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The bumble bee (Hymenoptera, Apidae, Bombini, Bombus Latreille) fauna of the Nearctic and Palearctic regions are considered well known, with a few species occurring in both regions (i.e., with a Holarctic distribution), but much of the Arctic, especially in North America, remains undersampled or unsurveyed. Several bumble bee taxa have been described from northern North America, these considered either valid species or placed into synonymy with other taxa. However, some of these synonymies were made under the assumption of variable hair colour only, without detailed examination of other morphological characters (e.g., male genitalia, hidden sterna), and without the aid of molecular data. Recently, Bombus interacti Martinet, Brasero & Rasmont, 2019 was described from Alaska where it is considered endemic; based on both morphological and molecular data, it was considered a taxon distinct from B. lapponicus (Fabricius, 1793). Bombus interacti was also considered distinct from B. gelidus Cresson, 1878, a taxon from Alaska surmised to be a melanistic form of B. lapponicus sylvicola Kirby, 1837, the North American subspecies (Martinet et al. 2019). Unfortunately, Martinet et al. (2019) did not have DNA barcode sequences (COI) for females of B. interacti, but molecular data for a melanistic female specimen matching the DNA barcode sequence of the holotype of B. interacti have been available in the Barcodes of Life Data System (BOLD) since 2011. Since then, additional specimens have been obtained from across northern North America. Also unfortunate was that B. sylvicola var. johanseni Sladen, 1919, another melanistic taxon described from far northern Canada, was not considered. Bombus johanseni is here recognized as a distinct taxon from B. lapponicus sylvicola Kirby, 1837 (sensuMartinet et al. 2019) in the Nearctic region, showing the closest affinity to B. glacialis Friese, 1902 of the Old World. As the holotype male of B. interacti is genetically identical to material identified here as B. johanseni, it is placed into synonymy. Thus, we consider B. johanseni a widespread species occurring across arctic and subarctic North America in which most females are dark, with rarer pale forms (i.e., “interacti”) occurring in and seemingly restricted to Alaska. In addition to B. johanseni showing molecular affinities to B. glacialis of the Old World, both taxa also inhabit similar habitats in the arctic areas of both Nearctic and Palearctic, respectively. It is also likely that many of the specimens identified as B. lapponicus sylvicola from far northern Canada and Alaska might actually be B. johanseni, so that should be considered for future studies of taxonomy, distribution, and conservation assessment of North American bumble bees.

The fauna and ecology of bumblebees in the European North are quite well-studied. However, there is a scarcity of information about the distribution and ecology of certain species of bumblebees, especially for the territory of Northern Russia. In this study, we summarised materials concerning Bombus (Pyrobombus) jonellus (Kirby, 1802), which is typical bumblebee species for the north-western portion of the Russian Plain and surrounding areas. The studied territory includes the Arkhangelsk Region and the western part of the Nenets Autonomous District, i.e. a wide strip from taiga to tundra ecosystems. Due to the studies of materials that were collected over a period 17 years, we established thatB. jonellusis widely distributed and the northern border of its range within the studied region reaches the northern part of the Kanin Peninsula. In the north-western Russian Plain,B. jonellushas been found in various types of habitats, the most common being coniferous and birch forests, secondary meadows and ruderal patches. In the Solovetsky Islands, White Sea, Russia,B. jonellusis typical on coastal heathlands. In the northern part of the studied region,B. jonellushas a tendency to forage in open habitats and visits a wide range of entomophilous plants, mostly of the family Ericaceae. Our findings highlight that the territory of the north-western Russian Plain and surrounding areas is whereB. jonellusis widely distributed and abundant, being recorded in different types of habitats.

Simple Summary Evidence of bumble bee population declines has led to an increase in conservation efforts to protect these important pollinators. However, effective conservation requires accurate species identification. We provide quantitative methods to accurately identify three cryptic species of bumble bees using morphometric measurements of the cheek length and width, and antennal segments. We validated the accuracy of our methods with DNA analysis. We predicted that these methods would reliably identify both the queens and worker bees of Bombus vagans and B. sandersoni. We expanded these methods to include an uncommon form of Bombus perplexus with all light hair on its thorax, rather than the more common light on top and dark below, that can mistakenly be identified as B. vagans or B. sandersoni. Although the species we consider here, Bombus vagans, B. sandersoni and B. perplexus, are not currently listed as species of concern in North America, there is uncertainty of their population status, some of which is due to difficulty in species identification, which we have resolved. Recent history informs us that some bumble bee species experience rapid declines within a few decades. Our methods to correctly identify these cryptic species is key to monitoring their status and population trends. Abstract Despite their large size and striking markings, the identification of bumble bees (Bombus spp.) is surprisingly difficult. This is particularly true for three North American sympatric species in the subgenus Pyrobombus that are often misidentified: B. sandersoni Franklin, B. vagans Smith B. perplexus Cresson. Traditionally, the identification of these cryptic species was based on observations of differences in hair coloration and pattern and qualitative comparisons of morphological characters including malar length. Unfortunately, these characteristics do not reliably separate these species. We present quantitative morphometric methods to separate these species based on the malar length to width ratio (MRL) and the ratios of the malar length to flagellar segments 1 (MR1) and 3 (MR3) for queens and workers, and validated our determinations based on DNA barcoding. All three measurements discriminated queens of B. sandersoni and B. vagans with 100% accuracy. For workers, we achieved 99% accuracy by combining both MR1 and MR3 measurements, and 100% accuracy differentiating workers using MRL. Moreover, measurements were highly repeatable within and among both experienced and inexperienced observers. Our results, validated by genetic evidence, demonstrate that malar measurements provide accurate identifications of B. vagans and B. sandersoni. There was considerable overlap in the measurements between B. perplexus and B. sandersoni. However, these species can usually be reliably separated by combining malar ratio measurements with other morphological features like hair color. The ability to identify bumble bees is key to monitoring the status and trends of their populations, and the methods we present here advance these efforts.

Bumblebees have been the focus of much research, but the taxonomy of many species groups is still unclear, especially for circumpolar species. Delimiting species based on multisource datasets provides a solution to overcome current systematic issues of closely related populations. Here, we use an integrative taxonomic approach based on new genetic and eco-chemical datasets to resolve the taxonomic status of Bombus lapponicus and Bombus sylvicola. Our results support the conspecific status of B. lapponicus and B. sylvicola and that the low gradual divergence around the Arctic Circle between Fennoscandia and Alaska does not imply speciation in this species complex. Therefore, based on our molecular and morphological analyses, we propose to assign them subspecific status: Bombus lapponicus lapponicus from Fennoscandia and West Siberia and Bombus lapponicus sylvicola comb. nov. from Alaska and Yukon. In addition, our analyses reveal a cryptic species in the B. lapponicus complex from Alaska, which we describe here as new: Bombus (Pyrobombus) interacti sp. nov.

This contribution results from an investigation of four commercially obtained colonies of Bombus (Pyrobombus) impatiens Cresson in an attempt to understand the functional anatomy and behavior of its immature stages. Eggs are described in detail, and their chorionic microstructure is contrasted with that of Bombus (Cullumanobombus) griseocollis (De Geer). They are deposited in groups consisting of a few to more than nine eggs into a single chamber. The study confirms that larvae pass through four instars. Although increasing in size dramatically from one instar to the next, larval anatomy and behavior change little during the first three instars. The last instar is the one that commences defecation and production of silk resulting in cocoon construction. In contrast to most bees, its larval activities result in substantial changes in size and shape of its brood chamber, whereas brood chambers of most bees are constructed by the female and modified little by the offspring. This study is a part of a series of investigations into the similarities and differences in the developmental biologies among corbiculate bees.

Herein I summarize what is known about Cockerell's bumblebee, Bombus cockerelli Franklin, a New Mexican bumblebee species whose existence has been largely overlooked for decades because of a combination of rarity, geographic restriction, and taxonomic confusion. It is noteworthy that the known distribution covers only about 777 km2, giving it the smallest known range of any bumblebee in the world. There are 34 known specimens, and I present historical details regarding their collection (dates, places, and host plants), deposition, and identification; hopefully, this information will allow others to locate additional specimens of this species. It is further notable that most of the known specimens are late-season queens, and males remain unknown, suggesting that the species may nest and forage in areas of dense forest.

Bumble bees (Hymenoptera: Apidae, Bombus) are important pollinators and models for studying mechanisms underlying developmental plasticity, such as factors influencing size, immunity, and social behaviors. Research on such processes, as well as expanding use of gene-manipulation and gene expression technologies, requires a detailed understanding of how these bees develop. Developmental research often uses time-staging of pupae, however dramatic size differences in these bees can generate variation in developmental timing. To study developmental mechanisms in bumble bees, appropriate staging of developing bees using morphology is necessary. In this study, we describe morphological changes across development in several bumble bee species and use this to establish morphology-based staging criteria, establishing 20 distinct illustrated stages. These criteria, defined largely by eye and cuticle pigmentation patterns, are generalizable across members of the subgenus Pyrobombus, and can be used as a framework for study of other bumble bee subgenera. We examine the effects of temperature, caste, size, and species on pupal development, revealing that pupal duration shifts with each of these factors, confirming the importance of staging pupae based on morphology rather than age and the need for standardizing sampling.

The volatile components from the labial glands of males of six Japanese bumblebee species were analyzed and compared. Clear species-specificity was found. Ethyl dodecanoate was identified as the major component from the glands of Bombus (Bombus) hypocrita hypocrita and Bombus (Bombus) hypocrita sapporoensis while dihydrofarnesal and dihydrofarnesol were the major components from Bombus (Bombus) ignitus. Citronellol and trans,trans-farnesol were found from Bombus (Pyrobombus) ardens ardens and Bombus (Diversobombus) diversus diversus, respectively. trans,trans-Farnesol was also found from Bombus (Diversobombus) diversus tersatus in Hokkaido. Such differences strongly suggest that these chemicals play an important role in reproductive isolation between sympatric species of Japanese bumblebees.

Bumblebees are important pollinators in mountainous regions. The highland region of Sichuan and Chongqing (together, Sichuan in the former broad sense) includes part of the greatest hotspot of bumblebee diversity worldwide, with half of the species of China and more than a fifth of the world's species. In this paper we present the first review of this diverse but particularly poorly known fauna, drawing on 6705 bees from selective samples made by the authors during field work and from museum collections, together with 1123 literature records (an overlapping set). Among this material we recognise 56 species that have 847 names (including infrasubspecific names). One new species, Bombus (Pyrobombus) wangae, is described from Sichuan and Gansu. B. laesus is found to have a colour pattern in this part of its range that was previously undescribed. Six species are recorded from the Sichuan‐Chongqing region for the first time (B. avanus, B. branickii, B. difficillimus B. humilis, B. norvegicus, B. tibet...

Historic data in the form of pinned specimens in entomological collections offer the potential to determine trends in genetic diversity of bumble bees (Bombus). We screened eight microsatellite loci in pinned bumble bee specimens from the U. S. National Pollinating Insects Collection. We tested three species (Bombus appositus, Bombus huntii and Bombus occidentalis) representing three subgenera of bumble bees (Subterraneobombus, Pyrobombus and Bombus sensu stricto) respectively. Bombus occidentalis is a species of particular concern for conservation biologists. Single mid-legs of ninety-six individuals from each species were assayed to determine microsatellite amplification success rates of historic material in a museum collection. Microsatellite alleles amplified in specimens up to 101 years old, but the rate of amplification success was significantly lower in material over 60 years of age. Loci with shorter allele sizes amplified more frequently than relatively longer alleles in samples from all age classes. We correlate the age of specimens to the age at which loci fail to amplify and discuss potential impacts of using certain markers for population genetic studies of museum specimens.

This study used the microsatellite locus B10 to determine the frequency of colonies with multiple patrilines in a previously unexamined group, the North American bumble bees (Bombus). The effective mating frequency (me) was greater than 1 in six of 28 colonies. Five of 11 species tested showed at least one incidence of polyandry: four species from the subgenus Pyrobombus (B. bimaculatus, B. impatiens, B. mixtus, B. ternarius) and one species from the parasitic subgenus Psithyrus (B. citrinus). The B10 locus showed high cross-species amplification success for North American Bombus.

Fifteen species and subspecies of the genus Pyrobombus are recorded in Turkey. They are listed together with their horizontal and altitudinal distribution, habitats and flowers visited. P. serrisquama is recorded for Turkey for the first time. With 2274 specimens collected, P. incertus proved to be the most widespread and abundant species, recorded from about sea level up to more than 3000 m. It was followed by P. niveatus with 1467 specimens and P. soroeensis with 1400 specimens. P. sulfureus was found at only two localities with five specimens, and it should be classified as »endangered«.

Resume Cette etude met en evidence l'efficacite du depot d'un marquage odorant dans la reconnaissance de l'entree du nid par les butineuses de bourdons. L'etude du comportement olfactif de ces ouvrieres a consiste a observer leur reponse en presence d'un marqueur odorant depose par d'autres ouvrieres en utilisant la methode du choix binaire. Les observations ont ete faites avec des colonies de plusieurs especes: Pyrobombus (P.) hypnorum L., Pyrobombus (M.) lapidarius L., Bombus lucorum L., Megabombus (T.) pascuorum Scop., Pyrobombus (P.) pratorum L. et Bombus terrestris L. L'experimentation a consiste egalement a faire varier qualitativement la stimulation, ce qui a permis d'etudier la capacite des ouvrieres a distinguer l'odeur de la substance deposee par les individus de leur propre colonie de celle deposee par les individus d'une autre colonie, isospecifique ou heterospecifique. Pour chaque espece etudiee, les ouvrieres retournant au nid font un choix en fonction de la nature du marquage. L'ecart entre les pourcentages de reponses est plus important dans le cas du choix entre ‘papier marque’ et ‘papier vierge’ (experience 1) que dans celui entre ‘papier marque par la colonie’ et ‘papier marque par une colonie etrangere heterospecifique’ (experience 3). Une moindre dispersion des reponses apparait dans le choix entre ‘papier marque par la colonie’ et ‘papier marque par une colonie etrangere isospecifique’ (experience 2). La discussion porte egalement sur le marquage de l'entree du nid chez des especes d'Hymenopteres solitaires terricoles, fonction attribuee a la secretion de la glande de Dufour. Le mecanisme de ce marquage chez les Apoides sociaux reste a etudier. Summary This study shows the efficiency of depositing an odoriferous marking to recognize the nest entrance by foragers of bumblebees. The study of the olfactory behaviour of these workers consisted in observing their responses to an odoriferous marker deposited by other workers, using the binary choice method. The observations were conducted with colonies of several species: Pyrobombus (P.) hypnorum L., Pyrobombus (M.) lapidarius L., Bombus lucorum L., Megabombus (Th.) pascuorum Scop., Pyrobombus (P.) pratorum L. and Bombus terrestris L. The stimulation was varied qualitatively, which made it possible to study the ability of workers to distinguish the odour of the substance deposited by individuals of their own colony from that deposited by individuals of another colony, isospecific or heterospecific. For each species studied, the returning nest workers made a choice depending on the nature of the marking. The difference between the percentages of responses was greater in the case of the choice between ‘impregnated-paper’ and ‘non-impregnated paper’ (experiment 1) than in the choice between ‘paper impregnated by their own colony’ and ‘paper impregnated by a foreign heterospecific colony’ (experiment 3). The responses were less dispersed in the choice between ‘paper impregnated by their own colony’ and ‘paper impregnated by a foreign isospecific colony’ (experiment 2). The discussion also concerns the marking of the nest entrance in solitary terricolous Hymenoptera, a function allocated to the secretion of the Dufour gland. The mechanism of this marking in social bees remains to be studied.

The last tarsal segment and pretarsus of adult bumble bees are described. The tarsal gland on the fifth tarsomere of each leg in all individuals of a colony consists of simple glandular epithelium surrounding a reservoir in which its secretory products accumulate. Movement of the pretarsus in and out of the fifth tarsomere helps to discharge the secretion of the gland onto the ventral surface of the arolium. Study of the fine structure of the glandular cells reveals the presence of cytoplasmic organelles involved in secretion. The apical surface of the cells bears numerous microvilli associated with a smooth endoplasmic reticulum. Ergastoplasm is mainly located in the basal region. The spherical or ovoid nucleus is generally located basally and the cytoplasm contains uniformly distributed Golgi complexes, ribosomes which vary in number from one area to another, more or less electron-dense multivesicular bodies, mitochondria, and pinocytotic vesicles and coated vesicles in the cytoplasm of the apical area. Interdigitations and desmosomes contribute to the cohesion of cells within the epithelium. The tarsal gland of bumble bees is compared with that of other insects, and the function of its secretion is considered.

1. 1. Dufour's gland secretions of nine westpalaearctic bumble bee species, representing Terrestribombus, Pyrobombus and Megabombus, were analysed by gas chromatography and mass spectrometry. 2. 2. The secretions were dominated by uneven numbered straight chain alkanes from heneicosane to hentriacontane, each alkane accompanied by up to 10 positional alkene isomers. 3. 3. Various esters dominate among the 64 oxygen-containing compounds found. 4. 4. This is the first report on Dufour's gland secretion of bumble bees. The secretion is species specific. Subgeneric and tribe specific patterns are indicated. 5. 5. Characteristics for species separation of workers of the Terrestribombus group are presented. 6. 6. The possible communicative function of the secretion is discussed.

The labial gland secretions from males of the bumble bee Bombus (Pyrobombus) perplexus Cresson were analysed by gas chromatography/mass spectrometry (GC/MS) in the electron impact and positive ion chemical ionization mode. The major compound of the complex mixture of alkenols, alkenals, fatty acids, hydrocarbons, wax type esters and steroids is 3,7,11,15-tetramethyl-2,6,10-hexadecatrien-1-ol (geranylcitronellol), considerable amounts of hexadecan-1-ol and Z-9-hexadecen-1-ol were also found. All alcohols were present as esters of the detected acids. In older samples both the acids and the alcohols sometimes could not be detected in the GC; therefore, the possibility to check the detected acid-alcohol pattern by interpreting the wax type ester peaks is very instructive. Moreover, the labial gland contains a rich mixture of mono- and di-unsaturated straight chain hydrocarbons. The similarity in composition of the labial glands of the North American B. (Pyrobombus) perplexus with the Eurasian species B. (Pyrobombus) hypnorum corroborates the assumption that the two species are conspecific. The likely supposition that the hydrocarbons could play an essential role in the chemical communication in bumble bees is discussed.

Chromosome counts were obtained for 14 Bombus Latr. species (the social bumble bees) belonging to four subgenera and for one Psithyrus Lep. species (the social parasitic bumble bees). In Bombus the haploid numbers were consistent within each subgenus and there was variation between subgenera; the subgenera Bombus s.s. and Pyrobombus have n = 18, while Separatobombus and Cullumanobombus have n = 19. Thus considerable morphological divergence between subgenera is often, but not always, paralleled by divergence in chromosome number. Psithyrus ashtoni has n = 25, higher than all Bombus species yet examined. This provides support for the monophyletic origin of Psithyrus, but the high n is not expected if eusociality selects for increase in chromosome number.

The volatile secretions produced by the labial gland in male bumble-bees,Bombus Latr., belonging to the subgenusPyrobombus D. T., have been studied in six species:B. cingulatus Wahlb.,B. hypnorum L.,B. jonellus K.,B. pratorum L.,B. lapponicus Fabr. andB. scandinavicus Friese. Totally, 181 specimens have been analyzed. The secretions, which are used for marking different objects along the flight-route, have been analyzed by capillary gas chromatography and combined capillary gas chromatography/mass spectrometry. Isoprenoids and fatty acid derivates together make up the secretions. The former group of compounds dominates the marking secretions from the species studied, with the exception ofB. scandinavicus. The compositions of the secretions are characteristic for each species.

Temperature records were kept from the time the new queens ofBombus (Pyrobombus) impatiens burrowed into the soil until they emerged the following spring. Statistical analysis is presented on the relationship of solar radiation and temperature as they affected emergence.