Bumble bees are essential pollinators that have an annual eusocial lifestyle where new cohorts of queens establish colonies each season. The early stages of colony establishment are critical for colony success and are heavily impacted by how readily queens activate their ovaries and initiate egg laying at the start of the season. Understanding the social and nesting factors that influence queen reproduction may provide key insights into early colony establishment. Here, we examine how social conditions and nest cavity size affect the onset of egg laying in early nesting Bombus impatiens queens. In the first experiment, queens were assigned to a social condition where they were placed into nesting boxes that either completely restricted contact with nestmates (and were smaller in size) or allowed direct physical contact and then housed either alone or with nestmates (males or workers). We found that contact with either workers or males accelerated egg laying in queens relative to being housed alone. Unexpectedly, queens housed in the restricted cages, regardless of whether alone or with nestmates, also initiated egg laying earlier. This led us to a second experiment, where we examined ovarian activation and hemolymph juvenile hormone (JH-III) concentrations in early queens housed in different nesting cavity sizes. Here, we found that smaller nest cavity sizes lead to a greater degree of ovarian activation in gynes (young, unmated queens), but juvenile hormone concentrations did not differ. Our findings demonstrate that both social conditions and nest cavity size influence reproductive timing in queens in early-stage bumble bee colonies.
Maintaining pollinators in greenhouses can provide a semi-field environment to investigate the effects of biotic and abiotic factors on bee activity, including pesticide exposure, while enabling studies of behavioral ecology under controlled but realistic conditions. In this study, we evaluated the survival, behavior, and nesting of the solitary bee Centris analis under greenhouse conditions to identify the conditions required to maintain this species in semi-field experiments. Greenhouses were constructed and supplied with floral resources known to be used by C. analis. Male and female bees were released, and survival was monitored daily. Survival was significantly influenced by sex and mating status, with mated males exhibiting longer survival than unmated individuals. Bees survived for more than 30 days under greenhouse conditions, and females consistently outlived males. Nest establishment was primarily driven by the density of Malpighia emarginata flowers rather than female lifespan. Behavioral observations showed that females were most active between 10:00 and 13:00. This study demonstrates, for the first time, that C. analis can be maintained under semi-field (greenhouse) conditions, where individuals exhibited survival and behavioral patterns similar to those observed in the field. However, improving nesting success remains necessary for studies focusing on reproduction. Overall, our findings provide a practical framework for future studies in behavioral ecology, ecotoxicology, and other semi-field experiments with Neotropical solitary bees.
Nest is an essential habitat for social insects. In the bumblebee colonies, the darkening of nest color is a prominent indicator of colony collapse. However, the reason for nest darkening remains uncertain. In this study, we used Bombus terrestris L. as a model insect to investigate the factors influencing the darkening of the nest color. We used nuclear colonies to confirm the influence of social factors in the colony on the color change of the nest. The results revealed that in the nuclear colonies, the male is a primary contributor to nest darkening. Specifically, when the ratio of males to workers exceeded 1:1, the process of nest darkening accelerated. Additionally, we found that removing males during the later stages of colony development not only delayed nest darkening but also prolonged overall colony growth and development.
The Neotropical bumblebee Bombus pauloensis is a native alternative to the exotic commercial pollinators currently used in South American agriculture, most notably Bombus terrestris (Linnaeus, 1758). We evaluated the effect of nest box volume on colony initiation success in 215 field-collected queens from Argentina. Queens were housed in small plastic boxes (400 cm3) or larger wooden boxes (1100 cm3) under controlled laboratory conditions. Overall initiation probability was 61
Biparental care is rare in insects and is commonly attributed to genetic monogamy, which yields high fitness benefits for caring males. The discovery of biparental care despite low male paternity in the bee Ceratina nigrolabiata challenges this view. We tested whether this pattern is population-specific or evolutionarily stable by examining the frequency of biparental care and male paternity in two additional populations of C. nigrolabiata and three closely related species. Biparental care occurred in all studied populations and species, although at varying frequencies. Guarding males exhibited low paternity due to female multiple mating. These results indicate that biparental care can persist over evolutionary timescales (ca. 5–8 million years) even under low paternity, suggesting that mate guarding may be a key selective force promoting its evolution.
Nosema infection negatively affects colony health, productivity, and survival. The most commonly used drug for treating Nosema infection is fumagillin, but due to its side effects and being banned in some regions, alternative approaches need to be explored. This study aimed to examine the effects of an infusion prepared from the aerial parts of wormwood and the buds of European red pine on bee health and Nosema infection. The effects of the infusion on bee health were determined by a chronic toxicity test (10-day toxicity), locomotor activity, and histopathological examination of the midgut. Also, the anti-Nosema activity of the infusion was determined by comparison with fumagillin under laboratory conditions. The 10-day toxicity test showed that the infusion was well-tolerated, maintaining a high survival rate of 99.2
Numerous studies have used electronic bee counters to gain a better understanding of the impact of environmental conditions on bee flight activity. In addition to meteorological data, the impact of plant protection products is also of great interest. In this work, we present data from bee counters collected in three semi-field studies, wherein some of the colonies were exposed to well-known chemical treatments, dimethoate or λ-cyhalothrin. We first analyze the bee flight activity of the untreated hives combined with meteorological data: multiple regression models confirm solar radiation and air temperature as the main drivers, while linear mixed models that account for temporal autocorrelation support a richer fixed-effects structure. Furthermore, we investigate the relation between visually assessed foraging activity, flight activity, and meteorological parameters. For our trials, we find weak to moderate Pearson correlations (0.21 to 0.40) between foraging and flight activity. Temperature data can improve the fit, but additional parameters are required to fully explain the foraging activity. We then analyze the signatures of the different chemical treatments in the bee flight data using Bayesian structural time series models. Our approach enables the differentiation between weather and treatment effects and facilitates the analysis of treatment signatures in the data from individual exposed colonies.
Orchid bees are exclusive to the Neotropical region. This study aimed to identify Euglossini areas of endemism (AE) across the Neotropics and to compare them with existing regionalizations. We compiled 4,317 unique occurrence records for 182 species. AEs were identified using NDM/VNDM software with 3-degree and 4-degree grids, and quantitatively compared using V-measure and relative inhomogeneity. Analyses yielded 11 consensus AEs (3°) and 19 (4°). Strongest global association was found with previous orchid bee’s areas as expected. Locally, AEs strongly corresponded with Panama + Chocó, Amazon Basin, and Atlantic Forest. Local correspondence was notably weaker in the Andean region, and surprisingly, no AEs were identified within the previously suggested Paraguayan Corridor. These robust spatial patterns of endemism offer critical insights to refine current biogeographic regionalizations of the Euglossini tribe.
The European beewolf (Philanthus triangulum Fabricius, 1775) is a solitary wasp that preys on honey bees and has recently expanded its range to the Canary Islands. This study investigates whether P. triangulum could act as a vector for honey bee gut pathogens and evaluates the reliability of their PCR-based detection in non-target hosts. Ninety-four beewolf individuals were screened for microsporidia and trypanosomatids using family and species-specific primers. Amplification was successful for pathogens at family level, but sequencing revealed non-specific amplification of host microsatellite regions. Only in one beewolf individual the pathogen amplicon showed identity with multiple trypanosomatid species, though infection could not be confirmed. These findings highlight the risk of misinterpretation when using primers specific to trypanosomatids and microsporidia to other taxa than honey bees and emphasize the need for sequencing confirmation. Our results underscore methodological challenges in pathogen spillover studies and call for robust diagnostic protocols to avoid false positives and improve pollinator health research.
The small hive beetle (Aethina tumida) is known to infest colonies of cavity nesting honey bees, Apis mellifera, Apis cerana, bumble bees and stingless bees. The adult beetles lay eggs inside the invaded colony and together with their larvae feed on the honey, pollen and young bees and consequently induce colony collapse or absconding. Here, we present the first evidence of small hive beetles infesting colonies of open nesting giant honey bees, Apis dorsata. In May 2024, some unknown beetles and larvae were found associated with damaged wild colonies of A. dorsata in a routine survey in the Sundarbans mangrove forest in India. The infested combs were covered by a slimy substance and smelled like fermented honey, like known clinical symptoms of small hive beetle infestation. The observations also suggest that the beetles can induce absconding in infested A. dorsata colonies like in A. mellifera. Morphological and molecular data confirmed the beetles to be A. tumida. The present study suggests that the pest has expanded its host range towards wild A. dorsata colonies. Our observations are raising serious concern for the conservation of this native honey bee population and are calling for adequate mitigation.
While relative abundance data have revealed compositional shifts in the gut microbiome of bumblebees before and after diapause, such data alone cannot reliably assess microbial load dynamics. Notably, the gut microbiome’s temporal variation during diapause remains unexplored, particularly in terms of absolute quantification. Here, we conducted a longitudinal experiment to investigate the temporal variation in gut microbiome of bumblebees during diapause (0, 30, and 60 days) using both relative quantitative and absolute quantitative data. Our study based on absolute quantification data showed a simplification of microbial network structure, a reduced observed richness of alpha diversity, and a decline in the core bacterial genus Gilliamella during diapause—contrary to trends inferred from our study based on relative abundance data and previous research. We propose that temporal variation of gut microbiome may be associated with the host’s fasting state and isolation from environmental microbes during diapause, which could contribute to a reduction in microbial load. Therefore, we advocate for cautious interpretation of relative abundance data and emphasize the importance of absolute quantification in ecological and host-associated microbiome research.
Cold anesthesia, as used in honey bee research, is often considered a safe alternative to carbon dioxide. Yet evidence in the literature shows this assumption is only partly justified. Early work demonstrated effects on behaviors such as hoarding and learning, while more recent studies report impacts on neuromodulators, memory consolidation, and locomotion. Although often nonlethal, these effects can alter physiology and behavior in ways relevant to experimental outcomes. Despite calls for greater methodological transparency, reporting of cooling protocols remains inconsistent. A review of historical and recent literature shows that although cold anesthesia is nearly ubiquitous, duration, temperature, and handling details are frequently omitted in published methods, precluding replication and complicating interpretation. While some studies indicate recovery within an hour after cooling, insect physiology research highlights risks of neural or muscular injury. Taken together, these findings suggest that anesthetic handling may be an underappreciated source of variation in contemporary studies of honey bee cognition and behavior.
We described the foraging behavior, nest architecture, and the influence of abiotic factors in Ptiloglossa pretiosa, from a fragment of Atlantic Rainforest in southeastern Brazil. Females showed a bimodal activity pattern, with a primary peak at dawn and a shorter period at dusk. The number and duration of trips with and without pollen loads did not differ significantly. Soil was predominantly composed of clay, and nests consisted of a straight main tunnel with lateral branches and brood cells provisioned with liquid pollen–nectar mixtures. Light intensity and humidity significantly predicted foraging frequency. These results reveal a combination of traits widely shared within Diphaglossinae, as well as unique aspects of the natural history of this species.
Honey bees (Apis mellifera) play a critical role in pollination and agricultural productivity, contributing significantly to global food security and ecosystem stability. However, their populations are increasingly threatened by multiple stressors, and pesticide exposure, especially from agricultural insecticides and in-hive acaricides, has become a major concern due to its potentially low lethal and synergistic effects on bee health. This study investigates the potential synergistic effects of two organophosphate insecticides, dimethoate and chlorpyrifos, when combined with amitraz, a widely used acaricide for Varroa destructor control. Acute oral toxicity assays revealed that dimethoate exhibited the highest toxicity (LC₅0 = 2.6 ppm), followed by chlorpyrifos (56.3 ppm) and amitraz (432.3 ppm). Co-exposure to organophosphates and amitraz significantly reduced survival compared to single-compound treatments, with the most pronounced effect observed in the A10D30 treatment group. To understand the underlying physiological effects, we analyzed the expression of key detoxification (Am-CYP1, Am-CYP2, Am-CYP3, Am-GST) and oxidative stress-related genes (Am-Cat, Am-SOD), as well as Am-Vg. Vitellogenin expression was significantly suppressed at 24 h post-exposure (F = 19.271, p < 0.001), particularly under mixture treatments, while stress-response genes (Am-Cat and Am-SOD) were consistently downregulated. In contrast, co-exposure induced significant upregulation of detoxification-related genes, including Am-CYP2, Am-CYP3, and Am-GST (p < 0.01 in several treatments). These findings highlight the compounded risk posed by pesticide mixtures and emphasize the importance of conducting integrative risk assessments that consider realistic, multi-chemical exposure scenarios encountered by foraging bees.
The invasive small hive beetle (SHB) (Aethina tumida Murray) has been extending its geographical range globally. It was first reported from West Bengal, India, in 2022 and has further spread to the states of Andhra Pradesh and Assam. Despite the invasiveness of SHB, its origin remained unexplored, and little is known about its distribution and effects on the bee colonies. The present study summarizes a possible single introduction event of SHB to India from Bangladesh and its occurrence and spread to other Indian states of Bihar, Uttar Pradesh, and Jharkhand. Initial infestation was noted in Muzaffarpur district, Bihar, in October 2023, with subsequent spread to neighboring states. A total of 4, 575 bee colonies were surveyed, of which 1119 Apis mellifera L. and 16 A. cerana F. colonies were infested. Bihar had a significantly higher infestation rate than Jharkhand and Uttar Pradesh. The phylogenetic analysis revealed that the SHB from India clustered within a single sub-clade, indicating the absence of genetic variation. Both adults and grubs significantly weakened the colonies by reducing the bee population. The severity of infestation mostly occurred from July to November. Migratory beekeeping was identified as a major factor in SHB spread, with seasonal movements across Bihar and neighboring states accelerating its spread. Beekeepers employed various control measures, including sulfur, thymol, boric acid and cultural practices like hive cleaning, which reduced beetle numbers but did not achieve eradication. This highlights the urgent need for systematic monitoring and regulation of migratory beekeeping, along with the development of integrated management strategies to prevent further spread.
Stingless bees from Andean ecosystems exhibit selective foraging over a diverse array of floral resources. A few studies have examined how their selection of pollen resources changes with varying degrees of habitat disturbance in forest environments. The pollen species composition of honey and stored pollen pots from managed hives of Tetragonisca angustula and Melipona costaricensis was monthly recorded over 15 months. Hives were located in three vegetation covers: secondary forests, fallows, and crop fields. Additionally, pollen from corbicula loads was also sampled during three distinct periods. For both bee species, colonies located in crop fields yielded the fewest samples for palynological analysis and exhibited the lowest proportion of pollen from arboreal sources. Each bee species demonstrated differentiated pollen selection among the monthly available flowers. The highest abundance of palynomorphs selected by M. costaricensis came from nectar and pollen-producing tree genera, such as Miconia, Vochysia, Cupania, Clethra, and Myrcia, as well as the herb, Mimosa pudica. This contrasts with the selection made by T. angustula, which primarily derives from pollen-producing flowers of arboreal, shrubby, and herbaceous species, including Pourouma, Phyllanthus, Hedyosmum, Rhynchospora, and Scleria. Consistent selection for nectar- and pollen-rewarding tree flowers by M. costaricensis suggests a more specialized diet than T. angustula, indicating greater vulnerability of M. costaricensis colonies to small-scale forest ecosystem degradation.
The Carniolan honey bee (Apis mellifera carnica) represents a key subspecies in Central European apiculture and is the only officially recognized honey bee subspecies in Slovakia. In this study, we performed a complete mitogenomic analysis of eight honey bee colonies, all originating from officially registered Carniolan breeding lines with one exception originating from a non-selected colony from a relatively isolated apiary (“wild”). Phylogenetic analysis based on whole mitogenome alignment placed all Slovak samples within the C evolutionary lineage, clustering closely with A. m. carnica reference sequences. Analysis of the tRNA-Leu–COX2 intergenic region and in silico DraI restriction confirmed their affiliation with the C1/C1a haplotype group. Sequence comparison and BLASTn analysis revealed three distinct haplotypes among the eight Slovak samples: one predominant variant shared by five lines (wild, Sitňanka, Košičanka, Júlia, and Carnica Sokol), a second shared by two lines (Vojničanka and Tatranka), and a third represented by a single unique (singleton) haplotype (Šahanka). These results are consistent with the placement of Slovak Carniolan honey bees within the Southeast European lineage C and their affiliation with the C1/C1a haplotype group, while also revealing region-specific mitochondrial variants that may reflect natural diversification within managed breeding lines.
Wild bees are parasitized by a variety of organisms, including those that attack brood cells within nests. Brood parasitism reduces reproductive output by increasing offspring mortality, with potential impacts on the persistence of bee populations. Understanding the biotic and abiotic drivers of parasitism in solitary bees becomes crucial under current anthropogenic environmental changes. We evaluated how nest and brood cell abundance, climate, and latitude drive brood parasitism in cavity-nesting solitary bee communities across a broad environmental gradient in the Monte Desert of Argentina. Parasitism rates at the community level increased with decreasing total nest and brood cell abundance and temperature. Across the gradient, parasitism decreased with increasing latitude. The overall parasitism rate was mainly determined by the prevalence of parasitized nests rather than by parasitism intensity within those nests, suggesting that parasitism pressure depends more on the likelihood of hosts being parasitized than on the extent of infestation within each parasitized nest.
