Bee Species Research Articles

Discovery of Anthophora onosmarum Morawitz, 1876 in Europe (Hymenoptera, Apidae)

Anthophora onosmarum is a poorly known bee species described from the Caucasus (Georgia). New fieldwork has revealed that the species is present in Bulgaria and Greece, and is also widespread across Turkey, predominantly on the Anatolian plateau. New behavioural data shows that A. onosmarum is likely narrowly oligolectic on the plant genus Onosma (Boraginaceae), and is capable of buzzing flowers to release pollen. This finding illustrates the growing trend of overlooked bee species with more Caucasian, Anatolian, or even Middle Eastern distributions occurring in under-surveyed mountainous parts of the Southern Balkans.

Relationships between flower-visiting insects and forest cover in cocoa-growing landscapes in Ghana

Abstract Context Increased cocoa cultivation (Theobroma cacao) has led to the conversion of over 6 million hectares of rainforest to cocoa farmlands in West Africa. Globally, pollinator decline has been driven by land use changes. Though land use change through cocoa expansion may affect insect pollinators and, by extension, pollination services, this has rarely been assessed. Objectives Our study examined the relationships between the proportion of natural forest in the landscape (reduced primarily due to cocoa expansion) and flower-visiting insect abundance, and bee abundance, richness, diversity and community composition. The effect of pan trap type (aerial or ground) was also tested. Methods Eighteen sites were selected along a gradient of an increasing proportion of natural forests in the surrounding landscape (from 9 to 100%). Ground and aerial pan traps were deployed in each site to sample flower-visiting insects. Two sampling sessions were conducted; during the rainy season in 2021 and during the dry season in 2022. Results The abundances of Coleoptera, Hymenoptera and Hemiptera increased with increasing proportion of natural forests in the landscape, while Diptera decreased. Natural forest and trap type did not significantly influence bee abundance, species richness, and Shannon diversity. However, bee community composition differed along the forest gradient, indicating that forests and cocoa farms harbour different bee communities. Ground pan traps captured more insects (61% of 19,927 flower-visiting insects) than aerial pan traps, which was driven by the Diptera as the abundances of the other orders were not significantly related to trap type. Conclusions Preserving natural forest in cocoa-growing landscapes is important to sustain the coexistence of diverse flower-visiting insect communities owing to their differential responses to the proportions of natural forests.

Into the Buzzing World: Integrating Artwork with Fieldwork to Learn About Bees

This article describes a pedagogical approach that integrated artistic expression with experiential fieldwork to enhance pupils’ learning of bees. Initially, pupils were tasked with creating an artwork of a bee or bees based on their preconceived notions, allowing teachers to identify their prior ideas of bees. Afterward, an immersive field activity was conducted to provide pupils with an opportunity to close-up observe live honey and native bees in canola fields and their pollination processes. Through teacher-guided explorations, pupils systematically inspected the morphology of various bee species, relating their external structures to associated functions. The fieldwork allowed for detailed observations of bees’ features, such as the proboscis, antennae, and legs, and their roles in nectar collection and pollen distribution. In addition, exposure to honey and native bees informed pupils of the differences in their stinging, nesting and sociality. Pupils’ summative reflections post-fieldwork suggest that the immersive fieldwork enabled multi-sensory modes of learning barely available in a traditional classroom setting. By juxtaposing the new insights from field observations with the prior ideas of bees embodied in their initial artworks, pupils achieved gains in both their conceptual understandings and perceptual knowledge about bees. Pupils acknowledged deeper understandings of bee anatomy, pollination processes and the diversity within bee species. This approach to learning about bees epitomizes the value of empirical investigation for advancing pupils’ scientific practices and understanding life science core ideas of how animals' external structures fulfill various functions and of how plants and pollinators are interdependent, as highlighted in <i>the Next Generation Science Standards</i>. The integration of artwork creation and experiential fieldwork exemplifies an effective pedagogical approach for enhancing pupils' engagement and learning of biological ideas.

Tree traits are a stronger predictor of bee traits and species richness than taxonomic diversity

Abstract Functional traits help to understand biological diversity and the mechanism by which ecological communities are structured and how they respond to the environment. For example, the high tree species diversity within tropical forests can be grouped into a few functional attributes, wood density, size and dependence on animal pollination or seed dispersal. However, little is known about how these traits influence animal taxonomic and functional diversity in the forests. We carried out a vegetation census on six plots (20 × 100 m) within the National Forest of Carajás (Amazon biome) to identify forest canopy species and their functional traits. Within the same plot, we also applied three bee sampling methods (entomological nets, honey traps and scent traps). By characterizing the functional traits of trees and bees, we were able to predict bee functional diversity better than with taxonomic diversity alone via combinations of tree traits like size, wood density, dependence on pollinators and extinction risk. We found that larger trees with low wood density were negatively associated with small, eusocial tree cavity nesting bees. The richness and abundance of trees with high extinction risk was positively associated with the richness of medium‐sized solitary bees. The dominance in the community of pollinator‐dependent trees (average diameter in the basal area) was negatively associated with the richness of above‐ground and cavity nesting bees. Our findings suggest that the composition of the tree community limits the availability of nesting resources for specific groups of bees. Moreover, the presence of trees with higher extinction risk (conservation value) was associated with a greater variety of bee traits and was the only metric associated with overall bee richness. As expected, functional traits shed light on the mechanism that might drive high diversity within tropical forests. In addition, there appears to be complementarity in terms of conservation value and carbon stock potential, as areas that habour tree species with higher extinction risk and higher wood density are also those with overall greater bee and functional diversity. Finally, our study can contribute to the restoration of plant—pollinator community by providing an understanding of the vegetation community that contributes to biodiversity maintenance. Read the free Plain Language Summary for this article on the Journal blog.

Landscape diversity, habitat connectivity, age and size determine the conservation value of limestone quarries for diverse wild bee communities

Abstract Abandoned and even active limestone quarries (excavation sites) can represent important secondary habitats for many species, including wild bees, associated with dry grasslands, which are threatened biodiversity hotspots in Europe. However, is not well understood how interactions between local habitat and landscape characteristics influence the value of limestone quarries for wild bees and how this could guide conservation schemes. We studied how wild bee communities in limestone quarries are affected by landscape variables (connectivity to neighbouring dry grasslands, landscape diversity), local quarry characteristics (area, age, woody vegetation cover, flowering plant species) and their interactions. We surveyed bee communities during 208 transects in 19 quarries in southern Lower Saxony, Germany. In total, we recorded 114 bee species (2360 individuals), including 35 endangered species. High flowering plant species richness positively affected bee abundance and richness. Large quarry area was important for determining the presence of endangered bee species. High levels of woody vegetation cover had a negative effect on bee abundance and richness. Bee abundance and richness can increase with quarry age, but only at sites with moderate woody vegetation cover. We found potentially positive interactions between quarry age and landscape diversity and/or habitat connectivity to neighbouring dry grasslands. In particular, high habitat connectivity ensured stable richness of endangered species in old quarries. Synthesis and applications. Observed negative effects of high woody vegetation cover on bee communities highlight the importance of local management to reduce shrub encroachment and reset successional processes in limestone quarries. Local management is particularly important in old quarries of great ecological value, where the adverse impact of high woody vegetation cover on wild bees appears to be most severe. Large and old quarries with high connectivity to neighbouring dry grasslands are especially valuable for endangered bee species. Therefore, landscape‐scale restoration and conservation of dry grasslands is the most promising approach to promote endangered bee species through enhanced habitat connectivity.

Island Biogeography Theory and the Island Rule in Orchid Bees in Panama

ABSTRACTAimThe study of the theory of island biogeographic (TIB) has focused mainly on plants and vertebrates, with support for the predictions that species richness decreases with distance from the mainland and increases with island size. However, less work has been done on invertebrates. Similarly, the study of the island rule has been studied mainly in vertebrates. A group of invertebrates that can facilitate the study of TIB and the island rule are orchid bees (Apidae: Euglossini), because they are easily collected and show powerful flight performances that allows them to travel long distances. We wondered if these bees would follow the predictions of island biogeography, given that their populations may not be isolated across islands. To test if there is an homogenitazion of orchid bee communities across islands, we evaluated orchid bees abundance and species composition across islands. Besides, we tested the island rule by examining body size variations in individuals collected across islands.LocationCoiba National Park (Panama).Time PeriodMay and June 2023.TaxaOrchid bees (Hymenoptera: Apidae: Euglossini).MethodsBy using traps with chemical attractants, we sampled male bees from five islands and the mainland in Coiba National Park in the Pacific side of Panama. We tested the TIB by evaluating whether richness decreased with distance from the mainland or whether increased with island area. To investigate the island rule, and whether there is variation in body size across islands, we used Euglossa imperialis and Euglossa mixta as models, the two most abundant species in the study area.ResultsFor the overall orchid bee community, we found that our results fit one of the predictions of IBT, increases in orchid bee abundance with island area; however, species richness did not decrease with isolation and did not increase with island area as predicted by TIB. An interesting result was that as distance from the mainland increased few species became more dominant. Regarding the island rule, we found in the two Euglossa species a marked pattern of reduction in body size as distance from the mainland increased, which seems to outweigh the effect of island size, since the largest island and one of the farthest showed some of the smallest body sizes.Main ConclusionsWhether euglossine bees travel long distances across islands in marine environments remain unclear. As distance from the mainland increases, few species become dominant, which may be caused by a decrease of resources that favours generalist species. This increase in abundance may explain the decrease in body size with isolation, as perhaps competition for resources increases. Our study provides novel insights to better appraise the dynamics of orchid bees' communities in insular habitats.

Taxonomic Status of Stingless Bee Lepidotrigona arcifera (Hymenoptera: Meliponini) from the Southwest China - Tibetan Plateau

Abstract The stingless bee, Lepidotrigona arcifera, which was first reported in northeast India is a pollinating insect of the tropical and subtropical regions of the world. However, little information about this species is known in terms of taxonomic status as well as detailed morphological characteristics. In this study, we discovered a stingless bee in Tibet that belongs to an Alpine climate region. The morphological comparison with the India stingless bee, confirms that this newly discovered species is L. arcifera from the Tibet plateau. To determine the taxonomic status of this Tibetan stingless bee, we sequenced the 16S rRNA and COI genes of samples from a dozen colonies and compared them to some other known bee species. Phylogenetic analysis shows that Tibetan L. arcifera is grouped with the other stingless bee species and most closely sistered to the stingless bee, L. flavibasis. The genetic distance between Tibetan L. arcifera and the other stingless bee species is approaching those between pairwise bee species belonging to other such bee genera as Bombus and Apis. Hence, our results not only offer new information on species distribution and morphological characteristics of L. arcifera but also confirm its taxonomic status among stingless bees for the first time, which will contribute to understanding the biodiversity of stingless bees in the future.

Repeated Shifts in Sociality Are Associated With Fine-tuning of Highly Conserved and Lineage-Specific Enhancers in a Socially Flexible Bee.

Comparative genomic studies of social insects suggest that changes in gene regulation are associated with evolutionary transitions in social behavior, but the activity of predicted regulatory regions has not been tested empirically. We used self-transcribing active regulatory region sequencing, a high-throughput enhancer discovery tool, to identify and measure the activity of enhancers in the socially variable sweat bee, Lasioglossum albipes. We identified over 36,000 enhancers in the L. albipes genome from 3 social and 3 solitary populations. Many enhancers were identified in only a subset of L. albipes populations, revealing rapid divergence in regulatory regions within this species. Population-specific enhancers were often proximal to the same genes across populations, suggesting compensatory gains and losses of regulatory regions may preserve gene activity. We also identified 1,182 enhancers with significant differences in activity between social and solitary populations, some of which are conserved regulatory regions across species of bees. These results indicate that social trait variation in L. albipes is associated with the fine-tuning of ancient enhancers as well as lineage-specific regulatory changes. Combining enhancer activity with population genetic data revealed variants associated with differences in enhancer activity and identified a subset of differential enhancers with signatures of selection associated with social behavior. Together, these results provide the first empirical map of enhancers in a socially flexible bee and highlight links between cis-regulatory variation and the evolution of social behavior.

An annotated checklist of the bees of Washington state

Bees (Hymenoptera: Apoidea) are vital components of global ecosystems, yet knowledge of their distribution is limited in many regions. Washington state is located in an ecologically diverse part of North America and encompasses habitat types and plant communities known for high bee species richness. To establish a baseline for future studies on bee communities in the state, we used published and unpublished datasets to develop a preliminary annotated checklist of bees occurring in Washington state. We document, with high confidence, 565 species of bees in Washington and identify an additional 102 species likely to occur in the state. We anticipate future research survey efforts, such as the newly initiated Washington Bee Atlas, will discover several species that have the potential to occur in Washington and provide new data for 84 species which have not been recorded in more than 50 years.

Exploring network governance in sustainable beekeeping management in the Mekong subregion and its challenges

This research paper aims to explore a network governance in sustainable apiculture management and identify its challenges to government and non-governmental policy makers. Qualitative data was collected through participant observation during field visits and Focus Group Discussions (FGDs) with regional apiculture management. The research results show that each country in the Mekong subregion has different network governances in supporting a sustainable apiculture management. Some countries have a collaborative network between the government, the civil society, entrepreneurs, and scholars. In contrary, some countries lack a policy framework from the government. This difference becomes challenges for the six governments of the Mekong subregion countries to commonly support the sustainable apiculture management in the subregion. The identified challenges in the paper are: (1) a capacity gap between the six countries of the region; (2) no common policies and regulations that would facilitate local beekeepers’ access to wider regional bee products; (3) no support for inter-regional transport of bees and honey for academic purposes; (4) inadequate native bee species preservation and pesticides use; (5) local beekeepers’ limited access to a regional bee diseases and pesticides use database; and, (6) a lack of regional standards for general honeybee product support.

Assessing Apicultural Practices and Bee Species Identification from Northern and Southern Guinea Savannah zones of Niger State

Assessing Apicultural Practices and Bee Species Identification from Northern and Southern Guinea Savannah zones of Niger State

150 years after Ferdinand Morawitz: a survey of megachilid bees (Hymenoptera, Megachilidae) of Dagestan, Russia.

A list of 148 species of megachilid bees from 16 genera and five tribes is reported for the Republic of Dagestan. The list is based on more than 2,500 examined specimens and one reliable literature record. Twelve species are new to Russia: Chelostoma (Chelostoma) emarginatum (Nylander, 1856), C. (Foveosmia) maidli (Benoist, 1935), Hoplitis (Alcidamea) campanularis (Morawitz, 1877), H. (A.) caucasica (Friese, 1920), H. (Anthocopa) perezi (Ferton, 1894), H. (Pentadentosmia) tringa (Warncke, 1991), Osmia (Allosmia) melanura Morawitz, 1871, O. (Helicosmia) breviata Warncke, 1988, O. (Osmia) scheherazade Peters, 1978, O. (Pyrosmia) saxicola Ducke, 1899, Anthidium (Anthidium) taeniatum Latreille, 1809, and Megachile (Chalicodoma) montenegrensis Dours, 1873. Nine other species are new to the North Caucasus, and 46 other species are new to Dagestan. Compared to the first list of the bees of Dagestan published by F. Morawitz 150 years ago, the number of species of Megachilidae known from the republic was increased by five times.

Karyotypes and chromosomal mapping of some repetitive DNAs in two stingless bee species (Apidae: Meliponini), with the description of a B chromosome in Plebeia genus.

Cytogenetic studies on stingless bees have significantly contributed to our understanding of karyotypic evolution and the composition of euchromatin and heterochromatin regions, including repetitive sequences. In this study, we performed classical cytogenetics, chromosomal banding, and mapping of some repetitive sequences in two stingless bee species, Frieseomelitta trichocerata and Plebeia poecilochroa. The species exhibit the typical diploid chromosome number of each genera, 2n=30 for Frieseomelitta and 2n=34 for Plebeia. Additionally, some individuals of P. poecilochroa presented a small heterochromatic B chromosome, showing a numeric variation of n=17 to 18 in males and 2n=34 to 35 in females. In both species heterochromatin is primarily distributed in the short arm and centromeric regions. Centromeric regions were found to be AT-rich in both species, while subterminal/terminal regions of the short arms of one and six chromosomes presented GC-rich sites in P. poecilochroa and F. trichocerata, respectively. The rDNA clusters mapped on two chromosome pairs in F. trichocerata, and in only one in P. poecilochroa. Microsatellites (GA)n, (GAG)n, and (CAA)n were predominantly mapped in euchromatic regions, while the telomeric motif (TTAGG)n mapped to the ends of most chromosomes, including the B chromosome of P. poecilochroa. The other repetitive probes used, including the rDNA clusters, do not label the B chromosome of P. poecilochroa. Our cytogenetic data highlight both similarities and differences when compared to other congeneric species, expanding the chromosomal data for both genera.

Corymbia calophylla (Marri) (K. D. Hill & L. A. S. Johnson) (Myrtaceae) is a major resource for native bees in the southwest western Australian biodiversity hotspot

Context A theoretical paradigm proposes that certain species can serve as ‘keystone species’ or ‘magnets’, being particularly important for biodiversity. Aims We present evidence that in the context of supporting Indigenous native bees, this is indeed the case for the tree Corymbia calophylla (Marri), a Myrtaceae endemic to southwest Western Australia. Methods To assess the role of C. calophylla as a resource for native bees, we collated the number of species recorded from surveys across 16 sites, and specimens lodged in the WA Museum. Its capacity to support wild bees was assessed from abundance of bees visiting this species (total and relative to other plants visited) from 24 sites. Key results Corymbia calophylla was visited by 81 species of native bees, and is often the main, or only, plant species visited. It blooms at a crucial time when most species have finished flowering at the end of summer. Conclusions We argue that C. calophylla represents a crucial landscape resource for native bees. Implications Protection and management of C. calophylla is likely to be important for preservation of native bee biodiversity.

ANTIOXIDANT ACTIVITIES AND PHYTOCHEMICAL COMPOSITION OF STINGLESS BEE (Heterotrigona itama) HONEY COLLECTED FROM Calliandra calothyrsus PLANTATION IN EAST KALIMANTAN, INDONESIA

Stingless bee honey is one of the most valuable insect products. The increasing popularity of stingless bee honey can be attributed to its composition, which has been linked to medicinal properties. Beekeeping with stingless bees is well-known in Indonesia, with Heterotrigona itama is the most popular stingless bee species cultivated in East Kalimantan, Indonesia. Stingless bees utilize various plant species as sustenance sources. Among those plants, Calliandra calothyrsus is popular planting in Indonesian bee plantations. This study analyzed the antioxidant (DPPH assay), phytochemical (qualitative method), water, and sugar content of H. itama stingless bee honey collected from a C. calothyrsus plantation. The results show that the water and sugar contents of the honey in this study were higher than in other research. Meanwhile, antioxidant capacity was also higher than in other studies. The phytochemical contents detected from honey in this study were carotenoids, coumarins, flavonoids, saponins, steroids, tannins, and triterpenoids. Even though the properties of stingless bee honey can differ based on vegetation and geographical origin, H. itama stingless bee honey collected from C. calothyrsus plantation in East Kalimantan, Indonesia, showed potential antioxidant activity and phytochemical content, which is advantageous to human health.

Spatiotemporal variability and foraging behavior of bee visitors to a rare long-lived iteroparous forb, Silene spaldingii (Caryophyllaceae).

Silene spaldingii S Watson is a rare long-lived forb (Caryophyllaceae) found primarily in open native grasslands of the Inland Pacific Northwest and is putatively pollinated by one key bumble bee pollinator, Bombus fervidus (Fabricius). However, populations of bumble bees and their visitation patterns can vary dramatically, and some species are in decline including B. fervidus. Understanding the role of co-pollinators such as sweat bees (Halictidae) could be crucial as the plight of rare plants and pollinators intensifies. We collected data across three seasons (2015-2017) on the Bombus-S. spaldingii pollination system, focusing on three Key Conservation Areas in the Channeled Scablands of eastern Washington. Bee visitors to S. spaldingii were monitored and the pool-of-pollinators was surveyed with blue vane traps. Nine species of bees were observed foraging on the plant, while 2211 bees comprised of five families, 22 genera and 81 taxa were captured in blue vane traps, meaning only 11.1% of species in the pollinator pool visited S. spaldingii. Halictus tripartitus Cockerell, a sweat bee, was a common visitor to the plant, but this was the first record of visitation for several other species, including Lasioglossum buccale (Pérez) which has never before been recorded in the Americas. These sweat bees appear to vector S. spaldingii pollen, suggesting they are co-pollinators of the plant. Weather and patch characteristics affected visitation patterns and the pool-of-pollinators. We conclude that sweat bees are likely co-pollinators of S. spaldingii and that they could become increasingly important if B. fervidus populations continue to decline.

An update on the wild bee fauna (Hymenoptera, Apoidea, Anthophila) of Serbia

Numerous wild bee (Hymenoptera, Apoidea, Anthophila) species show negative population trends, while the knowledge gaps on their occurrences and distributions prevent adequate conservation actions. The need for continuous updating of species records and reconfirmation of their presence has been recognized, especially in understudied areas. The present study presents the results of bee monitoring at 30 Serbian localities, each surveyed three times during 2023. Two sampling methods were used, the transect walks and the pan traps, resulting in a detection of 232 wild bee species. Among them, 13 species found at 13 localities, represent the first published records from Serbia: Andrena ferox Smith, 1847, A. nana (Kirby, 1802), A. praecox (Scopoli, 1763), A. pusilla Pérez, 1903, A. susterai Alfken, 1914, A. angustior (Kirby,1802), A. curvungula Thomson,1870, A. falsifica Perkins, 1915, Hoplitis mitis (Nylander, 1852), Hylaeus friesei (Alfken, 1904), Melitta melanura (Nylander, 1852), Nomada trapeziformis Schmiedeknecht, 1882, and Osmia uncinata Gerstaecker, 1869. This study contributes to an update of the list of bee species in Serbia, that now counts 744 species, and also provides additional data on European distributions. The new information on Melitta melanura is especially noteworthy, since this species has been assessed as Endangered by the European Red List of Bees due to its small area of occupancy and a severely fragmented distribution. Other important findings include the confirmation of the presence of some wild bee species in Serbia, i.e., 10 species reported as new records within the previous update, and 19 species that were without previously available records from the 21st century. Additionally, the present study indicates the effectiveness of both conducted monitoring techniques, in terms of different recorded species and numbers of specimens. These results lead to the conclusion that corroborates the application of complementary sampling methods as an adequate way to survey bee diversity and abundance.

On Butterflies and the Carpenter Bees (Xylocopa caffra): Perceived Ecological Roles and Description of Traditional Children’s Games in Mayotte (French island, Indian Ocean of East Africa)

With over a million described species, insects are the most diverse group of animals on Earth. Insects, particularly those responsible for pollination, play a major ecological role that is often overlooked or even ignored. Indeed, apart from honeybees, many species are not recognized for the services they provide. What is more, all pollinating insects do not attract the same affection. Some, such as butterflies, enjoy a very positive image, while others are feared or hated, often because they can sting. During a semi-structured interview study (N = 35) on the island of Mayotte, we confirmed these views. On the other hand, butterflies and one species of carpenter bee were the subject of many children’s play and games, which have now been abandoned. Those who played with them in the past, and more simply enjoyed watching children play, seem to bitterly regret it.

Neither nectar nor deception: the role of floral rewards in the pollination system of Laelia (Orchidaceae: Laeliinae).

Orchids offer a variety of floral rewards to pollinators. In many orchid groups, however, the transfer of pollen is based on food-deception, as in the case of Laelia (including Schomburgkia s.s.), a genus assigned to the Neotropical subtribe Laeliinae. Here, we report on the reproductive biology of a Brazilian member of this subtribe, namely, Laelia gloriosa, occurring in the forested areas of southeastern Brazil. The study includes analyses of floral morphology, histochemistry, and the chemical analysis of floral rewards and scents. Pollinators and pollination mechanism data were collected in the field by means of focal observations. Analyses of breeding systems and the percentage of potentially viable seed were also recorded. The floral morphology of Laelia gloriosa indicates that this species is melittophilous. The flowers release a citrus-like fragrance that attracts many species of bee. The flowers offer waxy material as a reward, and this is collected exclusively by Meliponini bees. Several bee species visit the flowers. However, those of L. gloriosa are pollinated exclusively by Trigona spinipes. Pollinaria are deposited on the bee's scutellum. Plants of the studied population were entirely self-compatible, but pollinator-dependent. The frequency of visits to these flowers was greater than in rewardless Laeliinae. Our study provides the first evidence of lipoidal substances as a resource in Laeliinae. The discovery that an orchid species (Laelia gloriosa) of this subtribe, hitherto considered to be entirely pollinated by nectar-seeking pollinators, offers a floral waxy material and provides new insights into the evolution of this important subtribe.

A test method for assessing chronic oral toxicity of a pesticide to solitary nesting orchard bees, Osmia spp. (Hymenoptera: Megachilidae).

Orchard bees of the genus Osmia Panzerare important pollinators of fruit trees in various regions of the world, with some species commercially available in the United States and Europe. In addition to their pollination services, Osmia lignaria, Osmia cornifrons, Osmia bicornis, and Osmia cornuta have been identified as potential model species for solitary bees in pesticide risk assessment and have been used for the development of new methods to test acute lethal effects via contact and oral routes of exposure. Our goal was to expand the available methodology to characterize the toxicity of pesticides for these solitary bees through a chronic oral test for adult bees. Chronic oral toxicity of pesticides to orchard bees has been reported, but methods differ among research groups. In our study, O. lignaria, O. cornifrons, O. bicornis, and O. cornuta female bees had access to sucrose solution ad libitum in separate, species-specific 10-day tests. Mean body mass, mean daily consumption, and survival differed among the studied bee species. The dose-response test design was validated with dimethoate, a reference toxic compound, and chronic toxicity endpoints were estimated for the 4 Osmia species. The median lethal daily doses normalized by weight for O. lignaria, O. bicornis, O. cornuta, and O. cornifrons were within the same order of magnitude at 0.23, 0.26, 0.49, and 0.61 µg dimethoate/g bee/day, respectively. The methodology described here was aligned as much as possible with the available honey bee and bumble bee standard methods to facilitate the comparison of chronic toxicity profiles among bee species.