host plant, and hair type may be due to the sticky pollenkitt of asteraceous pollen grains and the viscin threads of Onagraceae pollen, which provide alternates to the binding properties of nectar. These findings suggest that the hypothesis that dry transport is ancestral in bees should be reexamined.

Pollen is the primary protein and nutrient source for bees and they employ many different behaviors to gather it. Numerous terms have been coined to describe pollen gathering behaviors, creating confusion as many are not clearly-defined or overlap with existing terms. There is a need for a clear yet flexible classification that enables accurate, succinct descriptions of pollen gathering behaviors to enable meaningful discussion and comparison. Here, we classify the different pollen gathering behaviors into two main classes: active and incidental pollen collection. Active pollen collection is subdivided into six behaviors: scraping with the extremities, buzzing, rubbing with the body and/or scopae, rubbing with the face, tapping, and rasping. In addition to the active and incidental pollen gathering behaviors, many bees have an intermediate step in which they temporarily accumulate pollen on a discrete patch of specialized hairs. Each behavior is described and illustrated with video examples. Many of these behaviors can be further broken down based on the variations found in different bee species. Different species or individual bees mix and match these pollen collecting behaviors depending on their behavioral plasticity and host plant morphology. Taken together, the different behaviors are combined to create complex behavioral repertoires built on a foundation of simple and basic steps. This classification sets the groundwork for further research on various topics, including behavioral plasticity in different species, comparisons between generalists and specialists, and the relative effectiveness of different pollen gathering behaviors.